Dear Editor,
We thank the respondent for their insightful comments on our article. The definition of high altitude (HA) is varied (1260m-4540m). Heath and William in their monogram ‘Man at high altitude’ have taken elevation of 3000m or more to mean HA [1]. This figure has been selected because at this point “in the majority of subjects ascending high mountains, unequivocal signs and symptoms associated with the ascent appear”[1]. Above this altitude biochemical, physiological and anatomical features of acclimatization become progressively more pronounced [1]. We agree that in Armed Forces for publication of Part II orders, altitudes above 2700m is taken as HA, though many first stage transit camps are situated above this altitude.
LakeLouise consensus group criteria have been quoted to use the term “recently arrived at HA” which carries same meaning as “recent gain in altitude”[2].
We agree that acclimatization schedule for our Armed Forces are applicable from altitudes above 2700m.
The incidence of High altitude pulmonary oedema (HAPO) is related to various factors, which include rate of ascent, the altitude reached, individual susceptibility and exertion. There are a few isolated case reports of similar illness at moderate altitudes also[3]. Peripheral oedema though uncommon may be seen in few cases of HAPO [4].
Recent studies suggest that inhaled Beta agonists are useful in prevention of HAPO [2, 5] as mentioned in our paper. They increase the clearance of fluid from alveolar space and may also lower pulmonary artery pressure. Hence their use in treatment also holds promise, though not a routine practice yet [2].
We thank the respondents for agreeing with us. We reiterate that antibiotics are not indicated in HAPO but should not be withheld when there is definite evidence of infection such as purulent sputum or high-grade fever. Problem is in diagnosing pulmonary infection in setting of HAPO as symptoms and signs may overlap.
DGAFMS memorandum issued in 1997 states that in view of the likelihood of recurrence in an individual who has had an episode of HAPO, such individuals should be made unfit for service at HA. The revised draft memorandum, which is yet to be published and circulated, does state that only patients with severe HAPO, recurrent HAPO (>1 episode) or with associated pulmonary arterial hypertension are made unfit for service in HA. Inhaled nitric oxide has shown promising results in various trials [6]. However no cost-benefit analysis has been done so far. This novel form of therapy should be used whenever indicated to save every precious life.
We agree that the reported incidence of HAPO is decreasing. This does not mean we should lower our guard, as it remains a potentially fatal condition. Need for continued education for everchanging troops cannot be overemphasized.
References
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