Mechanism of Ear Pain During Flights
Ear pain during flights occurs because atmospheric pressure changes cause gas volume expansion or contraction in the middle ear space, and when the Eustachian tube fails to equalize this pressure difference, the tympanic membrane is stretched or retracted, causing pain and inflammation. 1
The Physics Behind the Pain
Boyle's Law is the fundamental principle: As cabin pressure falls during ascent (or rises during descent), gas volumes in enclosed body spaces change inversely and proportionally. 1
Cabin Pressure Changes
- Commercial aircraft cabins are pressurized to approximately 2,438 meters (8,000 feet) equivalent altitude, not sea level, even when flying at 11,582 meters (38,000 feet). 1
- Small altitude changes at lower elevations cause much greater pressure changes than the same altitude change at higher elevations due to the logarithmic decline in atmospheric pressure. 1
- This creates a pressure differential across the cabin wall of up to 9 pounds per square inch. 1
The Pathophysiology Sequence
During Ascent
- As cabin pressure decreases, gas trapped in the middle ear expands. 1
- The Eustachian tube typically opens passively to allow excess air to escape, so ascent rarely causes problems. 2
During Descent (Where Most Problems Occur)
- As cabin pressure increases, gas in the middle ear contracts, creating negative pressure. 1
- The Eustachian tube requires active muscular opening (via swallowing, yawning, or Valsalva maneuver) to allow air to enter and equalize pressure. 3, 2
- When the Eustachian tube fails to open adequately, negative middle ear pressure develops, retracting the tympanic membrane inward. 2, 4
- This retraction causes stretching of the tympanic membrane and traumatic inflammation of the middle ear mucosa, resulting in pain. 2
Why Some People Are More Susceptible
Eustachian Tube Dysfunction is the Primary Risk Factor
- Patients with partial middle ear fluid are at highest risk for pain during descent, while ears completely full of fluid typically cause no problems because the incompressible fluid prevents pressure differentials. 3, 5
- Complete Eustachian tube obstruction can paradoxically be less problematic than partial dysfunction, because a tube that passively opens but fails to actively dilate creates worse pressure imbalances. 4
- Upper respiratory infections, allergies, or chronic inflammation impair the muscular opening mechanism. 2, 6
Buffering Mechanisms That Protect Some Individuals
- The ratio of maximum tympanic membrane volume displacement to middle ear volume affects susceptibility—greater displacement capacity requires less efficient Eustachian tube function. 4
- The relative difference between departure and destination elevations matters; smaller differences require less pressure equalization. 4
Severe Complications When Pressure Cannot Equalize
- Continued negative pressure can cause tympanic membrane perforation. 2, 6
- In extreme cases, round window membrane rupture can occur, leading to permanent sensorineural hearing loss and vestibular symptoms. 6
- Middle ear effusion (fluid accumulation) develops from the inflammatory response and can persist for an average of 8.23 days in aircrew members. 5
Common Pitfall to Understand
The problem is mechanical injury from pressure differential, not infection. 7 The inflammation is traumatic, not infectious, which is why antibiotics have no role unless secondary bacterial infection develops with purulent otorrhea. 7, 3