66 - 70 Physics SBAs for the Primary
Question 66
You have a 49 year old lady on the table having laser surgery to her vocal cords. You have intubated her with a laser-safe tube and are running TIVA like a boss, with the ventilator set to 45% oxygen and 6 litres of fresh gas flow.
The surgeon has finished setting up her laryngoscope and asks if she can start lasering.
Which of the following should you do next to minimise the risk of an airway fire?
- Increase fresh gas flow at the current inspired fraction of oxygen
- Start delivering nitrous oxide
- Inflate the cuff with saline
- Reduce the inspired oxygen concentration to below 30%
- Ask the surgeon to place wet swabs around the mouth and face
Answer
- Reduce the inspired oxygen concentration to below 30%
Lasering carries a rather sporting risk of airway fires.
To recap, fire requires:
- Heat (and a source of ignition)
- Fuel
- Oxygen
The surgeon is providing the heat and ignition with their laser, and a plastic PVC tube will burn quite nicely, thank you very much, especially in the presence of lots of extra oxygen.
Recipe for disaster.
Increasing the fresh gas flow at the current FiO2 will ensure there's plenty of fresh oxygen to encourage a fire to burn, so that's not a great plan.
Equally, nitrous oxide is a rather useful oxidising agent so that's not the best idea either.
The cuff should ideally already be inflated with saline, and faffing about with the cuff now that the patient is fully prepped and draped isn't particularly sensible.
The surgeon should already have placed wet swabs around the mouth and face, so this isn't what you personally should be prioritising next.
The best thing to do is reduce the FiO2 to the lowest level that will maintain adequate oxygenation, to reduce the risk of fire as much as possible, and then be ready to deal with one should it arise.