Effect of nasal-CPAP on patients with chronic obstructive pulmonary disease.

Patients with chronic obstructive pulmonary disease [COPD] breath at large lung volumes because of dynamic hyperinflation. Their end-tidal lung volumes will then be much above the equilibrium position of the respiratory system and the elastic recoil pressure would be above zero at end-tidal exhalation. This auto or intrinsic positive end-expiratory pressure [auto-PEEP] contributes to the elastic work of inspiration and the sensation of dyspnoea. The purpose of this study was to offset the auto-PEEP in patients with exacerbated chronic airflow obstruction by applying continuous positive airway pressure via the nose [nasal-CPAP]. Nine out of 14 patients experienced alleviation of dyspnoea while on nasal-CPAP [4 to 8 cmH2O]. These 9 patients had significantly more severe hyperinflation than the 5 patients who did not respond positively to nasal-CPAP. While there is a complex relationship between intrinsic and extrinsically applied PEEP in patients with COPD, the result of this study is consistent with the notion that CPAP may alleviate dyspnoea by reducing auto-PEEP, improving lung mechanics and unloading the inspiratory muscles. Nasal-CPAP may have a potential therapeutic role in exacerbations of COPD.