Comparing volume control versus pressure control mechanical ventilation after cardiac surgery on respiratory parameters

Abstract

The aim of this study was to compare the two volume control (VCV) versus pressure control (PCV) mechanical ventilation methods on the respiratory parameters and complications after cardiac surgery. Materials and Methods: The target population of this randomized clinical trial included adult patients over 18 years of age who were candidates for elective cardiac surgery using cardiopulmonary bypass in Shahid Madani Hospital in Tabriz in 1998-99. After obtaining the approval of the ethics committee of Tabriz University of Medical Sciences and obtaining informed written consent, 120 cardiac surgery patients who were admitted to the ICU allocated to one of two groups: VCV or PCV groups (n=60). Mechanical ventilation performed with Hamilton Raphael color ventilator. In VCV group, mechanical ventilation was performed by SIMV method with 12 breaths per minute, 70% oxygen, tidal volume of 10 cc / kg body weight, PEEP and PS of 5 and 15 cmH2O, respectively and I/E ratio of 1/2. In PCV group, mechanical ventilation was performed by PSIMV method with 12 breaths per minute, 70% oxygen, insoiratory pressure, PEEP and PS of 20, 5 and 15 cmH2O, respectively and I/E ratio of 1/2. Arterial blood gas testing was performed every two hour, up to 6 hours after admission, and after extubation. In addition to demographic data, arterial blood gas analysis (including PO2, PH, PCO2), hemodynamic parameters, need for inotropes and duration of mechanical ventilation, pulmonary, cardiac, renal, cerebral and infection complications and length of hospital stay In the ICU and the need for reintubation and changes in these ventilation methods were collected and compared between the two groups. Results: The two groups were same due to the demographic variables including age, gender and BMI. In terms of left ventricular ejection fraction, the distribution of the underlying disease and the types of surgeries and variables related to the intraoperative (operation time and CPB) and postoperative (hemodynamic variables, need for cardiac drugs and blood products) were not different. Although the rate of non-pulmonary complications was the same, but the pulmonary complications and the time required for mechanical ventilation and the duration of ICU stay were significantly lower in the PCV group than VCV group (P-value = 0.031, 0.006 and 0.035; respectively). The mean airway pressure was always higher in the VCV group patients than PCV group. Although most of the respiratory parameters including required FiO2 and PO2, PCO2, arterial pH were not significantly different at different times, but at all times the oxygen index in the VCV group was higher than PCV group.