Respiratory Mechanics During Laparoscopic Cholecystectomy

Abstract

We are very pleased to see increasing interest in the use of abdominal wall lift (AWL) techniques to avoid the harmful side effects of CO2 pneumoperitoneum and increased intraabdominal pressure. As stated in Carry et al.’s article (1), conventional CO2 insufflation may be deleterious to patients with underlying pulmonary pathology because CO2 can only be removed through the lungs. Patients, especially those with chronic obstructive pulmonary disease, are not able to eliminate excessive CO2 despite increased minute volume of ventilation, which then results in severe postoperative respiratory hypercarbia and acidosis requiring prolonged mechanical ventilation. Some of these patients also have accompanying heart disease and cannot tolerate any increased ventilation. Thus, the only way to treat their gallstones is to use surgical methods without CO2 insufflation. We have been performing studies comparing conventional CO2 pneumoperitoneum with AWL techniques in which small (8 L) CO2 insufflation was used, or in CO2 which is not needed at all (2–7). Unfortunately, Carry et al. had no control group in their study with which they would have been able to show even more marked benefits of the AWL technique over CO2 insufflation. Carry et al. referred to a few of our studies, but they did not carefully read the first of those studies (5). That study compared CO2 pneumoperitoneum with the AWL method, not with open laparotomy, as they stated. In our study, the AWL method was superior to CO2 pneumoperitoneum, resulting in remarkably easier and faster recovery after laparoscopic cholecystectomy. In two of our studies (2,6), we measured pulmonary dynamic compliance (Cdyn) with Side-Stream Spirometry® (Datex-Engström Instrumentarium Inc., Helsinki, Finland). This method allows measurement of peak, plateau (Pplat), and end-expiratory (PEEP) pressures, inspiratory and expiratory (TVexp) tidal and minute volumes of ventilation, and the expiratory volume during the first second of ventilation. The calculation formula for pulmonary dynamic compliance is TVexp/(Pplat − PEEP), correlating directly with tidal volume and inversely with airway pressures. Thus, changes in compliance reflect alterations in one or both of these parameters. In our studies, we only reported Cdyn because it is an adequate method to show rapid and clinically relevant changes in pulmonary elasticity (i.e., obstruction, pneumothorax). These studies were not mentioned by Carry et al. Carry et al. did not give the total amount of CO2 used during their study. We have shown that 8 L of CO2 is enough to cause mild respiratory hypercarbia (2). Thus, the protocol of Carry et al., which did not allow for the increase of the minute volume of ventilation, is not ethically acceptable. In our first study (2), we did not perform blood-gas analysis as in our later study (7). Based on these studies, it is expected that a mild increase in the end-tidal expiratory CO2 concentration also causes hypercarbia and acidosis. Our studies indicate many benefits of AWL methods, without CO2 insufflation or high intraabdominal pressure, over conventional CO2 pneumoperitoneum. Now we look forward to more confirmation of our data. Some surgeons are also aware of the harmful effects of CO2 insufflation. They are developing more practical and easier methods to lift the anterior part of the abdominal wall; therefore, surgeons will be more willing to accept AWL methods. Anna-Maria Koivusalo MD, PhD Leena Lindgren MD, PhD