%0 Journal Article
%T The lung at high altitude
%A Annalisa Cogo
%J Multidisciplinary Respiratory Medicine
%D 2011
%I BioMed Central
%R 10.1186/2049-6958-6-1-14
%X A new classification of altitude levels based on the effects on performance and well-being has been recently proposed [1]: the decrease in partial pressure of oxygen reduces maximal oxygen uptake and impairs "aerobic" performance by reducing maximal aerobic power. Submaximal exercise performance is also impaired at altitude. When the acclimatization is not adequate, hypoxia triggers maladaptive responses that lead to various forms of high altitude illness or acute mountain sickness (AMS), characterized by headache plus gastrointestinal symptoms (anorexia, nausea) and sleep disturbances. AMS is present in 10-30% of subjects at altitudes between 2500 and 3000 m a.s.l. and is usually due to a fast ascent. It is well defined by the short phrase: "Too fast, too high". Less frequent, but much more serious, consequences are high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE).The lung response to acute altitude exposure is mainly hyperventilation which, together with elevated heart rate, aims at achieving an adequate supply of oxygen to the tissues. At rest, ventilation increases by firstly increasing the tidal volume, at least up to 3500 m. Above this altitude, also the breathing rate significantly increases. Besides the compensatory response, other mechanisms affect lung physiology during hypoxic exposure: the increase of pulmonary artery pressure and endothelial permeability which can explain the extravascular lung fluid accumulation described in many papers [2]. It must be underlined that the interstitial fluid accumulation which affects a large part of climbers at high altitude should be considered a para-physiological mechanism and does not predict subsequent pulmonary edema [3].The role of the lung in the acute exposure to altitude was first described by Angelo Mosso, physiologist at the University of Torino, at the end of the 19th century. He very well pointed out the changes in ventilation and the reduction of lung volumes consistent with
%U http://www.mrmjournal.com/content/6/1/14