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 (PsqO₂) in 20 patients with a body mass index (BMI) ≥40 kg/m² (obese group) and 15 patients with BMI <30 kg/m² (non-obese group) undergoing laparoscopic surgery with standardized anaesthesia technique and fluid administration. Arterial oxygen tension was maintained near 150 mmHg. PsqO₂ 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). PsqO₂ 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.