Kelly Susyn Joan, Martinsen Paul, Tatkov Stanislav
Fisher & Paykel Healthcare Limited, 15 Maurice Paykel Place, East Tamaki, 2013, Auckland, New Zealand.
Blue Leaf Software Limited, Hamilton, New Zealand.
Intensive Care Med Exp. 2021 Mar 17;9(1):8. doi: 10.1186/s40635-021-00374-y.
Inspired air is heated and humidified in the nose before it reaches lower airways. This mechanism is bypassed during tracheostomy, directly exposing the airways to colder and drier air from the environment, known to negatively affect mucociliary transport; however, little is known about how quickly mucociliary transport deteriorates. This study determines the short-term effect of flowing room air and nebulized hypertonic saline and mannitol on mucociliary transport in the trachea. In an ovine perfused in vitro tracheal model (N = 9) the epithelium was exposed to 25 L/min of flow, heated to lamb body temperature (38 °C) and fully saturated with water vapor as the control, followed by either room air (22 °C and 50% relative humidity) or nebulized solutions of NaCl 7% and mannitol 20% up to 1 min for a short duration, until mucociliary transport had visually changed. Mucus transport velocity (MTV) and cilia beat frequency (CBF) were continuously measured with video-microscopy.
Exposing the tracheal epithelium to air heated to body temperature and fully humidified had stable MTV 9.5 ± 1.1 mm/min and CBF 13.4 ± 0.6 Hz. When exposed to flow of room air, MTV slowed down to 0.1 ± 0.1 mm/min in 2.0 ± 0.4 s followed by a decrease in CBF to 6.7 ± 1.9 Hz, after 2.3 ± 0.8 s. Both MTV and CBF recovered to their initial state when heated and humidified air-flow was re-introduced. Exposing the tracheal epithelium to nebulized hypertonic saline and nebulized mannitol for 1 min increased MTV without a subsequent increase in CBF.
This study demonstrates mucociliary transport can deteriorate within seconds of exposing the tracheal epithelium to flowing room air and increase rapidly when exposed to nebulized hypertonic solutions. The reduction in MTV precedes slowing of CBF with room air and MTV increases without a subsequent increase in CBF during the nebulization. Their relationship is non-linear and a minimum CBF of approximately 6 Hz is required for MTV > 0, while MTV can reach 10.9 mm/min without CBF increasing. Clinically these findings indicate a potential rapid detrimental effect of breathing with non-humidified air via bypassed upper airways and the short-term effects of nebulized osmotic agents that increase MTV.
吸入的空气在到达下呼吸道之前会在鼻腔中被加热和加湿。气管切开术期间会绕过这一机制，使气道直接暴露于来自环境的更冷、更干燥的空气中，已知这会对黏液纤毛运输产生负面影响；然而，对于黏液纤毛运输恶化的速度知之甚少。本研究确定了流动的室内空气以及雾化的高渗盐水和甘露醇对气管黏液纤毛运输的短期影响。在一个体外羊气管灌注模型（N = 9）中，上皮细胞暴露于流速为25 L/min、加热至羊体温（38°C）并完全被水蒸气饱和的气流中作为对照，随后短时间（最长1分钟）暴露于室内空气（22°C和50%相对湿度）或雾化的7%氯化钠溶液和20%甘露醇溶液中，直到黏液纤毛运输在视觉上发生变化。通过视频显微镜连续测量黏液运输速度（MTV）和纤毛摆动频率（CBF）。
将气管上皮暴露于加热至体温并完全加湿的空气中时，MTV稳定在9.5±1.1 mm/min，CBF稳定在13.4±0.6 Hz。当暴露于室内空气流时，MTV在2.0±0.4秒内减慢至0.1±0.1 mm/min，随后CBF在2.3±0.8秒后降至6.7±1.9 Hz。当重新引入加热和加湿的气流时，MTV和CBF均恢复到初始状态。将气管上皮暴露于雾化的高渗盐水和雾化的甘露醇中1分钟会增加MTV，而CBF随后并未增加。
本研究表明，将气管上皮暴露于流动的室内空气后，黏液纤毛运输在数秒内就会恶化，而暴露于雾化的高渗溶液中时会迅速增加。在暴露于室内空气时，MTV的降低先于CBF的减慢，并且在雾化过程中MTV增加而CBF随后并未增加。它们之间的关系是非线性的，MTV>0时需要约6 Hz的最低CBF，而MTV在CBF不增加的情况下可达到10.9 mm/min。临床上，这些发现表明通过绕过的上呼吸道呼吸未加湿空气可能会产生快速的有害影响，以及雾化渗透剂增加MTV的短期影响。
