Physiological responses to the six minute walk test and maximal exercise testing in pulmonary hypertension

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Morris, N
Lin, A
Harris, J
Sabaratnam, M
Feenstra, J
Seale, H
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Adelaide, Australia


Introduction/Aim The six minute walk test (6MWT) remains the most commonly used clinical measure of exercise capacity in pulmonary hypertension (PH). Whilst maximal exercise testing using a cardiopulmonary exercise test (CPET), remains the gold standard estimate of exercise capacity, this test is much less common in clinical practice. The purpose of this study was to compare the physiological responses to the 6MWT and CPET in a group of PH subjects.

Methods Eighteen individuals with Group I/IV PH patients (Functional Class I‐III) completed a CPET on a cycle ergometer and a 6MWT on separate days. During both tests, gas exchange was measured using a calibrated portable metabolic system (Cortex, Metamax). Oxygen uptake (VO2), carbon dioxide production (VCO2), ventilation (VE), heart rate (HR), oxygen (O2) pulse, VE/VCO2, end tidal carbon dioxide (PETCO2), oxygen saturation (SPO2) and breathlessness (Borg, 0‐10) were averaged over the final 30s and compared between the 6MWT and CPET. In a subgroup of 8 participants, end exercise lactate (HLa) was also measured using a portable lactate analyser (Lactate Scout).

Results The mean peak power achieved by participants was 74 ± 20 W, whilst the mean 6MWT distance was 574 ± 89m. There was no significant difference between CPET and the 6MWT for peak VO2 (CPET: 16.3±6.6 vs 6MWT: 15.5±3.8‐1.min‐1), VE (54.7±13.8 vs 49.7±15.8 L.min‐1), HR (136±22 vs 143±27 beats.min‐1), O2 pulse (6.8±1.3 vs 7.0±1.7 ml.beat ‐1), VE/VCO2 (35±6 vs 36±5), PETCO2 (30±5 vs 29±4 mmHg) or SpO2 (88±11 vs 87 ± 14%). Peak VCO2 (1.43±0.46 vs 1.20±0.31 L.min‐1), breathlessness (5.5±2.2 vs 3.6±1.9) and lactate (8.5±1.5 vs 5.0±1.9) were all significantly higher(p<0.05) with CPET.

Conclusion We found that the physiological responses to CPET and 6MWT in our group of PH participants were similar. This would suggest that the 6MWT is similar to a peak exercise challenge the PH population.

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Morris, N; Lin, A; Harris, J; Sabaratnam, M; Feenstra, J; Seale, H, Physiological responses to the six minute walk test and maximal exercise testing in pulmonary hypertension, Respirology, 2018, 23, pp. 77-77