FOAM Eye-Catchers 10: Apnoeic Oxygenation – new trial questions value of NODESAT

A new RCT called the FELLOW trial examining the benefits of NODESAT (Nasal Oxygenation During Attempts at Larngoscopy) has been published online and Emcrit has just released a podcast interviewing the leader author. There is also a brief review of this paper at emlitofnote.

This is a RCT in a single medical ICU randomising patients to NODESAT or usual care. Surprisingly it found no benefit in the primary outcome – the lowest measured arterial oxygen saturation.

However there was some key aspects of this trial that seriously affect its generalisability to ED and operating room patients:

  • They used oxygenation saturation nadir rather than time to desaturation as their outcome measure which the author rationalised as being perhaps a better marker of potential harm to the patient. This may be true but time to desaturation affects practice in the ED intubation e.g. warrants withdrawal of intubation attempt, ventilation by BVM and further intubations or escalation of care to LMA/cric which themselves can be harmful compared to a single intubation attempt without desaturation.
  • These were sick medical ICU patients, primarily being intubated for respiratory failure. Many of these patients were on high oxygenation delivery requirements prior to intubation often with sub-optimal obtained sats before intubation suggesting shunt physiology was at play, a problem which apnoeic oxygenation is unlikely to fix.
  • About 1/3 of these patients required BIPAP prior to intubation and this was continued during the apnoeic period, before the laryngoscope blade was placed. Another approximately 1/3 were receiving  Bag-Valve-Mask (BVM) ventilation during this same apnoeic period. Consequently only about 1/3 of patients received no assisted ventilation during the apnoea period which is really the group most reflective of the ED/operating room population. The use of assisted ventilation during apnoea  is likely to reduce any additional benefit that apnoea oxygenation would provide.

In short, this was of a trial of patients who were the least likely to benefit, most of whom were provided additional ventilation during apnoea reducing the likely benefit of NODESAT. So essentially this was a trial of apnoeic oxygenation in patients with shunt physiology, who for the most part, were not left apnoeic. 

Many in the ED world would consider NODESAT standard of care in ED intubations currently and I don’t think this small ICU trial with the limitations described above would change this, based on the balance of the evidence pertaining to our patients. Most ED patients are being intubated for airway protection and maintenance, rather than severe respiratory failure with shunt physiology.

Additionally nasal cannula oxygenation substantially improves pre oxygenation using the commonly available sub-optimal ED methods (BVM or Non-rebreather face mask) in patients who are seldom receiving BIPAP either before or during the intubation. Optimising preoxygenation is critically important and this is reason alone to use nasal cannula before intubation which of course can then be left on during intubation to provide apnoeic oxygenation.

All that said, this is an interesting trial that suggests further larger studies are required to determine if there are sub-groups within our ED cohort of intubations where apnoeic oxygenation may possibly not have the benefit we believe it to have, such as patients with respiratory failure receiving non invasive ventilation before and during intubation.

 

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