Faculty of Medicine, Department of Anesthesiology and Critical Care, Medical Center-University of Freiburg, University of Freiburg, Freiburg, Germany.
PLoS One. 2024 Mar 21;19(3):e0299919. doi: 10.1371/journal.pone.0299919. eCollection 2024.
Wearing facepieces is discussed in the context of increasing the volume of rebreathed air. We hypothesized that rebreathed air volume increases with increasing filtering facepiece (FFP) class and that persons breathing via facepieces compensate for the additional dead-space. We have determined the effective amount of rebreathed air for a surgical masks and FFP2 and FFP3 respirators in a physical model and determined tidal volumes, breathing frequency, blood oxygen saturation, and transcutaneously measured blood carbon dioxide partial pressure (PCO2) in lung-healthy subjects breathing without and with facepieces at rest and during exercising on a recumbent ergometer. Rebreathed air volume increased with the facepieces' protection class and with increasing inspiration volume by 45 ± 2 ml to 247 ± 1 ml. Ambient airflow reduced rebreathed air volume by 17% up to 100% (all p < 0.001). When wearing facepieces, subjects increased tidal volume (p < 0.001) but not breathing frequency. Oxygen saturation was not influenced by facepieces. With FFP3 respirators PCO2 increased by up to 3.2 mmHg (p < 0.001) at rest but only up to 1.4 mmHg (p < 0.001) when exercising. Discomfort of breathing increased with increasing protection class of the facepiece but was consistently perceived as tolerable. We conclude that the amount of rebreathed air increases with increasing protection class of facepieces. Healthy adults were capable to compensate the facepieces' dead-space by adapting tidal volume at rest and during physical activity; thereby they tolerated moderate increases in PCO2. Ambient airflow may considerably reduce the amount of facepiece related rebreathed air.
在增加再呼吸空气量的背景下讨论了佩戴面罩。我们假设再呼吸空气量随过滤式面罩（FFP）级别增加而增加，并且通过面罩呼吸的人会补偿额外的死腔量。我们已经在物理模型中确定了手术口罩和 FFP2 和 FFP3 呼吸器的有效再呼吸空气量，并确定了在休息和在卧式测功机上进行运动时，肺健康受试者在不戴和戴面罩的情况下的潮气量、呼吸频率、血氧饱和度和经皮测量的血二氧化碳分压（PCO2）。再呼吸空气量随面罩的保护级别和吸气量增加而增加，从 45 ± 2 ml 增加到 247 ± 1 ml。环境气流将再呼吸空气量减少了 17%至 100%（所有 p < 0.001）。佩戴面罩时，受试者增加了潮气量（p < 0.001），但呼吸频率没有增加。氧饱和度不受面罩影响。使用 FFP3 呼吸器，在休息时 PCO2 增加高达 3.2 mmHg（p < 0.001），但在运动时仅增加高达 1.4 mmHg（p < 0.001）。随着面罩保护级别的增加，呼吸不适会增加，但始终被认为是可耐受的。我们得出结论，再呼吸空气量随面罩保护级别的增加而增加。健康成年人能够通过在休息和身体活动期间适应潮气量来补偿面罩的死腔量；因此，他们可以耐受 PCO2 的适度增加。环境气流可能会大大减少面罩相关再呼吸空气的量。
