Effects of Split Torso Positioning and Laparoscopic Surgery for Donor Nephrectomy on Respiratory Mechanics

Abstract

Study Objective: To test whether split torso positioning, abdominal insufflation, and other procedures performed during laparoscopic nephrectomy would affect mechanical impedances to inflation [i.e., elastance (E) and resistance (R) of the total respiratory system (E rs and R rs), lungs (E L and R L), and chest wall (E cw and R cw)] differently from previously studied laparoscopic procedures. Design: Unblinded study, each patient serving as own control. Setting: University hospital. Patients: 12 ASA physical status I and II patients scheduled for laparoscopic donor nephrectomy, all without cardiopulmonary disease. Interventions: Patients were anesthetized and paralyzed, tracheally intubated and mechanically ventilated at 10, 20, and 30 breaths/minute and at tidal volumes of 250, 500, and 800 ml. Measurements were made in the following positions: supine, split torso, abdominal insufflation (P ab = 15 mmHg), and supine after deflation. Measurements and Main Results: Airway flow and pressure and esophageal pressure were measured. Discrete Fourier transformation was used to calculate E and R. These were analyzed with repeated measures, linear multiple regression with accepted level of significance at p <0.05. E rs, E cw, and R cw increased (p <0.05) while E L decreased (p <0.05) when patients changed from supine to split torso. During P ab = 15 mmHg, E rs, E cw, and R cw increased further and R rs and R L increased (p <0.05). Following abdominal deflation, E cw and E rs remained elevated (p <0.05). The changes in E cw caused by laparoscopy and surgery were greater than we have previously measured in other laparoscopic procedures, while the changes in E L were less. Conclusions: Laparoscopic nephrectomy affects lung and chest wall mechanical properties differently from other laparoscopic procedures. This finding could be due to the split torso positioning, and the effects of abdominal swelling on the chest wall caused by administration of more perioperative fluids with laparoscopic nephrectomy.