Correspondence (reply): In Reply

We thank our correspondents for their comments and critical remarks, which enable us to explain the most important points raised in some more detail. We were asked to provide a review article that enables general practitioners to grasp the basics of altitude medicine, and not a systematic review; this would not have been feasible in view of the available space. Our recommendations are based on studies that are methodologically sound and in case of scarce data on experts’ opinions, which we referenced.

Our recommendation of a fixed time period of three months after acute events, such as myocardial infarction, stroke, thromboembolism, and/or after implantation of a cardioverter defibrillator came in for criticism. Our recommendation is shared with experts on altitude medicine (1). We thought that such expert opinions were useful for a non-specialized target audience. Whether the latency period may be shortened in some selected cases, if the conditions stipulated for a visit to altitudes between 2000 meters and 3000 meters are met (Box), is up for discussion. These conditions are of course determined by the type and severity of the illness, as emphasized by our correspondents.

When criticizing our comparison with migraine, Küpper and colleagues may have missed the fact that we were talking about acute altitude sickness and not headache. In acute altitude sickness, the headache is often intensified by physical exertion; nausea and vomiting are often present. This has been confirmed by a study of 1285 mountaineers, by using the Kiel Headache Questionnaire (Kieler Kopfschmerzfragebogen). In pronounced acute altitude sickness, at 4559 meters, the diagnostic criteria for migraine were met in 65% of cases (2).

We would like to point out to Küpper et al that all “deviations from the study protocol” in our publication (reference 2 of your letter) were explicitly mentioned—however, they did not affect the negative result. We think it is highly improbable that repeated short-term exposures to hypoxia, such as is nowadays offered by fitness studios, can achieve clinically relevant prevention of acute altitude sickness in rapid ascents to altitudes higher than 4000 meters.

The study cited by Küpper et al (reference 3 in your letter) for the prophylaxis of acute altitude sickness with 2×125 mg acetazolamide was conducted in a highly selected study cohort at low risk of acute altitude sickness during trekking at altitudes between 4200 and 4900 meters. The findings cannot be generalized beyond this special setting, especially since a meta-analysis (3) and a study on Kilimanjaro (4) question even the effectiveness of 2×250 mg. We therefore continue to recommend 2×250 mg for non-acclimatized individuals living at or near sea level, who have to or want to rapidly ascend to altitudes beyond 4000 meters.

In conclusion, we would like to point out that tadalafil is also recommended for the prevention of altitude pulmonary edema by the experts whom Küpper et al cite in their reference 1, and that we do not think that nifedipine and dexamethasone should be essential in any mountaineer’s backpack. These drugs should be given only to mountaineers who, on the basis of their medical history, are at particularly high risk, who have been trained accordingly, and who are able to handle these drugs responsibly.