Using Enhanced External Counterpulsation to Recover Cardiovascular Function for Patient of Chronic Diseases

Peak oxygen uptake was measured during symptom-limited cardiopulmonary exercise testing (CPET) performed on a cycle ergometer using a ramp protocol (0 W initial workload with increments of 10-15 W per minute). Breath-by-breath gas exchange was continuously recorded using a metabolic cart. Peak VO₂ was defined as the highest 30-second averaged oxygen uptake during the test and expressed in mL·kg-¹·min-¹. Continuous ECG and pulse oximetry monitoring were performed during the test. Exercise was terminated at volitional fatigue or standardized safety criteria.

The Six-Minute Walk Test (6MWT) was used to assess aerobic capacity and endurance. Participants were instructed to walk at their maximal comfortable pace back-and-forth along a 30-meter corridor for 6 minutes, and the total distance walked (in meters) was recorded. One practice trial was done at baseline to familiarize patients, followed by a measured 6MWT at baseline and again within one week after completing EECP. Standard encouragement and stopping criteria were applied.

Resting blood pressure (BP) (systolic and diastolic) and resting heart rate were measured after 5 minutes seated, at baseline and post-intervention. We also tracked any change in these vital signs immediately before and after individual EECP sessions to monitor acute effects. For analysis, we focused on the baseline vs post-intervention resting BP and HR changes.

Physical health status was assessed using the PROMIS Adult Health Profile short form. The Physical Health domain includes items related to fatigue, pain, and physical functioning. Scores were calculated using a summed short-form scale ranging from 4 to 20, with higher scores indicating better physical health.

Mental health status was assessed using the PROMIS Adult Health Profile short form. The Mental Health domain includes items related to depression, anxiety, and social role functioning. Scores were calculated using a summed short-form scale ranging from 4 to 20, with higher scores indicating better mental health.

Sleep disturbance was evaluated using the PROMIS Sleep Disturbance domain. This measure assesses perceived sleep quality and sleep-related problems, with higher scores indicating greater sleep disturbance.

Cardiovascular health status was assessed using the Seattle Angina Questionnaire-7 (SAQ-7), a validated instrument evaluating angina frequency, physical limitation, and disease-specific quality of life related to coronary artery disease. Scores range from 0 to 100, with higher scores indicating fewer angina symptoms and better quality of life.

Respiratory symptom burden was measured using the COPD Assessment Test (CAT), an 8-item questionnaire evaluating symptoms such as cough, dyspnea, chest tightness, and energy level. Total scores range from 0 to 40, with lower scores indicating fewer respiratory symptoms.

Breathlessness severity was evaluated using the Rose Dyspnea Scale (RDS), a 4-item scale assessing dyspnea during physical activities. Scores range from 0 to 4, with higher grades indicating more severe dyspnea.

Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), a validated questionnaire measuring sleep quality and disturbances over the previous month. The instrument includes seven components that generate a global score ranging from 0 to 21. Higher scores indicate worse sleep quality, and a global score greater than 5 indicates poor sleep quality.