Apnoeic Oxygenation (ApOx) is the process of providing a constant flow of oxygen to an apnoeic patient, without ventilation, in order to extend the duration of safe apnoea. In ED this is primarily provided during the process of intubation via nasal cannula at an oxygen flow rate of 15L/min. While awake patients may not tolerate this flow rate on the nasal mucosa, once sedated this is a non-issue. Consequently, practically, sometimes the flow rate is kept low if the patient is awake and non-compliant with a high flow rate, and then the flow rate is increased once the patient is sedated. Additionally a 2nd oxygen source is required so if a 2nd wall oxygen port is unavailable or being used (by a BVM or non-rebreather bag) then an oxygen cylinder should be brought to the bedside to connect to the nasal cannula.[/EXPAND] [EXPAND HOW DOES IT WORK?]
The concept is that during apnoea less carbon dioxide enters the alveoli from the blood (10ml/min) compared with oxygen that is absorbed from alveoli into blood (250ml/min). As a result a negative partial pressure gradient draws oxygen from the pharynx into the lungs where it is absorbed into the bloodstream.[/EXPAND] [EXPAND WHAT’S THE EVIDENCE?]
While initially studied more than half a century ago, this innovation has only gained popularity since the publication of a seminal airway article “Preoxygenation & Prevention of Desaturation During Emergency Airway Management” by Scott Weingart and Richard Levitan, published in Annals of Emergency Medicine in 2011. It has been popularised by the apt mnemonic NO DESAT – Nasal Oxygen During Efforts at Securing A Tube.
In one of the first studies in 1959 of healthy electively intubated patients, a constant oxygen flow connected to the endotracheal tube without ventilation prevented desaturation for up to 53 minutes (though with attendant sky high CO2). Using nasal cannula, safe apnoea has been extended by more than 10 minutes. In sick ED patients we are likely to only gain an extra few minutes or less before desaturation occurs but this additional time can be of critical importance during attempts at intubation.[/EXPAND] [EXPAND WHEN SHOULD WE USE IT?]
Given the types of urgent intubations we manage in ED and the lack of a significant downside to this technique, ApOx should now be considered a routine part of our ED intubation management.[/EXPAND] [EXPAND ADDITIONAL RESOURCES]