Weisberger S A, Carlo W A, Fouke J M, Chatburn R L, Tillander T, Martin R J
Pediatr Res. 1986 Jan;20(1):45-8. doi: 10.1203/00006450-198601000-00012.
The measurement of tidal volume during high-frequency jet ventilation is difficult due to the high-frequency components of the inspiratory flow. To validate tidal volume measured with a screen pneumotachograph placed on the expiratory limb, we simultaneously determined tidal volume with a body plethysmograph in seven anesthetized normal adult New Zealand rabbits before and after saline lung lavage. Four to six comparisons of tidal volume were obtained by varying peak inspiratory pressures at each combination of frequency (120, 240, and 480/min) and inspiratory to expiratory time ratio (1:1, 1:3, 1:5, 1:9). Overall, 90% of the tidal volumes measured with the pneumotachograph were within 10% of 1 ml of the volumes determined with the plethysmograph, independent of frequency, inspiratory to expiratory time ratio, and lung compliance. There was unidirectional outward flow at the pneumotachograph during inspiration when both normal and saline lavaged lungs were being ventilated, suggesting a lack of gas entrainment. We conclude that a pneumotachograph on the expiratory limb may be used to measure tidal volume and gas entrainment in vivo during high-frequency jet ventilation. Determination of tidal volume may serve to optimize ventilator settings during high-frequency jet ventilations and facilitate an understanding of the mechanism involved in gas exchange.
由于吸气气流的高频成分，高频喷射通气期间潮气量的测量很困难。为了验证放置在呼气支路上的筛孔式呼吸流速计所测量的潮气量，我们在七只麻醉的正常成年新西兰兔进行盐水肺灌洗前后，同时用体容积描记法测定潮气量。通过在频率（120、240和480次/分钟）和吸气与呼气时间比（1:1、1:3、1:5、1:9）的每种组合下改变吸气峰压，获得了四到六次潮气量比较。总体而言，无论频率、吸气与呼气时间比以及肺顺应性如何，用呼吸流速计测量的潮气量中有90%在与容积描记法测定的容积相差1毫升的10%以内。在正常肺和盐水灌洗肺通气时，吸气期间呼吸流速计处有单向向外流动，提示无气体夹带。我们得出结论，呼气支路上的呼吸流速计可用于在高频喷射通气期间体内测量潮气量和气体夹带。潮气量的测定有助于优化高频喷射通气期间的呼吸机设置，并有助于理解气体交换所涉及的机制。
