ABSTRACT
Patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) form the largest single group of those treated successfully using noninvasive ventilation (NIV) (1). The respiratory muscle pump in patients with severe COPD is often functioning close to the point at which it can no longer maintain effective ventilation due to hyperinflation, airways obstruction, and intrinsic positive end-expiratory pressure (PEEP). During an acute exacerbation, the load on the respiratory muscle pump becomes excessive and effective ventilation can no longer be maintained, worsening hypoxia, hypercapnia, and most importantly acidosis. Worsening acidosis causes further impairment of respiratory muscle function, which in turn has a deleterious effect on pH and arterial blood gas tensions. The use of NIV aims to break this vicious circle.
