title: Continuous positive airway pressure increases inspiratory capacity of COPD patients.
abstract: OBJECTIVE
  Hyperinflation with a decrease in inspiratory capacity (IC) is a common presentation for both unstable and stable COPD patients. As CPAP can reduce inspiratory load, possibly secondary to a reduction in hyperinflation, this study examined whether CPAP would increase IC in stable COPD patients.
  
  
  METHODS
  Twenty-one stable COPD patients (nine emphysema, 12 chronic bronchitis) received a trial of CPAP for 5 min at 4, 7 and 11 cmH(2)O. Fast and slow VC (SVC) were measured before and after each CPAP trial. In patients in whom all three CPAP levels resulted in a decreased IC, an additional trial of CPAP at 2 cmH(2)O was conducted. For each patient, a 'best CPAP' level was defined as the one associated with the greatest IC. This pressure was then applied for an additional 10 min followed by spirometry.
  
  
  RESULTS
  Following application of the 'best CPAP', the IC and SVC increased in 15 patients (nine emphysema, six chronic bronchitis). The mean change in IC was 159 mL (95% CI: 80-237 mL) and the mean change in SVC was 240 mL (95% CI: 97-386 mL). Among these patients, those with emphysema demonstrated a mean increase in IC of 216 mL (95% CI: 94-337 mL). Six patients (all with chronic bronchitis) did not demonstrate any improvement in IC.
  
  
  CONCLUSIONS
  The best individualized CPAP can increase inspiratory capacity in patients with stable COPD, especially in those with emphysema.
authors.affiliation: Intensive Care Unit, State University of Campinas, Brazil.
authors.forename: Silvia M T P
authors.initials: SM
authors.lastname: Soares
authors.forename: Rosmari A R A
authors.initials: RA
authors.lastname: Oliveira
authors.forename: Suelene A
authors.initials: SA
authors.lastname: Franca
authors.forename: Silvio M
authors.initials: SM
authors.lastname: Rezende
authors.forename: Desanka
authors.initials: D
authors.lastname: Dragosavac
authors.forename: Robert M
authors.initials: RM
authors.lastname: Kacmarek
authors.forename: Carlos R R
authors.initials: CR
authors.lastname: Carvalho
mesh_terms: D000368:Aged; D029481:Bronchitis, Chronic / Q000503:physiopathology / Q000628:therapy; D045422:Continuous Positive Airway Pressure; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate / Q000502:physiology; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000628:therapy*; D011656:Pulmonary Emphysema / Q000503:physiopathology / Q000628:therapy; D013147:Spirometry