Assessment of the severity of primary respiratory muscle failure

Abstract

Respiratory muscle weakness results either from disorders of the respiratory motor unit (primary type) or from muscle fatigue due to severe underlying pulmonary disease (secondary type). Blood gases reflect the effects of muscle fatigue but are too insensitive to be relied upon in primary muscle weakness. The reasons for this are discussed. It is emphasized that the ventilatory reserve should be monitored, in patients with primary respiratory muscle weakness and that a decision to provide assisted ventilation should be based upon it, not on blood gas estimates.