Eur Respir J 1997; 10: 1431–1432DOI: 10.1183/09031936.97.10071431Printed in UK - all rights reservedCopyright ERS Journals Ltd 1997European Respiratory JournalISSN 0903 - 1936Pulmonary gas exchange on Mount EverestJ.B. WestThe paper by PEACOCK and JONES [1], "Gas Exchangeat Extreme Altitude: Results from the British 40th Anni-versary Expedition", presented in this issue of the Jour-nal, reports fascinating new data recorded at extremealtitudes (up to 8,000 m) on Mount Everest. Among theinteresting findings, was the fact that, on the South Col(altitude 8000 m), alveolar oxygen tension (PA,O2) (mea-sured with a fuel cell) was about 5.1 kPa (38 torr) andarterial oxygen saturation (Sa,O2) (measured with a pulseoximeter) was about 70%, emphasizing the extraord-inary degree of hypoxaemia experienced by climbers atextreme altitudes. The results of the British 40th Anni-versary Expedition agree remarkably well with thoseof the 1981 American Medical Research Expedition toEverest [2, 3].The most important factor in the process of acclima-tization, which helps to maintain the arterial oxygentension (Pa,O2) and Sa,O2at viable levels, is extreme hy-perventilation. This defends the alveolar PA,O2in theface of the fall in partial pressure of oxygen (PO2) inthe surrounding air. In addition, the reduction in partialpressure of carbon dioxide (PCO2) causes a respiratoryalkalosis, which also assists in maintaining Sa,O2byincreasing the oxygen affinity of the haemoglobin. It isinteresting that, as shown in the paper by PEACOCK andJONES [1], the values for PA,O2measured on OperationEverest II were much lower [4], apparently becausethese subjects were less well acclimatized [5].One of the most stimulating topics in the area of high-altitude medicine and physiology this century has beenthe challenge of climbing Mount Everest, especially with-out supplementary oxygen. In the closing stages of thelast century, climbers were very pessimistic about rea-ching such great altitudes. For example, in 1876, T.W.Hinchliff, President of the (British) Alpine Club, wrotegloomily after visiting Santiago, Chile [6]: "I could notrepress a strange feeling as I looked at Tupungato(21,550 feet) and Aconcagua (23,080 feet) and reflect-ed that endless successions of men must in all proba-bility be forever debarred from their lofty crests....Those who, like Major Godwin-Austen, have had all theadvantages of experience and acclimatization to aidthem in attacks upon the higher Himalayas agree that21,500 feet (7,050 m) is near the limit at which manceases to be capable of the slightest further exertion".However, in 1909, an Italian aristocrat, the Duke ofthe Abruzzi, led an expedition to the Karakorum, which,as the Duke's biographer and physician, DE FILIPPI [7]wrote, was designed "to contribute to the solution ofthe problem as to the greatest height to which man mayattain in mountain climbing". The expedition reached7,500 m and the feat prompted DOUGLAS et al. [8] toargue that the lung must have secreted oxygen. Indeed,during the Pikes Peak expedition of 1911, DOUGLAS etal. [8] believed that they had found strong evidence ofoxygen secretion in acclimatized subjects.In 1919, Alexander M. Kellas, a Scottish chemist andphysiologist, made an extensive theoretical study of thephysiological problems associated with climbing Everest[9], but the work was never published in an accessibleform, and most high-altitude physiologists are unawareof it. Kellas concluded that the mountain could be clim-bed without supplementary oxygen if the technical diff-iculties were not too great, but he died dramatically whenthe initial Everest reconnaissance had its first view ofEverest in 1921.In 1924, E.F. Norton climbed to within 300 m of theEverest summit without supplementary oxygen, but itwas 54 yrs before the last 300 m were eventually con-quered! In 1930, the Italian physiologist MARGARIA [10]measured maximal oxygen consumptions at very lowbarometric pressures in a low-pressure chamber, and con-cluded that man could not reach the Everest summit with-out supplementary oxygen. A few years later, HENDERSON[11] came to the same conclusion based on measure-ments of maximal oxygen consumption made in thefield. But by 1958, 5 yrs after Hillary and Tenzing hadmade the first ascent (with supplementary oxygen), theBritish physiologist PUGH [12] was less willing to makea categorical statement, and wrote that it was "unlike-ly that the mountain could be climbed without oxygenequipment without serious risk".It was not until 1978 that Reinhold Messner and PeterHabeler astounded both physiologists and mountaineerswith their "oxygenless" ascent of Everest. MESSNER [13]reported his sensations on reaching the summit in lyri-cal terms: "Now, when... I have nothing more to do thanbreathe, a great peace floods my whole being. I breathelike someone who has run the race of his life and knowsthat he may now rest for ever... In my state of spiritualabstraction, I no longer belong to myself and to my eye-sight. I am nothing more than a single, narrow, gasp-ing lung, floating over the mists and the summits".Some physiologists were reluctant to believe the featat first (emergency oxygen had been taken), but other"oxygenless" ascents soon followed, including the spec-tacular solo ascent by Messner in 1981.This first ascent without supplementary oxygen promp-ted a theoretical analysis of the most critical factors onthe Everest summit [14]. These were: 1) the barometricpressure; 2) the extent of the hyperventilation; and 3)EDITORIALCorrespondence: J.B. West, University of California, San Diego, Deptof Medicine 0623, 9500 Gilman Drive, La Jolla, CA 92093-0623,USA.the maximal oxygen uptake. The first measurements ofthe barometric pressure and PA,CO2on the summit wereobtained by the 1981 American Medical Research Expe-dition to Everest. Barometric pressure was a little higherthan expected at 33.7 kPa (253 torr), probably becausethe weather was so fine [15]. The PA,CO2was astonish-ingly low at 0.9–1.1 kPa (7–8 torr) [3]. Maximal oxygenuptake was not measured on the actual summit but inthe Laboratory Camp at 6,300 m, when the well-accli-matized climbers breathed 14% oxygen, which gave thesame PO2as the Everest summit [16]. The value of justover 1 L·min-1agreed well with the ascent rate of Messnerand Habeler near the summit. Four years later in 1985,a simulated climb of Everest in a low-pressure chamber,Operation Everest II, greatly clarified the