Can wearable technology be used to approximate cardiopulmonary exercise testing metrics?

Background: Consumer wrist-worn wearable activity monitors are widely available, low cost and are able to provide a direct measurement of several markers of physical activity. Despite this, there is limited data on their use in perioperative risk prediction. We explored whether these wearables could accurately approximate metrics (anaerobic threshold, peak oxygen uptake and peak work) derived using formalised cardiopulmonary exercise testing (CPET) in patients undergoing high-risk surgery.

Methods: Patients scheduled for major elective intra-abdominal surgery and undergoing CPET were included. Physical activity levels were estimated through direct measures (step count, floors climbed and total distance travelled) obtained through continuous wear of a wrist worn activity monitor (Garmin Vivosmart HR+) for 7 days prior to surgery and self-report through completion of the short International Physical Activity Questionnaire (IPAQ). Correlations and receiver operating characteristic (ROC) curve analysis explored the relationships between parameters provided by CPET and physical activity.

Device Selection: Our choice of consumer wearable device was made to maximise feasibility outcomes for this study. The Garmin Vivosmart HR+ had the longest battery life and best waterproof characteristics of the available low-cost devices.

Results: Of 55 patients invited to participate, 49 (mean age 65.3 ± 13.6 years; 32 males) were enrolled; 37 provided complete wearable data for analyses and 36 patients provided full IPAQ data. Floors climbed, total steps and total travelled as measured by the wearable device all showed moderate correlation with CPET parameters of peak oxygen uptake (peak VO) (R = 0.57 (CI 0.29-0.76), R = 0.59 (CI 0.31-0.77) and R = 0.62 (CI 0.35-0.79) respectively), anaerobic threshold (R = 0.37 (CI 0.01-0.64), R = 0.39 (CI 0.04-0.66) and R = 0.42 (CI 0.07-0.68) respectively) and peak work (R = 0.56 (CI 0.27-0.75), R = 0.48 (CI 0.17-0.70) and R = 0.50 (CI 0.2-0.72) respectively). Receiver operator curve (ROC) analysis for direct and self-reported measures of 7-day physical activity could accurately approximate the ventilatory equivalent for carbon dioxide (V/VCO) and the anaerobic threshold. The area under these curves was 0.89 for V/VCO and 0.91 for the anaerobic threshold. For peak VO and peak work, models fitted using just the wearable data were 0.93 for peak VO and 1.00 for peak work.

Conclusions: Data recorded by the wearable device was able to consistently approximate CPET results, both with and without the addition of patient reported activity measures via IPAQ scores. This highlights the potential utility of wearable devices in formal assessment of physical functioning and suggests they could play a larger role in pre-operative risk assessment.

Ethics: This study entitled "uSing wearable TEchnology to Predict perioperative high-riSk patient outcomes (STEPS)" gained favourable ethical opinion on 24 January 2017 from the Welsh Research Ethics Committee 3 reference number 17/WA/0006. It was registered on ClinicalTrials.gov with identifier NCT03328039.