Pre‐oxygenation in patients living with obesity

We read with interest the recent best practice recommendations on airway management in patients living with obesity [1]. We are concerned about the recommendation that patients should be pre-oxygenated in a ramped, head-up position with a high inspiratory fraction of oxygen. There was no mention of the use of spontaneous facemask positive pressure ventilation during the pre-oxygenation period. There was also no mention of the reverse Trendelenburg position as an alternative to the 30° head-up ramped position during pre-oxygenation. In our recent randomised controlled trial [2], we compared the effect of two techniques on the duration of the safe apnoea period after pre-oxygenation in patients living with obesity. The comparison was made between a ramped position combined with spontaneous facemask breathing without positive pressure, and pre-oxygenation in a reverse Trendelenburg position with inspiratory pressure support of 8 cmH2O and a peak end-expiratory pressure of 10 cmH2O. We found a longer safe apnoea period in the reverse Trendelenburg group (258 (55.1) vs. 217 (42.3) s; p = 0.005). Other benefits associated with this technique were also reported [2]. We based our reverse Trendelenburg positive pressure technique on a physiological assessment of the functional residual capacity using different combinations of body position and ventilation strategies in awake patients before bariatric surgery [3]. An increase in functional residual capacity was observed when spontaneous ventilation without positive pressure was converted to positive pressure ventilation. Moreover, compared with supine positioning, the ramped position had no measurable impact on the functional residual capacity. The reverse Trendelenburg position was the only position that resulted in an improved functional residual capacity regardless of the ventilation strategy used [3]. We believe that reverse Trendelenburg positioning with the use of positive pressure ventilation in spontaneously breathing patients living with obesity should be recommended for safer pre-oxygenation in this highly vulnerable population.