There are many potential reasons why people feel “under the weather” after an extended flight; cramped seating, lack of sleep, airline food and excessive alcoholic beverages can all take their toll. However, one additional cause of air travel malaise that is not as well known is the effect of changing cabin pressure. During every pre-flight safety message, flight attendants explain, “In the event of a loss in cabin pressure, oxygen will be provided, a mask like this will fall from the panel above, pull it to your face…” But what is cabin pressure?
Most people have experienced changes in pressure while swimming. If you dive to the bottom of a pool you can feel an increased pressure on your ears and sinus, conversely the pressure is reduced as you rise to the surface. Atmospheric pressure behaves in a similar way. As you move upward into the atmosphere there is less pressure. However, as a passenger in relatively air tight fuselage, the pressure remains the same as when the cockpit door was closed. Right? Maybe.
Federal aviation regulations specify air pressure in the cabin of a commercial airliner must not be lower than that found at an altitude of 8,000 ft (2,438 m).
The reason for this seemingly arbitrary level is two fold. First, the cruising altitude of jet airplane is around 30,000 feet. Humans suddenly exposed to that altitude would lose consciousness within a few minutes. The body cannot quickly adapt to the reduced oxygen per breath at such an extreme elevation, so for passenger safety and comfort a lower altitude (increase in cabin pressure) must be maintained. Second, the greater the difference between the pressure inside and outside of the plane the greater the forces on the structure of the plane. A common example can be seen if you purchase a bag of potato chips at sea level and then drive up to a mountain pass or ski resort. The result of the increase in elevation (and decrease in atmospheric pressure) makes the air inside the bag expand to the point of rupturing the bag. Obviously, having the shell of the plane expanding and shrinking, as it gains or losses elevation, is a very bad thing. Cabin pressure equivalent of that found at 8,000 feet was found to be a good compromise for preventing altitude related illness and maintaining the integrity of the aircraft’s shape.
This past summer as Szu-ting Yi and I were flying from Seattle WA to Taipei, Taiwan to lead a LittlePo Adventures trip, Taiwan Rock Climbing and Cultural Experience, I monitored the cabin pressure during the 12 hour flight across the Pacific using the altimeter function on my watch. While flying at nearly 30,000 my watch showed the inside cabin was at the equivalent of 6,500 feet during most of the flight.
So what does this really mean to passengers on a long flight? Most people do not develop altitude illness below 10,000 feet. However, such a sudden change in elevation can have an effect, especially for those acclimated to a sea level environment.
According to the NOLS Wilderness Medicine, signs and symptoms of acute mountain sickness can include headache, malaise, loss of appetite, nausea and disturbed sleep. Sound familiar to how you have felt after a long flight? So, what can you do?
1. Water the giver of life: Stay Hydrated!
At higher altitude there is less oxygen available with each breath and your body, especially your lungs have to work overtime to maintain normal levels of oxygen in your blood. In addition, airline cabins have very low humidity levels similar to the dry summer climate of the southwestern United States. Increased respirations combined with an extremely dry environment of the cabin makes drinking water essential. The actual amount of water a person should drink during a flight will vary considerably depending on a number of factors, but the body can process up to one quart of water per hour, so drink up!
Staying hydrated on a long flight can be challenging. Bringing your own empty water bottle to the airport and filling it once you are through security can save you money on overpriced airport bottle water. In addition, studies have shown public water supplies are often healthier than bottled water and having your own reusable water bottle decreases your carbon footprint. Also, booking an aisle seat will allow you to get up stretch your legs, have quick access to the bathroom and you can walk to the galley to request more beverages from the flight attendants
2. Everyone likes to party but: No alcohol while flying!
Alcohol is a depressant. As mentioned above your body needs to breath more often to get the proper amount of oxygen into the blood stream at higher altitudes and alcohol will only subdue this process. In addition, alcohol is a diuretic and will cause you visit the lavatory more often and potentially become further dehydrated.
3. A little drop might help: Sinuses pressure and ear pressure:
Many people have issues with their ears popping and feeling pressure in their sinuses during take-offs and landings. Individuals with cold or other sinus issues can sometimes develop severe pain as the cabin pressure changes. Swallowing liquids or chewing gum can often alleviate minor discomfort. For more blocked sinus conditions purchasing decongestant nose drops from a pharmacy and taking a few drops 30 minutes before take-off and 30 minutes before landing have been known to help relieve sinus pressure and headaches.
Even if you follow all of these tips religiously, chances are you might feel groggy after a seven hour flight from New York to Paris. But remember the same trip in 1930 would have taken two weeks by boat across the often turbulent Atlantic ocean!