Ploysongsang Y, Rashkin M C, Ranganathan V H
Department of Internal Medicine, University of Cincinnati College of Medicine, Ohio.
Respiration. 1990;57(2):122-6. doi: 10.1159/000195832.
A patient with severe chronic obstructive pulmonary disease was studied during acute respiratory failure. On the day of intubation his respiratory rate was 42, the tidal volume 295 ml, and the maximal inspiratory pressure 8 cm H2O. These parameters improved with rest by mechanical ventilation to 16, 620 ml, and 30 cm H2O, respectively, on the day of successful weaning. Daily tidal volumes correlated significantly with maximal inspiratory muscle pressures (r = 0.936; p less than 0.001). Respiratory system compliances and resistances were measured by the inflation, the end-inspiratory occlusion, and the interrupter methods. In general, inflation compliance and occlusion compliance were comparable and significantly smaller than the interrupter compliance (p less than 0.002 and p less than 0.003, respectively), whereas inflation resistance and occlusion maximal resistance were also comparable but significantly smaller than the interrupter resistance (p less than 0.0008 and p less than 0.0006, respectively). The former was due to increased hysteresis of the pressure volume curves and the latter due to expiratory compression of airways. The compliance was low, and the resistance was high on the day of intubation and became much higher and lower, respectively, on the day of successful extubation. These physiological changes were associated with weaning difficulty. We conclude that respiratory failure and weaning are complex physiologic events under the influence of muscle strength, lung mechanics, gas exchange, and control of breathing. Therefore, prediction of weaning success based upon one or two measured parameters as has been done is probably inadequate in difficult patients.
对一名患有严重慢性阻塞性肺疾病的患者在急性呼吸衰竭期间进行了研究。在插管当天，其呼吸频率为42次/分钟，潮气量为295毫升，最大吸气压力为8厘米水柱。通过机械通气休息后，这些参数在成功脱机当天分别改善为16次/分钟、620毫升和30厘米水柱。每日潮气量与最大吸气肌压力显著相关（r = 0.936；p < 0.001）。通过充气法、吸气末阻断法和间断气流法测量呼吸系统顺应性和阻力。一般来说，充气顺应性和阻断顺应性相当，且显著小于间断气流顺应性（分别为p < 0.002和p < 0.003），而充气阻力和阻断最大阻力也相当，但显著小于间断气流阻力（分别为p < 0.0008和p < 0.0006）。前者是由于压力 - 容积曲线滞后增加，后者是由于气道呼气期受压。在插管当天顺应性较低，阻力较高，而在成功拔管当天分别变得更高和更低。这些生理变化与脱机困难相关。我们得出结论，呼吸衰竭和脱机是受肌肉力量、肺力学、气体交换和呼吸控制影响的复杂生理事件。因此，像过去那样基于一两个测量参数来预测脱机成功对于病情复杂的患者可能是不够的。
