title: Do field walking tests produce similar cardiopulmonary demands to an incremental treadmill test in obese individuals with treated OSA?
abstract: BACKGROUND
  Cardiorespiratory fitness, assessed during cardiopulmonary exercise tests by peak oxygen uptake (Vo2pk), is an independent predictor of mortality in obesity. We investigated whether Vo2pk and systemic responses measured during field walking tests were similar to those measured during an incremental treadmill test (ITMT) in obese individuals with treated OSA.
  
  
  METHODS
  Individuals with treated OSA and a BMI > 30 kg/m2 were recruited. Participants completed an ITMT, two 6-min walk tests (6MWTs), and two incremental shuttle walk tests (ISWTs) on three separate days in a randomized order. Expired gas analysis was performed during all tests.
  
  
  RESULTS
  The study was completed by 16 patients (nine men) (mean [SD] age, 58 [12] y; BMI, 36.1 [7.6] kg/m2). There was no difference (P = .27) in Vo2pk assessed by the ITMT and the ISWT (2,266 [478] and 2,017 [561] mL/min, respectively). The Vo2pk measured by the 6MWT (1,778 [360] mL/min) was lower than that measured by the ITMT (P < .01). The limits of agreement for Vo2pk between the ISWT and the ITM were ± 730 mL/min. Cardiorespiratory responses during the ISWT and the ITMT reflected a graded response to a peak, whereas the 6MWT demonstrated a rapid rise to a plateau.
  
  
  CONCLUSIONS
  The ISWT can be used instead of an ITMT and in preference to the 6MWT to assess cardiorespiratory fitness for a cohort of obese people with treated OSA. However, the imprecision of the agreement in Vo2pk between the ITMT and ISWT means they cannot be used interchangeably in an individual.
  
  
  BACKGROUND
  ClinicalTrials.gov; No.: NCT01930513; www.clinicaltrials.gov.
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, England; Department of Medicine, University of Toronto, Toronto, ON, Canada. Electronic address: rachael.evans@uhl-tr.nhs.uk.
authors.forename: Rachael A
authors.initials: RA
authors.lastname: Evans
authors.affiliation: Department of Respiratory Diagnostic & Evaluation Services, West Park Healthcare Centre, Toronto, ON, Canada; Department of Respiratory Medicine, West Park Healthcare Centre, Toronto, ON, Canada.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Dolmage
authors.affiliation: Department of Respiratory Medicine, West Park Healthcare Centre, Toronto, ON, Canada; Department of Physical Therapy (Ms Robles, Dr Goldstein, and Prof Brooks), University of Toronto, Toronto, ON, Canada.
authors.forename: Priscila G
authors.initials: PG
authors.lastname: Robles
authors.affiliation: Department of Respiratory Medicine, West Park Healthcare Centre, Toronto, ON, Canada; Department of Respiratory Diagnostic & Evaluation Services, West Park Healthcare Centre, Toronto, ON, Canada; Department of Medicine, University of Toronto, Toronto, ON, Canada; Department of Physical Therapy (Ms Robles, Dr Goldstein, and Prof Brooks), University of Toronto, Toronto, ON, Canada.
authors.forename: Roger S
authors.initials: RS
authors.lastname: Goldstein
authors.affiliation: Department of Respiratory Medicine, West Park Healthcare Centre, Toronto, ON, Canada; Department of Physical Therapy (Ms Robles, Dr Goldstein, and Prof Brooks), University of Toronto, Toronto, ON, Canada.
authors.forename: Dina
authors.initials: D
authors.lastname: Brooks
mesh_terms: D003430:Cross-Sectional Studies; D005080:Exercise Test / Q000379:methods*; D005081:Exercise Therapy / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology*; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000401:mortality / Q000534:rehabilitation*; D009864:Ontario / Q000453:epidemiology; D010101:Oxygen Consumption / Q000502:physiology; D011446:Prospective Studies; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D015996:Survival Rate / Q000639:trends; D016138:Walking / Q000502:physiology*