Function and fatigue of respiratory muscles.

The functional anatomy of the respiratory muscles and their actions and interactions are presented, particularly of the diaphragm. The large amount of blood flow to respiratory muscles and the determination of blood flow are reviewed, while the role these muscles play in the overall economy of the body in health and disease are discussed. Finally the failure of the respiratory muscles in the context of the development of hypercapnic respiratory failure is examined. It is argued that as the respiratory muscles become fatigued, afferent information from the respiratory muscles modifies the breathing pattern, which might be beneficial to respiratory muscle function, but it might compromise alveolar ventilation.