DIAPHRAGMATIC ELECTRICAL-ACTIVITY DURING CONTROLLED AND ASSISTED MECHANICAL VENTILATION IN CONSCIOUS HUMAN-SUBJECTS

Breathing during mechanical ventilation was analyzed in 8 conscious he althy volunteers by application of intermittent positive pressure vent ilation through a mouthpiece. In controlled mechanical ventilation (CM V), the respiratory rate and tidal volume were fixed at 110 and 120% o f the subject's corresponding spontaneous breathing parameters. The di aphragmatic electromyogram (EMGdi) decreased significantly but become synchronous with the rhythm of the CMV. In assisted mechanical ventila tion (AMV), the EMGdi response developed prior to and during the inspi ratory phase of AMV. Application of an unexpected mechanical breath el icited the EMGdi. As the triggering sensitivity was decreased, the EMG di prior to and during a mechanical breath was augmented, however, its rate of rise was unaffected. Our results suggest that the EMGdi durin g mechanical ventilation in conscious subjects is initiated by the res piratory center, however, this activity is modulated strongly by input from the pulmonary afferents and from the cerebral cortex.