A symptom-limited incremental step test determines maximum physiological responses in patients with chronic obstructive pulmonary disease
Data
2013-12-01
Autores
Dal Corso, Simone 
Izbicki, Meyer
Malaguti, Carla
Nery, Luiz Eduardo
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Artigo
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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 151 (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 SpO(2) (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. (C) 2013 Elsevier B.V. All rights reserved.
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Respiratory Medicine. London: W B Saunders Co Ltd, v. 107, n. 12, p. 1993-1999, 2013.