I’ve previously written about air travel after pneumothorax. The issue is that air expands as you ascend to aircraft level heights. That means that air bubbles in your chest can double or almost triple in size on the average airliner at altitude. For the official recommendations for when it is safe to travel after a pneumothorax, see the link to my previous post below.

And I covered pneumocephalus previously as well. This is a very infrequent condition, and there is very little literature about it. After doing a thorough search, I found two additional papers on it. The first was a computer simulation from Sweden. As expected, it found that air bubbles expand 30% when cabin altitude reaches 8000 ft. They were also able to model changes in intracranial pressure (ICP), and found that it increased as well. The amount was related to the size of the original air bubbles and the rate of the ascent (faster ascent = higher ICP). The worst case ICP increase with a 30cc bubble was 11 torr.

The other paper was from the UK and described a survey of neurosurgeons regarding their advice to patients on air travel after craniotomy. The fear is that there may be residual bubbles around the brain from the surgery. The results of this type of survey are usually all over the place, and more so when you ask neurosurgeons. To their credit, 92% advised their patients not to fly for a period of time. Unfortunately, the timeframes ranged from <2 to >8 weeks!

How about some practical info? I previously wrote about an actual clinical study by the US military who transported soldiers with pneumocephalus by air. Their series of 21 patients showed no neurological deterioration during flight, and 3 who had ICP monitors had no significant changes in pressure.

Bottom line: Computer models (and common sense) tell us that it’s a bad idea to fly commercially with air around your brain. It may work for the military because they have to fly, and the soldier is in a flying ICU. But in civilian aircraft, there is little to be done if medical problems occur short of an emergency landing and transport to a hospital. What’s the magic number of weeks to wait to fly? That is not known, but 2 weeks has worked well for pneumothorax so it seems like a reasonable place to start. But it should be easy for someone to do a retrospective review of serial head CTs from craniotomy patients to see how long it takes for the bubbles to actually reabsorb. And don’t worry about helicopter flights; altitudes are too low to make a difference!

Related post:

• Pneumothorax and air transport
• Pneumocephalus and air transport

References:

• Air transport of patients with intracranial air: computer model of pressure effects. Aviat Space Environ Med Feb 74(2):138-44, 2003.
• Air travel after intracranial surgery: a survey of advice given to patients by consultant neurosurgeons in the UK. Br J Neurosurg 2012 Aug 30, epub ahead of print.

Everybody remembers Boyle’s law, right?

Volume of a gas = k / Pressure     (where K is a constant)

Which means that, as pressure goes down, the volume of a gas increases. This is important for patients who have a pneumothorax and get on an airplane. As the plane ascends the pneumothorax gets bigger and they may have serious problems. Click here to see guidelines on flying after pneumothorax.

Well, what happens if you have air bubbles in your head (pneumocephalus)? Some patients with serious head injury may have this condition but need to be transported by air to definitive care. Most recently, this has been a consideration in military medical evacuation flights out of Afghanistan.

A paper from the US Army and Air Force studied 21 soldiers (small series) who were evacuated by air with known pneumocephalus. The volume of air was estimated by CT prior to transport, and ranged from less than 1ml to 43ml. None of the patients suffered neurologic deterioration during flight, and 3 who had external ventricular drainage (EVD) showed no significant change in intracranial pressure.

Bottom line: Only two cases of tension pneumocephalus have ever been described. Neither occurred in trauma patients. While expanding pneumothorax may be a problem during commercial flight, there is still little data on tension pneumocephalus. It works for the military because the soldiers are in a flying ICU and can be treated immediately if a problem develops. Not so in commercial aircraft, so beware! But remember, medical helicopters don’t fly high enough to create tension problems in any part of the body, so they are not an issue.

Related posts:

• Flying after pneumothorax
• Flying after pneumocephalus, part 2

Reference: Aeromedical evacuation of patients with pneumocephalus: outcomes in 21 cases. Aviation Space Env Med 79(1):30-35, 2008.