Changes in Breathing Pattern during Pressure Support Ventilation

Abstract

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 H₂O. 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.