Weiler N, Eberle B, Latorre F, von Paczynski S, Heinrichs W
Klinik für Anästhesiologie, Johannes Gutenberg-Universität Mainz.
Anaesthesist. 1996 Oct;45(10):950-6. doi: 10.1007/s001010050329.
The lateral decubitus position is the standard position for nephrectomies. There is a lack of data about the effects of this extreme position upon respiratory mechanics and gas exchange. In 20 patients undergoing surgery in the nephrectomy position, we compared a new closed-loop-controlled ventilation algorithm, adaptive lung ventilation (ALV), which adapts the breathing pattern automatically, to the respiratory mechanics with conventionally controlled mandatory ventilation (CMV). The aims of our study were (1) to describe positioning effects on respiratory mechanics and gas exchange, (2) to compare ventilatory parameters selected by the ALV controller with traditional settings of CMV, and (3) to assess the individual adaptation of the ventilatory parameters by the ALV controller. The respirator used was a modified Amadeus ventilator, which is controlled by an external computer and possesses an integrated lung function analyzer. In a first set of measurements, we compared parameters of respiratory mechanics and gas exchange in the horizontal supine position and 20 min after changing to the nephrectomy position. In a second set of measurements, patients were ventilated with ALV and CMV using a randomized crossover design. The CMV settings were a tidal volume of 10 ml/kg body weight, a respiratory rate of 10 breaths/min, an I:E ratio of 1:1.5, and an end-inspiratory pause of 30% of inspiratory time. With both ventilation modes F1O2 was set to 0.5 and PEEP to 3 cm H2O. During ALV a desired alveolar ventilation of 70 ml/ kg KG.min was preset. All other ventilatory parameters were determined by the ALV controller according to the instantaneously measured respiratory parameters. Positioning induced a reduction of compliance from 61.6 to 47.9 ml/cm H2O; the respiratory time constant shortened from 1.2 to 1.08 s, whereas physiological dead space increased from 158.9 to 207.5 ml. On average, the ventilatory parameters selected by the ALV controller resembled very closely those used with CMV. However, an adaptation to individual respiratory mechanics was clearly evident with ALV. In conclusion, we found that the effects of positioning for nephrectomy are minor and may give rise to problems only in patients with restrictive lung disease. The novel ALV controller automatically selects ventilatory parameters that are clinically sound and are better adapted to the respiratory mechanics of ventilated patients than the standardized settings of CMV are.
侧卧位是肾切除术的标准体位。关于这种极端体位对呼吸力学和气体交换的影响，目前缺乏相关数据。在20例接受肾切除术体位手术的患者中，我们将一种新的闭环控制通气算法——自适应肺通气（ALV），它能自动调整呼吸模式，与传统控制的强制通气（CMV）的呼吸力学进行了比较。我们研究的目的是：（1）描述体位对呼吸力学和气体交换的影响；（2）比较ALV控制器选择的通气参数与CMV的传统设置；（3）评估ALV控制器对通气参数的个体适应性。使用的呼吸机是一台改良的阿马德乌斯呼吸机，由外部计算机控制，并配有集成的肺功能分析仪。在第一组测量中，我们比较了水平仰卧位和改为肾切除术体位20分钟后的呼吸力学和气体交换参数。在第二组测量中，患者采用随机交叉设计分别接受ALV和CMV通气。CMV的设置为潮气量10 ml/kg体重、呼吸频率10次/分钟、吸呼比1:1.5以及吸气末暂停时间为吸气时间的30%。两种通气模式下，FiO₂均设置为0.5，呼气末正压（PEEP）设置为3 cm H₂O。在ALV期间，预设期望的肺泡通气量为70 ml/kg体重·分钟。所有其他通气参数由ALV控制器根据即时测量的呼吸参数确定。体位改变导致顺应性从61.6 ml/cm H₂O降至47.9 ml/cm H₂O；呼吸时间常数从1.2秒缩短至1.08秒，而生理死腔从158.9 ml增加至207.5 ml。平均而言，ALV控制器选择的通气参数与CMV使用的参数非常接近。然而，ALV对个体呼吸力学的适应性明显可见。总之，我们发现肾切除术体位的影响较小，仅在限制性肺病患者中可能引发问题。新型ALV控制器能自动选择临床上合理的通气参数，且比CMV的标准化设置更能适应通气患者的呼吸力学。
