Influence of the patient positioning on respiratory mechanics during pneumoperitoneum

The aim of this study was to evaluate the effect of patient positioning during laparoscopic cholecystectomy on respiratory mechanics and arterial blood gases. Thirty patients of ASA I were included. Ventilation was controlled mechanically. Tidal volume and ventilator frequency were kept unchanged throughout the operation. Intra-abdominal pressure was kept constant at 12 mmHg. Ventrak respiratory system was used for measuring respiratory mechanics. The airway resistance (Raw), the dynamic compliance (Cdyn), and the peak inspiratory pressure (PIP) were monitored. Measurements were made in five intervals: "a" after induction of general anesthesia, "b" after insufflation, "c" in the Trendelenburg position of 40 degree, "d" in the Fowler position of 40 degree, and "e" after desufflation. Samples of arterial blood gases were collected while the respiratory mechanics were being recorded. The mean arterial pressure (MAP) and heart rate (HR) were also monitored. In our study, during intervals "c" and "d", PCO2, was increased and pH decreased. With the initiation of insufflation, Cdyn, PIP, and Rawx, were altered (P < 0.05). The patient positioning had a significant effect on respiratory mechanics. After desufflation only Cdyn changed (P < 0.05). Although HR remained in normal limits, MAP increased during pneumoperitoneum (P < 0.05). We conclude that blood gas changes and respiratory mechanics were affected by the duration of pneumoperitoneum and patient positioning. The Fowler position had the least influence on respiratory mechanics.