Performance Comparison of Oximetry Devices During 6-Minute Walk Tests

Background: Pulse oximetry is a common technique used to measure S_pO2, with increasing numbers of portable devices of different designs and technical specifications. This study examined accuracy of commercial and medical-grade portable oximetry devices (BioBeat wristwatch, Nonin WristOx₂ 3150, and Heart Sure A320) in measuring S_pO2 compared with the reference standard (Masimo Rad-5) during 6-min walk tests (6MWTs). Methods: This prospective study included 50 subjects, with 10 recruited for each of the five target groups, including COPD, interstitial lung disease, pulmonary hypertension, oxygen therapy users, and other cardiac/respiratory diseases. All subjects underwent 6MWT using the reference standard and the three test oximetry devices. Accuracy was measured by comparing mean nadir S_pO2. Subjects were asked to rate their preference for different oximetry devices at test completion. Results: In contrast to the Masimo, the Nonin had lower nadir and mean S_pO2 (P ≤ .001 for both), with higher measurements for the BioBeat (P < .001 for both) and no differences for the Heart Sure (P = .18 for nadir S_pO2, P = .96 for mean S_pO2). Time spent at S_pO2 ≤ 88 was higher for the Nonin (70%, P < .001) but lower for the Heart Sure (58%, P < .001), compared with the Masimo (64%). There were no significant differences observed in peak heart rate measurements between the Masimo with the Nonin and BioBeat (P < .05 for both), with lower measurements using the Heart Sure (P < .001). The BioBeat was most preferable amongst subjects (n = 31), with all test oximeters having high patient satisfaction (mean \7-point Likert scale scores of 6-7). Conclusion: The Heart Sure A320 and Nonin Wrist-Ox₂ 3150 had comparable performance in detecting nadir S_pO2 within a mean difference of 3% in comparison with the Masimo Rad-5, with potential use for remote monitoring.