Remembering Medical Ventilators and Masks in the Days of COVID-19: Patenting in the Last Decade in Respiratory Technologies

Abstract

Health systems, which have been under great pressure
with the COVID-19 outbreak, encountered problems in accessing
some urgently needed medical resources. One of these resources has
been the medical ventilators needed in acute respiratory distress
syndrome developing with COVID-19. As a result of the calls made,
many manufacturers have modified their facilities to produce med-
ical ventilators and the problem has been solved to a great extent.
While we focus on the urgent requirement for ventilators in these
troubled days of COVID-19, we do not seem to be worth discussing
their technical developments. How did the countries perform in the
development of novel respiratory technologies in the pre-COVID
period? While patents are seen as a measure of inventive activ-
ity, we attempt to draw a general picture of patents granted in
the field of medical respiratory technologies. Our study examines
27 397 respiratory patents listed in the Derwent Innovations Index
database at the last 50 years and focuses on the last decade for
further evaluation. In addition to the analysis of patent numbers, we
identified the core ventilation technologies of the last two decades
with the topic modeling technique and compared them. We used
the claims section of the patents collected. It is seen that focus of
ventilation patents granted between 2001 and 2010 was on oxygen,
flow generation, and pressure sensors while it shifted to the pipes,
measurement methods, and plates between 2011 and 2022.

Full text

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IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT 1
Remembering Medical Ventilators and Masks in the
Days of COVID-19: Patenting in the Last Decade in
Respiratory Technologies
Alptekin Durmu¸so˘glu and Zeynep Didem Unutmaz Durmu¸so˘glu
Abstract—Health systems, which have been under great pressure
with the COVID-19 outbreak, encountered problems in accessing
some urgently needed medical resources. One of these resourceshas
been the medical ventilators needed in acute respiratory distress
syndrome developing with COVID-19. As a result of the calls made,
many manufacturers have modified their facilities to produce med-
ical ventilators and the problem has been solved to a great extent.
While we focus on the urgent requirement for ventilators in these
troubled days of COVID-19, we do not seem to be worth discussing
their technical developments. How did the countries perform in the
development of novel respiratory technologies in the pre-COVID
period? While patents are seen as a measure of inventive activ-
ity, we attempt to draw a general picture of patents granted in
the field of medical respiratory technologies. Our study examines
27 397 respiratory patents listed in the Derwent Innovations Index
database at the last 50 years and focuses on the last decade for
further evaluation. In addition to the analysis of patent numbers, we
identified the core ventilation technologies of the last two decades
with the topic modeling technique and compared them. We used
the claims section of the patents collected. It is seen that focus of
ventilation patents granted between 2001 and 2010 was on oxygen,
flow generation, and pressure sensors while it shifted to the pipes,
measurement methods, and plates between 2011 and 2020.
Index Terms—Medical masks, medical ventilators, patent
analysis, strategic patenting.
I. INTRODUCTION
APANDEMIC necessitates broad-scale action across na-
tional and international innovation systems to deploy re-
sources for creating and producing crisis-critical items in big
quantities [1]. Unfortunately, with the COVID-19 outbreak,
there have been insufficiencies in meeting the necessary medical
resources for patient needs [2], [3]. The COVID-19 pandemic
has had a significant and unclear influence on healthcare op-
erations [4]. Acute respiratory distress syndrome encountered
during the course of the disease caused patients to experience
Manuscript received August 18, 2021; revised December 13, 2021 and Febru-
ary 7, 2022; accepted February 9, 2022. Review of this manuscript was arranged
by Department Editor T. Daim. (Corresponding author: Alptekin Durmu¸so ˘glu.)
The authors are with the Department of Industrial Engineering, Gaziantep
University, 27310 Gaziantep, Turkey (e-mail: durmusoglu@gantep.edu.tr; un-
utmaz@gantep.edu.tr).
Color versions of one or more figures in this article are available at
https://doi.org/10.1109/TEM.2022.3151636.
Digital Object Identifier 10.1109/TEM.2022.3151636
respiratory problems and therefore most of these patients re-
quired long-term mechanical ventilation [5]. Medical ventilators
are among the most complex resources that have been lacking
during the epidemic [6]. In the face of the shortage of medical
ventilators, the urgency of the situation has prompted countries
to develop creative solutions. It is seen that the joint solutions
developed for the medical ventilator need has been impressive.
It is not surprising that in the troubled days when COVID-19 af-
fected millions, the public focused on the number of ventilators.
However, we ignored how they were invented. What was the
level of innovative activity in ventilation technologies? While
patenting has been a good proxy of innovative activity, which
country/countries have patented these respiratory technologies?
Although more than 27 397 medical ventilator technologies have
been patented in the last decade, to date, there is no known
research detailing the general trends and evolution of this tech-
nological development. Current studies are mostly limited by
the historical journey of medical ventilators from a long time
ago. Therefore, this study seeks to provide an overall picture
of progress by analyzing proprietary technologies in the field
of medical ventilation technologies over the past 10 years in
order to seek (perhaps partially) answers to the aforementioned
questions.
We began by searching for all medical ventilator patents
issued between 2011 and 2020 using the International Patent
Classification (IPC) scheme subclass code A61M-016. Follow-
ing that, we examined trends, growth, national dynamics, and top
applicants among all A61M-016 patents released, and identified
countries with proven expertise in specific fields. In the second
part of the analysis, the novelties listed in the novelties section
of the patents are subjected to topic modeling for the last two
decades. We compared the central focus of the inventions of
the two decades, taking into account the frequency of respective
terms in the specified list of novelties.
To our knowledge, this is the first study to provide a com-
prehensive picture of the evolution of medical ventilation tech-
nologies. As with all patent mapping studies, our study presents
numerical distributions of patents according to their subclass,
geographical and ownership status, and times cited. In addition,
our study also reveals the focal differences between the tech-
nological innovations of the last two decades by analyzing the
textual contents that list the promised innovations of the patents
with an approach that can be seen as innovative. Relevant patent
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2IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT
Fig. 1. Drawing of the iron lung patented by Alfred F. [16].
texts are prepared for the analysis with a pre-processing process,
words are divided into parts considering their roots and the
technologies are clustered together with similar ones according
to the frequency of use of terms with distinctive features. We
hope that this study will contribute to the development and
growth of R&D activities in ventilator development by high-
lighting countries that contribute more to this field, identifying
countries with specific ventilator specializations, and revealing
general trends in this area.
II. LITERATURE REVIEW
A. A Brief History of Ventilation Technologies
Ventilation is simply the process of pumping air into the lungs
of patients who cannot breathe for themselves. The documenta-
tions indicate that the history of artificial ventilation dates back to
ancient times. In Egyptian mythology, Isis, the healing goddess,
restores her husband (Osiris) by breathing into his mouth [7].
Very long after these initial attempts, Andreas Vesalius has
introduced mechanics of breathing in the mid-16th century [8].
He explained the role of atmospheric pressure carrying the air
into lungs [9] and he also described the idea of blowing air from
a tube of reed into animal’s trachea to keep it alive [10].
Robert Hooke [11] repeated the experiments of Vesalius
on a thoracotomized dog by providing a reduced atmospheric
pressure. He also built the first human low-pressure chamber
and described his experiences when the pressure was reduced
to the equivalent of an altitude of ∼2400 m [12]. Until the
mid-18th century, some authorities were encouraging the use
of mouth-to-mouth method [13]. The method was criticized due
to use of expired air and aesthetic distaste [14]. In 1864, one of
the earliest ventilator, called iron lung, was patented by Alfred F.
Jones in Kentucky [15]. The patient should be in sitting position
to be able to use this machine, as shown in Fig. 1 [16]. The main
principle of this machine was to generate negative pressure for
Fig. 2. Drinker respirator and Drinker–Collins respirator [18].
inspiration by providing cyclical positive pressure at the end of
each breath for expiration [15].
In 1876, a new ventilation machine named spirophore was
introduced by a French doctor, Joseph Woillez, having obtained
skilled engineering assistance [17]. The first spirophore was
like metal cylinder surrounding the body of the patient. The
cylinder was closed on one end and covered on the other with a
rubber diaphragm seal that fit snugly around the patient’s neck. A
separate bellows with a 1-L capacity was used to extract air from
the cylinder [16]. Spirophore was met with a lot of enthusiasm.
Ventilators based on (currently) established physiological
concepts were established in the late nineteenth century. Essen-
tially, sub atmospheric pressure was applied around the patient’s
body to replace or supplement the work performed by the respi-
ratory muscles. Mechanical ventilation, which was not widely
used until the 20th century, began to be used frequently with the
spread of seasonal polio epidemics, the idea of using devices to
aid breathing was advanced during the early 20th century [18].
One issue with the existing instruments was that nursing pa-
tients was incredibly problematic due to the difficulty in gaining
access to the patient’s body [8]. In 1908, Peter Lord of Worcester,
USA, patented a respirator room [17]. In his sketches, a space is
portrayed with large pistons in the ceiling that supply fresh air
and generate negative pressure.
Dr. Phillip Drinker, an engineer at Harvard University in
Boston, USA invented what was essentially the first fully prac-
tical cabinet breathing machine in 1929. His work is essentially
the same as Woillez’s Spirophore, and it is this machine that is
now in widespread use around the world, though with various
differences in detail nature. Drinker’s respirator was pictured as
shown Fig. 2. For the next 25 years, the body respirator, or iron
lung, was the mainstay of artificial breathing for the treatment
of respiratory paralysis caused by anterior poliomyelitis in the
United States [19].
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DURMU¸SO ˘
GLU AND DURMU¸SO ˘
GLU: REMEMBERING MEDICAL VENTILATORS AND MASKS IN THE DAYS OF COVID-19 3
During a trip to the United States in 1932, Dr. Robert Hender-
son saw The Drinker’s Respirator in motion and made careful
notes on its design and service. When he returned, he partnered
with Mr. John Mitchell, the City Hospital engineer, to construct
one of their own [20]. For months, they worked together in se-
crecy in the hospital, fabricating the equipment with components
bought from nearby manufacturing companies, portholes and
specially plated screws acquired from a ship chandler, and the
cabinet built was placed on the base of a hospital children’s cot.
During the polio epidemics that devastated Los Angeles in
1948 and Scandinavia in 1952, negative pressure ventilators
were commonly used [21]. There have been important improve-
ments in ventilator technologies in responding to requirement
for better ventilators. One of the most significance was Ray
Bennett’s positive pressure respirator attachment, which was in
operation after September 1948 and turned a Negative Pressure
Ventilation (NPV) unit, the Drinker’s ventilator, into one capable
of delivering “intratracheal” intermittent positive pressure ven-
tilation in addition to its NPV [22]. These devices were much
easier to use than the negative pressure iron lung which offered
adequate respiratory support [23].
In brief, during the first half of the 20th century, PPV had gone
a long way; however, the priority at the time was on using sci-
ence to “normalize” physiology of breathing. After this period,
much of the information on the management of ventilation was
coming from the operating rooms. Known as ventilator-induced
lung injury, mechanical ventilation may cause or exacerbate
lung injury [24]–[26]. Therefore, we can state that the most
important focus of technological development was on prevention
of the side effects of ventilation [23]. The advancement of
lung-protective ventilatory techniques, based on our knowledge
of the iatrogenic effects of mechanical ventilation, such as
ventilator-induced lung damage, has been one of the most recent
events in ventilatory support over the last few decades. [8].
According to MacIntyre (2001), as soon as the symptoms that
required the use of a ventilator relax and continue to improve,
the ventilator should be removed as soon as possible [27]. A
crucial but unanswered question has been what degree a specific
ventilation should be reduced to face with the minimum damage.
This fact makes it important to control and monitor functions
of ventilation. The new generation of ventilators must generate
alerts when too much or too little oxygen is delivered to the lungs
[28]. In this regard, these machines are expected to use advanced
algorithms to control flow based on the patient’s ability to
inhale.
During the late 1970s and early 1980s, with the introduction
of modern, more advanced pressure-targeted ventilators engi-
neered primarily to provide positive-pressure noninvasive venti-
lation (NIV), pressure-targeted ventilation became the industry
standard for NIV [29]. NIV modes are also available on the
majority of modern ventilators on the market, and the use of
them through an interface substantially increased [30], [31].
At the end of 1980s, the integration of microcomputer power
into some of these ventilators has resulted in greater precision
and a smaller number of automated responses to sense patient
changes [32]. This was a major event in the development of
mechanical ventilators, because it meant that any approach to
gas delivery and monitoring was possible [29]. These ventilators
were noticeably more open to patient demand than prior models
of mechanical ventilators. With this generation of ventilators,
the use of airway pressure release ventilation was possible as
pioneered by Stock et al. [33].
Safety, effective ventilation or oxygenating, and improving
patient–ventilator synchrony have been the focus of new venti-
lation technologies in the coming years [29]. In this respect,
adaptive support ventilation (ASV) was introduced. ASV is
a microprocessor-controlled mechanical ventilation mode that
retains a predefined minute ventilation with an appropriate
breathing rhythm (tidal volume and intensity) by automatically
adjusting inspiratory pressure and ventilator rate in response to
changes in the patient’s position [34], [35]. The user is only
expected to set two key controls: the ideal body weight (IBW)
and the minimum minute ventilation (MinVol) [36]. A third
input (maximal inspiratory pressure) was introduced as new
mode in the next versions of these ventilators [37]. Following
that, knowledge-based technologies were adopted as an assistive
service that automatically decreases ventilatory assistance and
shows when weaning readiness requirements are met [38], [39].
When the pressure-support volume is lowered to a fixed level,
the ventilator performs a spontaneous breathing trial (SBT) auto-
matically. If the patient fails the SBT, the ventilator restores ven-
tilation immediately. When the patient passes the SBT, the venti-
lator alerts the patient that extubation should be considered [38].
Proportional assist ventilation (PAV) [40] and neurally ad-
justed ventilatory support (NAVA) [41] were introduced as new
modes of ventilatory support. PAV is regulated by changes in
the patient’s work of breathing, while NAVA is controlled by
changes in the diaphragm’s electromyographic action. There-
fore, the health professional does not adjust pressure, flow,
volume, or time for either PAV or NAVA: Both of these pa-
rameters are completely under the control of the patient. In this
regard, PAV and NAVA have been preferable form of mechanical
ventilation by providing assistance in sync with patient efforts
[42]. These ventilators are all readily upgradeable, have wave-
forms as a normal operating feature, and provide comprehensive
monitoring—one contains tracking data for 20–40 different
variables [29].
B. Patent Analysis
A patent is a contract in which the government prevents
others from making, using, and selling that invention for a
certain period of time in exchange for an inventor’s disclosure
of his invention to the public [43]. The solution proposed for
an invention to be registered as a patent must contain novelty,
involve a nonobvious inventive step, and should be industri-
ally applicable. Patents made available to the public provide
rich, detailed information about the solutions offered defining
the persons, locations, periods, and technological features of a
registered invention [44]. Patents, which are a means of trans-
ferring scientific results to technological applications [45], can
be intensively used for measuring innovation activity [46].
The biggest advantage of patent sources is that they contain
large volumes of data as well as the ease of accessing the
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4IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT
information they contain. Analysis of patent data is valuable
in providing a consistent understanding of the evolution of a
particular technology. This helps us determine what develop-
ments an invention results in and predict what will happen in
the future [47]. Patents are also useful metrics for measuring the
innovativeness level of firms [48]. They can also be used as a
proxy to identify links among innovators [49].
Besides the numerous benefits that can be achieved with
patents, there are also some reservations regarding the use of
patent data as a proxy for monitoring technological progress
[50]. All inventions are not patented [51]. Firms also use
alternative methods such as industrial secrecy to secure their
inventions [52]. Also, analysis based on patent counts tends to
ignore the fact that the economic value of inventions has changed
significantly [53]. Despite these limitations, patent analysis has
been used frequently for some technology areas where industrial
development is determined. We see patent analysis for battery
electrical vehicle technologies [54], low-emission vehicle
technologies [55], traffic control technologies [56], Internet
of Things technologies [57], photovoltaic technologies [58],
low-carbon energy technologies [59], wind energy technologies
[60], radiofrequency identification technologies [61], integrated
circuits [62], CNC technologies [63], and blockchain-related
technologies [64].
Since the patent data in the Derwent World Patents Index
(DWPI) database contains no keywords (and there are no key-
words in other large patent databases either), direct keyword
statistics using the typical bibliometrics approach are not avail-
able [66]. Therefore, in most patent analyses, technological
priorities are determined by taking into account the patent
classes (often selected by the inventor from a list of several
technology alternatives) to which the patents belong. There are
certain limitations of these classification approaches, while it is
very difficult to find a perfect match between the innovative
technology and the assigned technology class. Therefore, a
textual analysis of the patens is expected to be more informative
to understand directions of the innovations. In this study, unlike
other studies, the claims of the patents are examined textually
while exact novelties are provided in this section by the patent
owners. Claims are a list of novelties approved by the patent
authority but they remain uncategorized as a text. Focusing to
claims is expected to save lots of time and memory while patent
documents are high-volume documents. The classification of
patents according to their claims indicates that different time
periods have different focuses (on different components and
parts), as demonstrated in this study.
The most current technique in textual analysis, topic model-
ing, uses a semantic-based mining method to describe compo-
nents in large datasets such as patent databases or journal articles
[65]. The use of topic modeling in patent analysis is not very
common. Topic modeling was rather used for finding the correct
class of a technology. In this study, the terms used in patent
claims were broken down to their roots and their frequency of use
was calculated. The information that is more valuable than the
frequency of terms is that the use of terms together (at the same
claim) enables us to evaluate similar patents in the same cluster.
Another difference of this study from other known studies is
TAB L E I
INTERNATIONAL PATENT CLASSIFICATION (IPC) SYSTEM DEFINITIONS FOR
BREATHING TECHNOLOGIES
that use of k-mean clustering of patents (medical ventilation
components) to find the core technologies of the field.
III. RESEARCH METHODOLOGY
We can consider the analyses used in this study in two main
categories. The first category is numerical analysis, where the
number of patents is taken into account, and the second is content
analysis, where patent contents are mined.
For the first part of our research, numerical analysis, we
focused on patent information obtained from the Derwent Inno-
vations Index (DII) database (Thomson Reuters). We conducted
a search using the International Patent Classification (IPC)
codes. The IPC classification system is a structure developed
by the World Intellectual Property Organization (WIPO) and is
currently used in more than 170 countries [67]. Table I represents
the specific patent codes (A61M-016/00 and subclasses) that
were used in our search to find all medical ventilator patents. We
included all patent applications filed between 2011 and 2020.
In the second part of the analysis, the novelties listed in the
summaries of the patents are subjected to topic modeling for the
last two decades. Text data is preprocessed using the techniques
below.
1) Transfer Cases: Text datasets are changed to lower case in
order to avoid word differences.
2) Tokenization: Tokens are generated from text collections
(words). The tokenization process extracts meaningful
terms from text data. The tokens are the input for the next
step.
3) Stop Terms: The text datasets have the stop words re-
moved. Several words such as “and,” “are,” and “but”
appear frequently in a document, although they are fun-
damentally not contributing since they are used to unite
words together in a phrase. Stop words, as is widely as-
sumed, do not directly affect the context of text documents.
Because of the high frequency of occurrence of stop words
in documents, they create a barrier for understanding the
content of the document. Therefore, all stop words are
eliminated from the patent text documents.
4) Short Words: The short words with two characters are
eliminated from the text datasets.
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DURMU¸SO ˘
GLU AND DURMU¸SO ˘
GLU: REMEMBERING MEDICAL VENTILATORS AND MASKS IN THE DAYS OF COVID-19 5
Fig. 3. Ten-year distributions of breath technology patents.
5) When the terms are found, the weight of each term is
determined by using term frequency-inverse document
frequency (TF-IDF), which is one of the most well-known
algorithms used in text mining research. The term “fre-
quency” refers to the number of times a phrase appears in
a text, while IDF refers to a technique used to compute
the inverse probability of discovering a word in a text.
wij given in (1) represents the weight of the word Iin
document j,Nrepresents the number of documents in the
set of total documents, tfij represents the frequency of the
word Iin document j, and dfirepresents the number of
documents containing the word i.
wij =tfij ×logN/dfi.(1)
Subsequent to preprocessing, we tried to cluster the similar
patents by considering the term frequencies. In this step, the
k-means clustering method is used to cluster the patents. Davies–
Bouldin Index (DBI) is used to measure the performance of
the clustering. DBI is one method used to measuring cluster
validity in a clustering method. Measuring with DBI maximizes
intercluster distance and at the same time tries to minimize the
distance between points in a cluster. If the intercluster distance
is maximal, it means that the characteristics of each cluster are
small so that the differences between clusters are more apparent.
A. An Analysis of the Patent Counts
Although the aim of this analysis is to closely examine the
last 10 years of breathing technologies, we also wanted to take
a look at what happened in 10-year periods of the past. In the
searches made in the database of Derwent’s Innovation Index,
a total of 27 397 medical respiratory inventions were patented
between 1967 (the oldest available date) and 2020 (since 2021
was not complete, we thought it would not be fair to include it in
the analysis). As can be seen in Fig. 3, the number of inventions
increased with an ever-increasing momentum in 10-year periods.
The total number of patents received in the 10 years between
2011 and 2020 increased by 181% compared to the years 2001–
2010. This has been the largest increase in the 10-year periods
examined. The second largest 10-year increase (177%) occurred
in the previous decade (2001–2010).
Fig. 4. Numerical distribution of breathing technology patents between 2011
and 2020.
In order to understand the situation better, Fig. 4, which shows
the patents granted in the last 10 years, can be examined. It can
be stated that there is a general increase trend in the number
of patents over the years, but the increase rate in the last two
years (2019 and 2020) has been significantly higher (around
48%) than the others. Increases in 2019 and 2020 reached their
highest level in history after an increase of 6900.5% seen in 1974.
The increase in 2019 and 2020 is as notable as the one in 1974.
In 1974, American Hospital Supply Corporation was one the
leading owner of those granted patents. The patent dominance
of the USA is clearly evident. Disposable filters for medical use,
registered as a patent [68] and being the most cited invention of
its time (105 citations), have the potential to be the pioneer of
the developments in the following years.
Rapid increases in the number of patents point to increased
interest and investment in respiratory technologies. The in-
creases in 2019 and 2020 first bring to mind the impact of
the COVID-19 outbreak. Since the patents dealt with in this
study are registered patents, it can be stated that at least 1 year
has passed since their applications. This period can be up to 2
years for the USPTO [69]. Therefore, it is highly probable that
the applications for patents registered in 2019 were filed before
the COVID-19 outbreak. More detailed research is required to
understand whether this increase implies a preparatory stage of
any epidemic. We see that, by 2020, COVID-19 became visible
in patents. In the content of the patents (summary, title, claims),
seven patents with an emphasis on COVID-19 were detected.
In patent analysis, the number of citations per patent is ac-
cepted as an indicator of the qualitative importance of a patent
[70]. The most notable patent of the decade under review relates
to a method for monitoring the oxygen supersaturation index
[71] referred to by 141 patents. This patent covers a method for
calculating a patient’s rising oxygen supersaturation index levels
during intubation therapy using a pulse oximeter device. The
proposed method is sensor-free, allowing the patient to control
oxygen oversaturation noninvasively while avoiding severe side
effects.
The second most cited patent [72] of the same period (citing
123) deals with an oximetry system that monitors the physi-
ological parameters of a single patient. Some parameters kept
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6IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT
TAB L E I I
DISTRIBUTION OF PATENT NUMBERS ACCORDING TO IPC SUBGROUPS
under monitoring by the system are as follows: oxygen satura-
tion, carboxy hemoglobin, methemoglobin, total hemoglobin,
glucose, bilirubin, fractional saturation, pulse rate, respiratory
rate, respiratory cycle components, perfusion indicator, i.e.,
perfusion index, signal quality, and confidence, plethysmograph
data, changes in respiratory rate, expiratory flow, tidal volume,
minute volume, apnea time, breath sound, rile, rhonchi, stridor,
and breath sound. This device correlates data flowing from the
center with the patient being monitored, thus enabling electronic
measurement and therapy information to be transferred to the
caregiver’s data management systems without the caregiver
needing to associate the device with the patient.
B. Patent Applications Per IPC Subclass
The annual number of patent applications for each IPC sub-
group of medical ventilators is as shown in Table II. It should
be noted that a single patent application is normally listed in
several IPC subclasses in the same file. Therefore, the total
number of patents filed in all subclasses is usually greater than
the total number of applications for a generic IPC class, since
the same patent is included in the total for several times. For
example, while a total of 17 012 patents were registered in
the general respiratory technology category (A61M-016/00), the
total number of patents in the subcategories of the same category
is 30 009. This indicates that at least 46% of the aforementioned
ventilation technology inventions are labeled at least with two
subclasses (ventilation technology class and a subclass thereof).
A multiclass patent may claim rights for different types of
components or technologies created and combined to create a
new product [73].
Since a patent is classified in more than one IPC at the
same time, seeing which technology category medical ventilator
technologies fall into at the same time will help us identify the
areas of technology that have been collaborated. As Lubango
and Pouris (2010) stated in their work, patents contain extensive
information about the technical characteristics of an invention
as well as its connections with other technologies. Of the 17 012
medical ventilation inventions, 854 are also labeled as “Diag-
nostic measurements, identification of persons” (IPC: A61B-
005/00) technology. This indicates that ventilation technologies
are not only therapeutic tools used in emergency services, but are
also used for diagnostic purposes. Similarly, 854 of ventilatory
technologies are also in the A61M-011/00 class (devices for
inserting media into or out of the body; devices for converting
or extracting body media; devices for producing or terminating
drowsiness or dizziness).
Another IPC subclass in which medical ventilation tech-
nologies are labeled together (852 patents are available) is
A61B-005/08, which includes devices that measure respiratory
organs. The sensor operating in connection with a tube placed
in the patient’s trachea [75] is a good example of the inventions
where these two classes intersect. This sensor is designed to be
used in the diagnosis of respiratory tract disease and evaluating
respiratory function by measuring intrachest pressure.
As can be seen from Table II, approximately 29.5% of
all breathing inventions are in the category of tracheal tubes
(A61M-016/04). The idea of intubating the human trachea with
a device needed to support ventilation dates back to Hippocrates
(460–380 BC) [76]. The intubation procedure is to support venti-
lation by keeping the airway open by placing a kind of reed called
tracheal tube into the trachea of the patient who has difficulty in
breathing. These tubes are a part of lifesaving intervention along
with ventilators. Although the high share of these technologies
among breathing inventions in the 10-year period is reasonable,
the large increase in the application rates seen in 2020 was
relatively limited (27%) in this technology group. Among these
remarkable increases, which are clearly seen when the figures of
2020 and 2019 are compared, the biggest increase was seen in
the technologies “used in the preparation of respiratory gases or
vapors” (A61M-016/10) with a growth of 71%. What inventions
are meant by “technologies used in the preparation of respiratory
gases or vapors”? The technologies mentioned here are devices
used to deliver pressurized respirable gas to the patient’s air-
ways. The patent [77] describing the interface system developed
to deliver pressurized breathable gas to the patient airways
to provide continuous positive airway pressure (CPAP) therapy
to the patient in the treatment of sleep-disordered breathing is
an example of this category. With this technology, oxygen is al-
lowed to pass from the air to the venous blood and carbon dioxide
is allowed to exit. Thus, the occurrence of respiratory disorders
is prevented. It is remarkable that 703 of the 963 patents (73%
of all) registered in this technology subclass (A61M-016/10) in
2020 were carried out by Chinese inventors. In the same year,
the Chinese Nanjing Superstar Medical Equipment Co Ltd was
registered with the highest number of patents on this subject (13
inventions). Founded in 1993, Nanjing Superstar is known for its
intensive R&D activities focusing on ICU devices. The strategic
nature of China’s focus in this technology area emerges as an
issue that needs to be emphasized and researched.
In the last decade, the second most patented technology
category has been “respirator or anesthetic masks.” Inventions
in the same category are again in the second place with an
increase of 63% in the amount of increase in 2020. Respirator
masks are technologies that provide a barrier to prevent exposure
of the respiratory tract to droplets and airborne aerosols [78].
With the COVID-19 outbreak, textile companies started to take
nanotechnologies and specialty nanomaterials to develop new
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DURMU¸SO ˘
GLU AND DURMU¸SO ˘
GLU: REMEMBERING MEDICAL VENTILATORS AND MASKS IN THE DAYS OF COVID-19 7
solutions to the challenges of the pandemic [79]. With the
nanofiber, nanocomposite, and nanoparticle technology added to
the respirator masks, high breathability and increased filtration
efficiency, washability, and antiviral and antibacterial properties
are provided [80]. A total of 67% of the registered patents on
masks are patents issued in China. It is understood that 1362 of
7637 patents in this field are related to polymer science.
One issue we need to clarify at this point is that breathing
technologies are also being used to treat sleep-related breathing
disorders such as “obstructive sleep apnea,” “central sleep ap-
nea,” and “sleep-related hypoventilation” [81]. When we search
for the word “sleep” in the content of 17 012 patents (abstract,
title, and claims) that fall within the scope of this study, we are
faced with 957 patents. This corresponds to 5.6% of all breathing
inventions registered in the last decade.
In order to understand the development of respiratory tech-
nologies, we had to search for the existence of some terms
in the collected patent texts (title, summary, claims). For this
purpose, Durmu¸so ˘glu and Unutmaz Durmusoglu [56] studied
traffic control technology patents. For example, we were able
to define the term “algorithm” in 126 patent texts in these
electronically supported inventions. It was seen that 331 arti-
ficial intelligence-supported technologies containing the word
“intelligence” were patented (such as smart oxygen monitoring,
smart oxygen generation, smart atomizer, and smart breathing
apparatus). Interestingly, 321 of these 341 inventions were found
to be patents registered in China. It was also seen that 2392
inventions mentioned sensor support. Compared to traffic con-
trol technologies [56], we have found that the most important
terms of recent technological development (such as “intelli-
gence,” “algorithm,” and “sensor”) are relatively less involved
in respiratory technologies. This situation can be interpreted as
that there are still opportunities for the relevant technological
developments. In addition, 1137 patents had an emphasis on
“emergency.” Oxygen gas was mentioned in 7061 patents. As
we mentioned earlier, there were 957 technologies that talked
about sleep breathing problems. A total of 114 patents were
found with the word “virus.”
Bearing in mind the importance of generating real-time alerts
for related technologies, we were able to identify 727 patents
with “alarms” and “alarms.”
C. National and Institutional Leaders
Inventors can make patent applications to their national offices
in the country/countries where they request legal protection. It
is also possible to obtain collective protection rights by making
applications through the World International Property Organiza-
tion (WIPO) or the European Patent Office (EPO). The distribu-
tion of the countries where applications are made for breathing
technology inventions is shown in Fig. 5. Although it is not
completely possible to understand whether the aforementioned
patent applications are filed by the citizens of that country or
from other countries, according to the statistics of the OECD
[82], cross-border property patents constitute a limited part of
all patents. The countries that received the most breathing tech-
nology patent applications between 2011 and 2020 are China, the
Fig. 5. Distribution of patent applications by country.
United States of America, Japan, and Canada. 11% of the appli-
cations were made to WIPO and 9% to EPO. China’s dominant
influence on the relevant technology (46% of all applications)
is quite evident. When we remove the applications made by
European and US companies in China to see the real power of
China in respiratory technologies, we see that there are around
10 000 patents left. This situation indicates that China’s interest
in these technologies is undeniable. The Chinese Patent Office
faced almost three times as many applications from its closest
competitor, the United States. Examining the history of China’s
dominant influence on these technologies, it is seen that 2010
was the first year in which the number of applications in China
exceeded the United States. Before 2010, these technologies
were centered in the USA.
Philips (Koninklijke Philips NV and Koninklijke Philips
Electronics) has been the company that resulted in the highest
number of patent registrations in these technologies related to
breath, with 443 patents. A total of 28.66% of these patents
(127 patents) are about sleep-related breathing disorders. Philips
alone developed 13% of the 957 patented inventions used in
sleep-related respiratory disorders over the last decade.
ResMed, which ranked second with 384 patents, is a med-
ical equipment company based in San Diego, California. The
company’s primary focus is cloud-connected medical devices
for the treatment of sleep apnea (such as CPAP devices and
masks), chronic obstructive pulmonary disease, and other res-
piratory ailments. ResMed is known to produce a fairly large
number of ventilators to help treat respiratory symptoms of
COVID-19 patients. Fisher & Paykel Healthcare Corporation
Limited, known as the manufacturer, designer, and marketer
of products and systems for respiratory care, acute care, and
the treatment of obstructive sleep apnea, ranked third with 219
patents. Covidien, with decades of experience in respiratory
care, ranked fourth with 178 patents. Two companies based in
China stand out as the fifth (Beijing Aeonmed) and the sixth
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8IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT
(Hunan Micomme Zhongjin Medical) in the rankings. Founded
in 2001, Beijing Aeonmed Co., Ltd. has been one of the leading
R&D and manufacturing enterprises in the field of anesthesia and
respiratory medical devices and holds 128 breathing technology
patents. Since 2013, Hunan Micomme Zhongjin Medical has
been focusing on equipment innovation and chronic respiratory
disease management services in the field of respiratory diagnosis
and treatment, and has 125 patent registrations covered in this
study. Dräger is the first German company to enter the list
of companies with patented technology. This firm alone owns
22% of 479 breath technologies registered in Germany in the
last 10 years. One of the company’s best-known inventions
is the Lubeca valve. With the present invention, it has been
possible to precisely control the removal of carbon dioxide from
a high-pressure tank. Puritan Bennett company, known for its
ventilation devices, is also at the top of the list with 91 patents.
Wang Youchun attracts attention with 71 individual invention
applications, which brought China to the top in respiratory
technology patent numbers.
Academic patents have been used as a main indicator of the
contribution of universities to the knowledge economy [83].
In the research we conducted to determine the contribution of
universities to this field of technology, we found that 5% (1629
patents) of breathing technology inventions in the last decade
were made by universities. However, what is striking here is
that the majority of these universities are Chinese universities.
Moreover, Army Medical Universities in China are at the top of
the rankings (with 137 patents in total) in terms of number of
patents. Military medical universities in China are institutions
that train military medical professionals in a specific setting
[84]. The comprehensive studies of military universities on this
subject can be considered as an indicator of the strategic value
of respiratory technologies. The third university with the most
patents in the ranking is The Affiliated Hospital of Qingdao
University, a civil university serving in China. There are also
American universities such as the University of Florida Research
Foundation (17 patents), New York University (17 patents), and
The University of California (15 patents) in the list of universities
with the highest number of patents registered.
D. Core Technology Analysis of the Last Two Decades
In the second part of the analysis, the novelties listed in
the summaries of the patents are collected and analyzed. Text
data were prepared using the steps described in Section III.
We removed stop terms, short/irrelevant, nonspecific words and
tokenized the words. Frequency of words for the last decade
(2011–2020) and the previous one (2001–2010) was calculated
and the top 450 terms were ranked for both of the decades. Top 20
of these terms are illustrated in Table III. Increases and decreases
in the frequency of some terms can be seen at first glance. These
differences are important in terms of seeing the differences
in technological occupations between the two-decade period.
While the most striking term of the patents received between
2001 and 2010 was “independence,” the emphasis was on con-
nectivity in the patents received between 2011 and 2020. While
40.1% of all ventilation patents mention about independence
TABLE III
DISTRIBUTION OF KEY PHRASES IN THE PATENT TEXTS
for 2001–2010 patent, it decreases to 21.9% for 2011–2020
patents. As it is known, patents protect not only new devices
but also new methods. The comparison between the two decades
indicates that method innovation decreased (from 32% to 20.1%)
in 2011–2020. The rate of mentioning the same terms in the
previous 10 years is 20%.
We used the WOS software1to make this situation more
evident, which can only be seen by looking at the co-occurrence
frequencies of the terms taken from the patent texts. The
VOSviewer software may be used to create bibliometric net-
works using data acquired from sources like Web of Science and
Scopus [85]. VOSviewer uses a co-occurrence matrix to create
a map. The process of making a map is broken down into three
phases. The co-occurrence matrix is used to create a similarity
matrix in the first stage. In the second stage, the similarity matrix
is used to create a map using the VOS mapping approach. Terms
that have a high similarity are located close to each other. Finally,
the map is translated, rotated, and reflected as described in [86].
In Figs. 6 and 7, you can see the relevance maps of words
that are repeated more than 400 times for the years 2001–2010
and 2011–2020, respectively. We see two cluster of phrases in
both Figs. 6 and 7. Closely related terms are at the same side (as
red ones and green ones). We see that there are typical phrases
(such as advantage, novelty, description) in the relevance map
1[Online]. Available: www.vosviewer.com
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DURMU¸SO ˘
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GLU: REMEMBERING MEDICAL VENTILATORS AND MASKS IN THE DAYS OF COVID-19 9
Fig. 6. Co-occurrence view of terms in ventilation technologies granted between 2001 and 2010.
Fig. 7. Co-occurrence view of terms in ventilation technologies granted between 2011 and 2020.
of 2001–2010, which we expect to occur frequently in a patent
document. We see a noticeable focus on the terms “pressure” and
“apparatus.” On the other hand, we see some key phrases which
reflect specific focus of the 2011–2020 period. “Pipes” and
“plates” appear to be at the heart of the ventilation technologies
on the last decade.
By using the cited patents, we identified the central patents
that inspired others to develop new technologies. The network
can be seen in Fig. 8. Tanaka’s ventilation patents are at the
center of the map. Because each point in the network has a
connection with this patent. The patented device is about lung
reduction with one-way valve that allows air from the lung to
vent to region external of the lung but prevents air from area
external of the lung from re-entering the lung through a device
for eliminating trapped air in emphysematous lungs.
Citation network for 2011–2020 patents is as shown in Fig. 9.
Olsen’s invention relates to a sealing interface designed as part
of the supply apparatus for the flow of breathing gases to the user.
The interface has an inner cushion which includes hinged region
adapted to flex substantially independently on inner cushion
cheek regions.
We attempted to find the core technologies by using TF-IDF
and k-means clustering. The k-means clustering method was
used to cluster the patents having similar TF-IDF values for
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10 IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT
Fig. 8. Citation network of ventilation patents granted between 2001 and 2010.
Fig. 9. Citation network of ventilation patents granted between 2011 and 2020.
Fig. 10. Core technology clusters in ventilation technologies granted between 2001 and 2010.
the similar phrases. For finding a suitable k–value, we used DBI
which is used to measure the performance of the clustering. DBI
is one method used to measure cluster validity in a clustering
method. We found that k=3 (Euclidian distance) performs
the best with the smallest DBI value. We used RapidMiner
software [87] to find corresponding technology clusters. Three
core technology focuses of the years 2001–2010 and 2011–2020
are as shown in Figs. 10 and 11, respectively. Focus of patents
granted between 2001 and 2010 have been on oxygen, flow
generation, and pressure sensors. It can be seen that patents on
the field of pressure sensor and values accounted for 56% of all
the ventilation patents. Pressure sensors are known to be vital
for ventilators to function properly.
Pipes, measurement methods, and plates have been three main
focus of the technologies patented between 2011 and 2020. It
can be seen that patents on the field of measurement methods
accounted for 47% of all the ventilation patents. A measuring
method that provides specific, dependable, and sophisticated
insight into the mechanical characteristics of the lungs has
always been vital for these technologies. Pipes have been the
second top priority of the medical ventilation technologies in
this decade. It is known that the ventilator systems are composed
of a network of tubes and pipes. We see that material structure
of the pipes has been the main focus of pipe-related ventilation
inventions. Flexibility of the pipes is of another consideration in
these technologies.
IV. CONCLUSION
Medical ventilator and mask insufficiencies experienced with
the COVID-19 outbreak first appeared as a quantitative defi-
ciency problem. Many companies have agreed to be collabora-
tive in order to get these technologies faster and the problem has
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DURMU¸SO ˘
GLU AND DURMU¸SO ˘
GLU: REMEMBERING MEDICAL VENTILATORS AND MASKS IN THE DAYS OF COVID-19 11
Fig. 11. Core technology clusters in ventilation technologies granted between 2011 and 2020.
been solved to a great extent. The strategic nature of a technology
becomes clear when countries cannot set a price to give that
technology to others. Most of the time, it is not possible to obtain
some weapons and COVID-19 vaccines, which we have recently
witnessed closely, only by paying the price. We encountered
similar situations at the beginning of the epidemic in breathing
technologies such as medical masks and medical ventilators.
However, the troubles experienced in times of war justify the
questioning of what was done in peace time. With this work, we
tried to trace the efforts made to develop breathing technologies
over the last decade. To our knowledge, this is the first study to
present a comprehensive picture of the development of breathing
technologies.
Based on the knowledge that patents can be used as a good
indicator of technological development, we examined breathing
technology patents to achieve our goal. To this end, we searched
for patents tagged with a technology class category (A61M-
016/00 and subclasses) that only includes breathing/breath sup-
port technologies in a trusted resource Derwent Innovations
Index (DII) database (Thomson Reuters). By examining the
decade-old status of the number of inventions, we have demon-
strated that breath technology has grown at the fastest pace in
the last decade. In the decade between 2011 and 2020, the total
number of patents filed increased by 181% compared to 2001–
2010. The years 2019 and 2020, the last two years of the last
decade, were not ordinary years in terms of increase. The amount
of increase was above the known rate of increase. The unusual
increase in the number of patents whose applications were made
before COVID-19 and registeredin 2019 is a mysterious increase
that may be the subject of various speculations. Deeper research
may shed light on this point. With the year 2020, the expression
“COVID-19” began to appear in patent texts.
Tracheal tubes are the first among respiratory discoveries in
the last decade with approximately 29.5%. Together with venti-
lators, these tubes are known to be a vital part of the life-saving
intervention. Interestingly, the enormous increase in the number
of inventions over the past two years has had a huge impact
on this category. A comparison of the 2019 and 2020 patent
numbers shows us that the highest increase with an increase of
71% is experienced in technologies “used in the preparation of
respiratory gases or vapors” (A61M-016/10). These technolo-
gies are devices used to deliver pressurized breathable gas to
the patient’s airways. The Chinese origin Nanjing Superstar
Medical Device company, which entered the sector in 2013,
creates the impression that it will become a permanent player
in the market. The second technology category that attracted
the most interest and investment of the last decade has been
“respirator or anesthetic masks.” Due to COVID-19, the number
of patents on masks, which are on the agenda, increased by 63%
in 2020.
When we examined the subcategories of related technologies,
we saw that 854 of the 17 012 medical ventilation inventions
were developed for “Diagnostic measurements, identification
of individuals.” This showed that breathing technologies are
not only therapeutic tools used in emergency rooms, but also
used for diagnostic purposes. Similarly, 854 of ventilation in-
ventions include devices for placing media inside or outside the
body, which showed that there are devices for transforming or
removing the body environment. It should also be noted that
respiratory technologies used in the treatment of sleep-related
respiratory disorders constitute 5.6% of related technology
inventions.
The countries that received the most breathing technology
patent applications in the last decade were China, the United
States, Japan, and Canada, respectively. China alone holds 46%
of all breath technology patents, which means almost three times
as many patents as its closest competitor, the United States. The
USA lost its dominance in this technology area to China in 2010.
Philips, ResMed, Fisher & Paykel Healthcare Corporation, Cov-
iden, and Dräger have become leading companies in respira-
tory technology. However, Chinese companies such as Beijing
Aeonmed and Hunan Micomme Zhongjin Medical, which were
established in the 2000s, have also started to become assertive in
the sector. It seems that most of the prolific patent applicants are
private companies. Although the quantitative insufficiency ex-
perienced during pandemic times is a problem that governments
deal with, it is understood that profit-oriented organizations play
a central role in the development of respiratory technology. The
discoveries of the Chinese army medical universities on the
subject are quite remarkable in terms of showing the strategic
nature of the related technology.
Apart from the universities in China, it is understood that
several US universities are also carrying out studies on the sub-
ject. However, the low number of university patents in general
is an issue that should be taken into account by policymakers.
It may be possible to establish research institutes specialized in
this field. There are also important mechanisms to support and
improve the patenting activities of universities [88].
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12 IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT
When we investigated the existence of some terms in the
collected patent texts (claims), we came across the terms such as
“algorithm” in 126 inventions, “intelligence” in 331 inventions,
and “sensor” in 2392 inventions. We interpreted this situation as
there are still opportunities for relevant technological develop-
ments.
This research could also be done on catalogs of technologies
that have been released instead of patents. However, as Chatburn
[89] stated in his study, although the commercially available
medical ventilator has a wide variety of ventilation modes,
it was difficult to understand the distinctive nature of these
modes for technologies. As MacIntyre et al. [23] pointed out,
modern technologies should have advanced monitoring/alarm
mechanisms, improved patient–ventilator synchronization, and
safe ventilation loops, and we identified 727 inventions that
included the term “alarm” in this context.
Although it does not seem comparable, we think that it will be
useful to mention some similar and dissimilar findings found in
the study conducted by Durmusoglu and Unutmaz Durmusoglu
[56] for traffic control technologies. China’s increasing number
of patents is evident in both technologies. However, the Ger-
many’s effect, which is noticeable in traffic control technologies,
is not evident in respiratory technologies. Intelligent systems,
algorithms, and sensors are not as much on the agenda in
breathing technologies as in traffic control technologies. The
intensive efforts of universities have not yet created the expected
intensity for respiratory technologies. These evaluations indicate
that the opportunities for respiratory technologies are enormous.
The analysis in the second part of the study reveals the focus
of technological development efforts in the last two decades,
based on patent texts. While the most striking term of the
patents received between 2001 and 2010 was “independence,”
the emphasis was on connectivity in the patents receivedbetween
2011 and 2020. Connectivity and independence are contra-
dictory concepts. While independent/standalone technologies
indicate the ability to work without the need for other tools,
connectivity refers to the ability of devices with different tasks
to communicate with each other in such a way that they can
exchange data and information. The prominence of connectivity
in the last decade is in line with the developments in Internet and
wireless connection devices.
Our efforts to find key technologies using TF-IDF and k-
means clustering show that the focus of patents from 2001 to
2010 is “oxygen,” “flow generation,” and “pressure sensors.” It
is seen that patents in the field of pressure sensors and values
account for 56% of all medical ventilation patents. Pressure sen-
sors are known to be vital to the proper operation of ventilators.
The three main focuses of the technologies patented between
2011 and 2020 were pipes, measuring methods, and plates. It is
seen that patents in the field of measurement methods account
for 47% of all ventilation patents. As it is known, patents protect
not only new devices but also new methods. Comparison over
two decades shows that method innovation fell (from 32% to
20.1%) in 2011–2020. The rate of using the same terms in the
last 10 years is 20%.
Finally, the practical implications of the situation outlined
above for policymakers and researchers can be listed as follows.
1) China’s increasing interest in medical ventilation tech-
nologies should be analyzed in detail. The Western world
should question its deficiencies and needs in this area in
detail and update the necessary policies in accordance with
the situation.
2) The final goals to be achieved with innovation activities
related to breathing tubes should be determined, and re-
search bodies should create road maps suitable for these
goals.
3) Methods and practices should be developed to increase the
interest of universities in Europe and the USA to medical
ventilation technologies.
4) The opportunities that arise with smart technologies (sen-
sors, Internet of Things, big data) that affect the world
should be reconsidered in medical ventilation technolo-
gies.
5) Considering the emphasis on connectivity in medical
ventilation technologies developed in the last 10 years,
software and hardware possibilities should be reviewed
for the integration of data from ventilation devices with
other medical devices.
6) Just like preventive maintenance activities that predict
machine failures, approaches such as deep learning should
be used to prevent the patient from encountering problems
based on respiratory parameters.
Finally, our research has some limitations to consider. Al-
though it is not possible to give a holistic picture of developments
in a technological field with patents alone, with the advantage of
accessibility and structure, patents have been seen as a reliable
source to show the official and proprietary part of the overall
picture. It can be stated that patent analysis studies, which are
mentioned in Section II and which are cited in many prestigious
journals, provide important information in practical terms. Many
other data that will be required to present the whole picture are
often not available and free of charge due to their strategic nature.
On the other hand, resources such as scientific publications and
other research-based projects may also be included in future
studies. One other limitation of this study is that not all inventions
reflected in the numbers in this study are of equal value. It is
possible to carry out studies that take into account the quality
and commercial values of patents in the future.
REFERENCES
[1] F. Tietze, P. Vimalnath, L. Aristodemou, and J. Molloy, “Crisis-critical in-
tellectual property: Findings from the COVID-19 pandemic,” IEEE Trans.
Eng. Manag., pp. 1–18, Jun. 2020, doi: 10.1109/TEM.2020.2996982.
[2] R. Jouffroy et al., “Prehospital management of acute respiratory dis-
tress in suspected COVID-19 patients,” Amer.J.Emerg.Med., vol. 45,
pp. 410–414, Sep. 2020, doi: 10.1016/j.ajem.2020.09.022.
[3] A. Nazir et al., “The rise of 3D printing entangled with smart computer
aided design during COVID-19 era,” J. Manuf. Syst., vol. 60, pp. 774–786,
Oct. 2020, doi: 10.1016/j.jmsy.2020.10.009.
[4] J. P. Devarajan, A. Manimuthu, and V. R. Sreedharan, “Healthcare
operations and black swan event for COVID-19 pandemic: A pre-
dictive analytics,” IEEE Trans. Eng. Manag., 2021, to be published,
doi: 10.1109/TEM.2021.3076603.
[5] J. Chang et al., “Masi: A mechanical ventilator based on a manual
resuscitator with telemedicine capabilities for patients with ARDS dur-
ing the COVID-19 crisis,” HardwareX, vol. 9, pp. e00187, Apr. 2021,
doi: 10.1016/j.ohx.2021.e00187.
Authorized licensed use limited to: ULAKBIM UASL - GAZIANTEP UNIVERSITESI. Downloaded on May 12,2022 at 13:57:08 UTC from IEEE Xplore. Restrictions apply.

This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination.
DURMU¸SO ˘
GLU AND DURMU¸SO ˘
GLU: REMEMBERING MEDICAL VENTILATORS AND MASKS IN THE DAYS OF COVID-19 13
[6] A. A. Malik, T. Masood, and R. Kousar, “Reconfiguring and
ramping-up ventilator production in the face of COVID-19: Can
robots help?,” J. Manuf. Syst., vol. 60, pp. 864–875, Oct. 2020,
doi: 10.1016/j.jmsy.2020.09.008.
[7] J. Varon and G. L. Sternbach, “Cardiopulmonary resuscitation: Lessons
from the past,” J. Emerg. Med., vol. 9, no. 6, pp. 503–507, Nov. 1991,
doi: 10.1016/0736-4679(91)90224-4.
[8] A. S. Slutsky, “History of mechanical ventilation. From vesalius to
ventilator-induced lung injury,” Amer. J. Respir. Crit. Care Med., vol. 191,
no. 10, pp. 1106–1115, Apr. 2015, doi: 10.1164/rccm.201503-0421PP.
[9] J. J. Hage and R. J. Brinkman, “Andreas Vesalius’ understanding of
pulmonary ventilation,” Respir. Physiol. Neurobiol., vol. 231, pp. 37–44,
Sep. 2016, doi: 10.1016/j.resp.2016.05.015.
[10] T. Pham, L. J. Brochard, and A. S. Slutsky, “Mechanical ventilation: State
of the art,” Mayo Clin. Proc., vol. 92, no. 9, pp. 1382–1400, Sep. 2017,
doi: 10.1016/j.mayocp.2017.05.004.
[11] R. Hooke, “An account of an experiment made by M. Hook, of pre-
serving animals alive by blowing through their lungs with bellows,”
Philos. Trans. Roy. Soc. London, vol. 2, no. 28, pp. 539–540, Oct. 1667,
doi: 10.1098/rstl.1666.0043.
[12] J. B. West, “Robert Hooke: Early respiratory physiologist, polymath, and
mechanical genius,” Physiology, vol. 29, no. 4, pp. 222–233, Jul. 2014,
doi: 10.1152/physiol.00005.2014.
[13] R. V. Trubuhovich, “History of mouth-to-mouth rescue breathing. Part 2:
The 18th century,” Crit. Care Resuscitation J. Australas. Acad. Crit. Care
Med., vol. 8, no. 2, pp. 157–171, Jun. 2006.
[14] R. V. Trubuhovich, “History of mouth-to-mouth ventilation. Part 3: The
19th to mid-20th centuries and ‘rediscovery’,” Crit. Care Resuscitation J.
Australas. Acad. Crit. Care Med., vol. 9, no. 2, pp. 221–237, Jun. 2007.
[15] A. Grenvik, B. Eross, and D. Powner, “Historical survey of mechanical
ventilation,” Int. Anesthesiology Clin., vol. 18, no. 2, pp. 1–10, 1980,
doi: 10.1097/00004311-198001820-00002.
[16] C. H. M. Woollam, “The development of apparatus for in-
termittent negative pressure respiration (1) 1832–1918,” Anaes-
thesia, vol. 31, no. 4, pp. 537–547, 1976, doi: https://doi.org/
10.1111/j.1365-2044.1976.tb12364.x.
[17] G. T. Smith-Clarke, “Mechanical breathing machines,” Proc. Inst.
Mech. Eng., vol. 171, no. 1, pp. 52–74, Jun. 1957, doi: 10.1243/
PIME_PROC_1957_171_013_02.
[18] C. A. McGuire, The Respirator and the Mechanisation of Normal
Breathing. Manchester Univ. Press. Accessed: Apr. 2021. [Online].
Available: https://www.manchesteropenhive.com/view/9781526143167/
9781526143167.00014.xml
[19] G. L. Snider, “Historical perspective on mechanical ventilation: From
simple life support system to ethical dilemma,” Amer.Rev.Respir.Dis.,
vol. 140, no. 2, pp. S2–S7, Dec. 2012, doi: 10.1164/ajrccm/140.2_Pt_2.S2.
[20] I. A. Porter and M. J. Williams, “Scotland’s first iron lung,” Scot-
land. Med. J., vol. 42, no. 4, pp. 122–124, Aug. 1997, doi: 10.1177/
003693309704200408.
[21] A.Hasan, “Historical aspects of mechanical ventilation,” in Understanding
Mechanical Ventilation: A Practical Handbook, A. Hasan, Ed. London:
Springer, 2010, pp. 1–8, doi: 10.1007/978-1-84882-869-8_1.
[22] R. V. Trubuhovich, “On the very first, successful, long term, large scale
use of IPPV. Albert Bower and V Ray Bennett: Los Angeles, 1948–1949,”
Crit. Care Resusc., vol. 9, pp. 91–100, 2007.
[23] N. MacIntyre, C. Rackley, and F. Khusid, “Fifty years of mechanical
ventilation—1970s to 2020,” Crit. Care Med., vol. 49, no. 4, pp. 558–574,
Apr. 2021, doi: 10.1097/CCM.0000000000004894.
[24] M. Briel et al., “Higher vs lower positive end-expiratory pressure in
patients with acute lung injury and acute respiratory distress syndrome:
Systematic review and meta-analysis,” J. Amer. Med. Assoc., vol. 303,
no. 9, pp. 865–873, Mar. 2010, doi: 10.1001/jama.2010.218.
[25] D. Dreyfuss and G. Saumon, “Ventilator-induced lung injury: Lessons
from experimental studies,” Amer. J. Respir. Crit. Care Med., vol. 157,
no. 1, pp. 294–323, Jan. 1998, doi: 10.1164/ajrccm.157.1.9604014.
[26] L. N. Tremblay and A. S. Slutsky, “Ventilator-induced lung injury: From
the bench to the bedside,” Intensive Care Med., vol. 32, no. 1, pp. 24–33,
Jan. 2006, doi: 10.1007/s00134-005-2817-8.
[27] N. R. MacIntyre, “Evidence-based guidelines for weaning and dis-
continuing ventilatory support: A collective task force facilitated by
the American College of Chest Physicians; the American Associ-
ation for Respiratory Care; and the American College of Critical
Care Medicine,” Chest, vol. 120, no. 6, pp. 375S–395S, Dec. 2001,
doi: 10.1378/chest.120.6_suppl.375S.
[28] Z. Elsahn and F. Siedlok, “Can we build it? Yes, we can!’ Complexities
of resource re-deployment to fight pandemic,” Ind. Marketing Manag.,
vol. 93, pp. 191–207, Feb. 2021, doi: 10.1016/j.indmarman.2021.01.013.
[29] R. M. Kacmarek, “The mechanical ventilator: Past, present, and future,”
Respir. Care, vol. 56, no. 8, pp. 1170–1180, Aug. 2011, doi: 10.4187/re-
spcare.01420.
[30] A. Mas and J. Masip, “Noninvasive ventilation in acute respiratory fail-
ure,” Int. J. Chronic Obstructive Pulmonary Dis., vol. 9, pp. 837–852,
Aug. 2014, doi: 10.2147/COPD.S42664.
[31] S. Mehta and N. S. Hill, “Noninvasive ventilation,” Amer. J. Respir. Crit.
Care Med., vol. 163, no. 2, pp. 540–577, Feb. 2001, doi: 10.1164/ajr-
ccm.163.2.9906116.
[32] A. D. Bersten, G. A. Skowronski, and T. E. Oh, “New generation venti-
lators,” Anaesth. Intensive Care, vol. 14, no. 3, pp. 293–305, Aug. 1986,
doi: 10.1177/0310057X8601400309.
[33] M. C. Stock, J. B. Downs, and D. A. Frolicher, “Airway pressure re-
lease ventilation,” Crit. Care Med., vol. 15, no. 5, pp. 462–466, May
1987.
[34] J.-M. Arnal et al., “Automatic selection of breathing pattern using adaptive
support ventilation,” Intensive Care Med., vol. 34, no. 1, pp. 75–81,
Jan. 2008, doi: 10.1007/s00134-007-0847-0.
[35] C. F. Sulzer, R. Chioléro, P.-G. Chassot, X. M. Mueller, and J.-P. Rev-
elly, “Adaptive support ventilation for fast tracheal extubation after car-
diac surgery: A randomized controlled study,” Anesthesiology, vol. 95,
no. 6, pp. 1339–1345, Dec. 2001, doi: 10.1097/00000542-200112000-
00010.
[36] J. X. Brunner and G. A. Iotti, “Adaptive support ventilation (ASV),”
Minerva Anestesiol, vol. 68, no. 5, pp. 365–368, May 2002.
[37] T. Cassina, R. Chioléro, R. Mauri, and J.-P. Revelly, “Clinical experi-
ence with adaptive support ventilation for fast-track cardiac surgery,” J.
Cardiothoracic Vasc. Anesth., vol. 17, no. 5, pp. 571–575, Oct. 2003,
doi: 10.1016/S1053-0770(03)00199-X.
[38] L. Bouadma et al., “Computer-driven management of prolonged mechan-
ical ventilation and weaning: A pilot study,” Intensive Care Med., vol. 31,
no. 10, pp. 1446–1450, Oct. 2005, doi: 10.1007/s00134-005-2766-2.
[39] M. Dojat, A. Harf, D. Touchard, F. Lemaire, and L. Brochard, “Clinical
evaluation of a computer-controlled pressure support mode,” Amer. J.
Respir. Crit. Care Med., vol. 161, no. 4, pp. 1161–1166, Apr. 2000,
doi: 10.1164/ajrccm.161.4.9904064.
[40] M. Younes, “Proportional assist ventilation, a new approach to ventilatory
support theory,” Amer. Rev. Respir. Dis., vol. 145, no. 1, pp. 114–120,
Jan. 1992, doi: 10.1164/ajrccm/145.1.114.
[41] C. Sinderby et al., “Neural control of mechanical ventilation in respi-
ratory failure,” Nat. Med., vol. 5, no. 12, pp. 1433–1436, Dec. 1999,
doi: 10.1038/71012.
[42] C. Sinderby and J. Beck, “Proportional assist ventilation and neurally
adjusted ventilatory assist–better approaches to patient ventilator syn-
chrony?,” Clin. Chest Med., vol. 29, no. 2, pp. 329–342, Jun. 2008,
doi: 10.1016/j.ccm.2008.01.007.
[43] T. Hufker and F. Alpert, “Patents: A managerial perspective,”
J. Prod. Brand Manag., vol. 3, no. 4, pp. 44–54, Jan. 1994,
doi: 10.1108/10610429410073138.
[44] M. Gittelman, “A note on the value of patents as indicators of innova-
tion: Implications for management research,” Acad. Manag. Perspectives,
vol. 22, no. 3, pp. 21–27, Aug. 2008, doi: 10.5465/amp.2008.34587992.
[45] A. Jain, S. Hallihosur, and L. Rangan, “Dynamics of nanotechnology
patenting: An Indian scenario,” Technol. Soc., vol. 33, no. 1, pp. 137–144,
Feb. 2011, doi: 10.1016/j.techsoc.2011.03.008.
[46] H.-N. Su, “How do patent-based measures inform patent collat-
eral? A holistic analysis on all USPTO patents between 1986
and 2016,” IEEE Trans. Eng. Manag., 2020, to be published,
doi: 10.1109/TEM.2020.3038855.
[47] I. M. P. Linares, A. F. De Paulo, and G. S. Porto, “Patent-based net-
work analysis to understand technological innovation pathways and
trends,” Technol. Soc., vol. 59, no. 101134, pp. 10–1016, Nov. 2019,
doi: 10.1016/j.techsoc.2019.04.010.
[48] S. Fernández-López, M. J. Rodríguez-Gulías, A. Dios-Vicente, and D.
Rodeiro-Pazos, “Individual and joint effect of patenting and exporting
on the university spin-offs’ survival,” Technol. Soc., vol. 62, Aug. 2020,
Art. no. 101326, doi: 10.1016/j.techsoc.2020.101326.
[49] D. E. Andersson, P. Galaso, and P. Sáiz, “Patent collaboration
networks in Sweden and Spain during the second industrial rev-
olution,” Ind. Innov., vol. 26, no. 9, pp. 1075–1102, Oct. 2019,
doi: 10.1080/13662716.2019.1577720.
Authorized licensed use limited to: ULAKBIM UASL - GAZIANTEP UNIVERSITESI. Downloaded on May 12,2022 at 13:57:08 UTC from IEEE Xplore. Restrictions apply.

This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination.
14 IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT
[50] S. Sharma and V. Thomas, “Inter-country R&D efficiency analysis: An
application of data envelopment analysis,” Scientometrics, vol. 76, no. 3,
pp. 483–501, Jul. 2008, doi: 10.1007/s11192-007-1896-4.
[51] A. Gambardella, “The economic value of patented inventions: Thoughts
and some open questions,” Int. J. Ind. Org., vol. 31, no. 5, pp. 626–633,
Sep. 2013, doi: 10.1016/j.ijindorg.2013.02.007.
[52] D. Archibugi, “Patenting as an indicator of technological innovation:
Areview,”Sci. Public Policy, vol. 19, no. 6, pp. 357–368, Dec. 1992,
doi: 10.1093/spp/19.6.357.
[53] M. Fritsch and M. Wyrwich, “Is innovation (increasingly) concentrated
in large cities? An international comparison,” Res. Policy, vol. 50, no. 6,
Jul. 2021, Art. no. 104237, doi: 10.1016/j.respol.2021.104237.
[54] X. Yuan and X. Li, “Mapping the technology diffusion of battery
electric vehicle based on patent analysis: A perspective of global in-
novation systems,” Energy, vol. 222, May 2021, Art. no. 119897,
doi: 10.1016/j.energy.2021.119897.
[55] X. Yuan and Y. Cai, “Forecasting the development trend of low
emission vehicle technologies: Based on patent data,” Technol.
Forecasting Soc. Change, vol. 166, May 2021, Art. no. 120651,
doi: 10.1016/j.techfore.2021.120651.
[56] A. Durmusoglu and Z. D. Unutmaz Durmusoglu, “Traffic control
system technologies for road vehicles: A patent analysis,” IEEE In-
tell. Transp. Syst. Mag., vol. 13, no. 1, pp. 31–41, Dec. 2021,
doi: 10.1109/MITS.2020.3037319.
[57] L. Ardito, D. D’Adda, and A. Messeni Petruzzelli, “Mapping innovation
dynamics in the internet of things domain: Evidence from patent analysis,”
Technol. Forecasting Soc. Change, vol. 136, pp. 317–330, Nov. 2018,
doi: 10.1016/j.techfore.2017.04.022.
[58] P. G. V. Sampaio, M. O. A. González, R. M. de Vasconcelos, M. A. T. dos
Santos, J. C. de Toledo, and J. P. P. Pereira, “Photovoltaic technologies:
Mapping from patent analysis,” Renewable Sustain. Energy Rev., vol. 93,
pp. 215–224, Oct. 2018, doi: 10.1016/j.rser.2018.05.033.
[59] V. Albino, L. Ardito, R. M. Dangelico, and A. Messeni Petruzzelli, “Un-
derstanding the development trends of low-carbon energy technologies:
A patent analysis,” Appl. Energy, vol. 135, pp. 836–854, Dec. 2014,
doi: 10.1016/j.apenergy.2014.08.012.
[60] T. Daim et al., “Patent analysis of wind energy technology using the
patent alert system,” World Pat. Inf., vol. 34, no. 1, pp. 37–47, Mar. 2012,
doi: 10.1016/j.wpi.2011.11.001.
[61] C. V. Trappey, H.-Y. Wu, F. Taghaboni-Dutta, and A. J. C. Trappey,
“Using patent data for technology forecasting: China RFID patent
analysis,” Adv. Eng. Inform., vol. 25, no. 1, pp. 53–64, Jan. 2011,
doi: 10.1016/j.aei.2010.05.007.
[62] E. F. Levitas, M. A. McFadyen, and D. Loree, “Survival and the intro-
duction of new technology: A patent analysis in the integrated circuit
industry,” J. Eng. Technol. Manag., vol. 23, no. 3, pp. 182–201, Sep. 2006,
doi: 10.1016/j.jengtecman.2006.06.008.
[63] H. Ernst, “The use of patent data for technological forecasting: The diffu-
sion of CNC-technology in the machine tool industry,” Small Bus. Econ.,
vol. 9, no. 4, pp. 361–381, Aug. 1997, doi: 10.1023/A:1007921808138.
[64] G. Zanella, C. Z. Liu, and K.-K. R. Choo, “Understanding the
trends in blockchain domain through an unsupervised systematic
patent analysis,” IEEE Trans. Eng. Manag., 2021, to be published,
doi: 10.1109/TEM.2021.3074310.
[65] H. Zhang, T. Daim, and Y. (Peggy) Zhang, “Integrating patent anal-
ysis into technology roadmapping: A latent Dirichlet allocation based
technology assessment and roadmapping in the field of blockchain,”
Technol. Forecasting Soc. Change, vol. 167, Jun. 2021, Art. no. 120729,
doi: 10.1016/j.techfore.2021.120729.
[66] S.-C. Ma, J.-H. Xu, and Y. Fan, “Characteristics and key trends of
global electric vehicle technology development: A multi-method patent
analysis,” J. Cleaner Prod., vol. 338, Mar. 2022, Art. no. 130502,
doi: 10.1016/j.jclepro.2022.130502.
[67] G. M. do C. Cavalheiro, L. A. Joia, and A. F. Van Veenstra, “Examining the
trajectory of a standard for patent classification: An institutional account of
a technical cooperation between EPO and USPTO,” Technol. Soc., vol. 46,
pp. 10–17, Aug. 2016, doi: 10.1016/j.techsoc.2016.04.004.
[68] D. Rosenberg and C. Glen, “Disposable filter for medical use with filter
element held between two plastic sections,” Belgium Patent BE788211-A,
Jan. 1973.
[69] USPTO, “USPTO year in review: New search tool, shorter examina-
tion times, and unexpected higher filing volume among highlights of
2020 for patents and trademarks,” Accessed: Apr. 2021. [Online]. Avail-
able: https://www.uspto.gov/about-us/news-updates/uspto- year-review-
new-search-tool-shorter-examination- times-and- unexpected
[70] Y. Park, B. Yoon, and S. Lee, “The idiosyncrasy and dynamism
of technological innovation across industries: Patent citation anal-
ysis,” Technol. Soc., vol. 27, no. 4, pp. 471–485, Nov. 2005,
doi: 10.1016/j.techsoc.2005.08.003.
[71] M. K. Diab, P. Iyengar, A. Sampath, A. Al-Ali, and M. Diab, “Method
for measuring patient’s rising oxygen hypersaturation index levels during
intubation treatment using pulse oximeter device, involves displaying
indication of rising oxygen levels by displaying graph of oxygen hyper-
saturation index,” U.S. Patent US2013274571-A1, Jan. 2013.
[72] A.Al-Ali et al., “Medical monitoring hub for monitoring e.g. physiological
parameter of single patient, has display sized approximately to height of
patient monitor, and communication ports for accepting data from elec-
tronic devices associated with patient,” U.S. Patent US2013262730-A1,
Jan. 2013.
[73] S. Petralia, “Mapping general purpose technologies with patent
data,” Res. Policy, vol. 49, no. 7, Sep. 2020, Art. no. 104013,
doi: 10.1016/j.respol.2020.104013.
[74] L. M. Lubango and A. Pouris, “Is patenting of technical inventions in
university sectors impeding the flow of scientific knowledge to the public?
A case study of South Africa,” Technol. Soc., vol. 32, no. 3, pp. 241–248,
Aug. 2010, doi: 10.1016/j.techsoc.2010.07.003.
[75] Y. Yamada, “Intrathoracic pressure sensor used in diagnosis of respi-
ratory disease, has tube that defines gas passage which is configured
to communicate with interior of cuff, and transducer to output signal
corresponding to pressure in gas passage,”U.S. Patent US2020397325-A1,
Jan. 2021.
[76] P. Szmuk, T. Ezri, S. Evron, Y. Roth, and J. Katz, “A brief history
of tracheostomy and tracheal intubation, from the bronze age to the
space age,” Intensive Care Med., vol. 34, no. 2, pp. 222–228, Feb. 2008,
doi: 10.1007/s00134-007-0931-5.
[77] A. K. Wells et al., “Patient interface system for providing pressurized
breathable gas to patient airways, has strap that is adjustable to fit range of
head sizes by stretching portion of strap over distal end of corresponding
rigidiser arms,” U.S. Patent US2018140795-A1, Mar. 2021.
[78] M. Liao et al., “A technical review of face mask wearing in prevent-
ing respiratory COVID-19 transmission,” Curr. Opin. Colloid Interface
Sci., vol. 52, Apr. 2021, Art. no. 101417, doi: 10.1016/j.cocis.2021.
101417.
[79] V. Palmieri, F. De Maio, M. De Spirito, and M. Papi, “Face masks and
nanotechnology: Keep the blue side up,” Nano Today, vol. 37, Apr. 2021,
Art. no. 101077, doi: 10.1016/j.nantod.2021.101077.
[80] V. Valdiglesias and B. Laffon, “The impact of nanotechnol-
ogy in the current universal COVID-19 crisis. Let’s not forget
nanosafety!,” Nanotoxicology, vol. 14, no. 8, pp. 1013–1016, Sep. 2020,
doi: 10.1080/17435390.2020.1780332.
[81] K. G. Johnson and D. C. Johnson, “Treatment of sleep-disordered
breathing with positive airway pressure devices: Technology up-
date,” Med. Devices Auckland NZ, vol. 8, pp. 425–437, Oct. 2015,
doi: 10.2147/MDER.S70062.
[82] D. Ma, Q. Yu, J. Li, and M. Ge, “Innovation diffusion enabler or barrier:
An investigation of international patenting based on temporal exponential
random graph models,” Technol. Soc., vol. 64, Feb. 2021, Art. no. 101456,
doi: 10.1016/j.techsoc.2020.101456.
[83] D. Ljungberg, E. Bourelos, and M. McKelvey, “Academic inventors,
technological profiles and patent value: An analysis of academic patents
owned by Swedish-based firms,” Ind. Innov., vol. 20, no. 5, pp. 473–487,
Jul. 2013, doi: 10.1080/13662716.2013.824193.
[84] J.-J. Yue, G. Chen, Z.-W. Wang, and W.-D. Liu, “Factor analy-
sis of teacher professional development in Chinese military medical
universities,” J. Biol. Educ., vol. 51, no. 1, pp. 66–78, Jan. 2017,
doi: 10.1080/00219266.2016.1171793.
[85] A. Perianes-Rodriguez, L. Waltman, and N. J. van Eck, “Construct-
ing bibliometric networks: A comparison between full and fractional
counting,” J. Informetrics, vol. 10, no. 4, pp. 1178–1195, Nov. 2016,
doi: 10.1016/j.joi.2016.10.006.
[86] N. J. van Eck and L. Waltman, “Software survey: VOSviewer, a com-
puter program for bibliometric mapping,” Scientometrics, vol. 84, no. 2,
pp. 523–538, Aug. 2010, doi: 10.1007/s11192-009-0146-3.
[87] I.Mierswa and R. Klinkenberg, “Rapidminer studio (9.1),” Data Sci. Mach.
Learn. Prediction Anal., 2018, [Online]. Available: https://rapidminer.
com/
[88] I. M. AR, S. Temel, M. Dabic, J. Howells, A. Mert, and R. Baris Yesi-
lay, “The role of supporting factors on patenting activities in emerging
entrepreneurial universities,” IEEE Trans. Eng. Manag., 2021, to be pub-
lished, doi: 10.1109/TEM.2021.3069147.
Authorized licensed use limited to: ULAKBIM UASL - GAZIANTEP UNIVERSITESI. Downloaded on May 12,2022 at 13:57:08 UTC from IEEE Xplore. Restrictions apply.

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DURMU¸SO ˘
GLU AND DURMU¸SO ˘
GLU: REMEMBERING MEDICAL VENTILATORS AND MASKS IN THE DAYS OF COVID-19 15
[89] R. L. Chatburn, “Understanding mechanical ventilators,” Expert Rev.
Respir. Med., vol. 4, no. 6, pp. 809–819, Dec. 2010, doi: 10.1586/ers.10.66.
Alptekin Durmu¸so˘glu received the M.S. and Ph.D.
degrees in industrial engineering from Gaziantep Uni-
versity, Gaziantep, Turkey, in 2008 and 2012, respec-
tively.
He is currently an Associate Professor with the In-
dustrial Engineering Department, Gaziantep Univer-
sity. His research interests include technology man-
agement patent analysis and data mining.
Dr. Durmu¸so ˘glu is a Member of editorial boards of
several academic journals such as IEEE TRANSAC-
TIONS ON ENGINEERING MANAGEMENT AND TECH-
NOLOGY IN SOCIETY.
Zeynep Didem Unutmaz Durmu¸so˘glu received the
B.S., M.S., and Ph.D. degrees in industrial engineer-
ing from Gaziantep University, Gaziantep, Turkey, in
2006, 2009 and 2012, respectively.
She is currently an Associate Professor with the In-
dustrial Engineering Department, Gaziantep Univer-
sity. Her research interests include decision-making,
simulation modeling, technology analysis, simulation
optimization, and heuristic optimization and negoti-
ation.
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