Test 'may predict altitude sickness'
Scientists say they have developed a way of predicting who will develop altitude sickness.
The condition, otherwise known as acute mountain sickness, occurs when people have difficulty adapting to low oxygen levels at high altitude.
Most cases are mild - but in rare cases there can be a potentially fatal build-up of fluid on the brain and lungs.
Altitude sickness often affects skiers and mountaineers.
It affects people only when they go above 8,000ft (2,500m).
Around 30% experience a mild form of the condition. Between 1%-2% develop the more severe form of the disease.
It is not possible to get altitude sickness in the UK because the highest mountain - Ben Nevis in Scotland - is only 4,406ft (1,344m) high.
The condition usually causes relatively mild symptoms such as headaches, nausea and dizziness. But it can in rare cases cause fluid to build up on the lungs or brain.
Current advice is to aim to acclimatise slowly to higher altitudes to give the body a chance to adapt.
Drugs which can reduce the severity of symptoms are also available, but can have side-effects.
Details of the new test are being presented to the EuroEcho-Imaging conference in Istanbul.
The researchers looked at how the heart responds to hypoxia - low oxygen levels.
They studied cardiovascular function, using non-invasive, ultrasound-based techniques, in 34 healthy volunteers once at sea level and again after going by cable car up Aiguille de Midi, a mountain in the French Alps, to a height of 12,600 ft (3,842m).
Around a third of them had experienced severe altitude sickness previously.
Participants had oxygen saturation levels monitored and had an ultrasound check of their heart function, using a portable device, after four hours on the mountain.
After 24 hours at high altitude, 13 out of 34 volunteers developed moderate to severe symptoms.
They had lower oxygen saturation levels and the ultrasound showed poorer function in the systolic (pumping) ability in the right ventricle.
The changes were not seen in people who did not display altitude sickness symptoms.
Dr Rosa Maria Bruno, who led the study, said: "If these results are confirmed by larger studies, it will be possible to identify vulnerable individuals and suggest particular behaviours and drugs.
"Thus we can limit drug use (and side-effects) only to those who will really need them, and give them special advice and recommendations such as avoiding high altitudes or spending more time ascending to allow time for acclimatisation."
She added: "At the moment we don't know exactly why some people can adapt successfully to high altitude and other people cannot, or how to identify susceptible individuals in whom preventative strategies may be applied.
"This can be an important problem since an increasing number of people of all ages go to high altitude, mainly for recreational purposes but also for working without being conscious of the potential risks."
The test can now only be done once people have spent at least four hours at high altitude but the team hope it can be developed so it can work sooner.