Tsuno K, Prato P, Kolobow T
Department of Anesthesiology, Kumamoto University Medical School, Japan.
J Appl Physiol (1985). 1990 Sep;69(3):956-61. doi: 10.1152/jappl.1990.69.3.956.
We have explored adverse pulmonary effects of mechanical ventilation at a peak inspiratory pressure of 30 cmH2O in paralyzed and anesthetized healthy sheep. A control group of eight sheep (group A) was mechanically ventilated with 40% oxygen at a tidal volume of 10 ml/kg, a frequency of 15 breaths/min, a peak inspiratory pressure less than 18 cmH2O, and a positive end-expiratory pressure of 3-5 cmH2O. During the ensuing 48 h, there were no measurable deleterious changes in lung function or arterial blood gases. Another 19 sheep were ventilated with 40% oxygen at a peak inspiratory pressure of 30 cmH2O under a different set of conditions and were randomly assigned to two groups. In group B, the respiratory rate was kept near 4 breaths/min to keep arterial PCO2 in the normal range; in group C, the frequency was kept near 15 breaths/min by including a variable dead space in the ventilator circuit to keep arterial PCO2 near baseline values. There was a progressive deterioration in total static lung compliance, functional residual capacity, and arterial blood gases. After some hours, there were abnormal chest roentgenographic changes. At time of death we found severe pulmonary atelectasis, increased wet lung weight, and an increase in the minimum surface tension of saline lung lavage fluid.
我们在麻痹和麻醉的健康绵羊中，探究了吸气峰压为30 cmH₂O时机械通气的不良肺部影响。八只绵羊组成的对照组（A组）以40%的氧气进行机械通气，潮气量为10 ml/kg，频率为15次/分钟，吸气峰压小于18 cmH₂O，呼气末正压为3 - 5 cmH₂O。在随后的48小时内，肺功能或动脉血气没有可测量的有害变化。另外19只绵羊在不同条件下以吸气峰压30 cmH₂O用40%的氧气进行通气，并随机分为两组。在B组中，呼吸频率保持在4次/分钟左右，以使动脉PCO₂保持在正常范围内；在C组中，通过在通气回路中加入可变死腔使频率保持在15次/分钟左右，以使动脉PCO₂接近基线值。总静态肺顺应性、功能残气量和动脉血气出现进行性恶化。数小时后，胸部X线出现异常变化。在死亡时，我们发现严重的肺不张、湿肺重量增加以及肺盐水灌洗液最小表面张力增加。
