The invention prevents dynamic airway compression during ventilatory support
of a patient. The respiratory airflow is determined by measurement or calculation,
and a measure of the degree of dynamic airway compression is derived from the determined
airflow. This measure is servo-controlled to be zero by increasing expiratory pressure
if the measure of the degree of dynamic airway compression is large or increasing,
and by reducing expiratory pressure if the measure of the degree of dynamic airway
compression is small or zero.
