Raux Mathieu, Ray Patrick, Prella Maura, Duguet Alexandre, Demoule Alexandre, Similowski Thomas
Assistance Publique-Hôpitaux de Paris, Laboratoire de Physiopathologie Respiratoire, Service de Pneumologie, Groupe Hospitalier Pitié Salpétrière, Paris, France.
Anesthesiology. 2007 Nov;107(5):746-55. doi: 10.1097/01.anes.0000287005.58761.e8.
Mechanical ventilation is delivered to sedated patients during anesthesia, but also to nonsedated patients (ventilator weaning, noninvasive ventilation). In these circumstances, patient-ventilator asynchrony may occur, provoking discomfort and unduly increasing work of breathing. In certain cases, it is associated with an increased inspiratory load. Inspiratory loading in awake humans activates the premotor cortical regions, as illustrated by the occurrence of electroencephalographic premotor potentials. In normal humans during noninvasive ventilation, the authors used an experimental model of patient-ventilator asynchrony to determine whether premotor cortical activation occurs in this setting.
Noninvasive pressure support ventilation was administered to seven healthy volunteers aged 22-27 yr with continuous electroencephalographic recordings in Cz. The ventilator settings were first adjusted to make the subjects feel comfortable ("comfort"), and then modified to induce respiratory "discomfort" (evaluated on a 10-cm visual analog scale). This was achieved by setting the ventilator to a higher trigger level, reducing the slope of the pressure support rise, and reducing the level of pressure support. The settings were finally brought back to their initial values. To identify a respiratory-related premotor activity, a minimum of 80 preinspiratory electroencephalographic epochs were averaged.
Altering ventilator settings induced respiratory discomfort (average visual scale 4 [1.5-6.0] vs. 0 [0-1.0] cm during "comfort"; P < 0.0001). This was associated with premotor potentials in all cases, which disappeared upon return to "comfort."
This study indicates that "ventilator fighting" in healthy humans is associated with an activation of higher cerebral areas. Premotor potentials could thus be markers of patient-ventilator asynchrony at the brain level. Both corroboration in patients and the elucidation of the causative or reactive nature of the association are needed before determining clinical implications.
机械通气用于麻醉期间的镇静患者，但也用于非镇静患者（呼吸机撤机、无创通气）。在这些情况下，可能会出现患者-呼吸机不同步，引发不适并过度增加呼吸功。在某些情况下，它与吸气负荷增加有关。清醒人类的吸气负荷会激活运动前皮质区域，脑电图运动前电位的出现就说明了这一点。在正常人类进行无创通气期间，作者使用患者-呼吸机不同步的实验模型来确定在这种情况下是否会发生运动前皮质激活。
对7名年龄在22 - 27岁的健康志愿者进行无创压力支持通气，并在Cz处进行连续脑电图记录。首先调整呼吸机设置以使受试者感到舒适（“舒适”状态），然后进行修改以诱发呼吸“不适”（通过10厘米视觉模拟量表评估）。这是通过将呼吸机设置为更高的触发水平、降低压力支持上升的斜率以及降低压力支持水平来实现的。最后将设置恢复到初始值。为了识别与呼吸相关的运动前活动，对至少80个吸气前脑电图时段进行平均。
改变呼吸机设置会诱发呼吸不适（“不适”状态下平均视觉量表评分为4[1.5 - 6.0]厘米，而“舒适”状态下为0[0 - 1.0]厘米；P < 0.0001）。在所有情况下，这都与运动前电位相关，恢复到“舒适”状态时运动前电位消失。
本研究表明，健康人类的“呼吸机对抗”与大脑高级区域的激活有关。因此，运动前电位可能是大脑水平上患者-呼吸机不同步的标志物。在确定临床意义之前，需要在患者中进行进一步证实，并阐明这种关联的因果或反应性质。
