Tissue oxygenation in obese and non-obese patients during laparoscopy

Background: Wound infection risk is inversely related to subcutaneous tissue oxygenation, which is reduced in obese patients and may be reduced even more during laparoscopic procedures. Methods: We evaluated subcutaneous tissue oxygenation (PsqO(2)) in 20 patients with a body mass index (BMI) >= 40 kg/m(2) (obese group) and 15 patients with BMI < 30 kg/m(2) (non-obese group) undergoing laparoscopic surgery with standardized anaesthesia technique and fluid administration. Arterial oxygen tension was maintained near 150 mmHg. PsqO(2) was measured from a surrogate wound on the upper arm. Results: A mean FIO2 of 51% (13%) was required in obese patients to reach an arterial oxygen tension of 150 mmHg; however, a mean FIO2 of only 40% (7%) was required to reach the same oxygen tension in non-obese patients (P=0.007). PsqO(2) was significantly less in obese patients: 41 (10) vs 57 (15) mmHg (P < 0.001). Conclusion: Obese patients having laparoscopic surgery require a significantly greater FIO2 to reach an arterial oxygen tension of about 150 mmHg than non-obese patients; they also have significantly lower subcutaneous oxygen tensions. Both factors probably contribute to an increased infection risk in obese patients.