Imsand C, Feihl F, Perret C, Fitting J W
Institut de Physiopathologie, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
Anesthesiology. 1994 Jan;80(1):13-22. doi: 10.1097/00000542-199401000-00006.
In synchronized intermittent mandatory ventilation, it is generally accepted that the work of the inspiratory muscles is decreased by the ventilator so that their activity can be modulated by the frequency of assisted breaths. We examined the validity of this concept, which recently has been questioned.
We studied five patients receiving synchronized intermittent mandatory ventilation because of an acute exacerbation of chronic obstructive pulmonary disease. The level of machine assistance, defined as the percentage of total ventilation delivered by the ventilator, was varied from a high (> 60%) to a medium (20-50%) and to the lowest tolerated value (0% in four patients). Esophageal pressure, air flow, and the electromyograms of the diaphragm and sternocleidomastoid muscles were recorded. At each level of machine assistance, distinguishing assisted from spontaneous breaths, the duration of electrical activation, the integrated electromyograms, and the work of breathing were computed.
The durations of electrical activation and the integrated electromyograms of the diaphragm and sternocleidomastoid were similar in successive spontaneous and assisted breaths. At > 60% of machine assistance, the cumulative values per minute of the integrated electromyograms of the diaphragm and sternocleidomastoid and the work of breathing were reduced only by 38, 32, and 44%, respectively, compared with the lowest tolerated level of machine assistance. The durations of electrical activation did not change with increasing level of machine assistance.
The degree of inspiratory muscle rest achieved by synchronized intermittent mandatory ventilation is not proportional to the level of machine assistance; furthermore, the inspiratory motor output is not regulated breath by breath but rather is constant for a given level of machine assistance.
在同步间歇指令通气中，人们普遍认为吸气肌的做功会因呼吸机而减少，从而其活动可由辅助呼吸频率调节。我们检验了这一最近受到质疑的概念的正确性。
我们研究了5例因慢性阻塞性肺疾病急性加重而接受同步间歇指令通气的患者。机器辅助水平定义为呼吸机提供的总通气量的百分比，范围从高（>60%）到中（20 - 50%），再到最低耐受值（4例患者为0%）。记录食管压力、气流以及膈肌和胸锁乳突肌的肌电图。在每个机器辅助水平，区分辅助呼吸和自主呼吸，计算电激活持续时间、肌电图积分以及呼吸功。
连续的自主呼吸和辅助呼吸中，膈肌和胸锁乳突肌的电激活持续时间和肌电图积分相似。在机器辅助水平>60%时，与最低耐受机器辅助水平相比，膈肌和胸锁乳突肌的肌电图积分每分钟累积值以及呼吸功仅分别降低了38%、32%和44%。电激活持续时间并不随机器辅助水平的增加而改变。
同步间歇指令通气实现的吸气肌休息程度与机器辅助水平不成比例；此外，吸气运动输出不是逐次呼吸调节的，而是在给定的机器辅助水平下保持恒定。
