Comparison of Respiratory Mechanics and Gas Exchange between Pressure-controlled and Volume-controlled Ventilation / 결핵

ABSTRACT

BACKGROUND: Pressure-controlled ventilation (PCV) is frequently used recently as the initial mode of mechanical ventilation in the patients with respiratory failure. Theoretically, because of its high initial inspiratory flow, pressure-controlled ventilation has lower peak inspiratory pressure and improved gas exchange than volume-controlled ventilation (VCV). But the data from previous studies showed controversial results about the gas exchange. Moreover, the comparison study between PCV and VCV with various inspirationexpiration time ratios (IE ratios) is rare. So this study was performed to compare the respiratory mechanics and gas exchange between PCV and VCV with various IE raitos. METHODS: Nine patients receiving mechanical ventilation for respiratory failure were enrolled. They were ventilated by both PCV and VCV with various IE ratios (12, 11.3 and 1.71). FiO2, tidal volume, respiratory rate and external positive end-expiratory pressure (PEEP) were kept constant throughout the study. After 20 minutes of each ventilation mode, arterial blood gas, airway pressures, expired CO2 were measured. RESULTS: In both PCV and VCV, as the IE ratio increased, the mean airway pressure was increased, and PaCO2 and physiologic dead space fraction were decreased. But P(A-a)O2 was not changed. In all three different IE ratios, peak inspiratory pressure was lower during PCV, and mean airway pressure was higher during PCV. But PaCO2 level, physiologic dead space fraction and P(A-a)O2 were not different between PCV and VCV with three different IE ratios. CONCLUSION: There was no difference in gas exchange between PCV and VCV under the same tidal voulme, frequency and IE ratio.