Effect of pressure support ventilation on breathing patterns and respiratory work

We assessed the effect of pressure support ventilation (PSV) on breathing patterns and the work of breathing in 10 postoperative patients. Minute ventilation (_E) increased by 8% with 5 cm H₂O PSV and 10% with 10 cm H₂O PSV compared to 0 cm H₂O PSV. The increase in _E was achieved by increased mean inspiratory flow (24% with 5 cm H₂O PSV and 67% with 10 cm H₂O PSV) and a decrease in duty cycle (13% with 5 cm H₂O PSV and 39% with 10 cm H₂O PSV). The decrease in duty cycle along with a decrease in respiratory frequency allowed a greater expiratory time including a rest period for the respiratory muscles, which might minimize the risk of muscle fatigue. Furthermore, the inspiratory work added by the ventilator was near zero with 5 cm H₂O PSV and 10 cm H₂O PSV. Oxygen consumption also decreased significantly with 5 cm H₂O PSV. We conclude that PSV improves the breathing patterns and minimizes the work of breathing spontaneously via a ventilator.