Human respiratory muscles: Three levels of control

The latest data on the mechanisms of the control of respiratory muscles are reviewed. For systematization of these mechanisms, it is suggested to classify them into three levels: the autonomous (basic) level, which controls pulmonary ventilation under conditions of eupnea; the adaptive level, which coordinates breathing with other motor functions and an additional load on the respiratory system; and the voluntary level, which is specific for humans. Mechanisms of breathing control when performing the speech function, as well as during an increase in the resistance to breathing, are considered as an example of the adaptive level of control. In this connection, much attention is paid to the function of muscles of the upper airways, whose role in the breathing act is often ignored.