Ruolo degli stimoli periferici nella regolazione dell'attività diaframmatica nelle apnee ostruttive da sonno

To evaluate the role of peripheral stimuli influencing the diaphragmatic contraction during obstructive sleep apneas, on six patients we studied the changes in respiratory timing and diaphragmatic activity analyzing the electromyogram (EMG) of the diaphragm treated as moving average. Six apneas for each subject were selected, and a breath-by-breath analysis was performed from the third-to-last pre-apneic breath to the third post-apneic breath. Due to the decreasing chemical drive, the inspiratory time (Ti) related to the diaphragmatic activity and the inspiratory peak of the diaphragmatic EMG moving average (EMGdia) progressively decreased during the pre-apneic phase; during the same period, the expiratory time (Te) increased because the increasing inspiratory and expiratory upper airway resistances. During apnea Ti and EMGdia increased in an out-of-phase fashion in relation to the initial increase in mechanical stimuli from upper airway mechanoceptors, followed by an increase in chemical drive. Due to airway obstruction and increasing chemical drive Te decreased in this phase. In the post-apneic phase Ti decreased, while EMGdia showed the highest peaks; this is related to the persistence of chemical stimulation without obstruction. The increase in Te is due to the resumption of ventilation and of the expiratory flow.