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The utility of iPhone oximetry apps: A comparison with standard pulse oximetry measurement in the emergency department
Abstract
Objectives:
To determine if a correlation exists between 3 iphone pulse ox applications' measurements and the standard pulse oximetry (SpO2) and whether these applications can accurately determine hypoxia.
Methods:
Three applications reportedly measuring SpO2 were downloaded onto an iPhone 5s. Two of these applications used the onboard light and camera lens "Pulse Oximeter" (Pox) and "Heart Rate and Pulse Oximeter" (Ox) and one used an external device that plugged into the iphone (iOx). Patients in the ED were enrolled with chief complaints of cardiac/pulmonary origin or a SpO2 ≤ 94%. All measurements were compared to controls. Concordance correlation coefficients, sensitivity, and specificity were calculated.
Results:
A total of 191 patients were enrolled. The concordance correlation of iOx with control was 0.55 (CI 0.46, 0.63), POx was 0.01 (CI -0.09, 0.11), and Ox was 0.07 (CI -0.02, 0.15). 68/191 patients (35%) were found to have hypoxemia. Sensitivities for detecting hypoxia were 69%, 0%, and 7% for iOx, POx, and Ox, respectively. Specificities were 89%, 100%, and 89%. Even iOx (the most accurate) 21 (11%) were incorrectly classified nonhypoxic, and 22 (12%) were incorrectly classified hypoxic.
Conclusions:
While iOx has modest concordance with control, Ox and POx showed almost none. The iOx device was best in correctly identifying hypoxia patients, but almost 1/4 of patients were incorrectly classified. The three apps provided inaccurate SpO2 measurements and had limited to no ability to accurately detect hypoxia. These apps should not be relied upon to provide accurate SpO2 measurements in emergent, even austere conditions.
... In addition, prior smartphone studies were conducted using different protocols within different patient populations, utilizing devices containing widely variable hardware. Jordan et al. compared pulse oximetry apps downloaded onto iPhones to reference monitors within an emergency room setting and found that the apps provided inaccurate measurements, with a sensitivity for detection of SpO 2 < 94% on the reference monitor ranging from 0 to 69% [39]. Two of these apps utilized the onboard light and camera lens (Pox and Ox), and one used an external device that plugged into the iPhone. ...
Background: The US Food and Drug Administration (FDA) and International Organization for Standardization (ISO) clearance standards for the clinical use of smart device pulse oximetry require in-laboratory human hypoxemia testing in healthy human individuals using arterial blood gas analysis. Methods: We evaluated the SpO2 measurements of the Samsung smartphone (Galaxy S9/10) and smartwatch (Galaxy 4) at stable arterial oxygen saturations (SaO2) between 70 and 100% in 24 healthy participants. Testing followed FDA/ISO-stipulated procedures for pulse oximetry performance validation, which include questionnaire estimation of skin tone based on Fitzpatrick estimation of skin types I–VI. During testing, inspired oxygen, nitrogen, and carbon dioxide partial pressures were monitored and adjusted via partial rebreathing circuits to achieve stable target arterial blood oxygen (SaO2) plateaus between 70% and 100%. Arterial blood samples were taken at each plateau, with device SpO2 readings taken at each sample extraction. An ABL-90FLEX blood gas analyzer determined arterial blood sample SaO2. Bias, calculated from device readings minus corresponding arterial blood measurements, was reported as root mean square deviation (RMSD). Results: Combined Participants demographics were: 62.5% female; median age 26 years (range 21–46); and race/ethnicity 16.7% African American, 33.3% Asian, 12.5% multi-ethnic, and 37.5% Caucasian. Fitzpatrick Skin Scale-identified skin tones were: white–fair (I&II), 20.8%; average–light brown (III–IV), 54% and brown–black (V–VI), 25%. There were no adverse events. The RMSD values of SpO2 measurements were: smartphone 2.6% (257 data pairs) and smartwatch 1.8% (247 data pairs). Conclusions: Device SpO2 demonstrated RMSD < 3.0% to SaO2, meeting FDA/ISO clearance standards at the time of study. However, additional testing in persons with darker skin tones is necessary. Smartphones and paired wearables, when cleared for clinical use following revision of FDA clearance standards, may expand access to remote pulse oximetry.
... It is possible to nd both mobile applications that connect themselves with a dedicated pulse oximeter, as well as applications that allow to perform pulse oximetry measurements using a phone camera. The latter solution, which does not require the presence of pulse oximeter, is still being tested, however, does not always provide correct results [3,4]. ...
Photoplethysmography is a non-invasive physical method used for measurement and monitoring of arterial blood flow in the subject's body with application of light. Pulse oximetry is the modification of photoplethysmography enriched with monitoring blood oxygen saturation. Acquisition of pulse oximetry data can be achieved using two types of pulse oximeters: transmission or reflectance. Both methods require the use of physical light sources and a receiver, set in specific positions. This results in different construction of devices and may lead to diverse ways of calculating the blood saturation values. One of these ways uses second-degree polynomial made from three constants and a variable calculated with ratio of red- to infrared-based variables. We used this method to develop the wireless pulse oximeter paired with the dedicated mobile application. The device acquired 400 samples per second and calculated oxygen saturation level and heart rate, as well as provided data for photoplethysmography curve. In this system data are transferred in real time to the application, which displays the saturation values and presents photoplethysmography curve for last several heartbeats. Calculation of the values was checked with a commercial pulse oximeter and the results were mostly similar, with the difference in SpO2 not greater than one percentage point and the difference in heart rate not greater than five beats per minute. The design of the pulse oximeter allows further miniaturization. Mobile application is intuitive for user and does not need any training.
... Several studies have evaluated their accuracy, but these examined only a tiny fraction of devices, and few studies have examined their accuracy in children. [4][5][6] We recently completed a study of fingertip oximeters marketed for adult or pediatric use, and an oximeter built into an Android smartphone. We found the adult fingertip and smartphone oximeters performed fairly well in normoxemic older children and youth. ...
Objectives
We evaluated what proportion of families have a consumer‐grade pulse oximeter, why they bought one, and how they choose to use it.
Working Hypothesis
We hypothesized that children followed in cardiorespiratory clinics would be more likely to have an oximeter than children attending a more general clinic.
Study Design and Subject Selection
We carried out a cross‐sectional study using a convenience sample of children attending a respirology, cardiology, or gastroenterology clinic at a children's hospital. Consenting guardians completed a survey.
Results
Two‐hundred families completed the survey. Fifty‐three (26.5%; 53/200) had an oximeter at home. The proportion of children attending a cardiorespiratory clinic who had an oximeter was higher than another clinic ( p = 0.08), but 15.5% of children attending the latter also had access to one. Of devices not funded by government insurance, over 80% of devices were “fingertip” clamp‐style oximeters, and 50% were purchased online. Most devices were used only when the child was ill (83.7%; 36/43). Only about 1/3 of families had received education about using an oximeter, and a similar proportion had compared their oximeter to a medical‐grade device. Only 2.4% (1/42) respondents did not feel that their device was “somewhat” or “very” accurate. The oxygen saturation that would prompt seeking emergency care was similar to most pediatric acute care guidelines.
Conclusions
Many children, particularly those with cardiorespiratory conditions, have access to consumer‐grade pulse oximeters. Asking about the presence of an oximeter should be part of the pediatric history, and families responding affirmatively should be offered education.
... Many devices are available for measuring SpO2 at clinics but very few available for home patients use, although, some studies indicated use of smartphone applications for measuring pulse oximetry by using camera and/or plug-in probe [92]. Also, many devices are available and use PPG technology in measuring SpO2 by wearable devices of pulse oximetry as well as fingertip oximetry but still below the acceptable limit of accuracy to be used for medical purposes [93]. Although, such technology can be used for monitoring individuals remotely especially during times of isolations and spread of infections to minimize number of infection and to help elder individuals who are recommended to stay at home as well as many other benefits [70]. ...
The COVID-19+ pandemic has brought into keen focus the necessity to utilize and enforce our digital infrastructure for remote patient monitoring based on IoT (Internet of Things) technology since quarantines and isolations are playing a vital role in containing its spread. As of date, many viral tests and vaccines are in use while few drugs are in experimental stages, but there is always need for possibilities for increasing reliability of disease detection and monitoring at both levels of individual and society, and such aim can be supported by wearable biomedical sensors devices. Previously, wearable devices have been used to monitor physiological parameters during daily human living activities. Still, the investment of such technologies toward predicting infection by COVID-19+ remains essential to alert potential patients and start sequence of health systems intervention. It was found that wearable devices increased patients’ compliance to healthcare advice. Thus, in this perspective review, we have proposed an IoT based system to monitor the quarantine / isolation subjects during COVID-19+ and similar pandemic and quarantine observation. This wearable prototype, associated with the bundled mobile app, act to reports and tracks/monitoring the quarantined individuals. IoT based quarantine/isolation monitoring system is contact-free that could benefit especially healthcare professionals to lower the risk of exposure to infective pathogens. Current manuscript describes clinically relevant physiological human parameters that can be measured by wearable biomedical sensors and monitored based on IoT technology and their role in health tracking, stability, and recovery of COVID-19++ve individuals and front-line health workers. This paper aimed at initiation of an approach among front-line healthcare workers as well as biomedical engineers for developing digital healthcare platforms of monitoring and managing such pandemic.
... While the software applications using the camera and flashlight showed almost no agreement with the control group, the software application of the external device had a moderate level of agreement, but this device also misclassified patients at a rate of 1/4. As a result, the authors concluded that such software applications should not be trusted [12]. ...
Objective:
With the increasing use of wearable technologies (smartphones and smartwatches), it has become possible to measure vital signs outside healthcare institutions without the need for an additional medical device. With the advancement in technologies, the accuracy of vital signs measured by smartphones and smartwatches has also increased. In this study, the accuracy of smart devices in the measurement of heart rate and saturation, which are two vital signs that are difficult to detect in conditions such as hypotension were investigated.
Materials and methods:
The study was prospectively conducted in a tertiary healthcare center. In hypotensive patients who presented to the emergency department (ED) and required an arterial blood gas evaluation, oxygen saturation and heart rate values measured by a smartphone, those measured with a vital signs monitor (VSM) at the time of admission to the ED and oxygen saturation values measured by a blood gas analyzer (BGA) were compared.
Results:
A total of 200 patients, 117 women and 83 men, were included in the study. It was determined that the correlation coefficients of the heart rate values measured by the vital signs monitor and smartphone were in a high statistical agreement. When the saturation values measured by the vital signs monitor, smartphone, and blood gas analyzer were compared, it was found that the intra-class correlation coefficients of the saturation values measured by the smartphone with reference to the blood gas analyzer and vital signs monitor were 0.957 and 0.949, respectively, indicating an excellent agreement.
Conclusion:
Smartphones have as high efficiency as reference devices in measuring heart rate and saturation in hypotensive patients. In this way, hypotensive patients who need medical help can also have the opportunity to measure their vital parameters with their smartphones, without the need for any other medical device, before applying to the hospital or emergency health system. This may contribute to the improvement of the quality of life of the patients and the early and accurate information of the health care providers about the patient's health parameters.
... The COVID-19 pandemic highlighted this need for an affordable remote oxygen desaturation detection tool that can be accurately and safely used for initial screening and monitoring, informing users whether or not they should seek expert medical attention. This potential is important to consider, as software applications are already being used in this manner even when those applications have not cleared the FDA regulatory requirements 40,41 . Our system is the first unmodified smartphone camera sensor to report accuracy at levels below 85% SpO 2 , and it achieved relatively high sensitivity (81%) and specificity (79%) when classifying subjects with SpO 2 below 90%. ...
Hypoxemia, a medical condition that occurs when the blood is not carrying enough oxygen to adequately supply the tissues, is a leading indicator for dangerous complications of respiratory diseases like asthma, COPD, and COVID-19. While purpose-built pulse oximeters can provide accurate blood-oxygen saturation (SpO 2 ) readings that allow for diagnosis of hypoxemia, enabling this capability in unmodified smartphone cameras via a software update could give more people access to important information about their health. Towards this goal, we performed the first clinical development validation on a smartphone camera-based SpO 2 sensing system using a varied fraction of inspired oxygen (FiO 2 ) protocol, creating a clinically relevant validation dataset for solely smartphone-based contact PPG methods on a wider range of SpO 2 values (70–100%) than prior studies (85–100%). We built a deep learning model using this data to demonstrate an overall MAE = 5.00% SpO 2 while identifying positive cases of low SpO 2 < 90% with 81% sensitivity and 79% specificity. We also provide the data in open-source format, so that others may build on this work.
... Glenn Allan Milikan devised the first oximeter in 1940 and introduced the term "oximeter" a year later [28]. In 1973, the Czesch physiologist Jan Peňáz introduced the volume clamp technique, where arterial pulse obtained from a finger is indirectly measured through vascular unloading [29]. ...
Blood pressure (BP) monitoring can be performed either invasively via arterial catheterization or non-invasively through a cuff sphygmomanometer. However, for conscious individuals, traditional cuff-based BP monitoring devices are often uncomfortable, intermittent, and impractical for frequent measurements. Continuous and non-invasive BP (NIBP) monitoring is currently gaining attention in the human health monitoring area due to its promising potentials in assessing the health status of an individual, enabled by machine learning (ML), for various purposes such as early prediction of disease and intervention treatment. This review presents the development of a non-invasive BP measuring tool called sphygmomanometer in brief, summarizes state-of-the-art NIBP sensors, and identifies extended works on continuous NIBP monitoring using commercial devices. Moreover, the NIBP predictive techniques including pulse arrival time, pulse transit time, pulse wave velocity, and ML are elaborated on the basis of bio-signals acquisition from these sensors. Additionally, the different BP values (systolic BP, diastolic BP, mean arterial pressure) of the various ML models adopted in several reported studies are compared in terms of the international validation standards developed by the Advancement of Medical Instrumentation (AAMI) and the British Hypertension Society (BHS) for clinically-approved BP monitors. Finally, several challenges and possible solutions for the implementation and realization of continuous NIBP technology are addressed.
... In the same manner, Lin et al. (25) developed a wearable and wireless finger base-type pulse oximeter, focusing only on the measurement of oxygen saturation. Smartphone app pulse oximeters were also developed with a wide range of accuracy, but the accessibility and reliability of these developments were limited (26). On the other hand, Shrading et al. (27) compared the SPO2 measurement accuracy of three consumer grade pulse oximeters by comparing them with bedside pulse oximeters and obtained clinically significant accuracy even though the test characteristics were not perfect and the pulse rate was not considered. ...
Background:
Measurement of blood oxygen saturation is a vital part of monitoring coronavirus 2019 (COVID-19) patients. Pulse oximetry is commonly used to measure blood oxygen saturation and pulse rate for appropriate clinical intervention. But the majority of direct-to-consumer grade pulse oximeters did not pass through in-vivo testing, which results in their accuracy being questionable. Besides this, the ongoing COVID-19 pandemic exposed the limitations of the device in resource limited areas since independent monitoring is needed for COVID-19 patients. The purpose of this study was to perform an in-vivo evaluation of a newly developed smartphone powered low-cost pulse oximeter.
Methods:
The new prototype of a smartphone powered pulse oximeter was evaluated against the standard pulse oximeter by taking measurements from fifteen healthy volunteers. The accuracy of measurement was evaluated by calculating the percentage error and standard deviation. A repeatability and reproducibility test were carried out using the ANOVA method.
Results:
The average accuracy for measuring spot oxygen saturation (SPO2) and pulse rate (PR) was 99.18% with a standard deviation of 0.57 and 98.78% with a standard deviation of 0.61, respectively, when compared with the standard pulse oximeter device. The repeatability and reproducibility of SPO2 measurements were 0.28 and 0.86, respectively, which is in the acceptable range.
Conclusion:
The new prototype of smartphone powered pulse oximeter demonstrated better performance compared to the existing low-cost fingertip pulse oximeters. The device could be used for independent monitoring of COVID-19 patients at health institutions and also for home care.
... Three iPhone apps that allegedly could give precise SpO 2 values were proven unreliable in a recent study. (38) This is also an important issue with portable, low-cost fingertip pulse oximeters, some of which demonstrate highly inaccurate readings. (39) Nevertheless, many studies have shown a good correlation between standard oximeters and smartphone-based oximeters. ...
... Three iPhone apps that allegedly could give precise SpO 2 values were proven unreliable in a recent study. (38) This is also an important issue with portable, low-cost fingertip pulse oximeters, some of which demonstrate highly inaccurate readings. (39) Nevertheless, many studies have shown a good correlation between standard oximeters and smartphone-based oximeters. ...
Although the PaO 2/FiO 2 derived from arterial blood gas analysis remains the gold standard for the diagnosis of acute respiratory failure, the SpO2/FiO2 has been investigated as a potential substitute. The current narrative review presents the state of the preclinical and clinical literature on the SpO2/FiO2 as a possible substitute for PaO2/FiO2 and for use as a diagnostic and prognostic marker; provides an overview of pulse oximetry and its limitations, and assesses the utility of SpO2/ FiO2 as a surrogate for PaO2/FiO2 in COVID-19 patients. Overall, 49 studies comparing SpO2/FiO2 and PaO2/FiO2 were found according to a minimal search strategy. Most were conducted on neonates, some were conducted on adults with acute respiratory distress syndrome, and a few were conducted in other clinical scenarios (including a very few on COVID-19 patients). There is some evidence that the SpO2/ FiO2 criteria can be a surrogate for PaO2/FiO2 in different clinical scenarios. This is reinforced by the fact that unnecessary invasive procedures should be avoided in patients with acute respiratory failure. It is undeniable that pulse oximeters are becoming increasingly widespread and can provide costless monitoring. Hence, replacing PaO2/FiO2 with SpO2/FiO2may allow resourcelimited facilities to objectively diagnose acute respiratory failure.
... By using this technology individuals can be capable of obtaining reliable and valid measurements helping them to monitor and consciously control their breathing patterns. Thus, these applications can facilitate individuals' hypoxic training (Jordan et al., 2020). ...
Low oxygen breathing has been the subject of considerable research in recent years. The present review aims to determine the physiological and neuropsychological benefits of low-oxygen training. Specifically, we explored the ways low oxygen affects hormones, neurotransmitters and growth factors responsible for neuroplasticity, higher cognition and positive emotions. In addition, we shed light on the importance of hypoxia to expand the conscious experience. Furthermore, we investigate the role of digital technologies in assisting hypoxic training. The results showed that, when hypoxia occurs, the human body puts into action the amazing survival mission which reveals unexplored alternative plans and healing pathways. Oxygen deprivation, under certain circumstances, has beneficial effects on cognition, mood and consciousness. It was observed an increase in growth factors, which are responsible for tissue repair and regeneration. Hypoxia also was found to stimulate the hormones of pleasure, happiness, pain tolerance, socialization and relaxation. Interestingly, people under hypoxic conditions are more likely to have transcendental experiences-even to develop 'superhuman' abilities. Digital technologies facilitate the safe implementation of hypoxic training enabling users to take control of a powerful tool, which is none other than breathing. Metacognition in breathing can help people consciously and safely manipulate their breathing by moving themselves away from their comfort zone and exploring new pathways to rewire their brains and plumb the depths of their physical, cognitive, emotional and spiritual potential. Our findings suggest that hypoxic training could be an effective intervention strategy with important therapeutic benefits for people with learning and other disabilities (i.e adhd, memory deficits, autism, motor, impairments, depression, generalized anxiety disorder). Future educators, therapists and families should be trained to appropriate apply simple hypoxic training exercises even in the educational context. For that reason, research into the physiological and neuropsychological mechanism that is affected by hypoxic training for individuals with learning or other disabilities is necessary.
... Smartphone app pulse oximeters have also been developed with a wide range of accuracy, but the accessibility and reliability of these developments are limited. 20 In addition to these, in developing countries, the high initial cost, pulse oximeter probe fragility, and inadequate electricity supply are the main barriers to the access of pulse oximeter. 21 In this study, a new prototype of a low-cost portable pulse oximeter device with better accuracy in the critical oxygen saturation region was developed, built, and tested. ...
Purpose
In a clinical setting, blood oxygen saturation is one of the most important vital sign indicators. A pulse oximeter is a device that measures the blood oxygen saturation and pulse rate of patients with various disorders. However, due to ethical concerns, commercially available pulse oximeters are limited in terms of calibration on critically sick patients, resulting in a significant error rate for measurement in the critical oxygen saturation range. The device’s accessibility in developing countries’ healthcare settings is also limited due to portability, cost implications, and a lack of recognized need. The purpose of this study was to develop a reliable, low-cost, and portable pulse oximeter device with improved accuracy in the critical oxygen saturation range.
Methods
The proposed device measures oxygen saturation and heart rate using the reflectance approach. The rechargeable battery and power supply from the smartphone were taken into account, and the calibration in critical oxygen saturation values was performed using Prosim 8 vital sign simulator, and by comparing with a standard pulse oximeter device over fifteen iterations.
Results
The device’s prototype was successfully developed and tested. Oxygen saturation and heart rate readings were both accurate to 97.74% and 97.37%, respectively, compared with the simulator, and an accuracy of 98.54% for the measurement of blood oxygen saturation was obtained compared with the standard device.
Conclusion
The accuracy of oxygen measurement attained in this study is significant for measuring oxygen saturation for patients in critical care, anesthesia, pre-operative and post-operative surgery, and COVID-19 patients. The advancements made in this research have the potential to increase the accessibility of pulse oximeter in resource limited areas.
... Three iPhone apps that allegedly could give precise SpO 2 values were proven unreliable in a recent study. (38) This is also an important issue with portable, low-cost fingertip pulse oximeters, some of which demonstrate highly inaccurate readings. (39) Nevertheless, many studies have shown a good correlation between standard oximeters and smartphone-based oximeters. ...
Although the PaO2/FiO2 derived from arterial blood gas analysis remains the gold standard for the diagnosis of acute respiratory failure, the SpO2/FiO2 has been investigated as a potential substitute. The current narrative review presents the state of the preclinical and clinical literature on the SpO2/FiO2 as a possible substitute for PaO2/FiO2 and for use as a diagnostic and prognostic marker; provides an overview of pulse oximetry and its limitations, and assesses the utility of SpO2/ FiO2 as a surrogate for PaO2/FiO2 in COVID-19 patients. Overall, 49 studies comparing SpO2/FiO2 and PaO2/FiO2 were found according to a minimal search strategy. Most were conducted on neonates, some were conducted on adults with acute respiratory distress syndrome, and a few were conducted in other clinical scenarios (including a very few on COVID-19 patients). There is some evidence that the SpO2/ FiO2 criteria can be a surrogate for PaO2/FiO2 in different clinical scenarios. This is reinforced by the fact that unnecessary invasive procedures should be avoided in patients with acute respiratory failure. It is undeniable that pulse oximeters are becoming increasingly widespread and can provide costless monitoring. Hence, replacing PaO2/FiO2 with SpO2/FiO2may allow resource-limited facilities to objectively diagnose acute respiratory failure. © 2022 Associacao de Medicina Intensiva Brasileira - AMIB. All rights reserved.
... Although some of these devices have been approved to measure heart rate and monitor for arrhythmia, it is important to note that they have not yet been shown to accurately measure pulse oximetry or temperature. 28 ...
... Hence, we can suggest that these smartphone applications for measuring oxygen saturation can produce valid results, which can be used for clinical decisions in the same manner portable finger pulse oximeters are used. Jordan et al. also found a moderate agreement for SpO 2 measurements using iPhone application; however, they conducted the study on real patients in clinical environments in contrast with our study that was conducted on healthy volunteers [7]. In situations such as the COVID-19 pandemic where healthcare settings become supersaturated and not all patients could be admitted to hospitals, oxygen saturations of otherwise stable individuals could be accurately monitored with these technologically advanced health applications in home settings, as well as clinics and hospitals. ...
Background
Smartphone technology is rapidly evolving and advancing, with many of them offering health applications being used for oximetry purposes, including the Samsung Health/S Health application. Measuring oxygen saturation is one of the important indications to monitor patients with COVID-19, as well as other health conditions. These applications can be used for measuring oxygen saturation to provide a convenient solution for clinical decisions.
Methods
Oxygen saturation measurements were collected using the Samsung Health application for Samsung Galaxy smartphone with a sensor and camera flash and a low-cost portable digital display (liquid crystal display (LCD)) finger pulse oximeter. Intra-session reliability was established to determine the consistency between the measures. Intra-class correlation coefficients (ICCs) were calculated with 95% confidence intervals (CIs) reported for both methods. The Bland-Altman plot was used to compare the level of agreement between the two measurement methods.
Results
There was a statistically significant average difference between pulse oximeter and Samsung Health application measurements (t125 = 4.407, p < 0.001), and on average, pulse oximeter measurement was 0.510 points higher than Samsung Health application measurement (95% CI = 0.281-0.740). The pulse oximeter and Samsung Health application scores were moderately correlated (r = 0.462). The results of the intra-session reliability test produced an acceptable ICC value of 0.557, indicating moderate reliability and consistent results for the measurement of oxygen saturation with both methods. The Bland-Altman plot showed a consistently equal distribution of data points scattered above and below zero.
Conclusion
Smartphone health applications can be used with moderate reliability to measure oxygen saturation.
... The COVID-19 pandemic highlighted this need for an affordable remote oxygen desaturation detection tool that can be accurately and safely used for initial screening and monitoring, informing users whether or not they should seek expert medical attention. This potential is important to consider, as software applications are already being used in this manner even when those applications have not cleared the FDA regulatory requirements (37,38). Our system is the first unmodified smartphone camera sensor to report accuracy at levels below 85% SpO 2 , and it achieved relatively high sensitivity (81%) and specificity (79%) when classifying subjects with SpO 2 below 90%. ...
Hypoxemia, a medical condition that occurs when the blood is not carrying enough oxygen to adequately supply the tissues, is a leading indicator for dangerous complications of respiratory diseases like asthma, COPD, and COVID-19. While purpose-built pulse oximeters can provide accurate blood-oxygen saturation (SpO) readings that allow for diagnosis of hypoxemia, enabling this capability in unmodified smartphone cameras via a software update could give more people access to important information about their health, as well as improve physicians' ability to remotely diagnose and treat respiratory conditions. In this work, we take a step towards this goal by performing the first clinical development validation on a smartphone-based SpO sensing system using a varied fraction of inspired oxygen (FiO) protocol, creating a clinically relevant validation dataset for solely smartphone-based methods on a wide range of SpO values (70%-100%) for the first time. This contrasts with previous studies, which evaluated performance on a far smaller range (85%-100%). We build a deep learning model using this data to demonstrate accurate reporting of SpO level with an overall MAE=5.00% SpO and identifying positive cases of low SpO<90% with 81% sensitivity and 79% specificity. We ground our analysis with a summary of recent literature in smartphone-based SpO2 monitoring, and we provide the data from the FiO study in open-source format, so that others may build on this work.
... 29,30 Mobile apps designed to measure vital signs are frequently inaccurate, providing false patient reassurance and potentiating patient harm. [31][32][33][34] Furthermore, the virtual care setting has been shown to change clinical decision-making, negatively impacting quality of care. For example, in some studies clinicians are more likely to overprescribe antibiotics and less likely to test for streptococcal pharyngitis during tele-heath visits, as compared to traditional care. ...
Digital health advances offer a multitude of possibilities to improve public health and individual wellbeing. Little attention has been paid, however, to digital health's potential to create low-value care - the reduction of which is increasingly appreciated as a policy priority. This commentary provides a framework to illustrate the potential for consumer-facing digital health to generate three distinct categories of low-value care; 1) ineffective care because it is underdeveloped, 2) inefficient care because it supplements rather than substitutes, or 3) unwanted care because it is not aligned with clinician and patient preferences. We offer specific policy recommendations to reduce each type of low-value care.
... We previously published a paper describing the inaccuracy of three smart phone apps which Luks and Swenson review in their article. 3 We agree in advising caution against the use of these devices. ...
... Limited research has been carried out to validate SpO 2 obtained from phone applications using healthy volunteers [38], [39] or patients admitted with low blood oxygen in the emergency room [40], with controlled data collected from electronic medical-grade SpO 2 measurement systems. Most phone applications showed moderate agreement with hospital/medical grade pulse oximeters. ...
This paper reviews the current state of the art in wearable sensors, including current challenges, that can alleviate the loads on hospitals and medical centers. During the COVID-19 Pandemic in 2020, healthcare systems were overwhelmed by people with mild to severe symptoms needing care. A careful study of pandemics and their symptoms in the past 100 years reveals common traits that should be monitored for managing the health and economic costs. Cheap, low power, and portable multi-modal-sensors that detect the common symptoms can be stockpiled and ready for the next pandemic. These sensors include temperature sensors for fever monitoring, pulse oximetry sensors for blood oxygen levels, impedance sensors for thoracic impedance, and other state sensors that can be integrated into a single system and connected to a smartphone or data center. Both research and commercial medically approved devices are reviewed with an emphasis on the electronics required to realize the sensing. The performance characteristics, such as accuracy, power, resolution, and size of each sensor modality are critically examined. A discussion of the characteristics, research challenges, and features of an ideal integrated wearable system is also presented.
... En referencia al testeo en diferentes situaciones ambientales, no se observó diferencia en la concordancia y fiabilidad en temperaturas más bajas, resultados concordantes con otros autores en dispositivos portátiles y aplicaciones de teléfonos celulares. 12,13 Tampoco en condiciones de reposo o post actividad física, en donde se encontraron valores concordantes de correlación y fiabilidad con los mencionados por otros autores. 10 Sí se encontró una baja correlación entre las mediciones de los dispositivos en ambientes con menor concentración de oxígeno, con resultados semejantes en estudios realizados en oxímetros de pulso en la altura de México. ...
ABSTRACT Introduction: Pulse oximeters for non-medical use would have an efficacy comparable to that of oximeters for medical use to rule out the presence of silent hypoxia in patients with COVID-19. There are biometric wristbands on the market with built-in oxygen saturation monitoring functions. The main objective was to evaluate the reliability and concordance of these devices and their possible usefulness to detect premature values of silent hipoxia. Methods: SatO 2 measurements were performed simultaneously in both devices, in the 10 healthy individuals participating and in different environmental situations and physical activity. Results: The interclass correlation coefficients (ICC) that were obtained when comparing the devices with each other, were between 0.767 and 0.854, except in the determinations in environments with low oxygen concentration (ICC: 0.441). A significant correlation was found between the devices (Pearson <0.001) and reliability (Cronbach's Alpha: 0.853). Conclusions: The evaluated biometric bracelet has a very good concordance and reliability compared to the pulse oximeter and would be very useful to identify the premature stages of silent hypoxemia, a pathognomonic symptom of COVID-19.
... We undertook this study after our previous work showed that iPhone applications proved to be inaccurate. 20 We were looking for tools for the clinician that were small, portable, and accurate and could be easily packed. An accurate device to measure oxygen saturation could be helpful as a fifth vital sign in an austere environment to assess a patient or victim having problems with respiration because of trauma, infection, or altitude. ...
Objective
To determine the correlation between 3 lightweight portable pulse oximeter devices compared to a standard wall mount pulse oximetry device.
Methods
We performed a single‐center, prospective, observational study of 4 pulse oximetry devices, 3 of which are commercially available to the public. A convenience sample of 200 emergency department (ED) patients with chief complaints of cardiopulmonary origin or a peripheral capillary oxygen saturation ≤ 94 percent were enrolled. Analysis of variance was performed to compare SpO2s and test characteristics of the 3 devices compared to control.
Results
Although differences in measured SpO2s were observed (P < 0.001) across groups, the differences were small (mean differences ranged from 1.00% to 1.87%). The correlation between test devices and the control were high (r range 0.70–0.79). Although the test characteristics were not perfect, the devices did have good sensitivity using a cutoff value of 94% (sensitivity ranging from 90% to 92%), which improved with lower SpO2 cutoff values to 92% (sensitivity ranging from 96% to 97%).
Conclusion
The 3 commercially available devices were accurate enough to be clinically useful when compared to a hospital bedside monitor pulse oximeter. Consumer‐grade portable pulse oximeters may be useful if overwhelming numbers of patients require oxygen saturation monitoring, such as during the COVID‐19 pandemic.
Background:
Pulse oximetry measurement is ubiquitous in acute health care settings in high-income countries and is familiar to any parent whose child has been treated in such a setting. Oximeters for home use are readily available online and are incorporated in several smartphones and smartwatches.
Methods:
We wished to determine how accurate are oximeters available online that are designated for adult and pediatric use, and the saturation monitor integrated in a smartphone, when used in children, compared to reference, hospital-grade oximeters. We evaluated a fingertip oximeter marketed for children purchased online; an adult fingertip oximeter purchased online; the oximeter integrated in a smartphone; and reference, hospital-grade oximeters. Participants were < 18 y of age. Bland-Altman charts were generated, and the estimated root mean square error (EARMS) was calculated. Rates of failure to obtain a measurement, relationship between device and time to successful measurement, relationship between age and time to successful measurement, and relationship between error (vs the reference device) and age were evaluated for each consumer-grade device.
Results:
We measured SpO2 in 74 children between 0.1-17.0 y of age. Subjects weighing < 30 kg had a median (interquartile range [IQR]) age of 2 (1.0 month-1.4 y) months, and subjects weighing ≥ 30 kg had a median (IQR) age of 14.3 (11.9-16.2) y. Readings could not be obtained in 7.5, 0, and 38.8% of subjects using the pediatric, adult, and smartphone oximeters, respectively. The time to successful reading had a modest negative correlation with age with the inexpensive adult and pediatric oximeters. The inexpensive pediatric oximeter had an overall negative bias, with a mean difference from the reference device of -4.5% (SD 7.9%) and an error that ranged from > 8% to < 33% the reference device. The EARMS was 7.92%. The inexpensive adult oximeter demonstrated no obvious trend in error in the limited saturation range evaluated of 87-99%. The overall mean difference was -0.7% (SD 2.5%). EARMS was 2.5%. The smartphone oximeter underestimated SpO2 at saturations < 94% and overestimated SpO2 for saturations > 94%. Saturations could read as much as > 4%, or < 17%, than the reference oximeter. The mean difference was -2.9% (SD 5.2%). EARMS was 5.1%.
Conclusions:
Our findings suggest that the performance of consumer-grade devices varies considerably by both subject age and device. The pediatric fingertip device and smartphone application we tested are poorly suited for use in infants. The adult fingertip device we tested performed quite well in larger children with relatively normal oxygen saturations, and the pediatric fingertip device performed moderately well in subjects > 1 y of age who weighed < 30 kg. Given the vast number of devices available online and ever-changing technology, research to evaluate nonclinical oximeters will continue to be required.
Purpose: Pulse oximetry is widely used in healthcare settings for both screening and continuous monitoring. In this article, it was aimed to review some aspects of pulse oximetry including clinical applications, portable devices, and recent advances in detail. Materials and Methods: The international and national reliable sources were used in the literature review for critical data analysis. A total of 31 articles including 19 prospective comparative clinical studies, 9 reviews, 1 meta-analysis, 1 retrospective study, and 1 experimental study were used for preparation of this part of the review. Results: In this part of the article, clinical applications of pulse oximeters, portable/wearable pulse oximeters, remote patient monitoring, and recent advances were all reviewed in detail. Conclusion: Pulse oximetry is a widely used and reliable noninvasive technique that provides useful information about blood oxygenation in individuals. This technique can guide oxygen therapy, reduce the occurrence of hypoxemia, and decrease the frequency of admissions to the intensive care unit, as well as arterial blood gas sampling. New multiwaveform sensors and advanced signal processing techniques can differentiate between different types of hemoglobin and may be useful for continuous measurement of total hemoglobin, as well as for detecting and providing information on blood loss and cardiac output.
Background
Many commodity pulse oximeters are insufficiently calibrated for patients with darker skin. We demonstrate a quantitative measurement of this disparity in peripheral blood oxygen saturation (SpO2) with a controlled experiment. To mitigate this, we present OptoBeat, an ultra–low-cost smartphone-based optical sensing system that captures SpO2 and heart rate while calibrating for differences in skin tone. Our sensing system can be constructed from commodity components and 3D-printed clips for approximately US $1. In our experiments, we demonstrate the efficacy of the OptoBeat system, which can measure SpO2 within 1% of the ground truth in levels as low as 75%.
Objective
The objective of this work is to test the following hypotheses and implement an ultra–low-cost smartphone adapter to measure SpO2: skin tone has a significant effect on pulse oximeter measurements (hypothesis 1), images of skin tone can be used to calibrate pulse oximeter error (hypothesis 2), and SpO2 can be measured with a smartphone camera using the screen as a light source (hypothesis 3).
Methods
Synthetic skin with the same optical properties as human skin was used in ex vivo experiments. A skin tone scale was placed in images for calibration and ground truth. To achieve a wide range of SpO2 for measurement, we reoxygenated sheep blood and pumped it through synthetic arteries. A custom optical system was connected from the smartphone screen (flashing red and blue) to the analyte and into the phone’s camera for measurement.
Results
The 3 skin tones were accurately classified according to the Fitzpatrick scale as types 2, 3, and 5. Classification was performed using the Euclidean distance between the measured red, green, and blue values. Traditional pulse oximeter measurements (n=2000) showed significant differences between skin tones in both alternating current and direct current measurements using ANOVA (direct current: F2,5997=3.1170 × 105, P<.01; alternating current: F2,5997=8.07 × 106, P<.01). Continuous SpO2 measurements (n=400; 10-second samples, 67 minutes total) from 95% to 75% were captured using OptoBeat in an ex vivo experiment. The accuracy was measured to be within 1% of the ground truth via quadratic support vector machine regression and 10-fold cross-validation (R2=0.97, root mean square error=0.7, mean square error=0.49, and mean absolute error=0.5). In the human-participant proof-of-concept experiment (N=3; samples=3 × N, duration=20-30 seconds per sample), SpO2 measurements were accurate to within 0.5% of the ground truth, and pulse rate measurements were accurate to within 1.7% of the ground truth.
Conclusions
In this work, we demonstrate that skin tone has a significant effect on SpO2 measurements and the design and evaluation of OptoBeat. The ultra-low-cost OptoBeat system enables smartphones to classify skin tone for calibration, reliably measure SpO2 as low as 75%, and normalize to avoid skin tone–based bias.
Background: Pulse oximetry is used as an assessment tool to gauge the severity of COVID-19 infection and identify patients at risk of poor outcomes. The pandemic highlights the need for accurate pulse oximetry, particularly at home, as infection rates increase in multiple global regions, including the UK, USA, and South Africa. Over 100 million Samsung smartphones containing dedicated biosensors (Maxim Integrated Inc, San Jose, CA) and preloaded Apps to perform pulse oximetry, are in use globally. We performed detailed in human hypoxia testing on the Samsung S9 smartphone to determine if this integrated hardware meets full FDA/ISO requirements for clinical pulse oximetry.
Methods: The accuracy of integrated pulse oximetry in the Samsung 9+ smartphone during stable oxygen saturation (SaO2) between 70% and 100% was evaluated in 12 healthy subjects. Inspired oxygen, nitrogen, and carbon dioxide partial pressures were monitored and adjusted via a partial rebreathing circuit to achieve stable target SaO2 plateaus between 70% and 100%. Arterial blood samples were taken at each plateau, and saturation measured on each blood sample using ABL-90FLEX blood gas analyzer. Bias, calculated from smartphone readings minus the corresponding arterial blood sample, was reported as root mean square deviation (RMSD).
Findings: The RMSD of the over 257 data points based on blood sample analysis obtained from 12 human volunteers tested was 2.6%.
Interpretation: Evaluation of the smartphone pulse oximeter performance is within requirements of <3.5% RMSD blood oxygen saturation (SpO2) value for FDA/ISO clearance for clinical pulse oximetry. This is the first report of smartphone derived pulse oximetry measurements that meet full FDA/ISO accuracy certification requirements. Both Samsung S9 and S10 contain the same integrated pulse oximeter, thus over 100 million smartphones in current global circulation could be used to obtain clinically accurate spot SpO2 measurements to support at home assessment of COVID-19 patients.
Introduction
Healthcare providers in resource-limited settings rely on the presence of tachypnoea and chest indrawing to establish a diagnosis of pneumonia in children. We aimed to determine the test characteristics of commonly assessed signs and symptoms for the radiographic diagnosis of pneumonia in children 0–59 months of age.
Methods
We conducted an analysis using patient-level pooled data from 41 shared datasets of paediatric pneumonia. We included hospital-based studies in which >80% of children had chest radiography performed. Primary endpoint pneumonia (presence of dense opacity occupying a portion or entire lobe of the lung or presence of pleural effusion on chest radiograph) was used as the reference criterion radiographic standard. We assessed the sensitivity, specificity, and likelihood ratios for clinical findings, and combinations of findings, for the diagnosis of primary endpoint pneumonia among children 0–59 months of age.
Results
Ten studies met inclusion criteria comprising 15 029 children; 24.9% (n=3743) had radiographic pneumonia. The presence of age-based tachypnoea demonstrated a sensitivity of 0.92 and a specificity of 0.22 while lower chest indrawing revealed a sensitivity of 0.74 and specificity of 0.15 for the diagnosis of radiographic pneumonia. The sensitivity and specificity for oxygen saturation <90% was 0.40 and 0.67, respectively, and was 0.17 and 0.88 for oxygen saturation <85%. Specificity was improved when individual clinical factors such as tachypnoea, fever and hypoxaemia were combined, however, the sensitivity was lower.
Conclusions
No single sign or symptom was strongly associated with radiographic primary end point pneumonia in children. Performance characteristics were improved by combining individual signs and symptoms.
During the ongoing COVID-19 pandemic, reports in social media and the lay press indicate that a subset of patients are presenting with severe hypoxemia in the absence of dyspnea, a problem unofficially referred to as "silent hypoxemia." To decrease the risk of complications in such patients, one proposed solution has been to have those diagnosed with COVID-19 but not sick enough to warrant admission monitor their arterial oxygenation by pulse oximetry at home and present for care when they show evidence of hypoxemia. While the ease of use and low cost of pulse oximetry makes this an attractive option for identifying problems at an early stage, there are important considerations with pulse oximetry about which patients and providers may not be aware that can interfere with successful implementation of such monitoring programs. Only a few independent studies have examined the performance of pocket oximeters and smart phone-based systems but the limited available data raise questions about their accuracy, particularly as saturation falls below 90%. There are also multiple sources of error in pulse oximetry that must be accounted for including rapid fluctuations in measurements when the PaO2 falls on the steep portion of the dissociation curve, data acquisition problems when pulsatile blood flow is diminished, accuracy in the setting of severe hypoxemia, dyshemoglobinemias and other problems. Recognition of these issues and careful counseling of patients about the proper means for measuring their oxygen saturation and when to seek assistance can help ensure successful implementation of needed monitoring programs.
Background
Heart surgery patients are more at risk of poor peripheral perfusion, and peripheral capillary oxygen saturation (SpO2) measurement is regular care for continuous analysis of blood oxygen saturation in these patients. With regard to controversial studies on accuracy of the current pulse oximetry probes and lack of data related to patients undergoing heart surgery, the present study was conducted to determine accuracy of pulse oximetry probes of finger, toe, forehead and earlobe in detection of oxygen saturation in patients admitted to intensive care units for coronary artery bypass surgery.
Methods
In this clinical trial, 67 patients were recruited based on convenience sampling method among those admitted to intensive care units for coronary artery bypass surgery. The SpO2 value was measured using finger, toe, forehead and earlobe probes and then compared with the standard value of arterial oxygen saturation (SaO2). Data were entered into STATA-11 software and analyzed using descriptive, inferential and Bland-Altman statistical analyses.
Results
Highest and lowest correlational mean values of SpO2 and SaO2 were related to finger and earlobe probes, respectively. The highest and lowest agreement of SpO2 and SaO2 were related to forehead and earlobe probes.
Conclusion
The SpO2 of earlobe probes due to lesser mean difference, more limited confidence level and higher agreement ration with SaO2 resulted by arterial blood gas (ABG) analysis had higher accuracy. Thus, it is suggested to use earlobe probes in patients admitted to the intensive care unit for coronary artery bypass surgery.
Trial registration
Registration of this trial protocol has been approved in Iranian Registry of Clinical Trials at 2018–03-19 with reference IRCT20100913004736N22. “Retrospectively registered.”
Purpose/hypothesis:
This study was designed to investigate the test-retest reliability, concurrent validity, and the standard error of measurement (SEm) of a pulse rate assessment application (Azumio®'s Instant Heart Rate) on both Android® and iOS® (iphone operating system) smartphones as compared to a FT7 Polar® Heart Rate monitor. Number of subjects: 111.
Materials/methods:
Resting (sitting) pulse rate was assessed twice and then the participants were asked to complete a 1-min standing step test and then immediately re-assessed. The smartphone assessors were blinded to their measurements.
Results:
Test-retest reliability (intraclass correlation coefficient [ICC 2,1] and 95% confidence interval) for the three tools at rest (time 1/time 2): iOS® (0.76 [0.67-0.83]); Polar® (0.84 [0.78-0.89]); and Android® (0.82 [0.75-0.88]). Concurrent validity at rest time 2 (ICC 2,1) with the Polar® device: IOS® (0.92 [0.88-0.94]) and Android® (0.95 [0.92-0.96]). Concurrent validity post-exercise (time 3) (ICC) with the Polar® device: iOS® (0.90 [0.86-0.93]) and Android® (0.94 [0.91-0.96]). The SEm values for the three devices at rest: iOS® (5.77 beats per minute [BPM]), Polar® (4.56 BPM) and Android® (4.96 BPM).
Conclusions:
The Android®, iOS®, and Polar® devices showed acceptable test-retest reliability at rest and post-exercise. Both the smartphone platforms demonstrated concurrent validity with the Polar® at rest and post-exercise.
Clinical relevance:
The Azumio® Instant Heart Rate application when used by either platform appears to be a reliable and valid tool to assess pulse rate in healthy individuals.
Use of healthcare-related smartphone applications is common. However, there is concern that inaccurate information from these applications may lead patients to make erroneous healthcare decisions. The objective of this study is to study smartphone applications purporting to measure vital sign data using only onboard technology compared with monitors used routinely in clinical practice. This is a prospective trial comparing correlation between a clinically utilized vital sign monitor (Propaq CS, WelchAllyn, Skaneateles Falls, NY, USA) and four smartphone application-based monitors Instant Blood Pressure, Instant Blood Pressure Pro, Pulse Oximeter, and Pulse Oximeter Pro. We performed measurements of heart rate (HR), systolic blood pressures (SBP), diastolic blood pressure (DBP), and oxygen saturation (SpO2) using standard monitor and four smartphone applications. Analysis of variance was used to compare measurements from the applications to the routine monitor. The study was completed on 100 healthy volunteers. Comparison of routine monitor with the smartphone applications shows significant differences in terms of HR, SpO2 and DBP. The SBP values from the applications were not significantly different from those from the routine monitor, but had wide limits of agreement signifying a large degree of variation in the compared values. The degree of correlation between monitors routinely used in clinical practice and the smartphone-based applications studied is insufficient to recommend clinical utilization. This lack of correlation suggests that the applications evaluated do not provide clinically meaningful data. The inaccurate data provided by these applications can potentially contribute to patient harm.
Context: The pulse oximeter is a device that noninvasively provides continuous information about the peripheral oxygen saturation (SpO2) rate. This device is utilized in the detection of hypoxemia, due to its able to sense changes in hemoglobin oxygen saturation.
Aims: The objective of this study was to verify the accuracy of the Choice® Medical MD300C3 Fingertip Pulse Oximeter, as compared to that of a hospital oximeter coupled with a Dräger® Infinity Delta monitor, with the purpose of using this first methodology in dental procedures to monitor the peripheral oxygen saturation (SpO2) of patients submitted to dental treatments.
Materials and Methods: Fifty-five adult patients, both genders, were selected in the Santa Casa Hospital of Maringa, Brazil. The volunteers did not present cardiac problems, prosthetic cardiac valves, pacemakers, or pulmonary diseases, and were not pregnant or children. Each patient received a portable fingertip pulse oximeter (PPO) on the middle finger of the left hand and the hospital oximeter (control device) on the forefinger of the same hand. A total of six measurements were developed. The Pearson correlation coefficient and the Bland and Altman method was used to calculate the statistical analysis.
Results: No statistically significant difference was found between the measurements taken by the utilized devices. The average of comparative analysis presented by the devices was 0.2337 ± 0.4355 (mean ± SD), suggesting a strong correlation between the obtained results.
Conclusion: According to the methodology of the research, the PPO has similar accuracy to the conventional hospital oximeter with digital sensor. The PPO can be used in dental treatments.
Background:
Pulse oximetry is routinely used to continuously and noninvasively monitor arterial oxygen saturation (SaO2) in critically ill patients. Although pulse oximeter oxygen saturation (SpO2) has been studied in several patient populations, including the critically ill, its accuracy has never been studied in emergency department (ED) patients with severe sepsis and septic shock. Sepsis results in characteristic microcirculatory derangements that could theoretically affect pulse oximeter accuracy. The purposes of the present study were twofold: 1) to determine the accuracy of pulse oximetry relative to SaO2 obtained from ABG in ED patients with severe sepsis and septic shock, and 2) to assess the impact of specific physiologic factors on this accuracy.
Methods:
This analysis consisted of a retrospective cohort of 88 consecutive ED patients with severe sepsis who had a simultaneous arterial blood gas and an SpO2 value recorded. Adult ICU patients that were admitted from any Calgary Health Region adult ED with a pre-specified, sepsis-related admission diagnosis between October 1, 2005 and September 30, 2006, were identified. Accuracy (SpO2 - SaO2) was analyzed by the method of Bland and Altman. The effects of hypoxemia, acidosis, hyperlactatemia, anemia, and the use of vasoactive drugs on bias were determined.
Results:
The cohort consisted of 88 subjects, with a mean age of 57 years (19 - 89). The mean difference (SpO2 - SaO2) was 2.75% and the standard deviation of the differences was 3.1%. Subgroup analysis demonstrated that hypoxemia (SaO2 < 90) significantly affected pulse oximeter accuracy. The mean difference was 4.9% in hypoxemic patients and 1.89% in non-hypoxemic patients (p < 0.004). In 50% (11/22) of cases in which SpO2 was in the 90-93% range the SaO2 was <90%. Though pulse oximeter accuracy was not affected by acidoisis, hyperlactatementa, anemia or vasoactive drugs, these factors worsened precision.
Conclusions:
Pulse oximetry overestimates ABG-determined SaO2 by a mean of 2.75% in emergency department patients with severe sepsis and septic shock. This overestimation is exacerbated by the presence of hypoxemia. When SaO2 needs to be determined with a high degree of accuracy arterial blood gases are recommended.
During conditions of poor perfusion, the accuracy of conventional extremity-based pulse oximeters may be limited. Limited evidence suggests that forehead perfusion may be better preserved during such periods, but pediatric experience with newer forehead reflectance sensors is limited. We prospectively compared the accuracy of a forehead reflectance sensor, the Max-Fast, with a new-generation digit sensor in pediatric patients.
Pediatric patients > 10 kg and who had arterial catheters were eligible for enrollment. Blood oxygen saturation was simultaneously measured with forehead and digit sensors, and compared to corresponding CO-oximetry-measured arterial oxygen saturation values (S(aO2)) taken at the same times. We used Bland-Altman analysis to calculate the bias and precision of the forehead sensor and the digit sensor relative to the S(aO2) values.
We obtained 116 sample sets from 28 patients. The S(aO2) values ranged from 84.1% to 99.2%. The bias and precision of the forehead-to-S(aO2) difference were 0.6% and 2.7%, respectively, versus 1.4% and 2.6%, respectively, for the digit-to-S(aO2) difference (p < 0.05). Bias and precision were 0.7% and 2.6% versus 1.7% and 2.3% for the forehead and digit sensors, respectively, (p < 0.05) in patients who received vasoactive medications, compared with 0.5% and 2.8% versus 1.1% and 2.8% (p = not significant), respectively, in patients who did not receive vasoactive medications.
The Max-Fast sensor estimated S(aO2) as accurately as did a new-generation digit sensor in well-perfused pediatric patients.
Program concord implements L. I. Lin's concordance correlation coefficient (Lin, 1989), as well as the limits-of-agreement procedure (Bland and Altman, 1986). Recently, Lin (2000) issued an erratum reporting a number of typographical errors in his seminal 1989 paper. Further, changes in Stata Version 7 required modification of concord. This note reports the effect of the errors and provides a corrected and updated program.
Background:
Pulse oximetry, a ubiquitous, noninvasive method to monitor oxygen saturation (SpO2), requires larger, nonportable equipment. Smartphone pulse oximeter applications (apps) provide a portable, cost-effective option, but are untested in children. We hypothesize that smartphone pulse oximetry will not be inferior to standard pulse oximetry measured in healthy children.
Materials and methods:
Two main types of pulse oximetry apps, a camera-based app (CBA) that uses a phone camera flash and lens and a probe-based app (PBA) that uses an external plug-in probe, were compared with standard pulse oximetry measured in children ages 2-13 years without a respiratory complaint and a triage SpO2 ≥97% seen in a pediatric Emergency Department. Two investigators obtained heart rate and SpO2 using each app. Inter-rater reliability was tested using interclass correlations (ICCs), and Bland-Altman method was used to compare app values to triage measurements.
Results:
Eighty-one patients were enrolled. ICC for SpO2 for PBA and CBA were 0.73 and -0.24, respectively. The 95% limits of agreement between the PBA SpO2 and triage SpO2 were -2.8 to +2.5 compared with -4.1 to +3.5 for the CBA SpO2 and triage SpO2. Mean differences between triage SpO2 and the PBA SpO2 (-0.17%) and triage SpO2 and CBA SpO2 (-0.33%) were not statistically significant.
Discussion and conclusions:
Smartphone-based pulse oximetry is not inferior to standard pulse oximetry in pediatric patients without hypoxia. Reliability was superior for PBA compared with CBA, with more precise agreement for the PBA compared with the CBA. Future studies should test pulse oximetry apps in a hypoxic pediatric population.
Background:
Pulse oximetry has become an essential tool in clinical practice. With patient self-management becoming more prevalent, pulse oximetry self-monitoring has the potential to become common practice in the near future. This study sought to compare the accuracy of two pulse oximeters, a high-quality standard pulse oximeter and an inexpensive pocket pulse oximeter, and to compare both devices with arterial blood co-oximetry oxygen saturation.
Methods:
A total of 95 patients (35.8% women; mean [±SD] age 63.1 ± 13.9 years; mean arterial pressure was 92 ± 12.0 mmHg; mean axillar temperature 36.3 ± 0.4°C) presenting to our hospital for blood gas analysis was evaluated. The Bland-Altman technique was performed to calculate bias and precision, as well as agreement limits. Student's t test was performed.
Results:
Standard oximeter presented 1.84% bias and a precision error of 1.80%. Pocket oximeter presented a bias of 1.85% and a precision error of 2.21%. Agreement limits were -1.69% to 5.37% (standard oximeter) and -2.48% to 6.18% (pocket oximeter).
Conclusion:
Both oximeters presented bias, which was expected given previous research. The pocket oximeter was less precise but had agreement limits that were comparable with current evidence. Pocket oximeters can be powerful allies in clinical monitoring of patients based on a self-monitoring/efficacy strategy.
Pulse rate is commonly measured manually or with commercial wrist or belt monitors. More recently, pulse rate monitoring has become convenient with the use of mobile technology that allows monitoring through the smartphone camera. This optical technology offers many benefits, albeit the clinimetric properties have not been extensively studied.
Observational study of reliability Setting: University kinesiology laboratory.
Thirty healthy, recreationally active adults.
Concurrent measurement of pulse rate using two smartphone applications (Fingertip, Face-scan,) with the Polar® H7™ belt and pulse oximeter.
Average resting pulse rate for 5 minutes in three positions (supine, sitting, and prone).
Concurrent validity in supine and standing was good between the two applications and the Polar H7™ (intraclass correlation coefficient: ICC-0.80-0.98) and pulse oximeter (ICC-0.82-0.98). For sitting, the validity was good between the fingertip application, Polar H7™ (ICC-0.97) and pulse oximeter (ICC-0.97). The face-scan application had moderate validity with the Polar H7™ (ICC-0.74) and pulse oximeter (ICC-0.69). The minimal detectable change (MDC90) between the fingertip application and Polar H7™ ranged from 1.38-4.36 beats per minute (BPM) and 0.69-2.97 BPM for the pulse oximeter with all three positions. The MDC90 between the face-scan application and Polar H7™ ranged from 11.88-12.83 BPM and 0.59-17.72 BPM for the pulse oximeter. The 95% limits of agreement (LOA) suggests that the fingertip application may vary between 2.40-3.59 BPM with the Polar H7™ and 3.40-3.42 BPM with the pulse oximeter. The face-scan application may vary between 3.46-3.52 BPM with the Polar H7™ and 2.54-3.46 BPM with the pulse oximeter.
Pulse rate measurements may be effective using a finger-tip application, belt monitor, and pulse oximeter. The fingertip scanner showed superior results compared to the face-scanner which only demonstrated modest validity when compared to the Polar H7™ and pulse oximeter.
This study of paediatric intensive care patients aimed to determine where pulse oximetry probes shouid be placed to obtain the most accurate and reliable readings of peripheral oxygen saturation (SpO2). Using arterial blood gas analysis (SaO2) as the gold standard and SpO2 92% and SaO2 < 90% as indicators of hypoxaemia, negative predictive values of SpO2 were 96%, 98% and 98% at the ear, thumb and big toe respectively in 110 children, and 93% at all 3 sites in 90 neonates. The highest clinical agreement between SaG, and SpO2 was for ear probes in children (kappa = 0.70) and the lowest was for big toe probes (kappa = 0.57 and 0.28 in children and neonates respectively).
Many statistical problems involve comparison and, in particular, the assessment of agreement or disagreement between data measured on identical scales. Some commonly used plots are often ineffective in assessing the fine structure of such data, especially scatterplots of highly correlated variables and plots of values measured "before" and "after" using tilted line segments. Valuable alternatives are available using horizontal reference patterns, changes plotted as parallel lines, and parallel coordinates plots. The quantities of interest (usually differences on some scale) should be shown as directly as possible, and the responses of given individuals should be identified as easily as possible. Copyright 2004 by StataCorp LP.
We compared loss of pulse oximetry signal (dropout rates) for both finger and forehead sensors in postanesthesia patients. Pulse oximetry is a widely practiced method for measuring oxygen saturation. Several studies in various patient populations have demonstrated that low flow states, patient movement, and hypothermia may result in poor signal quality with the use of finger oximetry sensors. These clinical conditions are common in patients as they emerge from anesthesia. New forehead sensors may reduce signal dropout. A method-comparison design was used to compare finger and forehead oximetry signal dropout rates. Of 48 subjects studied, only three had a signal dropout. Overall, there were seven episodes of signal dropout; six of seven occurred with the finger sensor. Signal dropout occurred rarely in PACU subjects. Use of finger sensors for routine postanesthesia monitoring should be adequate in the majority of patients.
A new reproducibility index is developed and studied. This index is the correlation between the two readings that fall on the 45 degree line through the origin. It is simple to use and possesses desirable properties. The statistical properties of this estimate can be satisfactorily evaluated using an inverse hyperbolic tangent transformation. A Monte Carlo experiment with 5,000 runs was performed to confirm the estimate's validity. An application using actual data is given.
Oximetry, the measurement of hemoglobin oxygen saturation in either blood or tissue, depends on the Lambert-Beer relationship between light transmission and optical density. Shortly after Bunsen and Kirchhoff invented the spectrometer in 1860, the oxygen transport function of hemoglobin was demonstrated by Stokes and Hoppe-Seyler, who showed color changes produced by aeration of hemoglobin solutions. In 1932 in Göttingen, Germany, Nicolai optically recorded the in vivo oxygen consumption of a hand after circulatory occlusion. Kramer showed that the Lambert-Beer law applied to hemoglobin solutions and approximately to whole blood, and measured saturation by the transmission of red light through unopened arteries. Matthes in Leipzig, Germany, built the first apparatus to measure ear oxygen saturation and introduced a second wavelength (green or infrared) insensitive to saturation to compensate for blood volume and tissue pigments. Millikan built a light-weight ear "oximeter" during World War II to train pilots for military aviation. Wood added a pneumatic cuff to obtain a bloodless zero. Brinkman and Zijlstra in Groningen, The Netherlands, showed that red light reflected from the forehead could be used to measure oxygen saturation. Zijlstra initiated cuvette and catheter reflection oximetry. Instrumentation Laboratory used multiple wavelengths to measure blood carboxyhemoglobin and methemoglobin is cuvette oximeters. Shaw devised an eight-wavelength ear oximeter. Nakajima and co-workers invented the pulse oximeter, which avoids the need for calibration with only two wavelengths by responding only to the pulsatile changes in transmitted red and infrared light. Lübbers developed catheter tip and cuvette fiberoptic sensors for oxygen tension, carbon dioxide tension, and pH.
The pulse oximeter has become an essential tool in the modern practice of emergency medicine. However, despite the reliance placed on the information this monitor offers, the underlying principles and associated limitations of pulse oximetry are poorly understood by medical practitioners. This article reviews the principles of pulse oximetry, with an eye toward recognizing the limitations of this tool. Among these are performance limitations in the settings of carboxyhemoglobinemia, methemoglobinemia, motion artifact, hypotension, vasoconstriction, and anemia. The accuracy of pulse oximetry is discussed in light of these factors, with further discussion of applications for pulse oximetry in emergency medicine, including both oximetric and plethysmographic operation. The pulse oximeter is an invaluable instrument for emergency medicine practice, but as with any test the data it offers must be critically appraised for proper interpretation and utilization.
Evaluation of the impact on clinical care of improved, innovative oximetry technology.
Randomized, prospective trial.
Postcardiac surgery intensive care unit in a major teaching hospital.
A total of 86 patients after undergoing coronary artery bypass surgery.
All patients were monitored with two oximeters, one employing conventional oximetry (conventional pulse oximeter, CPO) and one using an improved innovative technology (innovative pulse oximeter, IPO), on different fingers of the same hand. The outputs from both devices were collected continuously by computer, but only one device was randomly selected and displayed for clinicians.
The amount and percentage of nonfunctional monitoring time was collected and found to be much greater for the CPO than the IPO (8.7% +/- 16.4% for CPO vs. 1.2% +/- 3.3% for IPO, p =.000256). Time to extubation was not different between the two groups (634 +/- 328 mins for IPO vs. 706 +/- 459 mins for CPO). Clinicians managing patients with the more reliable IPO weaned patients faster to an FIO2 of 0.40 (176 +/- 111 mins for IPO vs. 348 +/- 425 mins for CPO, p =.0125), obtained fewer arterial blood gas measurements (2.7 +/- 1.2 for IPO vs. 4.1 +/- 1.6 for CPO, p =.000015), and made the same number of ventilator changes during this weaning process (2.9 +/- 1.2 for IPO vs. 2.9 +/- 1.7 for CPO).
Provision of more reliable oximetry allows caregivers to act in a more efficient and cost-effective manner in regard to oxygen weaning and use of arterial blood gas measurements. Investigating the effect of a monitor on the process of care, rather than simply its accuracy and precision, is a useful, relevant paradigm for evaluating the value and impact of a new technology.
Statistical methods for assessing agreement between two methods of clinical measurement
- Bland
Accuracy of smartphone-based pulse oximetry compared with hospital grade pulse oximetry in healthy children.
- Tomlinson S.
- Berhmann S.
- Cranford J.
- Louie M.
- Hashikawa A.
Assessing the circulation: oximetry, indicator dilution, and pulse contour analysis
- Pinsky
Validity of pulse oximetry in detention of hypoxemia in children: comparison of ear, thumb, and toe probe placements.
- Bilin N.
- Behbahan A.G.
- Abdinia B.
- Mahallei M.