title: Non-invasive ventilation improves peripheral oxygen saturation and reduces fatigability of quadriceps in patients with COPD.
abstract: OBJECTIVE
  Non-invasive ventilation (NIV) might improve peripheral muscle function and exercise capacity in severely disabled patients. This study evaluated the physiological impact of NIV on isokinetic concentric strength and endurance of lower limb muscles in patients with severe COPD.
  
  
  METHODS
  This clinical trial tested COPD patients (n = 24) and healthy subjects (n = 18). Subjects underwent isokinetic dynamometry tests while given either bi-level positive airway pressure ventilation (BV) or sham ventilation (SV), in a randomized order with 30 min of rest prior to each intervention. The inspiratory level of BV was set up to 14 cm H(2)O and expiratory pressure up to 6 cm H(2)O. Peripheral oxygen saturation (SpO(2)), heart rate (HR), systolic (SBP) and diastolic blood pressure (DBP) at the peak of exercise were measured for each intervention.
  
  
  RESULTS
  Compared with controls, COPD patients had lower values of SpO(2) and HR (P < 0.01) during both BV and SV and lower values of DBP (P < 0.01) during BV. BV improved SpO(2) (P < 0.01), and reduced SBP in both COPD (P < 0.01) and control groups (P < 0.05) and reduced DBP in COPD patients (P < 0.01). BV also reduced the fatigue index in COPD patients when compared with SV (P = 0.003). Variation (BV-SV) of total work at the peak of the test was higher in the control group than in the COPD group (P < 0.05).
  
  
  CONCLUSIONS
  BV improved SpO(2) and reduced the fatigability of the quadriceps muscle in patients with severe COPD. These results support the need for further evaluation of BV as adjunct during high-intensity strength exercise training in these patients.
authors.affiliation: Cardiopulmonary Physiotherapy Laboratory, Nucleus of Research in Physical Exercise, Federal University of São Carlos, São Paulo, Brazil. audrey@ufscar.br
authors.forename: Audrey
authors.initials: A
authors.lastname: Borghi-Silva
authors.forename: Luciana
authors.initials: L
authors.lastname: Di Thommazo
authors.forename: Camila B F
authors.initials: CB
authors.lastname: Pantoni
authors.forename: Renata G
authors.initials: RG
authors.lastname: Mendes
authors.forename: Tania De Fátima
authors.initials: Tde F
authors.lastname: Salvini
authors.forename: Dirceu
authors.initials: D
authors.lastname: Costa
mesh_terms: D000368:Aged; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology / Q000628:therapy*; D052097:Quadriceps Muscle / Q000503:physiopathology*; D012129:Respiratory Function Tests; D016896:Treatment Outcome