Pre-oxygenation Methods in Bariatric Patients

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General anaesthesia involves giving patients anaesthetic and muscle relaxant medications to allow transition to sleep and airway relaxation to permit laryngoscopy, respectively. During laryngoscopy, a breathing tube is placed to 'secure' the airway. There is therefore a length of time from administr...

General anaesthesia involves giving patients anaesthetic and muscle relaxant medications to allow transition to sleep and airway relaxation to permit laryngoscopy, respectively. During laryngoscopy, a breathing tube is placed to 'secure' the airway. There is therefore a length of time from administration of these medications to when the breathing tube is placed, when the patient is not breathing and the airway is not secured. This time is known as apnoea time. In a patient who is not breathing, blood oxygen levels fall to dangerously-low levels, within 1-2 minutes. In order to prevent this, patients breathe 100% oxygen before induction of anaesthesia as part of a process known as pre-oxygenation. There are different ways of delivering pre-oxygenation, but the common aim is to increase the oxygen reservoir within the lungs to give the anaesthetist more time to place the breathing tube. With good pre-oxygenation, apnoea times of up to 7 minutes are possible. Apnoea time is a potentially hazardous period during induction of anaesthesia and it is particularly so in patients with severe obesity. On the one hand, obesity makes the upper airway anatomy difficult, and on the other hand, lung collapse (atelectasis) caused by abdominal contents compressing the base of the lungs reduces the amount of oxygen available within the lungs. Apnoea time can be as short of 30 seconds. Identifying the most effective method of pre-oxygenating bariatric patients can therefore significantly improve the safety of delivering general anaesthesia to these patients.

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