A pilot study of respiratory rate derived from a wearable biosensor compared with capnography in emergency department patients

Purpose: Respiratory rate is assessed less frequently than other vital signs, and documented respiratory rates are often erroneous. This pilot study compared respiratory rates derived from a wearable biosensor to those derived from capnography. Methods: Emergency department patients with respiratory complaints were enrolled and had capnography via nasal cannula and a wireless, wearable biosensor from Philips applied for approximately one hour. Respiratory rates were obtained from both of these methods. We determined the difference between median respiratory rates obtained from the biosensor and capnography and the proportion of biosensor-derived respiratory rates that were within three breaths/minute of the capnography-derived respiratory rates for each patient. A Spearman correlation coefficient was calculated to assess the strength of the correlation between mean respiratory rates derived from both methods. Plots of minute-by-minute respiratory rates, per patient, for each monitoring method were shown to two physicians. The physicians identified time periods in which the respiratory rates appeared invalid. The proportion of time with invalid respiratory rates for each patient, for each method, was calculated and averaged. Results: We analyzed data for 17 patients. Median biosensor-derived respiratory rate was 20 breaths/minute (range: 7–40 breaths/minute) and median capnography-derived respiratory rate was 25 breaths/minute (range: 0–58 breaths/minute). Overall, 72.8% of biosensor-derived respiratory rates were within three breaths per minute of the capnography-derived respiratory rates. Overall mean difference was 3.5 breaths/minute (±5.2 breaths/minute). Respiratory rates appeared invalid 0.7% of the time for the biosensor and 5.0% of the time for capnography. Conclusion: Our pilot study suggests that the Philips wearable biosensor can continuously obtain respiratory rates that are comparable to capnography-derived respiratory rates among emergency department patients with respiratory complaints.