Influence of pneumoperitoneum and patient positioning on respiratory system compliance

Abstract

Study Objective: To investigate the influence of pneumoperitoneum (PP) and posture on respiratory compliance and ventilation pressures.

Design: Prospective, single blind trial.

Patients: 10 female ASA physical status I and II patients scheduled for elective gynecologic laparoscopy.

Setting: University medical center.

Interventions: Anesthesia was performed as total IV anesthesia (TIVA) with propofol, alfentanil, and atracurium. After induction of anesthesia and orotracheal intubation, the lungs were ventilated to maintain partial pressure of CO₂ (P_ETCO₂) of 30 ± 3 mmHg. Ventilation was kept constant. As gas mixture oxygen and air 1:1 was used without positive end-expiratory pressure (PEEP).

Measurements: Measurements were taken before and after creation of pneumoperitoneum with an intraabdominal pressure (IAP) of 10 mmHg, of 15 mmHg in 20° head-down tilt, then in 20° head-up tilt, and after deflation of PP. We determined peak inspiratory pressure (PIP), mean airway pressure (mPaw), P_ETCO₂ , expiratory minute volume (V̇_E), heart rate (HR), and systolic (SBP), diastolic (DBP), and mean arterial pressure (MAP). Respiratory system compliance (C_{eff rs}) was calculated as quotient of tidal volume (V_T) and PIP.

Main Results: After creation of PP (IAP 10 mmHg), there was a significant increase of median PIP (3 cmH₂O), mPaw (1 cm H₂O) and arterial pressure (BP), (MAP by 7 mmHg), C_{eff rs} decreased by 6 mL · cm H₂O^-1. Increase of IAP to 15 mmHg led to a further increase of PIP (2 cm H₂O) and mPaw (1 cm H₂O), and a further decrease of C_{eff rs} by 5 mL cm H₂O^-1; BP decreased (MAP by 5.5 mmHg). Head-up or head down positions showed no significant hemodynamic or pulmonary changes. P_ETCO₂increased from 29.5 to 36 mmHg at an IAP of 15 mmHg, but then no further changes were noticed. Five minutes after deflation of pneumoperitoneum all values returned to baseline levels.

Conclusions: Creation of PP at an IAP of 15 mmHg reduced respiratory system compliance, and increased peak inspiratory and mean airway pressures, which quickly returned to normal values after deflation. Head-down or head-up position did not further alter those parameters.

Introduction

In recent years, the number of laparoscopic surgeries has increased significantly; early discharge of patients challenges the anesthesiologists not only to choose fast-track techniques of anesthesia, but also to be aware of the respiratory effects and complications of pneumoperitoneum. The insufflation of carbon dioxide (CO₂) into the abdomen during pneumoperitoneum influences the intrathoracic pressures by pushing the diaphragm upward,1 thus decreasing respiratory system compliance. Additional alterations of patient positioning further changes the position of the intestines and the diaphragm and reduces lung volume.

Several studies2, 3, 4, 5 have investigated the changes in ventilatory mechanics during pneumoperitoneum in laparoscopic surgery. Some studies have shown better postoperative lung function in laparoscopic surgery than in open surgery.1, 6 So far, there is no intra-group comparison investigating the impact of different positions and different levels of intraabdominal pressures (IAPs) of pneumoperitoneum. The increased use of laparoscopic techniques in gynecology7 creates a new challenge for the anesthesiologist, with patient positions different from those used in upper abdominal surgery and the economic necessity for rapid recovery and early discharge. The current study examines the impact of pneumoperitoneum and different patient positions on respiratory system mechanics during laparoscopic procedures in gynecology.