PULMONARY ELIMINATION OF CARBON-DIOXIDE D URING LAPAROSCOPIC CHOLECYSTECTOMY - A CLINICAL-STUDY

Methods. We measured pulmonary elimination of carbon dioxide (VCO2), e nd-tidal and arterial CO2 tensions (PETCO2, PaCO2), dead-space ventila tion (VD/VT), and arterial oxygen tension (PaO2) using a Siemens 930 C O2 analyzer incorporated into a servoventilator and arterial blood gas analyses, respectively, in 31 patients undergoing laparoscopic cholec ystectomy with a median duration of pneumoperitoneum (PP) of 60 min. R esults. During the first 30 min of PP VCO2 increased significantly by a mean of 30 % (Fig. 1). At the same time, with constant minute ventil ation PETCO2 und PaCO2 increased by about 8 mm Hg each (Fig. 3, Table 1). In a subgroup of 10 patients who could be observed for up to 75 mi n of PP, we found a stepwise increase in minute ventilation with no fu rther increase in PETCO2 and PaCO2 after 30 min PP, but a slowly risin g VCO2 (Fig. 2). Arterial-to-end-tidal CO2 tension difference (Pa-PETC O2) remained constant at about 4 mm Hg with institution and during the course of PP (Fig. 4), as did VD/VT at a median value of 0.38-0.40 (F ig. 5). PaO2 (FIO2 = 0.5) did not change significantly with PP (Table 1). With desufflation we found a short-term increase in VCO2 (Table 2) . Conclusions. During PP, CO2 is reabsorbed from the peritoneal cavity . During the initial unstable phase with rising PaCO2, reabsorption of CO2 is the sum of increased pulmonary elimination of CO2 above baseli ne and uptake of CO2 into gas stores of the body. We estimated CO2 rea bsorption to be on the order of 70 ml/min during the first 30 min of P P. During the later, stable phase, reabsorption of CO2 equals increase d pulmonary elimination of CO2 above baseline and was estimated to be in the order of 90 ml/min in 10 patients with 30-75 min of PP (hatched are-a in Fig. 2). PETCO2 corresponded well with PaCO2 in these patien ts. VD/VT and arterial oxygenation did not change significantly with i nstitution or during the course of PP. Monitoring VCO2 probably is a u seful aid in the early detection of CO2 emphysema (Fig. 6).