Most of us who’ve spent long periods of time at high altitude are familiar with
the condition known as high altitude pulmonary edema (HAPE). This is a
situation of excess fluid in the lungs. Although full-blown HAPE is rare, its
symptoms of cough, breathlessness and fatigue seem to strike rapidly and almost
at random. Whilst in mild forms HAPE can simply spoil a summit day and
encourage a hasty retreat, if allowed to worsen and left untreated in a timely fashion,
it can prove fatal for even the strongest of mountaineers.
Historically, climbers and doctors have thought of HAPE as an “all or nothing” phenomenon. That is, either the fluid is present in the lungs and a person deteriorates quickly or the lungs are dry and they’re fit and well. However, a recent study (“Frequent subclinical high-altitude pulmonary edema detected by chest sonography as ultrasound lung comets in recreational climbers” in Critical Care Medicine 2010;38(9):1818-1823) showed that during an ascent to high altitude, most of us accumulate some amount of edema fluid in our lungs. Using portable, handheld ultrasound devices, a team from the Italian city of Aosta set out to look for “comet tails” in trekkers to Gorak Shep (5130m). These distinctive starbursts of ultrasound activity are only found when pulmonary edema is present. This technique has been shown to be useful in Emergency Department settings, where ultrasound can be used to help distinguish edema from other lung diseases, such as pneumonia or pneumothorax (collapsed lung). In the 18 healthy volunteers enrolled in this study, 15 were found to have “comet tails” at Namche Bazaar (3440m), and all 18 had them at Gorak Shep (5130m)! Unfortunately, three of the 18 volunteers developed HAPE during the trek and required treatment. These individuals were all found to have large numbers of “comet tails” on ultrasound that subsequently improved with treatment.
The results of this study would suggest that HAPE is by no means an “all or nothing” condition. Rather, it should be seen as the end manifestation of a spectrum of fluid accumulation in the lungs that probably occurs in many or most people as they ascend to altitude. It would be interesting to repeat this study with larger numbers of subjects in order to attempt to determine more accurately the true prevalence of this condition.