BACKGROUND: During laparoscopic cholecystectomy the arterial-end-tidal CO2 gradient (Fa-ETCO2) has been variously shown to be unchanged, increased, decreased or even negative. The goal of this study was to evaluate Fa-ETCO2, and to determine the proper contribution of VECO2 and VA in regard to the increase of FETCO2. METHODS: Ventilatory patterns were studied in 15 ASA 1-2 patients (mean age +/- SD: 48.5 +/- 15.0) undergoing laparoscopic cholecystectomy, with intraperitoneal CO2 insufflation limited to 12 mmHg, 15 degrees head-up position, during general anaesthesia and controlled ventilation. The following were studied before, during and after the pneumoperitoneum: FaCO2, FETCO2, nasopharyngeal temperature; dead space ventilation, and expired volumes using the Single Breath Test for CO2. VA was calculated as the alveolar fraction of expired VT multipled by the respiratory frequency. RESULTS: During pneumoperitoneum it is shown that: 1) Fa-ETCO2 either decreases and becomes even negative (n = 8) (P < 0.01), or stays unchanged (n = 7), but never elevates; 2) VECO2 increases (peak value: +22.6%) (P < 0.01); 3) VA is unchanged, and 4) dead space ventilation, determined in 7 patients, remains unchanged. CONCLUSION: We conclude that only exogenous CO2 loading, and not VA, can explain such increase in FETCO2 and FaCO2, in cases of limited CO2 insufflating pressure in ASA 1-2 patients.
BACKGROUND: During laparoscopic cholecystectomy the arterial-end-tidal CO2 gradient (Fa-ETCO2) has been variously shown to be unchanged, increased, decreased or even negative. The goal of this study was to evaluate Fa-ETCO2, and to determine the proper contribution of VECO2 and VA in regard to the increase of FETCO2. METHODS: Ventilatory patterns were studied in 15 ASA 1-2 patients (mean age +/- SD: 48.5 +/- 15.0) undergoing laparoscopic cholecystectomy, with intraperitoneal CO2 insufflation limited to 12 mmHg, 15 degrees head-up position, during general anaesthesia and controlled ventilation. The following were studied before, during and after the pneumoperitoneum: FaCO2, FETCO2, nasopharyngeal temperature; dead space ventilation, and expired volumes using the Single Breath Test for CO2. VA was calculated as the alveolar fraction of expired VT multipled by the respiratory frequency. RESULTS: During pneumoperitoneum it is shown that: 1) Fa-ETCO2 either decreases and becomes even negative (n = 8) (P < 0.01), or stays unchanged (n = 7), but never elevates; 2) VECO2 increases (peak value: +22.6%) (P < 0.01); 3) VA is unchanged, and 4) dead space ventilation, determined in 7 patients, remains unchanged. CONCLUSION: We conclude that only exogenous CO2 loading, and not VA, can explain such increase in FETCO2 and FaCO2, in cases of limited CO2 insufflating pressure in ASA 1-2 patients.
Authors: Mohammad Al-Haddad; Daniel McKenna; Jeff Ko; Stuart Sherman; Don J Selzer; Samer G Mattar; Thomas F Imperiale; Douglas K Rex; Attila Nakeeb; Seong Mok Jeong; Cynthia S Johnson; Lynetta J Freeman Journal: Surg Endosc Date: 2012-05-12 Impact factor: 4.584