Aström Elisabet, Uttman Leif, Niklason Lisbet, Aboab Jerome, Brochard Laurent, Jonson Björn
University Hospital, Department of Clinical Physiology, SE-221 85, Lund, Sweden.
Intensive Care Med. 2008 Feb;34(2):377-84. doi: 10.1007/s00134-007-0840-7. Epub 2007 Sep 1.
To avoid ventilator induced lung injury, tidal volume should be low in acute lung injury (ALI). Reducing dead space may be useful, for example by using a pattern of inspiration that prolongs the time available for gas distribution and diffusion within the respiratory zone, the mean distribution time (MDT). A study was conducted to investigate how MDT affects CO2 elimination in pigs at health and after ALI.
Randomised crossover study in the animal laboratory of Lund University Biomedical Center.
Healthy pigs and pigs with ALI, caused by surfactant perturbation and lung-damaging ventilation were ventilated with a computer-controlled ventilator. With this device each breath could be tailored with respect to insufflation time and pause time (TI and TP) as well as flow shape (square, increasing or decreasing flow).
The single-breath test for CO2 allowed analysis of the volume of expired CO2 and the volume of CO2 re-inspired from Y-piece and tubes. With a long MDT caused by long TI or TP, the expired volume of CO2 increased markedly in accordance with the MDT concept in both healthy and ALI pigs. High initial inspiratory flow caused by a short TI or decreasing flow increased the re-inspired volume of CO2. Arterial CO2 increased during a longer period of short MDT and decreased again when MDT was prolonged.
CO2 elimination can be enhanced by a pattern of ventilation that prolongs MDT. Positive effects of prolonged MDT caused by short TI and decreasing flow were attenuated by high initial inspiratory flow.
为避免呼吸机诱发的肺损伤，急性肺损伤（ALI）时潮气量应较低。减少死腔可能有用，例如通过采用一种吸气模式，该模式可延长呼吸区内气体分布和扩散的可用时间，即平均分布时间（MDT）。进行了一项研究，以调查MDT如何影响健康猪和ALI后猪的二氧化碳清除。
在隆德大学生物医学中心动物实验室进行的随机交叉研究。
对健康猪和因表面活性剂扰动及肺损伤性通气导致ALI的猪，使用计算机控制的呼吸机进行通气。使用该设备，每次呼吸可根据充气时间和暂停时间（TI和TP）以及气流形状（方形、递增或递减气流）进行调整。
二氧化碳单次呼吸测试允许分析呼出二氧化碳的体积以及从Y形管和管道中重新吸入的二氧化碳体积。在健康猪和ALI猪中，由长TI或TP导致的长MDT会使呼出二氧化碳体积根据MDT概念显著增加。由短TI或递减气流导致的高初始吸气流量会增加重新吸入的二氧化碳体积。在短MDT的较长时间段内动脉二氧化碳增加，而当MDT延长时又会再次下降。
通过延长MDT的通气模式可增强二氧化碳清除。由短TI和递减气流导致的MDT延长的积极作用会因高初始吸气流量而减弱。
