Noninvasive ventilation (NIV) has been one of the major advances in respiratory medicine in the last decade. In particular, it has found widespread application in the management of patients with chronic obstructive pulmonary disease (COPD). There is a robust evidence base for its use in acute exacerbations of COPD, but the evidence that it is effective in chronic COPD is much less strong. Despite this, COPD is one of the most common reasons for long-term home mechanical ventilation.
Early experience was with negative pressure devices, usually used for short periods in hospital 1–4. Studies were uncontrolled and with small numbers of patients, but did suggest possible benefits. The use of negative pressure devices at home and during sleep in patients with COPD has been largely unsuccessful 3, 5. In two controlled trials, patients were generally unable to sleep during negative pressure ventilation, and most either failed to complete the protocol because of lack of improvement or discomfort associated with the use of the equipment 5, or did not wish to continue treatment after the study was completed 3. Negative pressure devices are cumbersome and relatively inefficient, particularly when the impedance to inflation is high, and may not be able to provide adequate ventilation during sleep. They predispose to the development or accentuation of upper airway collapse 6, and this may be a particular problem during sleep in the obese patient with COPD.
In most studies of negative pressure ventilation in COPD, the primary focus of therapy was to rest respiratory muscles, which were thought to be in a state of chronic fatigue. Unfortunately, in the absence of any reliable test of respiratory muscle fatigue this approach remains speculative. In an attempt to definitively answer whether respiratory muscle fatigue exists in stable chronic …