NYC Health + Hospitals | Lincoln, Department of Emergency Medicine, Bronx, New York.
Royal Prince Alfred Hospital, Sydney, Department of Emergency Medicine, New South Wales, Australia.
West J Emerg Med. 2022 Nov 1;23(6):926-930. doi: 10.5811/westjem.2022.5.55378.
Prior to intubation, preoxygenation is performed to denitrogenate the lungs and create an oxygen reservoir. After oxygen is removed, it is unclear whether renitrogenation after preoxygenation occurs faster in the supine vs the sitting position.
We enrolled 80 healthy volunteers who underwent two preoxygenation and loss of preoxygenation procedures (one while supine and one while sitting) via bag-valve-mask ventilation with spontaneous breathing. End-tidal oxygen (ETO) measurements were recorded as fraction of expired oxygen prior to preoxygenation, at the time of adequate preoxygenation (ETO >85%), and then every five seconds after the oxygen was removed until the ETO values reached their recorded baseline.
The mean ETO at completion of preoxygenation was 86% (95% confidence interval 85-88%). Volunteers in both the supine and upright position lost >50% of their denitrogenation in less than 60 seconds. Within 25 seconds, all subjects had an ETO of <70%. Complete renitrogenation, defined as return to baseline ETO, occurred in less than 160 seconds for all volunteers.
Preoxygenation loss, or renitrogenation, occurred rapidly after oxygen removal and was not different in the supine and sitting positions. After maximal denitrogenation in healthy volunteers, renitrogenation occurred rapidly after oxygen removal and was not different in the supine and sitting positions.
在插管前，进行预充氧以使肺部脱氮并建立氧气储备。在氧气被移除后，尚不清楚预充氧后重新充氮在仰卧位与坐位之间哪个更快。
我们招募了 80 名健康志愿者，他们通过带有自主呼吸的球囊-面罩通气进行了两次预充氧和失氧过程（一次仰卧位，一次坐位）。在预充氧前、达到充分预充氧（ETO＞85%）时以及氧被移除后每 5 秒记录呼气末氧（ETO）的测量值，直到 ETO 值达到记录的基线。
预充氧完成时的平均 ETO 为 86%（95%置信区间 85-88%）。仰卧位和直立位的志愿者在不到 60 秒内失去了超过 50%的脱氮。在 25 秒内，所有受试者的 ETO 均＜70%。所有志愿者在不到 160 秒内 ETO 恢复到基线，定义为完全重新充氮。
氧去除后，预充氧损失（或重新充氮）迅速发生，且在仰卧位和坐位之间没有差异。在健康志愿者最大程度脱氮后，氧去除后重新充氮迅速发生，且在仰卧位和坐位之间没有差异。
