エベレスト登山に付いて行って，血ガス測った N Engl J Med 2009; 360:140-149

m3comカンファレンス　2015/04/23

8000m級の山でパルスオキシメーターをチェックしていたところ、眠りそうになっている隊員は%SpO2が25%を切ることがある。 もっとひどかったのは7%しかなかった。 深呼吸をされると95%くらいまですぐに回復「深呼吸は大事」 SpO2が25%くらいなら過換気では普通の状態でありそうです。 パルスオキシメーターは下限SpO2 70%までしか信頼できません（70-100%であれば±2%の誤差）

Arterial Blood Gases and Oxygen Content in Climbers on Mount Everest Michael P.W. Grocott, M.B., B.S., Daniel S. Martin, M.B., Ch.B., Denny Z.H. Levett, B.M., B.Ch., Roger McMorrow, M.B., B.Ch., Jeremy Windsor, M.B., Ch.B., and Hugh E. Montgomery, M.B., B.S., M.D. for the Caudwell Xtreme Everest Research Group N Engl J Med 2009; 360:140-149January 8, 2009DOI: 10.1056/NEJMoa0801581 METHODS We obtained samples of arterial blood from 10 climbers during their ascent to and descent from the summit of Mount Everest. The partial pressures of arterial oxygen (PaO2) and carbon dioxide (PaCO2), pH, and hemoglobin and lactate concentrations were measured. The arterial oxygen saturation (SaO2), bicarbonate concentration, base excess, and alveolar–arterial oxygen difference were calculated. Full Text of Methods... RESULTS PaO2 fell with increasing altitude, whereas SaO2 was relatively stable. The hemoglobin concentration increased such that the oxygen content of arterial blood was maintained at or above sea-level values until the climbers reached an elevation of 7100 m (23,294 ft). In four samples taken at 8400 m (27,559 ft) — at which altitude the barometric pressure was 272 mm Hg (36.3 kPa) — the mean PaO2 in subjects breathing ambient air was 24.6 mm Hg (3.28 kPa), with a range of 19.1 to 29.5 mm Hg (2.55 to 3.93 kPa). The mean PaCO2 was 13.3 mm Hg (1.77 kPa), with a range of 10.3 to 15.7 mm Hg (1.37 to 2.09 kPa). At 8400 m, the mean arterial oxygen content was 26% lower than it was at 7100 m (145.8 ml per liter as compared with 197.1 ml per liter). The mean calculated alveolar–arterial oxygen difference was 5.4 mm Hg (0.72 kPa). Full Text of Results... CONCLUSIONS The elevated alveolar–arterial oxygen difference that is seen in subjects who are in conditions of extreme hypoxia may represent a degree of subclinical high-altitude pulmonary edema or a functional limitation in pulmonary diffusion.

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