Mondoñedo Jarred R, McNeil John S, Herrmann Jacob, Simon Brett A, Kaczka David W
Department of Biomedical Engineering, Boston University College of Engineering and School of Medicine, Boston, Massachusetts.
Department of Anesthesiology, University of Virginia, Charlottesville, Virginia.
J Eng Sci Med Diagn Ther. 2018 Aug;1(3):031003-1-031003-10. doi: 10.1115/1.4040001. Epub 2018 May 9.
Volatile anesthetics have been shown to reduce lung resistance through dilation of constricted airways. In this study, we hypothesized that that diffusion of inhaled anesthetics from airway lumen to smooth muscle would yield significant bronchodilation , and systemic recirculation would not be necessary to reduce lung resistance ( ) and elastance ( ) during sustained bronchoconstriction. To test this hypothesis, we designed a delivery system for precise timing of inhaled volatile anesthetics during the course of a positive pressure breath. We compared changes in , , and anatomic dead space ( ) in canines (=5) during pharmacologically-induced bronchoconstriction with intravenous methacholine, and following treatments with: 1) targeted anesthetic delivery to ; and 2) continuous anesthetic delivery throughout inspiration. Both sevoflurane and isoflurane were used during each delivery regimen. Compared to continuous delivery, targeted delivery resulted in significantly lower doses of delivered anesthetic and decreased end-expiratory concentrations. However, we did not detect significant reductions in or for either anesthetic delivery regimen. This lack of response may have resulted from an insufficient dose of the anesthetic to cause bronchodilation, or from the preferential distribution of air flow with inhaled anesthetic delivery to less constricted, unobstructed regions of the lung, thereby enhancing airway heterogeneity and increasing apparent and .
挥发性麻醉剂已被证明可通过扩张狭窄气道来降低肺阻力。在本研究中，我们假设吸入麻醉剂从气道腔向平滑肌的扩散会产生显著的支气管扩张，并且在持续性支气管收缩期间，无需体循环来降低肺阻力（）和弹性（）。为了验证这一假设，我们设计了一种给药系统，用于在正压呼吸过程中精确控制吸入挥发性麻醉剂的时间。我们比较了犬类（=5）在静脉注射乙酰甲胆碱诱导的药理学支气管收缩期间以及在以下治疗后的、和解剖死腔（）的变化：1）将麻醉剂靶向递送至；2）在整个吸气过程中持续输送麻醉剂。在每种给药方案中均使用了七氟烷和异氟烷。与持续给药相比，靶向给药导致输送的麻醉剂剂量显著降低，呼气末浓度降低。然而，我们未检测到两种麻醉剂给药方案中的或有显著降低。这种无反应可能是由于麻醉剂剂量不足导致支气管扩张，或者是由于吸入麻醉剂给药时气流优先分布到肺的收缩较轻、无阻塞区域，从而增强了气道异质性并增加了表观和。
