Pattern of breathing in a case of generalized respiratory muscle weakness.

A patient with motor neuron disease is described. He had signs and laboratory data indicating generalized, symmetrical weakness, involving both inspiratory and expiratory muscle groups. The pattern of breathing involving recruitment of accessory muscles and expiratory contraction of abdominal muscles is similar to that seen in normal people at high minute ventilation, and suggests the compensating mechanism for increasing motor discharge to weak respiratory muscles is mediated centrally. Observation of this sort of respiratory activity gives a clinical clue to generalized respiratory muscle weakness.