title: Pursed lip breathing improves exercise tolerance in COPD: a randomized crossover study.
abstract: BACKGROUND
  Although pursed-lip breathing (PLB) has been advocated to reduce respiratory rate and improve oxygen saturation in patients with chronic obstructive pulmonary disease (COPD) at rest, the evidence of its effects on dynamic hyperinflation (DH) and exercise tolerance is scarce.
  
  
  OBJECTIVE
  To evaluate the effect of PLB on exercise tolerance, breathing pattern, dynamic hyperinflation and arterial oxygenation in COPD patients during high-intensity exercise.
  
  
  METHODS
  Randomized crossover study.
  
  
  METHODS
  Laboratory of Respiration Physiology, Federal University of Rio de Janeiro.
  
  
  METHODS
  Forty stable COPD patients aged 40-75 years and with FEV1<60%.
  
  
  METHODS
  In a randomized order, all patients performed PLB and control breathing (CB) during constant work-rate exercise in an electrically-braked cycloergometer. Dynamic hyperinflation, oxygen saturation and breathing pattern were recorded at rest, in isotime and in peak exercise.
  
  
  RESULTS
  The nine patients who increased their endurance time by more than 25% during PLB (6.42 ± 2.36 vs. 10.51 ± 3.83 min; P < 0.05) were considered as the Improver sub-group. Compared to the Non-improver subgroup, these patients presented a lower expiratory peak flow - EPF (40.2 ± 8.6 vs. 53.3 ± 17.8 % predicted, P<0.05). The ROC Curve analysis of the EPF as a percentage of the predicted values (%pred) was performed to identify cut-off values that had greater sensitivity and specificity in differentiating between IMPROVER and NON-IMPROVER. We observed 61% sensitivity and 89% specificity with a 47.7% pred EPF. At isotime, PLB yielded higher inspiratory capacity (IC) and oxygen saturation (1.19 ± 0.33 to 1.35 ± 0.39 L; P < 0.05 and 93.1 ± 4.6 to 94.0 ± 4.1%; P<0.05), and lower respiratory rate than CB only in Improver. Non-improver patients showed thoracoabdominal asynchrony during PLB in isotime. At peak exercise, PLB improved the arterial oxygenation in Improver, but there were no changes in the breathing pattern in the analyzed subgroups.
  
  
  CONCLUSIONS
  In COPD patients with low PEF, pursed-lip breathing reduces dynamic hyperinflation and improves exercise tolerance, breathing pattern and arterial oxygenation at submaximal intensity exercise.
  
  
  CONCLUSIONS
  This study points to a possible application of PLB in a selected group of COPD patients aiming at improving the exercise tolerance. PEF measurements can help to indicate PLB for COPD patients.
authors.affiliation: Physical Therapy School, Federal University of Juiz de Fora, Juiz de Fora, Brazil - fguimaraes_pg@yahoo.com.br.
authors.forename: L Ferracini
authors.initials: LF
authors.lastname: Cabral
authors.forename: T Da Cunha
authors.initials: Tda C
authors.lastname: D'Elia
authors.forename: D De Sousa
authors.initials: Dde S
authors.lastname: Marins
authors.forename: W Araujo
authors.initials: WA
authors.lastname: Zin
authors.forename: F Silva
authors.initials: FS
authors.lastname: Guimarães
mesh_terms: D000328:Adult; D000368:Aged; D018592:Cross-Over Studies; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D029424:Pulmonary Disease, Chronic Obstructive / Q000534:rehabilitation*; D012119:Respiration; D013147:Spirometry