在聖母峰脫褲 測出最低血氧量紀錄
發表於 : 週五 1月 09, 2009 10:58 am
from 自由時報 〔編譯羅彥傑／綜合報導〕
頂著攝氏零下二十五度低溫與二十節的風速，在世界最高峰頂端附近脫褲子，即使是為了科學實驗，也可能被譏是匹夫之勇。不過，三十五歲的英國麻醉科醫師與重症照護專家馬丁不做如是想。他照辦了，目的是為治療重症病患另謀新法，但同時他也被檢測出已知的人類最低血液含氧量，足以列入世界紀錄。
馬丁的血氧測量結果先前被認為不符合實際情況，但他在聖母峰下方四百公尺的小岩脊上，從自己大腿鼠蹊處動脈抽取血液樣本時，還能正常行走與聊天，甚至替其他九名一起爬山的同僚們抽血。這項二○○七年五月的實驗成果，刊登在最新一期《新英格蘭醫學期刊》上。
這項實驗的目的是要了解，該如何照護罹患諸如囊胞性纖維症、肺氣腫、敗血性休克、急性呼吸窘迫症候群（ＡＲＤＳ）及藍嬰症等出現血液含氧量過低症狀的病患。包含馬丁在內的十名醫師攀爬到聖母峰峰頂下方、海拔八千四百公尺處，然後脫下氧氣罩，呼吸四周空氣達二十分鐘。
他們測量當氧氣稀薄時的人類生理變化，馬丁的血氧濃度為二．二五千帕（kPa），比正常值十二至十四千帕低了八十％，而且還不到通常導致緊急送加護病房的血氧濃度的一半。他們揣測，高空造成肺部液體集結，可能導致血氧濃度低。研究團隊領隊葛洛卡特說，低含氧量幾乎是重症照護的共同問題，「我們使用的某些干預措施，譬如提供氧氣、積極換氣，都可能是有害的。如果病患可以忍受低含氧量，我們就可以縮手不管，可能造成的傷害更小。」
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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., Hugh E. Montgomery, M.B., B.S., M.D., for the Caudwell Xtreme Everest Research Group
ABSTRACT
Background
The level of environmental hypobaric hypoxia that affects climbers at the summit of Mount Everest (8848 m [29,029 ft]) is close to the limit of tolerance by humans. We performed direct field measurements of arterial blood gases in climbers breathing ambient air on Mount Everest.
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.
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).
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.
N Engl J Med 360;2,140-149, January 8, 2009
頂著攝氏零下二十五度低溫與二十節的風速，在世界最高峰頂端附近脫褲子，即使是為了科學實驗，也可能被譏是匹夫之勇。不過，三十五歲的英國麻醉科醫師與重症照護專家馬丁不做如是想。他照辦了，目的是為治療重症病患另謀新法，但同時他也被檢測出已知的人類最低血液含氧量，足以列入世界紀錄。
馬丁的血氧測量結果先前被認為不符合實際情況，但他在聖母峰下方四百公尺的小岩脊上，從自己大腿鼠蹊處動脈抽取血液樣本時，還能正常行走與聊天，甚至替其他九名一起爬山的同僚們抽血。這項二○○七年五月的實驗成果，刊登在最新一期《新英格蘭醫學期刊》上。
這項實驗的目的是要了解，該如何照護罹患諸如囊胞性纖維症、肺氣腫、敗血性休克、急性呼吸窘迫症候群（ＡＲＤＳ）及藍嬰症等出現血液含氧量過低症狀的病患。包含馬丁在內的十名醫師攀爬到聖母峰峰頂下方、海拔八千四百公尺處，然後脫下氧氣罩，呼吸四周空氣達二十分鐘。
他們測量當氧氣稀薄時的人類生理變化，馬丁的血氧濃度為二．二五千帕（kPa），比正常值十二至十四千帕低了八十％，而且還不到通常導致緊急送加護病房的血氧濃度的一半。他們揣測，高空造成肺部液體集結，可能導致血氧濃度低。研究團隊領隊葛洛卡特說，低含氧量幾乎是重症照護的共同問題，「我們使用的某些干預措施，譬如提供氧氣、積極換氣，都可能是有害的。如果病患可以忍受低含氧量，我們就可以縮手不管，可能造成的傷害更小。」
-------------------------------------------------
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., Hugh E. Montgomery, M.B., B.S., M.D., for the Caudwell Xtreme Everest Research Group
ABSTRACT
Background
The level of environmental hypobaric hypoxia that affects climbers at the summit of Mount Everest (8848 m [29,029 ft]) is close to the limit of tolerance by humans. We performed direct field measurements of arterial blood gases in climbers breathing ambient air on Mount Everest.
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.
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).
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.
N Engl J Med 360;2,140-149, January 8, 2009
