Why do the ears start acting funny in an airplane? Why do doctors prescribe nasal drops for an ear block? What's the similarity and difference between the middle ear and a packet of chips? Let’s find out.
Image by Sasha Freemind
In the last post we briefly discussed the Outer part of the ear, the function of the Pinna and the best way to prevent wax build up that can block the ear canals (Click here, in case you missed it). Today we go beyond the ear drum.
Image Courtesy University of Dundee
The Middle Ear is the part between the ear drum (aka Tympanic Membrane) and the inner ear. It’s like a box, not a sealed one though, and has a ventilation tube that opens in the nose (called the Eustachian Tube). When sound hits the ear drum, the drum vibrates and sends signals onwards to the nerve endings in the inner ear.
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For the ear drum to be sound sensitive, it is important that it is free from any other sort of pressure acting upon it. Which means it should be a tight membrane (like that of a tabla or a bongo) which is neither ballooned out, nor sucked in. This is possible only if the air pressure on both sides of the ear drum is equal. The pressure outside the ear drum (in the ear canal) is atmospheric pressure, because the ear is open to the atmosphere. The pressure behind the ear drum (in the middle ear) is maintained through the ventilation tube that opens every time we swallow.
Image by Swaroop Deshpande (Unsplash)
At high altitudes the air in the aeroplane thins out, thus decreasing the atmospheric pressure. However the air already present inside the middle ear retains the high pressure, which expands and pushes the ear drum out, just like a packet of chips in an aeroplane. This stiffens the ear drum which then does not vibrate well in response to sound : Hence Blocked Ear.
Image by Joselito Tagrao
Lucky for us the similarity between the ear and a packet of chips ends here. Because the middle ear has a ventilation tube, by frequent swallowing we can equalise the pressure difference, thus opening the ears. That's why chewing a gum during take off is a good idea. During landing the opposite happens, when the outside pressure becomes higher than the pressure in the ear, and one needs to push air inside the ear by closing the nose and the mouth and trying to breathe out. This is called the Valsalva manoeuvre.
How to perform the Valsalva Manoeuvre (image from fabhow.com)
Flu and Ear Block :
Why do people feel their ears to be blocked when they have a cold? It is again something to do with the Eustachian tube. During a cold the nose may have increased mucous secretions which can block the Eustachian tube's opening leading to poor pressure equalisation on both sides of the ear drum. This is why doctors prescribe steam inhalation and nasal drops/ sprays to open up the nose. Those of us who don’t know this fact are often flummoxed why the doctor is treating the nose when the problem area is the ear.