A symptom-limited incremental step test determines maximum physiological responses in patients with chronic obstructive pulmonary disease

Summary

Background

Step tests have been used to evaluate exercise tolerance and effort-related hypoxemia in different diseases. A symptom-limited incremental step test (IST) has never been tested in COPD patients.

Aim

To compare maximal physiological responses between an IST and cardiopulmonary exercise testing (CPET), to test the reproducibility of the IST on different days, and to provide a predict equation to estimate VO₂ from the IST in patients with COPD.

Material and methods

At the same day, thirty-four patients (VEF₁ 46 ± 14% of pred) underwent a CPET on cycle ergometer and the first IST (IST-1) (1 h apart). After 2–5 days, patients repeated the IST (IST-2). Pulmonary gas exchange was measured during all tests.

Results

Peak VO₂ was significantly higher in IST-1 and IST-2 than in CEPT (Mean ± SD: 1.19 ± 0.39 L, 1.20 ± 0.40 L, 1.07 ± 0.35 L) with no difference for ventilation (VE), heart rate (HR), and perception of effort. ISTs were highly reproducible, with significant intraclass correlation coefficient (CCI [95% confidence interval]) for number of steps (0.98[0.95–0.99]), VO₂ (0.99 [0.98–0.99]), VE (0.97[0.93–0.99]), HR (0.92[0.81–0.97]), and SpO₂ (0.96[0.90–0.98]). Desaturation was significantly higher for IST-1 and IST-2 compared with cycling (Mean ± SD: −6 ± 5%, −6 ± 4%, −3 ± 3%). Number of steps and patient weight explained 81% of the variance in peak VO₂ (p < 0.001).

Conclusion

A symptom-limited incremental step test, externally paced, elicits maximal cardiopulmonary and metabolic responses, and is well tolerated and reproducible in patients with COPD.