Eves Neil D, Petersen Stewart R, Jones Richard L
Faculty of Physical Education and Recreation, University of Alberta, Alberta, Canada, T6G 2H9.
Aviat Space Environ Med. 2003 Oct;74(10):1040-7.
The self-contained breathing apparatus (SCBA) used by firefighters, and other working in dangerous environments, adds an external resistance to expiration, which increases expiratory work during heavy exercise.
Compressed air is typically used with the SCBA and we hypothesized that changing the inspired oxygen concentration and/or gas density with helium would reduce the external expiratory resistance.
On separate days, 15 men completed four 30-min bouts of treadmill exercise dressed in protective clothing and breathing the test gases through the SCBA. Four different gas mixtures were assigned in random order: [compressed air (NOX: 21% O2, 79% N2), hyperoxia (HOX: 40% O2, 60% N2), normoxic-helium (HE-OX: 21% O2, 79% He), and helium-hyperoxia (HE-HOX: 40% O2, 60% He)].
Compared with NOX, the two helium mixtures (but not HOX), decreased the external breathing resistance and all three gas mixtures decreased the peak expired mask pressure and the ventilatory mass moved. Both hyperoxic mixtures decreased blood lactate and the rating of perceived exertion was decreased at 30 min with HE-HOX.
These results demonstrate that the helium-based gas mixtures, and to a lesser extent HOX, reduce the expiratory work associated with the SCBA during strenuous exercise.
消防员及其他在危险环境中工作的人员所使用的自给式呼吸器（SCBA）会增加呼气时的外部阻力，从而在剧烈运动时增加呼气功。
SCBA通常使用压缩空气，我们假设用氦气改变吸入氧浓度和/或气体密度会降低外部呼气阻力。
在不同日期，15名男性穿着防护服，通过SCBA呼吸测试气体，在跑步机上完成4次30分钟的运动。随机分配四种不同的气体混合物：[压缩空气（NOX：21%氧气，79%氮气）、高氧混合气（HOX：40%氧气，60%氮气）、常氧氦气混合气（HE - OX：21%氧气，79%氦气）和氦气 - 高氧混合气（HE - HOX：40%氧气，60%氦气）]。
与NOX相比，两种氦气混合物（而非HOX）降低了外部呼吸阻力，并且所有三种气体混合物均降低了呼气末面罩压力峰值和通气质量。两种高氧混合气均降低了血乳酸水平，且在30分钟时，HE - HOX组的主观用力感觉评分降低。
这些结果表明，基于氦气的气体混合物以及程度稍轻的HOX，在剧烈运动期间可降低与SCBA相关的呼气功。
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