Accuracy of vital sign monitoring using a photoplethysmography upper arm wearable device in postoperative non-cardiac surgery patients: a prospective observational clinical validation study

Vital sign monitoring in patients is essential for the early detection of deterioration of vital signs and timely medical intervention especially on general wards in hospitals. Traditionally performed manually and intermittently, wearable monitoring devices offer a promising alternative by automatically providing real-time, continuous data. In this prospective observational study in non-cardiac surgery patients, we aim to evaluate the accuracy of respiratory rate (RR), heart rate (HR), and peripheral oxygen saturation (SpO₂) measurements obtained from a photoplethysmography (PPG)-based upper arm wearable device viQtor® (smartQare, Eindhoven, The Netherlands), by simultaneously comparing its readings with standard monitoring equipment in the Post-Anesthesia Care Unit (PACU). Capnography was included as the gold-standard reference for RR. Agreement between the wearable and reference measurements were assessed using Bland–Altman analyses. Clinical accuracy was evaluated using Clarke Error Grid analyses. Vital sign data were collected from 42 postoperative patients (age: 65.5 years [IQR 37.4–74.7]; BMI: 24.1 kg/m2 [IQR 21.7–26.9]) over a median duration of 14.0 hours. The Average Root Mean Square (ARMS) between the wearable device and the reference for RR was 2.85 BRPM, with a bias of -0.40 (95% LoA –5.85 to 5.04); for HR 2.01 BPM, with a bias of 0.08 (95% LoA -3.83 to 3.99); and for SpO2 2.08%, with a bias of –0.03 (95% LoA –4.14 to 4.09). The viQtor® device demonstrated high accuracy for RR, HR, and SpO₂ in postoperative patients. Data availability was high across all three parameters, and patient satisfaction was excellent. These findings support its potential for continuous monitoring on general wards.