The Central Nervous System and Respiratory Muscle Coordination

¹ Professor of Medicine and Physiology, Case Western Reserve University, University Hospitals of Cleveland, Cleveland.

The respiratory system is complex, but it is not delicate. Severe disease must be present before the adequacy of CO₂ exchange is compromised. While lung disease can affect Po₂ levels more readily than it can alter levels of Pco₂, defects in O₂ supply to the tissues give rise to circulatory adjustment increases in cardiac output and red cell mass that can maintain O₂ exchange to tissues. Inadequate CO₂ exchange cannot be similarly compensated.

It may be useful to think of the system that controls the respiratory muscles as extremely resilient, adaptable, and capable of using a whole array of mechanisms to preserve gas exchange. The CNS mechanisms on which this system is based are highly redundant and not easily susceptible to damage by localized lesions. It is this redundancy that allows us the use of respiratory muscles for more than just breathing and permits respiration to be maintained despite the multitude of internal and external noxious possibilities that can adversely affect the respiratory controller and its controlled system.