Brugger Hermann, Sumann Günther, Meister Roland, Adler-Kastner Liselotte, Mair Peter, Gunga Hanns Christian, Schobersberger Wolfgang, Falk Markus
Mountain Rescue Service provided by the South Tyrolean Alpine Association, International Commission for Mountain Emergency Medicine, Europastrasse 17, I-39031 Bruneck, Italy.
Resuscitation. 2003 Jul;58(1):81-8. doi: 10.1016/s0300-9572(03)00113-8.
Snow avalanche case reports have documented the survival of skiers apparently without permanent hypoxic sequelae, after prolonged complete burial despite there being only a small air pocket on extrication. We investigated the underlying pathophysiological changes in a prospective, randomised 2 x 2 crossover study in 12 volunteers (28 tests) breathing into an artificial air pocket (1- or 2-l volume) in snow. Peripheral SpO(2), ETCO(2), arterialised capillary blood variables, air pocket O(2) and CO(2), snow density, and snow conditions at the inner surface of the air pocket were determined. SpO(2) decreased from a median of 99% (93-100%) to 88% (71-94%; P<0.001) within 4 min of breathing into the air pocket; the reduction was greater at 1 l, than 2 l, volume air pocket (P=0.013, intention to treat P=0.003) and correlated to snow density (r=0.50, P=0.021, partial correlation coefficient). ETCO(2) rose simultaneously from median 5.07 kPa (3.47-6.93 kPa) to 6.8 kPa (5.87-8.27 kPa; P<0.001), with consequent respiratory acidosis. Despite premature interruption due to hypoxia (SpO(2)</=75%) in 17 of 28 tests (61%), a respiratory steady state prevailed in five tests until protocol completion (30 min). We conclude that the degree of hypoxia following avalanche burial is dependent on air pocket volume, snow density and unknown individual personal characteristics, yet long-term survival is possible with only a small air pocket. Hence, the definition of an air pocket, "any space surrounding mouth and nose with the proviso of free air passages" is validated as the main criterion for triage and management of avalanche victims. Our experimental model will facilitate evaluating the interrelation between volume and inner surface area of an air pocket for survival of avalanche victims, whilst the present findings have laid the basis for future investigation of possible interactions between hypoxia, hypercapnia, and hypothermia (triple H syndrome) in snow burial.
雪崩病例报告记载，滑雪者在长时间完全被埋后仍能存活，显然没有永久性缺氧后遗症，尽管获救时只有一个小的气腔。我们在一项前瞻性、随机的2×2交叉研究中，对12名志愿者（进行了28次测试）进行了调查，让他们在雪中对着一个人工气腔（1升或2升容积）呼吸，以研究潜在的病理生理变化。测定了外周血氧饱和度（SpO₂）、呼气末二氧化碳分压（ETCO₂）、动脉化毛细血管血液变量、气腔中的氧气和二氧化碳、雪密度以及气腔内表面的雪况。在对着气腔呼吸4分钟内，SpO₂从中位数99%（93% - 100%）降至88%（71% - 94%；P<0.001）；1升容积气腔中的下降幅度大于2升容积气腔（P = 0.013，意向性分析P = 0.003），且与雪密度相关（r = 0.50，P = 0.021，偏相关系数）。ETCO₂同时从中位数5.07千帕（3.47 - 6.93千帕）升至6.8千帕（5.87 - 8.27千帕；P<0.001），继而出现呼吸性酸中毒。尽管在28次测试中有17次（61%）因缺氧（SpO₂≤75%）而提前中断，但仍有5次测试直至方案完成（30分钟）时维持了呼吸稳定状态。我们得出结论，雪崩被埋后的缺氧程度取决于气腔容积、雪密度以及未知的个体特征，但即使只有一个小气腔也有可能长期存活。因此，气腔的定义“围绕口鼻的任何空间，前提是有自由气道”被确认为雪崩受害者分诊和管理的主要标准。我们的实验模型将有助于评估气腔容积与内表面积之间的相互关系对雪崩受害者存活的影响，而目前的研究结果为未来研究雪中被埋时缺氧、高碳酸血症和低温（三重H综合征）之间可能的相互作用奠定了基础。
