Division of Intensive Care and Emergency Medicine, Department of Internal Medicine I, Medical University Innsbruck, Innsbruck, Austria.
BMC Emerg Med. 2024 Aug 13;24(1):146. doi: 10.1186/s12873-024-01066-y.
At the time of the COVID-19 pandemic, devastating incidents increased due to frequent oxygen administration to patients. The dangers associated with the use of oxygen, especially through local enrichments and formation of "oxygen clouds", have been well understood for years. Nevertheless, dramatic incidents continue to occur, since fire hazard increases exponentially with oxygen concentrations above 23%. Rescue helicopters are at a particular high risk, because of technical reasons such as oxygen use in a very small space, surrounded by kerosene lines, electronic relays and extremely hot surfaces.
In this study three different sized rescue helicopter models (Airbus H135, H145 and MD902) were examined. Oxygen enrichment in the cabin was measured with an oxymeter during a delivery rate of 15 l/min constant flow for 60 min. Furthermore, the clearance of the enriched atmosphere was tested in different situations and with different ventilation methods. To make the airflow visible, a fog machine was used to fill the helicopter cabin.
Oxygen accumulation above 21% was detected in every helicopter. After 10-15 min, the critical 23% threshold was exceeded in all three aircrafts. The highest concentration was detected in the smallest machine (MD902) after 60 min with 27.4%. Moreover, oxygen clouds persisted in the rear and the bottom of the aircrafts, even when the front doors were opened. This was most pronounced in the largest aircraft, the H145 from Airbus Helicopters. Complete and rapid removal of elevated oxygen concentrations was achieved only by cross-ventilation within 1 min.
Oxygen should be handled with particular care in rescue helicopters. Adapted checklists and precautions can help to prevent oxygen accumulation, and thus, fatal incidents. To our knowledge, this is the first study, which analyzed oxygen concentrations in different settings in rescue helicopters.
在 COVID-19 大流行期间，由于频繁给患者供氧，灾难性事件有所增加。多年来，人们已经充分了解与氧气使用相关的危险，尤其是通过局部富氧和形成“氧气云”。然而，由于氧气浓度超过 23%时火灾危险呈指数级增加，戏剧性事件仍在继续发生。由于技术原因，救援直升机风险特别高，例如在非常小的空间内使用氧气，周围有煤油管道、电子继电器和极热的表面。
在这项研究中，检查了三种不同大小的救援直升机模型（空客 H135、H145 和 MD902）。在 60 分钟内以 15 升/分钟的恒定流速输送氧气 60 分钟的过程中，使用血氧计测量机舱内的氧气富集情况。此外，还测试了不同情况下和不同通风方式下富集气氛的清除情况。为了使气流可见，使用烟雾机填充直升机机舱。
在每架直升机中都检测到氧气积累超过 21%。在所有三架飞机中，10-15 分钟后，超过了 23%的临界阈值。在 60 分钟后，最小的飞机（MD902）检测到的浓度最高，为 27.4%。此外，即使打开前门，飞机的后部和底部仍存在氧气云。在最大的飞机，即空客直升机的 H145 中，这一点最为明显。只有通过 1 分钟内的交叉通风才能完全快速地去除升高的氧气浓度。
在救援直升机中，应特别小心地处理氧气。适当的检查表和预防措施可以帮助防止氧气积聚，从而预防致命事件。据我们所知，这是第一项分析救援直升机中不同环境下氧气浓度的研究。
