Trial participants from Queen Mary Hospital and the University of Hong Kong will be recruited. Potential participants will be contacted and provided with a detailed explanation of the study, including its purpose, procedures, risks, and benefits. Written informed consent will be obtained from all participants before enrolment. This process involves providing individuals with the informed consent document, allowing time for review and questions, and obtaining their signature if they agree to participate. Participants will receive a copy of the signed consent form for their records.
At Visit 1, Comprehensive demographic and clinical data will be collected from each participant, Clinical Management System (CMS), Electronic Patient Record (ePR), and Clinical Data Analysis and Reporting System (CDARS) of the Hospital Authority in Hong Kong. This will include age, sex, height, weight, body mass index, and detailed medical history focusing on cardiovascular conditions. Information about current medications and smoking status will also be recorded. Additionally, participants will undergo a baseline clinical examination, including blood pressure measurement, heart rate, and a 12-lead electrocardiogram.
Participants will undergo a conventional cardiopulmonary exercise test (CPX) to determine their maximal oxygen uptake (VO2max) at Visit 1. This test will be conducted in a controlled clinical setting under the supervision of cardiologists. Participants will exercise on a treadmill while their respiratory gas exchange is measured using a metabolic cart. The exercise intensity will be gradually increased until the participant reaches volitional exhaustion or predetermined safety criteria are met. The highest oxygen uptake value achieved during the test will be recorded as the VO2max. Participant will concurrently be wearing the investigational smartwatch for pre- and post-SaO2 and VO2max assessment. This gold-standard measurement will serve as the reference for validating the smartwatch's continuous VO2max estimation.
The 6-minute walk distance will be assessed in a hospital setting at Visit 2 under the supervision of a research staff. Participants will be instructed to walk as far as possible in six minutes along a predetermined course, typically a straight hallway. The total distance walked will be measured and recorded. During the test, the research nurse will monitor the participant's heart rate, blood oxygen saturation, and perceived exertion at regular intervals. Participant will concurrently be wearing the investigational smartwatch for pre- and post SaO2 and VO2max assessment.
Participants will be provided with a medical-grade pulse oximeter for home use. They will be instructed to measure their oxygen saturation once daily throughout the one-week study period. Measurements should be taken at approximately the same time each day, preferably in the morning after waking and before any strenuous activity. Participants will record their oxygen saturation readings in a provided log. These daily measurements will serve as reference points for validating the continuous oxygen saturation data collected by the smartwatch.
