A study published in the New England journal of Medicine estimated that there are an average of 30 in-flight medical emergencies on U.S. flights every day. Most of them are not grave; fainting, dizziness and hyperventilation (换气过度) are the most frequent complaints, But 13% of them-roughly four a day-are serious enough to require a pilot to change course. The most common of the serious emergencies include heart trouble (46%), strokes and other neurological problems (18%), and difficult breathing (6%).
Let's face it: plane riders are stressful. For starters, cabin pressures at high altitudes are set at roughly what they would be if you lived at 5,000 to 8,000 feet above sea level. Most people can tolerate these pressures pretty easily, but passengers with heart disease may experience chest pains as a result of the reduced amount of oxygen flowing through their blood. Low pressure can also cause the air in body cavities to expand-as much as 30%+ Again, most people won't notice anything beyond mild stomach cramping. But if you've recently had an operation, your wound could open. And if' a medical device has been implanted in your body-a splint, a tracheotomy(气管切开术)tube or a catheter (导管)-it could expand and cause injury.
Another common in-flight problem is deep venous thrombosis(深静脉血栓)-the so-called economy-class syndrome, When you sit too long in a cramped position. the blood in our legs tends to clot. Most people just get sore calves. But blood clots, left untreated, could travel to the lungs, causing breathing difficulties and even death. Such clots are readily prevented by keeping blood flowing; walk and stretch your legs when possible,
Whatever you do, don't panic. Things are looking up on the in-flight-emergency front. Doctors who come to passengers' aid used to worry about getting sued; their fears have lifted somewhat since the 1998 Aviation Medical Assistance Act gave them"good Samaritan" protection. And thanks to more recent legislation, flights with at least one attendant are starting to install emergency medical kits with automated defibrillators (电击去颤器) to treat heart attacks.
Are you still wondering if you are healthy enough to fly? If you can walk 150 it. or climb a flight of stairs without getting winded, you'll probably do just fine, Having a doctor close by doesn't hurt, either.
16.Heart disease takes up about__________of the in-flight medical emergencies on US flights.
17.According to the passage, the expansion of air in body cavities can result in____________.
A) heart attack
B) chest pain
C) stomach cramping
D) difficult breathing
18.According to the passage, why does deep venous thrombosis usually happen?
A) Because the economy class is not spacious enough.
B) Because there are too many economy-class passengers.
C) Because passengers are not allowed to walk during the flight.
D) Because the low pressure in the cabin prevents blood flowing smoothly.
19.According to the J998 Aviation Medical Assistance Act, Doctors who came to passengers' aid__________.
A) do not have to be worried even if they give the patients improper treatment
B) will not be submitted to legal responsibility even if the patients didn't recover
C) are assisted by advanced emergency medical kits
D) will be greatly respected by the patient and the crew
20.The phrase "getting winded" (Line 2. Para. 5) is closest in meaning to____________.
A) falling over
B) being out of breath
C) spraining the ankle
D) moving in a curving line
19.[B]倒数第2段第3句提到，医生担心他们给予病人的医疗援助一旦出现意外就会遭到起诉，而这种害怕自从1998年《航空医疗救助法案》颁布后，在某种程度上就消失了，由此可推断，Aviation Medical Assistance Act让医生在出现意外时能避免承担法律资任，即选项B为本题答案。