Smartwatches in Respiratory Care: Ready for Prime Time or Stick to Telling Time?

Respiratory therapists and other clinicians have, for several years, relied on clinical information derived from noninvasive monitors.¹ The use of noninvasive monitoring offers various advantages that include convenience, cost-effectiveness, continuous monitoring capabilities, and reduced patient discomfort compared with invasive methods.^2,3 However, despite technologic advancements, certain limitations still exist with some noninvasive monitors. For instance, pulse oximetry, a widely used noninvasive monitoring technology, has long been found inaccurate in some individuals, particularly those with darker skin.⁴ The known inaccuracies of pulse oximetry have prompted researchers to propose strategies to mitigate the harmful effects of occult hypoxemia until more reliable technology is developed for different populations and conditions.⁵

With acknowledging the limitations of noninvasive monitoring, researchers are continuously working to validate noninvasive monitoring use in clinical settings.^3,6 By understanding both the benefits and limitations of evolving technology, clinicians can effectively incorporate it into their practices. However, keeping up with technologic advancements can be challenging, even for those who consider themselves tech savvy. A relatively new type of noninvasive technology that clinicians now must contend with is wearables. Wearables, such as smartwatches (eg, Apple Watch [Apple, Cupertino, California], Fitbit [Fitbit, San Francisco, California], Samsung Smartwatch [Samsung Electronics, Seoul, South Korea]), are small electronic devices or computers that can be worn and that have monitoring capabilities.⁷ Over the past 15 years, there has been a proliferation of wearable technologies, such as smartwatches, in our society.^7,8 This influx of commercially available monitoring devices has prompted researchers to investigate their usefulness for various clinical conditions.

In this issue of Respiratory Care, Støve et al⁹ sought to assess the accuracy of 2 wearable devices with integrated pulse oximetry technology for patients with COPD. The authors chose the Apple Watch Series 7, OS 8.51 and the Garmin Vivosmart 4 (Garmin International, Olathe, Kansas), both of which had been evaluated in previous studies for agreement with comparator devices and accuracy in related biologic data. Data provided by the wearable devices were compared with a standard finger pulse oximeter, the Contec Pulse Oximeter CMS50D (Contec Medical Systems, Qinhuangdao, Hebei, China). Study participants, all diagnosed with COPD, were simultaneously fitted with all 3 devices and asked to perform a standardized exercise protocol. For the Apple Watch Series 7 and the Garmin Vivosmart, the root mean square error was 3.5% and 3.3% at rest, 4.1% and 6.1% after 30-s sit-to-stand test, and 3.9% and 5.4% after the 6-min walk test, respectively. The authors observed that the Apple Watch 7 and the Garmin Vivosmart 4 tended to overestimate oxygen saturation when ${\text{S}}_{{\text{pO}}_{\text{2}}}$ was < 95% and underestimate ${\text{S}}_{{\text{pO}}_{\text{2}}}$ when oxygen saturation was > 95%. Consequently, they advised against using wearable devices to monitor oxygen saturation during pulmonary rehabilitation.

The strengths of this study include the inclusion of patients at risk for hypoxemia and the simultaneous measurement of ${\text{S}}_{{\text{pO}}_{\text{2}}}$ between the wearable devices and the standard pulse oximeter. Patients at risk for hypoxemia are more likely to need regular pulse oximetry monitoring. Although studies that demonstrated accurate assessment of ${\text{S}}_{{\text{pO}}_{\text{2}}}$ in healthy individuals are quite interesting, they do not sufficiently inform clinicians about the utility of these devices in individuals who are hypoxemic or in those prone to becoming hypoxemic.^10,11 Simultaneous measurements ensure that the devices were compared during periods of hypoxemia because wearable devices seem to perform poorly when oxygen saturations are low.¹² These study results align with a previous evaluation by Modi et al,¹³ who assessed smartphone pulse oximetry during a 6-min walk test. In that study, the Apple iPhone 6S with an attached external finger probe pulse oximeter (Kenek Edge, LionsGate Technologies, Vancouver, Canada) and a Samsung S8 with built-in pulse oximetry were compared with a Masimo pulse oximeter with a forehead probe (Masimo, Irvine, California). As with the Støve et al⁹ study, Modi et al¹³ noted that smartphone ${\text{S}}_{{\text{pO}}_{\text{2}}}$ values were consistently lower than those measured by the hospital device. These researchers also recommended against this newer commercially available technology for patients at risk for hypoxemia.

It is important to note that the study conducted by Støve et al⁹ had several limitations. The sample size was relatively small and the comparison of devices was not made to arterial oxygen saturation. To accurately evaluate the Apple Watch Series 7 and the Garmin Vivosmart, the authors would have had to calculate the root mean square of the differences between the measured and actual values, the reporting standard used by the FDA. However, due to the practical constraints of the study, blood oximetry was not feasible, which limits the interpretation of the findings.

The future of physiologic monitoring holds great potential because wearable devices such as smartwatches offer a convenient and promising avenue for early detection and continuous monitoring of various health conditions.⁸ Fields such as sleep medicine and cardiology are exploring the use of wearables to monitor conditions such as sleep-disordered breathing and atrial fibrillation, and the performance and accuracy of these devices show promising results.^14-17 However, as we embrace this technology with enthusiasm, we must be cautious of its application in clinical decision making. Many wearable devices have monitoring capabilities but no FDA approval, and the rapid advancement of technology means that device updates and software versions can impact their performance. Furthermore, there is a legitimate concern that some wearable monitors may generate erroneous data, potentially causing undue psychological distress.¹⁸

To gain a clearer understanding of the accuracy and performance of smartwatches and similar wearable devices for individuals with health conditions, further research studies such as the one conducted by Støve et al⁹ are necessary. Presently, smartwatches are not fully prepared for extensive clinical use or ready for prime time in respiratory care; for now, it seems that they are most suitable for entertainment, fitness tracking, and telling time.