Development of an individualized treadmill ramp protocol for cardiopulmonary exercise testing in people with cardiovascular disease based on a reference equation for the six-minute walk distance

Abstract Background Cardiopulmonary exercise test (CPX) is a key component in the assessment of cardiovascular diseases (CVD). Although ramp protocols are recommended for CPX, they often rely on subjective speed and grade selection. Purpose To develop a standardized and individualized treadmill CPX ramp protocol based on a reference equation for the six-minute walk distance (6MWD) in people with CVD. Methods We developed a treadmill CPX protocol based on the Brazilian reference equation for the 6MWD. Using the predicted distance, we calculated the speed (6MWS) in km/h (6MWD/3600*3.6). The protocol starts at 50% of the 6MWS and a 0% grade. It progresses at an individualized rate to reach 110% of the 6MWS and 10% grade within 10 minutes. Peak oxygen uptake (pVO2) of the protocol was estimated (0.1*speed) + (1.8*grade*speed) + 3.5. We also calculated peak workload (pWL = weight*9.81*speed*grade) and the WL increment rate (W/min). To test the protocol, individuals with stable CVD were included. The CPX recommendations to define the tests as maximum were followed. pVO2 and peak heart rate (pHR) were analyzed, and ventilatory thresholds (VTs) were identified by visual analysis. Data were compared using the paired samples t-test, with p0.05. Results Thirty-two participants (60.6±10 years, 23 males) were included. The most frequent diagnosis was coronary artery disease (n=29, 91%), and all participants used beta-blockers. The initial speed was 2.7±0.2km/h, the predicted final speed was 5.9±0.4 km/h, the estimated pWL and pVO2 were, respectively, 130.2±34.7W and 31.5±1.98ml/kg/min. The average test duration was 10.2±1.6minutes, and the peak RER was 1.21±0.11. All tests were considered maximum effort; just one was interrupted (angina). Peak speed (6.1±0.7km/h), peak grade (10.1±1.5%), and pWL (133.0±34.7W) were similar to the estimated values (p=0.241, 0.682, and 0.417, respectively). pVO2 was 18.1±4.7ml/kg/min (61.8±17.5% of predicted) and pHR was 130.7±20bpm (92.9±14.5% of predicted). The WL increase rate was 9.2±1.8 W/min, and the VO2/WL ratio was 10.7±2.3 ml/min/W. VTs were identified in all tests, within acceptable ranges. VT values were: VT1: VO2 = 11.0±2.2ml/kg/min (62.2±10.6% of pVO2; 38.1±12% of VO2predicted); HR = 90.8±11.7bpm (70±8.7% of pHR); VT2: VO2 = 15.6±4.3ml/kg/min (85.7±8.3% of pVO2); HR = 112.5±17bpm (86.6±6.7% of pHR). Conclusion The developed protocol is a standardized, individualized treadmill ramp protocol that adheres to international CPX recommendations. This new CPX protocol has been shown to be suitable for assessing individuals with CVD, inducing maximal responses within an appropriate timeframe, and enabling identification of the VTs.