Head­ing over­seas th­ese hol­i­days? Here’s what hap­pens to your body

WE TEND TO TAKE AIR TRAVEL FOR GRANTED TH­ESE DAYS BUT HAVE YOU EVER WON­DERED WHAT HAP­PENS TO YOUR BODY WHEN YOU’RE HIGH ABOVE THE EARTH? WE FIND OUT WHAT GOES ON IN­SIDE WHEN YOU’RE AT AL­TI­TUDE

Good Health Choices - - Content -

When we take a plane trip our body takes a jour­ney that af­fects our car­dio­vas­cu­lar sys­tem, our sen­sory per­cep­tions and pos­si­bly even our im­mune sys­tem.

In the space of just a few min­utes, your body is shot into an en­vi­ron­ment whose con­di­tions re­sem­ble those found at al­ti­tudes of 2.5km above sea level.

It’s as if you’ve sud­denly scaled Aus­tralia’s Mt Kosciuszko. The air pres­sure drops to around 750 hec­topas­cals – a quar­ter lower than at sea level. For per­spec­tive, air pres­sure at ground level doesn’t drop below 850 hec­topas­cals, even in the eye of the sever­est cy­clone or hur­ri­cane. And even then this process takes at least 24 hours.

If that wasn’t enough, the air­flow around your body is some­times an icy 5°C when it leaves the air-con­di­tion­ing vents. This semi-frost is de­signed to counter the heat ra­di­ated by your fel­low pas­sen­gers (as much as a 100-watt light bulb per per­son) and the equip­ment – from the boil­ing hot gal­ley to the en­ter­tain­ment sys­tem.

The air you breathe on­board a plane is usu­ally taken from the at­mos­phere via a ‘tap’ in the jet en­gines. It heats up from -50°C to +200°C within sec­onds, be­fore drop­ping back to zero. Mean­while, the air hu­mid­ity falls to around 10 per­cent or lower. Nor­mal room hu­mid­ity, in com­par­i­son, is around 60 per­cent – and even in the bone-dry Sa­hara it’s still around 20 per­cent. So con­di­tions are in­deed ex­treme when you’re on board an air­craft. But what ef­fect do they have on us?

Is there such thing as ‘healthy’ aero­planes?

“It is pos­si­ble to de­sign a plane whose on-board con­di­tions match those on the ground,” says the pres­i­dent of the Ger­man So­ci­ety of Aero­space Medicine, Pro­fes­sor Jochen Hinkel­bein from the Univer­sity Hospi­tal of Cologne. But this would re­quire an air­craft’s alu­minium skin to be much thicker, and thus weigh sev­eral tonnes more, in or­der to with­stand the higher air pres­sure in­side. Air­lines would also need hun­dreds of ex­tra kilo­grams of wa­ter per flight to keep the air hu­mid­i­fied.

“The on-board con­di­tions are a com­pro­mise between well­be­ing on the one hand, and prof­itabil­ity and eco-friendly prac­tices on the other.

“Long-haul flights do not pose a prob­lem for healthy peo­ple – which is why rel­a­tively lit­tle re­search has been con­ducted in this field,” Pro­fes­sor Hinkel­bein adds. “Only now that fly­ing has be­come a mass phe­nom­e­non, with a grow­ing num­ber of older, less healthy peo­ple trav­el­ling, is a greater in­ter­est be­ing shown.

How much pres­sure can my stom­ach han­dle?

Our body is sim­i­lar to a pres­sure hull. On the ground, the ex­ter­nal air pushes against it at about the same in­ten­sity as it pushes back from in­side. In the air, this bal­ance sud­denly falls out of sync – the pres­sure in the di­ges­tive sys­tem is higher than the low­ered air pres­sure. The gases in the stom­ach ex­pand, caus­ing bloat­ing and flat­u­lence, which try to find a way to es­cape. Pain in the ear or be­hind the fore­head, felt par­tic­u­larly by those suf­fer­ing from colds, is an­other con­se­quence of dif­fer­ing pres­sure between your sur­round­ings and your head dur­ing take-off and land­ing.

‘Long-haul flights do not pose a prob­lem for healthy peo­ple’

Why do I feel thirsty when I fly?

Without peo­ple, the cabin air hu­mid­ity would only be two per­cent, but the com­bined breath­ing and sweat of the crew and pas­sen­gers in­crease this to 15 per­cent. Dur­ing a flight, our body be­comes parched – we can lose up to 1.5 litres of fluid for every three hours of fly­ing. Up to 37 per­cent of the skin’s mois­ture evap­o­rates, which can be seen in the cal­louses on our fingers we get while fly­ing, while con­tact lens wear­ers of­ten suf­fer from eye ir­ri­ta­tions.

How of­ten am I x–rayed on the plane?

The higher above the earth’s sur­face you are, the less the at­mos­phere pro­tects you from cos­mic ra­di­a­tion, though pro­tec­tion is higher over the equa­tor com­pared to the Poles. An eight-hour flight in­creases the 2100 mi­crosiev­erts of ra­di­a­tion nat­u­rally ab­sorbed by hu­mans from their sur­round­ings by around five per cent – 20 hours on a plane is roughly equiv­a­lent to hav­ing a head x-ray. While this is not con­sid­ered dan­ger­ous, crew ex­po­sure to ra­di­a­tion is mon­i­tored.

Does fly­ing change my cir­cu­la­tion?

Faint­ing is the most com­mon med­i­cal emer­gency that oc­curs on board. Sus­cep­ti­ble peo­ple are also at risk of high blood pres­sure, car­diac ar­rhyth­mia and blood clots. This is due to a lack of oxy­gen in the blood and a lack of ex­er­cise dur­ing the flight. Without mus­cu­lar strength, leg veins are un­able to prop­erly trans­port blood back to the heart.

Does fly­ing weaken my im­m­mune sys­tem?

Ini­tial stud­ies on the im­pact of oxy­gen de­fi­cien­cies on the im­mune sys­tem have found that some pro­teins change the way they work in th­ese cases. Thus, the no­to­ri­ous ‘aero­plane cold’ could not just be due to the air­con­di­tion­ing sys­tem, but also to the body’s al­tered im­mune re­sponse to germs.

Is my eye­sight worse on a plane?

The pho­tore­cep­tors in our eyes need lots of oxy­gen – and they start show­ing signs of de­fi­ciency from al­ti­tudes of just 1500 me­tres. This re­duces our abil­ity to see sharply in dimmed light by 10 to 15 per­cent.

Why do I cry more eas­ily on a plane?

Stud­ies have found that 15 per­cent of men and six per­cent of women cry more when watch­ing in-flight en­ter­tain­ment com­pared to on the ground. Ac­cord­ing to re­searchers, this is due to the height­ened emo­tional sit­u­a­tion – such as be­ing away from home or ex­cite­ment about the trip – but pos­si­bly also to the slight lack of oxy­gen in the body.

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