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Non-linear evaluation of respiratory mechanics during laparoscopic cholecystectomy
M P Vassiliou1, L Rizzoti, V Laopodis
1Pneumonology Department, Medical School, University of Ioannina, Ioannina 45110, Greece. mvassil@cc.uoi.gr
Background/Aims:
Laparoscopic cholecystectomy is accompanied by significant increase of the respiratory system elastic and resistive properties. These changes are completely abolished after peritoneal deflation. In the present study we examine the volume and flow dependence of respiratory mechanics during four operation phases.
Methodology:
Airway pressure and flow were recorded from 17 patients undergoing laparoscopic cholecystectomy. Measurements were done at 4 distinct phases: 1) Before the induction of pneumoperitoneum. 2) Five minutes after pneumoperitoneum induction at Trendelenburg position. 3) Five minutes after positioning the patient at reverse. Trendelenburg. 4) Five minutes after the peritoneal deflation. Data of airway pressure, flow and volume were treated according to the non-linear regression model: Paw = E1.V + E2.V2 + k1.V' + k2.V'. |V'| + k3.V.V' + EEP.
Results:
The induction of pneumoperitoneum results in: Significant increase of linear elastance and resistance and significant decrease of flow and volume dependence of resistance. No significant changes are noted in volume dependence of elastance and end-expiratory pressure.
Conclusions:
The pneumoperitoneum and not the body position causes the changes in respiratory mechanics and their dependencies during laparoscopic cholecystectomy, which, although important, do not predispose to major risks (lung overdistension, alveolar collapse) and they are reversed after peritoneal deflation.