Comparison of cardiorespiratory responses between the incremental step test and the cardiopulmonary exercise test in people with chronic obstructive pulmonary disease

Introduction and objectives: The incremental step test (IST) is designed for people with COPD, but its cardiorespiratory response remains unknown. This study aimed to assess the cardiorespiratory response of the IST and compare it to CPET in people with COPD. Materials and methods: This cross-sectional study was conducted at a pulmonary rehabilitation centre in a general hospital. Participants completed the CPET (cycle ergometer) followed by the IST. Gas exchange, HR, %SpO₂, dyspnea and leg fatigue (modified Borg scale) were collected. Results: Twenty adults (67.8±8.62 years; 60% men) with stable COPD were included. At peak effort, VO₂ was similar between IST (15.6±3.4ml/kg/min) and CPET (14.7±3.3ml/kg/min), p>0.05. Similar results were observed in V_E (IST: 41.3±11.6ml/min; CPET: 44.2±12.7ml/min), HR (IST: 122±21bpm; CPET: 124±22bpm), and Δdyspnea (IST: 3.5 [2–4]; CPET: 3 [3,4]), p>0.05. VCO₂ (IST: 14.9±3.6ml/kg/min; CPET: 15.9±3.7ml/kg/min), RER (IST: 0.94±0.09; CPET: 1.07±0.11), Δ%SpO₂ (IST: −2.50 [−7; −0.25]%; CPET: 0.5 [−2; 1]%) and Δleg fatigue (IST: 3.75 [0.125; 5.0]; CPET: 4 [3.0; 7.0]) were significantly lower on the IST, p<0.05. Median V_E/MVV percentage was greater than 80% during both the IST (91.4 [73.4; 101.1]%) and the CPET (100.8 [78.4; 110.5]%). Conclusions: IST showed a cardiorespiratory response similar to the response observed during CPET, in terms of VO₂, V_E, HR and dyspnea. The ventilatory limitation can be a limiting factor in IST performance, which showed that this test can be considered a symptom-limited option to assess exercise capacity.