Negative pressure ventilation in COPD patients with acute on chronic respiratory failure.

Negative pressure ventilators act by exposing the surface of the chest wall to subatmospheric pressure during inspiration. During negative pressure ventilation (NPV), tidal volume is related to the peak of the inspiratory negative pressure and the pressure waveform generated by the ventilator pump; for the same peak of negative pressure a square wave produces a greater tidal volume than a half sine wave. Several uncontrolled studies suggest that NPV may have a potential therapeutic role in the treatment of acute on chronic respiratory failure in patients with chronic obstructive pulmonary disease (COPD), reducing the need for endotracheal intubation. Recently, NPV has been used with a good outcome as a first-line treatment in COPD patients with severe acute respiratory failure and hypoxic hypercapnic coma. The positive results of these reports need to be confirmed by further controlled studies before recommending the generalized use of NPV in COPD patients with acute respiratory failure as standard care.