Effects of adding pressure support and positive end expiratory pressure to deep breathing for obese patient preoxygenation and gastric ultrasonographic evaluation

It is known that anatomical and physiological differences in obese patients make preoxygenation difficult and limit its success. It has been suggested that deep breathing, noninvasive positive pressure ventilation or positive end-expiratory pressure (PEEP) support may be benefical to increase the effectiveness of preoxygenation in obese patients. In this study it was aimed to compare deep breathing, deep breathing + pressure support ventilation (PSV) and deep breathing + PSV + PEEP methods for preoxygenation in obese patients and to evaluate potential gastric distension with ultrasonography. Following the approval of the Ethics Committee, 75 patients planned for elective surgeries under generel anesthesia, between the ages of 18-65 years, with a body mass index (BMI) ≥30 kg/m2 and ASA 2-3 physical status were included. After the patients were divided into 3 groups; Group 1 received only deep breathing, Group 2 received deep breathing + 12 cmH2O PSV and Group 3 received deep breathing + 12 cmH2O PSV + 6 cmH2O PEEP for preoxygenation. The study was terminated when EtO2 reached 90%. In addition, the gastric antrum area was measured by ultrasonography before and after the preoxygenation procedure. Patient characteristics, pre- and post-procedure vital values, measurement of gastric antrum area and time for EtO2 to reach %90 were recorded. The groups were similar in terms of time for EtO2 reach %90 (96,4±33,1 sec, 82,2±15,1 sec ve 91,7±22,6 sec, respectively). The gastric antrum area was larger after the procedure (5,6±1,8 cm2, 5,6±1 cm2 ve 5,8±2,8 cm2, respectively) compared to before procedure (5,0±1,8 cm2, 4,4±1,3 cm2 ve 4,4±1,6 cm2, respectively) in all groups (p<0.05) and the growth in Group 3 was found to be more significant compared to Group 1 (p=0.038). In conclusion, adding PSV and PEEP to the deep breathing method for preoxygenation in obese patients both does not shorten the time and may increase gastric distension. Keywords: preoxygenation, obesity, PSV, PEEP, gastric antrum area