We investigated the effects of pressure support ventilation (PSV) on the breathing patterns of 14 patients who were difficult to wean from conventional mechanical ventilation. Method: Breathing pattern was recorded by respiratory inductive plethysmography at PSV levels of 0, 5, 10, 15, 20, and 25 cm H 2 O. Results: When PSV was used, respiratory frequency significantly decreased and tidal volume significantly increased, resulting in a stable minute ventilation. Total compartmental displacement/tidal volume, an index of rib cage-abdominal synchrony, significantly improved. Although inspiratory time lengthened, mean inspiratory flow was not significantly altered. Overall, these changes resulted in a more efficient breathing pattern that may have been helpful in the weaning of these ventilator-dependent patients. Six older patients developed central apneas averaging 19 seconds in length at the highest levels of PSV; the etiology and clinical importance of these apneas were not determined. Conclusion: PSV can be used to improve the efficiency of breathing patterns in some patients who are difficult to wean from conventional mechanical ventilation.
Ershowsky et al. (Sun,) studied this question.