title: Physiologic effects of an ambulatory ventilation system in chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Exercise intolerance limits the ability of patients with chronic obstructive pulmonary disease (COPD) to perform daily living activities. Noninvasive ventilation reduces dyspnea and improves exercise performance, but current systems are unsuitable for ambulatory use.
  
  
  OBJECTIVE
  In patients with COPD experiencing exercise-induced desaturation, we evaluated improvements in exercise tolerance facilitated by a wearable, 1-lb, noninvasive open ventilation (NIOV) system featuring a nasal pillow interface during constant work rate (CWR) cycle ergometer exercise and associated effects on dyspnea, respiratory muscle activation, and pulmonary gas exchange efficiency.
  
  
  METHODS
  Fifteen men with COPD (FEV₁ = 32.2 ± 12.0% predicted; FEV₁/FVC = 31.6 ± 7.1%; exercise oxygen saturation as measured by pulse oximetry [Spo₂] = 86.5 ± 2.9%) participated. After incremental testing establishing peak work rate, subjects completed three visits in which they performed CWR exercise to tolerance at 80% peak work rate: (1) unencumbered breathing room air, (2) using NIOV+compressed air, (3) using NIOV+compressed O₂, or (4) using O₂ via nasal cannula. Assessments included exercise duration, surface inspiratory muscle EMG, Spo₂, transcutaneous Pco₂, and Borg dyspnea scores.
  
  
  RESULTS
  Exercise endurance was 17.6 ± 5.7 minutes using NIOV+O₂, greatly prolonged compared with unencumbered (5.6 ± 1.9 min), nasal O₂ (11.4 ± 6.8 min), and NIOV+Air (6.3 ± 4.1 min). Isotime Spo₂ was higher and intercostal, scalene, and diaphragmatic EMG activity was reduced using NIOV+O₂ compared with unencumbered, nasal O₂, and NIOV+Air, signifying respiratory muscle unloading. Isotime dyspnea reduction correlated with isotime EMG reduction (r = 0.42, P = 0.0053). There were no significant differences in isotime VD/VT or transcutaneous Pco₂ among treatments.
  
  
  CONCLUSIONS
  NIOV+O₂ yielded substantial exercise endurance improvements accompanied by respiratory muscle unloading and dyspnea reductions in patients with severe hypoxemic COPD.
authors.affiliation: Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA 90502, USA.
authors.forename: Janos
authors.initials: J
authors.lastname: Porszasz
authors.forename: Robert
authors.initials: R
authors.lastname: Cao
authors.forename: Richard
authors.initials: R
authors.lastname: Morishige
authors.forename: Leo A
authors.initials: LA
authors.lastname: van Eykern
authors.forename: Alex
authors.initials: A
authors.lastname: Stenzler
authors.forename: Richard
authors.initials: R
authors.lastname: Casaburi
mesh_terms: D000368:Aged; D000553:Ambulatory Care / Q000379:methods*; D004867:Equipment Design; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D063087:Noninvasive Ventilation / Q000295:instrumentation*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000628:therapy; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012129:Respiratory Function Tests; D012132:Respiratory Muscles / Q000503:physiopathology