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Cardiac ultrasound test enables prediction of acute mountain sickness

By 11th February 2014No Comments

Details of the first test to
identify acute mountain sickness were presented by a team of researchers from
Italy and France at the recent EuroEcho-Imaging 2013 meeting in Istanbul. The
test could revolutionise trekking and climbing by predicting who will develop
the potentially deadly condition so they can avoid high altitudes, ascend more
gradually or take preventative medication.

Dr Rosa Maria Bruno, first
author of the study presented at Euroecho said: “When people go to high
altitude, above 2500m, they develop reduced content of O2 in the
blood and tissues. However the physiological response to hypoxia is very
different among individuals, ranging from successful adaptation to mild to
severe symptoms such as headache, nausea, dizziness, fatigue, loss of appetite,
insomnia, irritability, called acute mountain sickness (AMS). About 30% of
people exposed to hypobaric hypoxia develop AMS and 1-2% of people develop
potentially life-threatening conditions, such as cerebral and pulmonary edema.”

“At the moment it is unknown
why some people can adapt successfully to high altitude and other people
cannot, or how to identify susceptible subjects 


The researchers hypothesized
that cardiovascular maladaptation to hypoxia was responsible for AMS symptoms.
Thus its early identification could predict the future development of symptoms.
They studied cardiovascular function by means of ultrasound-based techniques in
34 healthy volunteers at sea level and after passive ascent (by cable car) to
3842m (Aiguille du Midi, France). About one third of the individuals had
previously experienced an episode of high-altitude cerebral and/or pulmonary


After 24 hours at 3842m, 13
out of the 34 volunteers developed symptoms of moderate to severe AMS. Their
cardiovascular function at sea level was similar to the remaining group. 
But they had significant
alterations in cardiovascular adaptation to hypoxia after only 4 hours from
arrival at high altitude. Their O
2 saturation was significantly
lower and the systolic function of the right ventricle, evaluated by means of
cardiac ultrasound (tricuspid annular plane systolic excursion, TAPSE),
decreased – all in the presence of a similar increase in pulmonary artery
pressure compared to subjects without AMS symptoms. In contrast, TAPSE was
unchanged in the individuals without AMS symptoms.

Dr Bruno said: “When
analyzed separately, none of these measures was sufficiently accurate to
predict AMS. But when we combined O2 saturation and TAPSE, both very
easily measurable parameters, we found that a TAPSE value <28mm and O2
saturation <87% after 4 hours of exposure to high altitude could predict who
will develop AMS the day after with excellent negative predictive value (94%)
and sensitivity (92%).”


She added: “The test is very
simple and quick: O2 saturation can be measured very easily by
anyone, and a low-cost, portable ultrasound machine is sufficient for the TAPSE
measurement. However you need to go and stay 4 hours at high altitude to do
this test. Future steps will be to test whether a shorter length of stay and/or
experimental hypoxia (induced in the lab by breathing air with a reduced
content of O2 with a mask) are equally informative. We also need to
confirm the validity of the test in a larger population. If we obtain good
results with these further experiments, this easy test could be used in the
very near future.” 
Dr Bruno concluded: “Our
results suggest that it is possible to identify vulnerable individuals and
suggest particular behaviors and drugs only to this subgroup”