Every time they caught the 11 hour-plus flight to their holiday home in Florida, businessman Shay Kearney and his wife Thelma took the correct precautions.
"Thelma and I always wore elasticated socks on these long flights," says Shay.
"We always made sure to drink a lot of water and to exercise by walking up and down the aisles of the plane because we were aware of the dangers of clots."
However, in October 2010, the Dubliner and father-of-three adult children caught another flight to the sunny US state - but this time with friends from his local golf club, not his wife - for a long-anticipated golfing holiday.
It was a break which the Rathfarnham resident, who had only recently recovered from pneumonia, had organised.
"I was just over pneumonia, but I was really looking forward to the golfing holiday with my friends," says Shay, now aged 66.
"I organised the trip because I knew the area. I'd been looking forward to it and so were my friends. I was raring to go and, physically, I was okay."
However, after boarding the plane with his buddies, Shay neglected to take the usual precautions he routinely took when travelling with Thelma.
"You sit down, you talk about golf and you have a few beverages," he says.
Within hours of disembarking in the US, his left leg swelled up.
"It was very painful and it looked around 12pc larger than my right leg. Initially, I thought I might have got a mosquito bite," he recalls.
Later on, however, having examined his leg and discovering no visible wounds, he knew something was very wrong.
However, instead of attending a doctor in Florida, he decided to return home to seek medical attention, landing in Dublin three days later.
"I went to hospital and was seen very quickly. After blood tests, it was confirmed that I had a clot. I was kept in and received a combination of injections and oral medication to thin the blood and allow the clot to dissipate."
Shay was released from hospital after six days but had to remain on medication for six months.
However, within a short time of coming off the medication, he experienced a similar problem, was medically examined and informed he now had another clot. He is currently on the blood-thinning medication indefinitely.
Blood clots in the legs or in the lungs are collectively known as venous thromboembolism (VTE), a condition all too many people have not even heard of, despite the fact it's the number one cause of deaths in our hospitals.
VTE is a combination of two conditions.
A clot in the vein (usually in the leg or pelvis) is known as deep vein thrombosis (DVT). A clot that breaks off and travels to the lungs is known as a pulmonary embolism (PE). Together, DVT and PE make up venous thromboembolism (VTE).
The need for more awareness of the serious risks posed by blood clots is highlighted by the formation, last autumn, of two groups which are now actively campaigning on the issue - VTE Ireland and Thrombosis Ireland. The two are working together to strengthen the campaign to highlight the risks of the condition, which has been linked to 4,000 deaths every year. The HSE has also put together a group of experts to draw up protocols for the assessment of patients for VTE risk and the administration of preventative medicine.
"VTE kills more people than Aids, breast cancer, prostate cancer or traffic accidents all put together," says Dr Tomás Breslin, VTE Ireland member and Consultant in Emergency Medicine at Dublin's Mater Hospital.
"You hear a lot about all of these conditions, but you don't hear about VTE, partly because these other conditions have strong advocacy groups, while VTE traditionally did not. There is a serious lack of awareness about it. VTE is the number one cause of preventable hospital-associated deaths - more so than infection. Everyone is aware there is infection in hospitals but VTE actually kills more people than infection when it comes to hospital admissions."
In fact, VTE is the third most common cause of death from cardiovascular disease after heart attack and stroke. In Europe, VTE kills over half a million people every year, while in Ireland, it's estimated the condition affects some 11,000 people every year.
More than 60pc of cases are linked to hospital admissions where patients are bed-bound and many are preventable - in fact, the introduction of clot prevention measures in the UK has seen an 8pc reduction in VTE deaths.
The proposed introduction of similar measures here is a major objective of the VTE Ireland campaign, which believes that, in Ireland, we are missing opportunities to save hundreds of lives every year through clot prevention by the use of a specific clot-prevention medication.
"Currently, in Ireland there are no national guidelines for the administration of this medication to hospital patients," says Dr Breslin, who says that about 1,900 of the 4,000 deaths from VTE every year are preventable.
"In the UK, they introduced national guidelines like this in 2010 and they estimate this reduced deaths from hospital-related clots by 8pc."
VTE is linked to three factors, first among which is the stagnation of, or an interruption in, the normal flow of blood through the body.
"We hear about people getting clots in their legs after a long flight or car journey because of immobility," explains Dr Breslin.
If you're sitting on a plane for 12 hours with your knees bent, it interrupts the flow of blood up and down the leg - something similar can happen when you are bed-bound and immobile in hospital. The second cause is hypercoagulability. "This means your blood is thicker than normal and more likely to clot - this can be genetic or can be associated with other conditions like cancer," explains Dr Breslin, who adds that VTE is also caused by injury to the blood vessels, for example during surgery.
"A clot kills when it travels through the blood vessel to the lungs, blocking blood from circulating through the lungs and to the heart, resulting in cardiac arrest.
"This only happens in a small percentage of patients, but it can be prevented if diagnosed and treated in time, or if the patient is given prophylactic medication as a precaution.
"We want to see a system of mandatory risk assessment introduced for all patients admitted to any Irish hospitals and we want to improve patient awareness of the condition."
VTE Ireland also wants to increase patients' awareness of their rights to risk assessment and about the symptoms and signs of blood clots.
* For more information, see vetireland.org