Porra L, Monfraix S, Berruyer G, Le Duc G, Nemoz C, Thomlinson W, Suortti P, Sovijärvi A R A, Bayat S
Department of Physical Sciences, University of Helsinki, Helsinki FIN 00014, Finland.
J Appl Physiol (1985). 2004 May;96(5):1899-908. doi: 10.1152/japplphysiol.00866.2003. Epub 2004 Feb 13.
A respiration-gated synchrotron radiation computed tomography (SRCT) technique, which allows visualization and direct quantification of inhaled stable xenon gas, was used to study the effect of tidal volume (Vt) on regional lung ventilation. High-resolution maps (pixel size 0.35 x 0.35 mm) of local washin time constants (tau) and regional specific ventilation were obtained in five anesthetized, paralyzed, and mechanically ventilated rabbits in upright body position at the fourth, sixth, and eighth dorsal vertebral levels with a Vt from 4.9 +/- 0.3 to 7.9 +/- 0.4 ml/kg (means +/- SE). Increasing Vt without an increase in minute ventilation resulted in a proportional increase of mean specific ventilation up to 65% in all studied lung levels and reduced the scattering of washin tau values. The tau values had log-normal distributions. The results indicate that an increase in Vt decreases nonuniformity of intraregional ventilatory gas exchange. The findings suggest that (SRCT) provides a new quantitative tool with high spatial discrimination ability for assessment of changes in peripheral pulmonary gas distribution during mechanical ventilation.
一种呼吸门控同步辐射计算机断层扫描（SRCT）技术，可实现对吸入的稳定氙气进行可视化和直接定量分析，被用于研究潮气量（Vt）对局部肺通气的影响。在五只麻醉、麻痹并机械通气的家兔处于直立体位时，于第四、第六和第八胸椎水平，以4.9±0.3至7.9±0.4 ml/kg（均值±标准误）的Vt获得了局部洗入时间常数（tau）和局部比通气量的高分辨率图谱（像素大小为0.35×0.35 mm）。在不增加分钟通气量的情况下增加Vt，导致所有研究肺水平的平均比通气量成比例增加，最高可达65%，并减少了洗入tau值的离散度。tau值呈对数正态分布。结果表明，Vt增加可降低区域内通气气体交换的不均匀性。这些发现提示，SRCT为评估机械通气期间外周肺气体分布变化提供了一种具有高空间分辨能力的新型定量工具。
