Benefits of Heated and Humidified High Flow Nasal Oxygen for Preoxygenation in Morbidly Obese Patients Undergoing Bariatric Surgery: A Randomized Controlled Study

Background: Due to loss of functional residual capacity, morbidly obese patients are threatened by hypoxemia during anesthesia induction. To prevent hypoxemia, optimal preoxygenation is mandatory for safe anesthesia induction in morbidly obese patients. The aim of this study was to assess the effect of three different preoxygenation procedures in his patient group. Secondary objective was to investigate, if extension of preoxygenation time from 3 minutes to 5 or 7 minutes leads to increased oxygen partial pressure levels. Methods: 33 morbidly obese patients undergoing laparoscopic bariatric surgery were randomly assigned to receive one of the following preoxygenation procedures for seven minutes: high flow heated humidified nasal oxygen (HFHHNO), continuous positive airway pressure (CPAP) or oxygen insufflation via a face mask (STAND) which is the standard procedure for preoxygenation. Repetitive arterial blood gas analysis at 0, 1, 3, 5, 7 and 8:30 minutes were used to monitor the arterial oxygen partial pressure (PaO2). Results: From homogenous median PaO2 baseline values (STAND 88 mmHg, CPAP 87 mmHg, HFHHNO 77 mmHg) the PaO2 values of all three groups increased significantly within one minute of preoxygenation. After three minutes of preoxygenation, the STANDgroup reached a median arterial oxygen partial pressure level of 337 mmHg (25% quartile: 295 mmHg/75% quartile: 390 mmHg), the CPAP group of 353 mmHg (293 mmHg/419 mmHg) and the HFHHNO-group of 380 mmHg (339 mmHg/443 mmHg). Irrespective of the preoxygenation method, arterial oxygen partial pressure did not reach significantly higher levels at any time compared with the 3 minute mark. Conclusions: Standard preoxygenation was inferior in terms of sustained arterial oxygen partial pressure. High flow heated humidified nasal oxygen could provide a rapid, safe and easy to use preoxygenation prior to general anesthesia and arterial oxygen partial pressure might be higher after HFHHNO preoxygenation compared to standard or CPAP breathing.