A model for the relation between respiratory neural and mechanical outputs. III. Validation

Abstract

The accuracy of a previously described model for the relation between respiratory neural and mechanical outputs was tested in predicting volume and flow from occlusion pressure wave forms, and vice versa. Single-breath airway occlusions were performed in 21 unconscious [human] subjects and the time course of occlusion pressure was determined. Passive properties of the respiratory system were also measured. The time course of volume and flow was predicted from the occlusion pressure wave forms, and the results were compared to the spontaneous breaths immediately preceding occlusion. Inspiratory duration, shape and amplitude of occlusion-pressure wave forms, and the passive properties of the respiratory system varied widely among subjects. There was good agreement between predicted and observed values in all cases. Except for some prolongation of inspiration (Hering-Breuer reflex), diaphragmatic activity did not change during occlusion. Since occlusion pressure is proportional to inspiratory activity, this model provides a good approximation of the relation between inspiratory activity and spirometric output.