ABSTRACT
Key elements in the human ventilatory control system include: (1) the central medullary integrator/pattern generator; (2) sensory inputs from feedback receptors concerned with blood and cell chemistry, the force output or tension developed by the respiratory muscles and airway patency; and (3) the coordination of efferent output to the upper airway and the chest wall pump muscles. In the awake healthy human, the coordination achieved among these elements insures a high degree of precision in the regulation of blood gases and acid/base status and in the mechanical efficiency of each breath in terms of minimizing the amount of work required by the respiratory musculature for a given ventilatory output. Furthermore, any significant disruption in ventilatory output, or in the precision or mechanical efficiency of ventilatory output, is usually short lived. For example, if tidal volume or breathing frequency is changed momentarily-by a sigh, a change in posture or increased mechanical load on the airway or sudden increase in metabolic rate (e.g., with exercise)—the appropriate compensation for these momentary errors are achieved quickly, and homeostasis is restored within a few breaths, and almost always with the subject not even being aware of the brief departure from the normal steady state.
