title: A symptom-limited incremental step test determines maximum physiological responses in patients with chronic obstructive pulmonary disease.
abstract: 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.
  
  
  OBJECTIVE
  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.
  
  
  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).
  
  
  CONCLUSIONS
  A symptom-limited incremental step test, externally paced, elicits maximal cardiopulmonary and metabolic responses, and is well tolerated and reproducible in patients with COPD.
authors.affiliation: Post-Graduate Program in Rehabilitation Sciences, Universidade Nove de Julho - UNINOVE, Rua Vergueiro 235/249 - 2o subsolo, 01504-001 São Paulo, Brazil. Electronic address: simonedc@uninove.br.
authors.forename: Simone
authors.initials: S
authors.lastname: Dal Corso
authors.forename: Anderson Alves
authors.initials: AA
authors.lastname: de Camargo
authors.forename: Meyer
authors.initials: M
authors.lastname: Izbicki
authors.forename: Carla
authors.initials: C
authors.lastname: Malaguti
authors.forename: Luiz Eduardo
authors.initials: LE
authors.lastname: Nery
mesh_terms: D000368:Aged; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance / Q000502:physiology*; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D014797:Vital Capacity / Q000502:physiology; D016138:Walking / Q000502:physiology
keywords: COPD; Cardiopulmonary exercise test; Exercise tolerance; Field test; Oxygen uptake; Step test