key: cord-1020705-1e93ow9v authors: Schrading, Walter A.; McCafferty, Ben; Grove, Jordan; Page, David B. title: Portable, consumer‐grade pulse oximeters are accurate for home and medical use: Implications for use in the COVID‐19 pandemic and other resource‐limited environments date: 2020-10-20 journal: J Am Coll Emerg Physicians Open DOI: 10.1002/emp2.12292 sha: d3b5f32b0b50e63ad0a23f8f6c86f4686edca7af doc_id: 1020705 cord_uid: 1e93ow9v 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. This study assessed the accuracy of 2 consumer grade and 1 medicalgrade portable pulse oximetry devices as compared to a standard- The accuracy of consumer and medical-grade home pulse oximetry devices has not been well studied. This study of 200 hypoxic emergency department patients demonstrated that three home pulse oximeters were accurate when compared to a standard emergency department monitor. of-care, wall-mounted pulse oximetry device. We postulated that the portable devices would be equivalent and reliably measure oxygen saturation. We also postulated that these devices would provide accurate measurements in patients with some degree of hypoxia (ie, SpO2 ≤ 94%). We performed a single-center, open-label, prospective observational study comparing the results of bedside pulse-oximetry across 4 devices using a convenience sample. Two consumer-grade and 1 medical-grade portable pulse oximetry devices were compared to a standard emergency department non-portable bedside unit ( Figure 1 ). The 2 consumer-grade models were Santa Medical SM-165 (SM) and Walgreen's OxyWatch C20 (OxyWatch). The medical-grade unit was a Nonin Onyx II 9550 (Onyx). The wall-mounted hospital control unit used was an ED TRAM 451 pulse oximeter (General Electrics, New York City, NY). All portable units used in testing were obtained by University of Alabama at Birmingham (UAB) emergency and wilderness medicine faculty. We recorded the demographic data, SpO2 measurements, the use of supplemental O2, and the reason for inclusion for each A total of 200 patients were evaluated. The characteristics of the enrolled patients are shown in Table 1 . The group was evenly distributed between white and African American patients and sex. The majority were not receiving supplemental O2 at enrollment. The distribution of patient complaints used to include patients is also shown. Note that the total is >100% because many patients had more than one complaint, for example, chest pain and shortness of breath. The distribution of SpO2 is depicted in Figure 2 . The mean SpO2 varied across devices, both in the entire population as well as those determined to be hypoxic based on a control SpO2 value of <94%, is shown in Tables 2 and 3 . Correlation between test groups and control SpO2 was high ( Table 2 ). The degree of correlation is also illustrated for all the devices by the Bland-Altman plots (Figures 3-5). The more expensive, medical-grade Onyx device showed a narrower distribution of SpO2 readings that more closely mirrored the control values ( Figure 2 ). The Bland-Altman plots also show this visually with fewer outliers in SpO2 readings for Onyx (Figures 3-5 ). The mean difference between the device readings and controls for the entire population was narrow-between 1% and 1.87% for all 3 devices ( Table 2 ). Note that there were 2 missing measurements in the OxyWatch group (N = 198). There were several outliers on individual patients, with SpO2 readings varying from control as much as 23%. In the subgroup of patients with hypoxia (SpO2 ≤94%), the distribution of measurements is also narrow. The mean difference from control readings were 1.95% for OxyWatch, 0.78% for SM, and 0.55% for the Onxy device (Table 3) . Although, there were statistical differences across groups, the clinical difference was less than 2% SpO2. To evaluate the ability of each device to detect hypoxia, we classified the test results as either no hypoxia or hypoxia (SpO2 ≤94). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of each device are shown in Table 4 . All Although the devices were tested on 200 patients, our sample was one of convenience. These were not sequential patients. We performed the study when the authors were available to spend time in the ED. The choice of a cutoff value of 94% for SpO2 is somewhat arbitrary, though consistent with our previous study 20 and the usual definition of normal SpO2 being between 95% and 100%. 21 We also calculated sensitivity analysis using a cutoff of 92% and provided this as a supplemental Nonetheless, an active treatment that was being instituted by the medical team caring for the patient might have improved the patient's saturation over the minute or 2 that it took to take 3 sequential measurements. We purposely included a significant subset of hypoxic patients, but these readings were taken under a controlled environment and by a trained observer, not under austere conditions or by a lay person. It is also possible that the utility of this device in austere conditions may be limited based on external factors (eg, excessive heat or cold). We did not explicitly exclude patients with hypotension, although patients who were critically ill did not represent a large subset of patients because they are often unable to provide consent, and screening/enrolling may have interfered with clinical care. Finally, this study was not blinded. The authors recording the data applied the devices in random order to the patient's finger and the data were collected by 2 separate authors (BM, JG). This minimizes but does not exclude observer bias. Portable pulse oximeters bridge the gap between the hospital and out- All 3 devices had rare outliers of mean differences from control being >5%. These occurred less often with the Onyx device and had the lowest mean difference from control of 1%. However, whether this possible advantage outweighs its almost 10-fold cost difference is questionable. 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. We did not envision our results having applicability to a pandemic of a novel coronavirus (severe acute respiratory syndrome coronavirus 2) that has infected more than 30 million persons and killed nearly 1 million people worldwide as of this writing. 23 The rapidity of spread of the virus and its lethality have overwhelmed healthcare systems worldwide. [24] [25] [26] [27] This has resulted in shortages of medical materials like ventilators for patients in respiratory failure 28 and personal protective equipment (masks, gloves, gowns) to protect health care practitioners. 29 In its more severe form, the disease affects the lungs by causing viral pneumonia, hypoxia, respiratory failure, and death. Overall, there were statistically significant differences between the 3 devices tested; however, the differences were minor and unlikely to be clinically significant. All had sufficient degrees of correlation with the control device, >90% sensitivity, and greater than 80% NPV for hypoxia. Although these devices were not tested in an austere environment or during a global pandemic, we expect that they would perform well under such conditions. Our study provides evidence that these devices can accurately detect hypoxia and may be a useful tool for health care practitioners or patients during this pandemic. Futures studies should analyze whether these findings are applicable to a wider range of ED patients with features not present in our population (hypotension, mechanical ventilation, anemia). Further study in specific environments, such as extreme cold or altitude, might be needed to further elucidate their utility in austere environments. A study of these consumer grade devices in patients suffering with COVID-19 infection would also be useful. The authors thank Jill W. Roberts, M.S., for editing assistance in the preparation of this manuscript. Each author takes public responsibility for appropriate portions of the content and agrees to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.All authors made substantial contributions to conception and design, acquisition of data, and analysis and interpretation of data.All authors were involved in drafting the manuscript or revising it critically for important intellectual content. WS gave final approval of the version to be published. Walter A. Schrading MD https://orcid.org/0000-0002-8303-7882 History of blood gas analysis. VI. 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