[Dynamic pressure-volume curve predicts the optimal positive end-expiratory pressure in patients with acute respiratory distress syndrome].

OBJECTIVE

To predict the best positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome (ARDS) patients with dynamic lung pressure-volume (P-V) curve.

METHODS

Dynamic and static lung P-V curves were determined in 8 patients with ARDS. The pressure of lower inflection point from dynamic lung P-V curve (Pinfd) was compared with the pressure of lower inflection point from static lung P-V curve (Pinfs). The effect of PEEP on hemodynamics, lung mechanics and gas exchange was observed.

RESULTS

When PEEP increased from Pinfd -6 cm H2O to Pinfd +6 cm H2O, partial pressure of arterial oxygen, saturation of arterial oxygen, peak inspiratory pressure and mean airway pressure increased significantly (P < 0.05). Dynamic compliance was improved markedly with PEEP at Pinfd -4 cm H2O when compared with PEEP at Pinfd +6 cm H2O. Cardiac index reduced at Pinf +6 cm H2O. Oxygen delivery was increased at Pinfd -4 cm H2O. When Pinfs and Pinfd were (11.0 +/- 3.2) cm H2O and (12.8 +/- 3.2) cm H2O, they were well correlated (r = 0.99, P < 0.05) and the regression equation was Pinfd = 1.66 + 1.01 x Pinfs. According to the regression equation, it was evident that Pinfd -4 cm H2O equaled to Pinfs -2 cm H2O.

CONCLUSION

When ARDS patients are treated with mechanical ventilation, Pinfd -4 cm H2O and Pinfs -2 cm H2O may yield the best PEEP and show maximal oxygen delivery.