"Karen used to say if there was anything you could do on or in water, she did it," Brad recalls.
In early 1999, the Perkins family set out for its winter vacation, a SCUBA trip to Belize, in Central America, a nine-hour flight from their home near San Francisco.
"We were both happy to be on vacation and were kind of excited about being in a tropical paradise," Brad said of him and his 40-year-old wife, also an attorney.
The morning after they arrived, they went for their first dive. Divemaster Gerald Leslie remembers Karen got a cramp as he was helping her with her equipment.
Despite the cramp, Karen was the first diver in the water. But just minutes later, she surfaced and told Leslie and her then 10-year-old daughter Clarice, who was in the boat, that said she wasn't going to do that dive.
"And suddenly, split second, she just - her eyes just rolled back," Leslie said . "And I grabbed her and I said, 'Ma'am, are you OK?'"
Brad, still in the water, got the signal to return to the boat and Leslie called for help. A doctor met them on shore, but it was already too late. Minutes later, he pronounced her dead.
"I kissed her good-bye on her forehead, because I probably wasn't going to see her again," Brad recalled.
Doctors in Belize said she died from a ruptured pancreas but that didn't make sense to Brad. Karen's parents, who are both doctors, believe her problems started not while she was diving, but while she was flying, They suspect she developed a blood clot while flying overnight from San Francisco to the East Coast.
"She was sitting on one side with a window seat," Brad said. "I don't think she moved for virtually the whole flight"
Researchers say as many as 1 in 10 long-haul flyers develop these clots in their legs - a condition called deep vein thrombosis. While most of these clots are harmless, some can break loose and travel to the lungs where they are frequently fatal.
Doctors are beginning to notice them more and, not surprisingly, there's a great deal of interest in blood clots in Hawaii, which is at least a five-hour flight from just about anywhere.
"We saw an increasing number of patients coming here from the airport or a few days after arrival in Hawaii with rather severe blood clots in their legs, said Dr. Bo Ekloff, a vascular surgeon at a Honolulu hospital. In just seven years, they treated 69 patients with these life-threatening blood clots.
Ekloff says people who are overweight, have heart or lung disease or a family history of blood clots are at increased risk.
Brad described Karen as a slightly heavy-set woman: "She had slightly high blood pressure and was taking medication for that, but there was nothing to indicate she wouldn't live to be a ripe old age of 70, 80 years old."
Norman Dupont, a retired hotel executive, also was healthy when he started feeling ill about a week after returning to Hawaii from a vacation in Morocco with his wife. Nicole.
"I had some strange pains", Dupont, 74, said. "My back was really bothering me, and then I couldn't breathe."
Doctors believe several clots probably developed while Norman was flying half way around the world - in coach class.
They also suspect blood clots are responsible for the death of 28-year-old friend Emma Christoffersen. Christoffersen and her friend Rhian Bevan took a three-week, action-adventure vacation in Australia in the fall of 2000. The two active young women flew back home to Wales exhausted, eight hours from Sydney to Singapore and 13 hours from Singapore to London.
When they finally landed, Bevan and Christoffersen had to run to catch a bus home.
"Emma got a bit out of breath and started to lag behind," Bevan recalled. "I said.'Are you OK,' and she said, 'Yes, we have to hurry'"
But Christoffersen, 28 and engaged to be married, was not OK.
"I turned around and she had just sort of slumped against the window. Her eyes just rolled back in her head and she was having difficulty breathing," Bevan recalled.
Paramedics rushed Christoffersen to a hospital not far from Heathrow Airport where she was pronounced dead. "She probably collapsed and died at the airport," said Dr. John Belstead, an emergency room physician at the hospital.
Ruth Christoffersen got the news about her daughter from a nurse. Ruth had never heard of a deep-vein thrombosis before but the hospital staff knew exactly what happened. Emma was another victim of what's come to be known as economy class syndrome.
Belstead said the hospital sees about 10 cases a year and all of them are people coming off long-haul flights.
Dr. Rusell Rayman , head of the Aerospace Medical Association says immobility may be to blame but that is not just confined to an airplane. Immobility can occur in your home, in your office, anywhere.
Ekloff, who has seen more than 70 cases of life-threatening blood clots, insists the combination of lowered oxygen pressure and dryer air on planes thickens the blood and increases the risk.
But Rayman doesn't buy it and says there is no proof or evidence. Proving it would cost money, money that Rayman said is better spent on "the far more pressing medical problems that challenge us."
Belstead says there are some things that passengers, once they are aware of the danger, can do on long flights. The most important exercise-is scrunching the toes up. If you make your ankle go up and down and around and around, that exercises the calf mscles and helps to keep the blood moving faster.
Belstead also recommends wearing support hose for long flights…
Some international airlines are beginning to encourage passengers to exercise in their seats, but U.S. carriers have only a few mentions on a Web site or in-flight magazine
But soon, airlines may be forced to do more. Lawsuits have been filed against major carriers on behalf of Australian and British survivors of flight-related blood clots. Since this story was first aired a year ago, the Christoffersens have joined a class action lawsuit against a number of airlines on Emma's behalf.
"These people knew that deep-vein thrombosis existed and we didn't, Emma didn't," Ruth said. "Emma wouldn't have rested until she let everybody know that people getting on an airplane are taking a risk."
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