【英语听和读】飞行

 

 
Jackie: Hello, this is Entertainment from BBC Learning English dot com with
me, Jackie Dalton. I've just got back from my Christmas holidays,
which involved taking a long flight. When I got off the plane, I felt
exhausted 1 and now I've got a cold and I've often wondered why flying
often makes you so tired and run down. Today we're going to find out.
This programme is all about how flying affects your body. If you’ve
ever flown, you may have noticed that when the plane takes off, your
breathing becomes quicker and your pulse rate – the speed at which
your heart is beating – goes up. This may partly be because you’re
excited or nervous, there’s another reason. What is it? Listen to
Michael Bagshaw professor of aviation medicine at Kings College,
London, to find out.
Michael
As you take off from sea level, there’s quite a significant pressure change. The pulse
rate will go up very slightly so that you take in more oxygen and remove the excess
carbon dioxide from the system.
Jackie: When you take off there’s a pressure change so get as your body works
harder to get more oxygen, your breathing and pulse rate speed up.
Another thing about our breathing when we’re flying is that the air in a
plane is recycled - or reused – very often, which means you’re
breathing in a lot of other people’s air. The ventilation – the movement
of air – isn’t great and lots of people are together in a small space. This
means you’re at a greater risk of catching 2 illnesses. According to
medical aviation expert Dr Mark Chanjo, some parts of the plane tend 
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to get better ventilation than others. Where is ventilation usually a bit
better?
Dr Mark Chanjo
The air is circulated about 12 to 15 times an hour. There is some variation, I mean, if
you’re sitting up in first class, you’re going to have better ventilation than if you’re
sitting in the back of the aircraft.
Jackie: Well, no surprises there. If you want better air, you’ll have to pay more
money and go in first class.
BBC Learning English
Jackie: Another flying-related problem which some people worry about is
called deep vein 3 thrombosis. This happens when the blood forms a clot 4
in the leg. A clot is when the blood in a part of your body stops being
as liquid as it should be and sort of clumps 5 together. But as Michael
Bagshaw tells us, it is a rare problem – studies show it doesn’t happen
often. How often does it happen, according to Michael?
Michael
It would appear that the risk of thrombosis is about 1 per cent in people undergoing
these really long flights of greater than ten hours or so.
Jackie: So only one in a hundred people is at risk of getting thrombosis on a
long flight. Michael says there’s also a study which shows that those
who did get the condition all had something in common about where
they were sitting. What was it? 
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Michael
All the deep vein thromboses that were detected occurred in people who were sitting
in non-aisle 6 seats, where, effectively, they were trapped and couldn’t easily get out to
walk around the cabin.
Jackie: Michael said all those who got deep vein thrombosis were sitting in
non-aisle sites. An 'aisle seat' is next to the part of the plane where
people walk up and down – 'the aisle' - so you’re usually more able to
move your legs around if you sit there. Non-aisle seats are in between
other seats or by the window and it’s not so easy to stretch your legs.
Why is this important when it comes to deep vein thrombosis? Listen
to find out.
Michael
Normally of course the blood is fluid in the body and as we’re walking around, the
blood that is in the legs is actually being massaged 7 by the muscles in the legs back
into the body. If you’re sitting in an aircraft, or indeed any other seat for a long period
of time and not able to move about, that natural movement of the blood back towards
the body simply doesn’t take place, the blood stagnates 8 in the leg, if you like, and in
some cases you’ll see the formation of a clot.
Jackie: Michael says that if you’re sitting and not able to move around much,
the blood doesn’t flow around your body properly. It stagnates – it
stays where it is – and could form a clot.
A common problem with long flights occurs when you cross time
zones. You might leave Japan in daylight, travel for 12 hours and when
you arrive in England you’re body is telling you it’s bed time and it
should be night – but the problem is daytime has only just started in
England. This is when you’re at risk of something we call jet lag.
Natural light plays an important part in affecting the natural rhythm or
cycle of our bodies, in particular, sleep. If we get a lot more daylight 
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than usual, it confuses our bodies. Listen to Michael. How long does it
usually take us to get used to the change?
Michael
Now the body’s rhythm will still follow its own cycle, but what’s now missing is the
trigger which resets 10 it is coming at the wrong time. So the sun is rising not when it
should it train with the body, so the body has to be reset 9 – its time clock has to be
reset - and it takes a few days for this to happen.
Jackie: Did you get the answer? It usually takes a few days for us to get over
jet lag because our body clock has to reset – start again and get used to
the new daylight hours. No wonder flying makes us so tired. Our
bodies have to work hard to cope with so many changes. I think next
time I go on holiday, I'll just take a short train ride down to the seaside
– much less stressful!