Continuous positive airway pressure increases inspiratory capacity of COPD patients

Respirology. 2008 May;13(3):387-93. doi: 10.1111/j.1440-1843.2008.01263.x.


Background and 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.

Publication types

  • Clinical Trial

MeSH terms

  • Aged
  • Bronchitis, Chronic / physiopathology
  • Bronchitis, Chronic / therapy
  • Continuous Positive Airway Pressure*
  • Female
  • Humans
  • Inhalation / physiology*
  • Male
  • Middle Aged
  • Peak Expiratory Flow Rate / physiology
  • Pulmonary Disease, Chronic Obstructive / physiopathology*
  • Pulmonary Disease, Chronic Obstructive / therapy*
  • Pulmonary Emphysema / physiopathology
  • Pulmonary Emphysema / therapy
  • Spirometry