Université Paris-Descartes, Paris, France.
Ann Intensive Care. 2011 Jul 6;1(1):24. doi: 10.1186/2110-5820-1-24.
Helium is a low-density inert gas whose physical properties are very different from those of nitrogen and oxygen. Such properties could be clinically useful in the adult critical care setting, especially in patients with upper to more distal airway obstruction requiring moderate to intermediate levels of FiO2. However, despite decades of utilization and reporting, it is still difficult to give any firm clinical recommendation in this setting. Numerous case reports are available in the context of upper airway obstruction of different origins, but there is a lack of controlled studies for this indication. One study reported a helium-induced beneficial effect on surrogates of work of breathing after extubation in non-COPD patients, possibly in relation to laryngeal consequences of tracheal intubation. Physiological benefits of helium-oxygen breathing have been demonstrated in the context of acute severe asthma, but there is a lack of large controlled studies demonstrating an effect on pertinent clinical endpoints, except for a study reported only as an abstract, which mentioned a reduction in the intubation rate in helium-treated patients. Finally, there are a number of physiological studies in the context of COLD-COPD patients demonstrating a beneficial effect, mainly by a reduction in the resistive inspiratory work of breathing but also by a reduction in hyperinflation. Reduction of hypercapnia was mainly observed in spontaneously breathing and noninvasively ventilated helium-treated patients but not in intubated patients during controlled ventilation, suggesting that the decrease in PaCO2 was mainly in relation to a diminution in CO2 production, related to the diminution in work of breathing and not an improved alveolar ventilation. Moreover, there is little evidence that helium-oxygen could improve parameters of heterogeneity in such patients. Two RCTs were unable to demonstrate a reduction in the intubation rate in such setting, but they were likely underpowered. An adequately powered international multicentric study is ongoing and will help to determinate the exact place of the helium-oxygen mixture in the future. The place of the mixture during the weaning period will deserve further evaluation.
氦气是一种低密度惰性气体，其物理性质与氮气和氧气有很大不同。这些特性在成人重症监护环境中可能具有临床应用价值，特别是在需要中等至高 FiO2 的上气道至更远端气道阻塞的患者中。然而，尽管已经使用和报告了几十年，但在这种情况下仍然难以给出任何明确的临床建议。有许多关于不同来源上气道阻塞的病例报告，但针对该适应证缺乏对照研究。一项研究报告称，氦气对非 COPD 患者拔管后呼吸功的替代指标有有益影响，这可能与气管插管后的喉部后果有关。在急性重度哮喘的情况下，已经证明了氦氧呼吸的生理益处，但缺乏大型对照研究证明其对相关临床终点有影响，除了一项仅作为摘要报告的研究，该研究提到氦气治疗患者的插管率降低。最后，在 COLD-COPD 患者中进行了多项生理研究，证明氦气具有有益作用，主要通过降低吸气阻力功，也通过减少过度充气。高碳酸血症的减少主要在自主呼吸和无创通气的氦气治疗患者中观察到，但在控制性通气的插管患者中未观察到，这表明 PaCO2 的降低主要与 CO2 生成减少有关，与呼吸功的减少有关，而不是肺泡通气的改善。此外，几乎没有证据表明氦氧混合气可以改善此类患者的异质性参数。两项 RCT 未能证明在这种情况下降低插管率，但它们可能没有足够的效力。一项充分效力的国际多中心研究正在进行中，将有助于确定氦氧混合物在未来的确切位置。混合气体在脱机期间的应用将需要进一步评估。
