The relationship between central carbon dioxide sensitivity and clinical features in patients with chronic airways obstruction.

A technique has been developed which enables respiratory motor output to be measured independently of lung mechanics. The maximum rate of change of pressure at the mouth during initial transient occlusion of the airway, (d P/dt) max., represents the rate of isometric force development by the inspiratory muscles. This technique was used to study central CO2 sensitivity in 40 patients with chronic airways obstruction. Subnormal CO2 sensitivity was associated with chronic cough and sputum production, relatively mild dyspnoea, raised arterial CO2 tension, hypoxaemia, polycythaemia and cor pulmonale. Normal CO2 sensitivity was associated with severe dyspnoea, normal blood gas tensions, and allergic features.