Do you suffer headaches or migraines while flying on commercial aircraft?  The cause may surprise you.

Ever since the 1950s commercial aircraft have featured pressurized cabins.  During flight, these pressurized cabins maintain a higher pressure inside the plane than outside, so that the aircraft can travel at higher, more efficient altitudes without subjecting those on board to headache, migraine, nausea, vomiting, fatigue and other symptoms of altitude sickness.  Symptoms like migraine may be caused by dilation of blood vessels in the brain in response to low pressures found at high altitudes.

But, if the aircraft cabin is pressurized, then why do people still suffer headaches and migraines during flights?   The answer is that even though pressurized cabins are higher pressure than the air outside of the aircraft at high altitudes, they are still a much lower pressure than that found at ground level.  Allow me to explain why.

When aircraft are still on the ground the cabin pressure is the same inside as it is outside.  As aircraft gain altitude the outside air pressure begins to decrease rapidly.  Importantly, modern aircraft can only withstand so much pressure inside, relative to the pressure outside, due to the materials they are made of.  So, as aircraft gain altitude, even pressurized cabins must release some pressure to avoid wearing out the materials which make up the aircraft.  Too much wear leads to metal fatigue and other concerns that threaten the structural integrity of the aircraft unless the cabin pressure is carefully controlled relative to the pressure outside the aircraft.

In summary, pressurized cabins help, but still expose those on board to extreme changes in pressure that may trigger symptoms like headache and migraine.

Measurements

We tested cabin pressure on a modern Boeing 787 aircraft.  Measurements were obtained from takeoff to a cruising altitude of 11,582 meters (~38,000 ft) during a trans-Pacific flight.

Most striking is the significant change in cabin pressure during such a short period of time.  If you’ve ever had your ears “pop” on an airplane, this is why.

We began our journey from a ground-level atmospheric pressure of 1,000 hectopascal (“hPa”).  Within just 15 minutes the cabin pressure dropped to 831 hPa, representing a change of 169 hPa.  After an hour the pressure stabilized at 812 hPa representing a total change of 188 hPa.  These are extreme and rapid changes in pressure.

To put these numbers in perspective, atmospheric pressure resulting from changing weather patterns known to contribute to migraines is typically around 5 to 10 hPa over the course of an entire day.  

At an altitude of 11,582 meters the pressure outside the aircraft is around 200 hPa. So, an inside pressure of 812 hPa shows that while pressurized cabins aren’t perfect, they are still quite helpful.

The good news is that such extreme changes in pressure are unlikely to be experienced anywhere other than commercial aircraft.  While advances in materials used in aircraft will help with cabin pressure, it’s unlikely to make a meaningful difference.

So, what can be done to avoid symptoms caused by extreme changes in pressure experienced on commercial aircraft?  Talk to your doctor about medications, such as triptans, which may help if taken 30 minutes before takeoff.

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