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R E S E A R C H A R T I C L E Open Access
Titration of oxygen therapy in critically ill
emergency department patients: a
feasibility study
Anna S. M. Dobbe
2
, Renate Stolmeijer
3
, Jan C. ter Maaten
4
and Jack J. M. Ligtenberg
1,4*
Abstract
Background: Liberal use of oxygen in an emergency situation is common. Today, most health care professionals
do not adjust the amount of oxygen given when a saturation of 100% or a PaO2 which exceeds the normal range
is reached- which may result in hyperoxia. There is increasing evidence for the toxic effects of hyperoxia. Therefore,
it seems justified to aim for normoxia when giving oxygen. This study evaluates whether it is feasible to aim for
normoxia when giving oxygen therapy to patients at the emergency department (ED).
Methods: A prospective cohort study was performed at the ED of the University Medical Center Groningen
(UMCG). A protocol was developed, aiming for normoxia. During a 14 week period all patients > 18 years arriving at
the ED between 8 a.m. and 23 p.m. requiring oxygen therapy registered for cardiology, internal medicine,
emergency medicine and pulmonology were included. Statistical analysis was performed using student
independent t-test, Mann–Whitney U-test, Fisher’s exact test or a Pearson’s chi-squared test.
Results: During the study period the study protocol was followed and normoxia was obtained after 1 h at the ED
in 86,4% of the patients. Patients with COPD were more at risk for not being titrated to normal oxygen levels.
Conclusions: We showed that it is feasible to titrate oxygen therapy to normoxia at the ED. The study results will
be used for further research assessing the potential beneficial effects of normoxia compared to hyper- or hypoxia in
ED patients and for the development of guidelines.
Keywords: Emergency medicine, Oxygen inhalation therapy, Hyperoxia, Normoxia, Hypoxia, Titration of oxygen therapy,
Emergency department, Critically ill patients, Pulmonary disease, chronic obstructive, Prospective studies, Oxygen
Background
Oxygen is one of the most widely used drugs and is applied
in a wide range of medical specialities [1]. Supplemental
oxygen is vital in many clinical situations; impaired oxygen
delivery in critically ill patients is associated with increased
mortality. Therefore, reassuring oxygen delivery has
become a cornerstone in resuscitation and liberal use of
supplemental oxygen in an emergency situation is com-
mon. [2] In acute medical care, toxicity of oxygen therapy
is not immediately obvious. Over the past years, several
studies have shown the potential harmful effects of
hyperoxia, resulting in increased mortality [3–5]. Guide-
lines for emergency oxygen use have been developed,
recommending to aim for normal or near-normal oxygen
saturation for all acutely ill patients, such as the British
Thoracic Society (BTS) guideline [1]. Despite these studies
and guidelines, in real-life the amount of oxygen given is
often not decreased if the SaO
2
measured by pulse oxim-
eter is 100%, or if PaO
2
levels are high [5,6]. Considering
that the Emergency Department (ED) is the department
where many critically ill patients arrive, it is important to
cause no additional harm due to hyperoxia and to treat pa-
tients with the right dose of oxygen. The only study outside
the ICU (in prehospital setting) aiming for normoxia had to
be stopped because it appeared to be not feasible [7]. That
is why we investigated if it is feasible to titrate oxygen ther-
apy immediately after arrival at the ED. This prospective
* Correspondence: j.j.m.ligtenberg@umcg.nl
1
Emergency Department, Internal Medicine, University Medical Center
Groningen (UMCG), Hanzeplein 1, 9700, RB, Groningen, The Netherlands
4
Internist acute medicine, Emergency physician, Emergency Department,
University Medical Center Groningen, Groningen, The Netherlands
Full list of author information is available at the end of the article
© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Dobbe et al. BMC Emergency Medicine (2018) 18:17
https://doi.org/10.1186/s12873-018-0169-2
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study evaluates the feasibility of a protocol aiming for nor-
moxia in adult, critically ill patients at the ED.
Methods
Study population & research design
This prospective cohort study was performed at the ED of
the University Medical Center Groningen, a tertiary care
teaching hospital with 33.000 ED visits/year. During a
14 week period from February until May 2016, consecutive
patients > 18 years arriving at the ED, registered for
cardiology, internal medicine, pulmonary medicine and
emergency medicine, requiring oxygen therapy (according
to the judgement of the ambulance nurse, ED nurse or ED
physician) were included from 8.00 h a.m. until 23.00 h p.m.
The institutional review board of our hospital waived in-
formed consent. Exclusion criteria were: intubated patients
or patients requiring immediate intubation, patients with
unreliable pulse oximetry recording [8]andpatientsusing
bleomycin, because high concentrations of inspired oxygen
(FiO2) increases lung toxicity in these patients.
Also, patients with a known specific target saturation
due to other causes at presentation were excluded, such
as patients with congenital heart disease in whom satu-
rations < 85% were normal.
A protocol was developed aiming for normoxia, defined
as PaO
2
9,5–13,5 kPa (70–100 mmHg) or a corresponding
oxygen saturation of 94–98%. Hyperoxia was defined - ac-
cording to normal values used in our hospital - as PaO
2
>
13.5 kPa or SaO
2
> 98%, and hypoxia as PaO
2
< 9.5 kPa or
SaO
2
< 94%. In consultation with our pulmonologists
saturations between 90 and 92% were used to aim for nor-
moxia in patients with known severe COPD (GOLD III or
IV), in order to avoid hypercapnia, while further using the
same study protocol (Fig. 1). The study protocol is shown
in Fig. 1. For example, if a patient was admitted with a
non-rebreathing mask (NRM) (15 L O
2
/minute, FiO
2
=±
0.8) and peripheral oxygen saturation (SaO
2
) immediately
after arrival was ≥98%, the nurse would apply aVentimask
(VM) 40% with 10 L O
2
/minute (FiO
2
= ± 0.4). If after
5 min, in arterial blood gas analysis PaO
2
was still >
13.5 kPa or (peripheral) SaO
2
was ≥98%, oxygen was
titrated towards an oxygen saturation (SaO
2
)between94
and 98%, preferably administered by a nasal oxygen
cannula. If the patient was admitted with a nasal oxygen
cannula and SaO
2
was ≥94% immediately after arrival,
oxygen was titrated towards a SaO
2
between 94 and 98%.
If SaO
2
was < 94%, a VM 40% with 10 L O
2
/minute (FiO
2
= ± 0.4) would be applied and the same procedure as de-
scribed above would be followed. Patients with known
Chronic Obstructive Pulmonary Disease (COPD) GOLD
III of IV dropped out of the study if they became hyper-
capnic (PaCO
2
> 6.0 kPa or > 45 mmHg) in the first hour
after arrival. This threshold was chosen in consultation
with our pulmonologists to prevent respiratory acidosis
caused by relative hyperoxia lowering the respiratory rate.
Oxygen saturation values were measured by non-invasive
pulse oximetry [Masimo Corporation, CA, USA] and if
the treating physician requested an arterial blood gas,
PaO
2
as well as oxygen saturation were used [ABL800 flex,
Radiometer, Copenhagen, DK].
NRM 15L O2/min
VM 40% 10L O2/min
Nasal cannulas 1-5L O2/min
(titrating)
Stop oxygen therapy
sat <94% and/or PaO2 <9,5 kPa
sat <94% and/or PaO2 <9,5 kPa
sat <94% and/or PaO2 <9,5 kPa
sat >98% and/or PaO2 >13,5 kPa
sat >98% and/or PaO2 >13,5 kPa
sat >98% and/or PaO2 >13,5 kPa
Fig. 1 Study protocol aiming for normoxia. In severe COPD patients the same protocol was used, but saturations were different (92% instead of
98 and 90% instead of 94%)
Dobbe et al. BMC Emergency Medicine (2018) 18:17 Page 2 of 7
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Data collection
All ED nurses and physicians were educated about the
purpose of the study and the protocol. Data was col-
lected using a case report form. The values of SpO
2
and
PaO
2
(if available) were measured at ED presentation
(T
0
), after 5–10 min (T
1
), after 1 h (T
2
), and after 3 h
(T
3
) together with the dose of oxygen and the method
used to administer oxygen. Vital signs were measured at
the same time points. When the patient was admitted to
a nursing ward or ICU, the same parameters were also
collected 24 h after arrival at the ED (T
4
). No advice was
given about aiming for normoxia at the nursing ward or
ICU. The Modified Early Warning Score (MEWS) was
calculated on arrival and after 3 h.
Outcome parameters
The primary outcome parameter was whether the protocol
was followed and whether normoxia was obtained. This was
based on the measurements made by the pulse oxymeter, to
enchance clinical applicability. The protocol was followed
when during the time the patient was admitted at the ED
(between arrival at the ED and 3 h after arrival at the ED)
normoxia was achieved. If only at the final measurement
(3 h after arrival at the ED) the SaO
2
was too high or too
low,butthefirstthreemeasurementswereinthenormal
range, it was also concluded that the protocol was followed.
Statistical analysis
Baseline characteristics and results are presented as mean
and standard deviation (SD) when normal distribution
was assumed by means of a Kolmogorov–Smirnov test.
Skewed variables are presented as median and interquar-
tile range. Categorical variables are presented as frequency
and percentage. For independent continuous variables
with a normal distribution, student independent t-test was
used. Other continuous variables were compared using
the Mann–Whitney U-test. Categorical variables were
compared using Fisher’s exact test or a Pearson’s
chi-squared test. A significance level of p< 0.05 was used.
Results
Study population
In the study period 201 patients were screened for inclusion;
162 patients were included. The flowchart of patient inclu-
sion and exclusion is shown in Fig. 2. In 140 patients the
protocol was followed and normoxia successfully achieved
(86,4%) within 1 h after arrival at the ED. In 7 normoxic pa-
tients multiple blood gases were additionally sampled during
ED admission, of these 6 were normoxic measuring both
SaO2 and PaO2. In 22 patients the protocol was not
followed, of which there were 5 known COPD patients who
dropped out due the development of hypercapnia in the first
hour at the ED. There were different reasons why the
Fig. 2 Flowchart of patient inclusion and exclusion
Dobbe et al. BMC Emergency Medicine (2018) 18:17 Page 3 of 7
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protocol was not followed in the other 17 patients. The most
important observation was thatmostofthesepatientssuf-
fered from COPD. It appeared that in some COPD patients
the threating physician seemed reluctant to follow the proto-
col, resulting in not reducing oxygen therapy in patients with
severe COPD (n= 11) or too low oxygen saturations in pa-
tients with mild COPD (n= 3). For other patients we could
not find a specific reason for not following the protocol.
The baseline characteristics of the 162 study patients
are shown in Table 1. Significantly more patients had
severe COPD (GOLD III or IV) in the group in which the
protocol was not followed (P< 0.001). This group also re-
ceived significantly more often oxygen before ED arrival.
Diagnosis at discharge
An overview of the diagnosis at discharge from the ED for
the total study population is shown in Table 2.Somepatients
were discharged with more than one diagnosis. In the group
in which the protocol was not followed more patients were
discharged with a COPD exacerbation (P=0.03) or with
other pulmonary conditions (P= 0.04) compared to the
group in which the protocol was followed. Other diagnoses
atdischargewerenotsignificantlydifferentbetweenthe
patient groups.
Prehospital oxygen
The median PaO
2
of patients arriving with prehospital
oxygen was 9.5 (8.1–11.8) kPa. There is an effect of the
method of oxygen delivery on causing hyperoxia at T
0.
In
patients arriving with a NRM, 50% was hyperoxic at T
0
compared to 18% of the patients with oxygen adminis-
tered via a nasal cannula (P<0.001).
Oxygen saturation at the ED and after 24 h
Figure 3shows the course of the oxygen saturation at the
ED and 24 h after arrival at the ED for all included pa-
tients. When patients stopped receiving oxygen therapy
and their saturation was > 94% or > 90% in severe COPD
patients, they were considered to be normoxic. In some
patients their oxygen saturation fluctuated during ED ad-
mission, resulting in shifting between hypoxia, normoxia
and hyperoxia at the different time points. From the figure
it becomes clear that most patients were in the normoxia
range after 1 h at the ED. In the first 10 min (T
0
-T
1
)it
was more difficult to attain normoxia, maybe due to the
amount of oxygen treatment in the ambulance or due to
the number of actions that have to be performed when a
patient arrives at the ED. Some patients were normoxic at
first but at T
3
they became hypoxic or hyperoxic, probably
because they were checked less frequently. When patients
were admitted to the ICU or nursing ward, most patients
stayed in the normoxia range.
Oxygen saturation of severe COPD patients
In patients with severe COPD the protocol was more
often not followed. For this reason, we made a separate
graph for this subgroup, shown in Fig. 4.
Table 1 Patient characteristics at ED arrival
Characteristics Patients in which the protocol
was followed (n= 140)
Patients in which the protocol
was not followed (n= 22)
Total (n = 162) P-value
Male sex [n (%)] 82 (59) 11 (50) 93 (57) 0.45
Age (years) 68 ± 13 68 ± 12 68 ± 13 0.78
Prehospital oxygen Yes [n (%)] 94 (67) 18 (82) 112 (69) 0.16
Within target at arrival* Yes [n (%)] 56 (60) 1 (6) 57 (51) 0.00
PaO
2
(kPa) 9 (8–12) 8 (8–11) 9 (8–12) 0.53
Systolic blood pressure (mmHg) 125 (107–141) 137 (119–165) 126 (109–145) 0.04
Diastolic blood pressure (mmHg) 76 (65–89) 76 (65–103) 76 (65–89) 0.49
Heart rate (beats/min) 88 (75–108) 95 (88–120) 91 (78–110) 0.06
Respiratory rate (breaths/min) 21 (18–25) 22 (20–27) 21 (18–25) 0.17
GCS [1–15]** 15 (15–15) 15 (15–15) 15 (15–15) 0.24
MEWS 4 (3–5) 4 (3–6) 4 (3–5) 0.27
Smoking [n (%)] 30 (21) 8 (36) 38 (24) 0.12
Cardiac condition [n (%)] 57 (41) 10 (46) 67 (41) 0.68
COPD GOLD I/II [n (%)] 27 (19) 3 (14) 30 (19) 0.53
COPD GOLD III/IV [n (%)] 14 (10) 11(50) 25 (15) 0.00
Other pulmonary condition [n (%)] 19 (14) 5 (23) 24 (15) 0.26
Neurological condition [n (%)] 1 (1) 1 (5) 2 (1) 0.13
*Within target saturation on arrival at the ED with prehospital oxygen
**GCS, Glasgow Coma Scale
Dobbe et al. BMC Emergency Medicine (2018) 18:17 Page 4 of 7
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Figure 4shows that almost half of the severe COPD
patients were hyperoxic during the first 3 h after arrival
at the ED. Almost none were hypoxic and at T
2
most
patients were in the normal range. After being admitted
to the nursing ward or ICU, more than half of the severe
COPD patients (69%) stayed hyperoxic.
Discussion
To our knowledge, this study is the first to investigate the
feasibility of aiming for normoxia in critically ill patients at
the ED. A study performed in the prehospital setting was
stopped early because it appeared that it was not feasible to
titrate prehospital oxygen therapy to normoxia [7]. We
found that it is feasible to titrate oxygen therapy aiming for
normoxia in critically ill patients at the ED; normoxia was
obtained in 86,4% of the patients within 1 h after arrival at
the ED. Furthermore, we found that patients for whom the
protocol was not followed were mostly severe COPD
(GOLD III/IV) patients (P< 0.001), patients with an COPD
exacerbation (P= 0.03) or other pulmonary conditions (P=
0.04). The clinical impression the COPD patient made in
the ED appeared to influence which saturation was aimed
for by the responsible physician, making it difficult to attain
the specific target saturations prescribed by our protocol.
Future research will need to validate the ideal target satur-
ation for patients with and without risk of hypercapnic re-
spiratory failure. Despite this, in our opinion, COPD
patients could also be treated with titrated oxygen therapy.
Of the patients who received prehospital oxygen, patients ar-
rivingwithaNRMweresignificantlymoreoftenhyperoxic
(P< 0.001) on arrival (T
0
) compared to patients arriving with
a nasal cannula.
Liberal oxygen use is still common. There is still uncer-
tainty about the ideal target saturation, mostly due to lack of
evidence from clinical trials [1]. The majority of studies
evaluating aiming for normoxia were performed at the ICU.
Most ICU clinicians acknowledge the potential adverse ef-
fects of hyperoxia and declare low tolerance for high oxygen
levels, but in clinical practice a substantial part of their pa-
tients were exposed to high arterial oxygen levels [9]. An-
other ICU study found that hyperoxia was frequently
observed but not resulted in adjustment of the ventilator set-
tings [6]. This study’s main strength is that it is a prospective
cohort study with inclusion of ED patients with different
Table 2 Diagnosis at discharge from the ED
Diagnosis at discharge from ED Protocol was followed [n (%)] Protocol was not followed [n (%)] Total [n (%)] P-value
Pneumonia 30 (21) 4 (18) 34 (21) 1.00
Infection 28 (20) 6 (27) 34 (21) 0.41
Heart failure 22 (16) 4 (18) 26 (16) 0.76
Other 23 (16) 1 (5) 24 (15) 0.20
Sepsis 22 (16) 2 (9) 24 (15) 0.54
COPD exacerbation 14 (10) 8 (36) 22 (14) 0.03
Cardiac condition other 17 (12) 0 (0) 17 (11) 0.13
Pulmonary condition other 10 (7) 5 (23) 15 (9) 0.04
Malignancy 11 (8) 1 (5) 12 (7) 1.00
Neurological 6 (4) 1 (5) 7 (4) 1.00
Fig. 3 Course of oxygen saturation for all study patients (n= 162). On arrival at the ED (T= 0), after 10 min ( T= 1), after 1 h (T= 2), after 3 h
(T= 3) and after 24 h ( T=4)
Dobbe et al. BMC Emergency Medicine (2018) 18:17 Page 5 of 7
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backgrounds. A limitation was that permission from the
neurology department could not be obtained. There are
several studies evaluating hyperoxia in neurology patients,
however we could not include this subgroup in our study
[10–15]. Education and feedback is needed to create more
awareness of the importance of aiming for normoxia and ap-
plying this in clinical practice. Following the validation of the
ideal target saturation, new guidelines for emergency oxygen
therapy should be developed. To further assess primary and
secondary outcome parameters, multicenter trials are re-
quired. Aiming for normoxia immediately after arrival in the
hospital could prevent the potential harmful effects of hyper-
oxia, this could lead to health gains on short- and long term
and reduced costs during hospital admission [16].
Conclusion
In this prospective cohort study we showed that it is feas-
ible to attain normoxia in critically ill patients at the ED,
demonstrating that it is possible to start titration of oxygen
therapy immediately after arrival at the hospital. These
study results can be a starting point for further research
assessing the potential beneficial effects of normoxia com-
pared to hyper- or hypoxia in the emergency department
and the subsequent development of guidelines.
Abbreviations
COPD: Chronic obstructive pulmonary disease; ED: Emergency department;
ICU: Intensive care unit; NRM: Non-rebreather mask; UMCG: University
Medical Center Groningen; VM: VentiMask
Availability of data and materials
The datasets used and/or analysed during the current study are available
from the corresponding author on reasonable request.
Authors’contributions
JL and RS designed and critically revised the study. AD collected the data,
interpreted and analyzed the data. AD was a major contributor in writing the
manuscript. JM contributed to the study design and critically revised the study
design and manuscript for important intellectual content. JM guided and
supervised the study. All authors read and approved the final manuscript.
Ethics approval and consent to participate
The study was reported to the medical ethics review committee (METc-UMCG)
at the University Medical Center Groningen. Since regular patient care would
be performed, the METc approved the study and waived provision of informed
consent to the patient. Reference number: 201500904.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Publisher’sNote
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
Author details
1
Emergency Department, Internal Medicine, University Medical Center
Groningen (UMCG), Hanzeplein 1, 9700, RB, Groningen, The Netherlands.
2
BSc of Medicine, Faculty of Medicine, University of Groningen, Groningen,
The Netherlands.
3
Emergency physician, Emergency Department, University
Medical Center Groningen, Groningen, The Netherlands.
4
Internist acute
medicine, Emergency physician, Emergency Department, University Medical
Center Groningen, Groningen, The Netherlands.
Received: 28 November 2017 Accepted: 11 June 2018
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