Aerts J G, van den Berg B, Bogaard J M
Dept of Pulmonary Diseases, Erasmus University, Rotterdam, The Netherlands.
Eur Respir J. 1997 Mar;10(3):550-6.
In patients with severe chronic obstructive pulmonary disease (COPD), lung emptying may be affected by flow limitation. We tested the hypothesis that the airway compression leading to flow limitation can be counteracted by controlling the expiratory flow. The effects of an external resistor on lung emptying were studied in six patients with COPD, who were mechanically ventilated whilst sedated and paralysed. Respiratory mechanics were obtained during ventilatory support with and without the resistor. Airway compression was assessed using the interruptor method. For the study, a turbulent resistor was applied with the highest resistance level that did not increase the end-expiratory lung volume. At this resistance level, external positive end-expiratory pressure (PEEP) was generated in all patients. As total PEEP levels remained unchanged at both settings during the controlled expiration, the levels of intrinsic PEEP were significantly decreased from 0.96+/-0.30 to 0.53+/-0.19 kPa (mean+/-SD). Comparison of the expiratory flow-volume curves at both settings revealed that, during the controlled expiration, the flows were significantly decreased during the first 40% of the expired volume and significantly increased during the last 60%. As the end-expiratory lung volumes remained unchanged during both settings, these increments in flow indicated a decrease in effective resistance. Airway compression was observed during unimpeded expirations in all patients using the interruptor method. During the application of the resistor, airway compression was no longer detectable. In patients with chronic obstructive pulmonary disease receiving ventilatory support, the application of an external resistor could decrease effective expiratory resistance by counteracting airway compression, without increments in end-expiratory lung volume.
在重度慢性阻塞性肺疾病（COPD）患者中，肺排空可能受气流受限的影响。我们检验了这样一个假设，即通过控制呼气气流可以抵消导致气流受限的气道压缩。在6例COPD患者中研究了外部阻力器对肺排空的影响，这些患者在镇静和麻痹状态下接受机械通气。在有和没有阻力器的通气支持过程中获取呼吸力学参数。使用阻断法评估气道压缩情况。在本研究中，应用了一个湍流阻力器，其阻力水平最高且不会增加呼气末肺容积。在这个阻力水平下，所有患者均产生了外部呼气末正压（PEEP）。由于在控制呼气过程中两种设置下的总PEEP水平均保持不变，内源性PEEP水平从0.96±0.30 kPa显著降至0.53±0.19 kPa（均值±标准差）。两种设置下呼气流量-容积曲线的比较显示，在控制呼气过程中，呼气量前40%期间流量显著降低，后60%期间流量显著增加。由于两种设置下呼气末肺容积均保持不变，这些流量增加表明有效阻力降低。使用阻断法在所有患者的自由呼气过程中均观察到气道压缩。在应用阻力器期间，气道压缩不再可检测到。在接受通气支持的慢性阻塞性肺疾病患者中，应用外部阻力器可通过抵消气道压缩来降低有效呼气阻力，而不会增加呼气末肺容积。
