Konyukov Y A, Kuwayama N, Fukuoka T, Takahashi T, Mayumi T, Hotta T, Takezawa J
Department of Emergency and Intensive Care Medicine, Nagoya University School of Medicine, Japan.
Intensive Care Med. 1996 Apr;22(4):363-8. doi: 10.1007/BF01700461.
The triggering capability of both the pressure and flow triggering systems of the Servo 300 ventilator (Siemens-Elema, Sweden) was compared at various levels of positive end-expiratory pressure (PEEP), airway resistance (R(aw)), inspiratory effort and air leak, using a mechanical lung model.
The ventilator was connected to a two bellows-in-series-type lung model with various mechanical properties. Lung compliance and chest wall compliance were 0.03 and 0.121/cmH2O, respectively. R(aw) was 5, 20 and 50 cmH2O/l/s. Respiratory rate was 15 breaths/min. To compare the triggering capability of both systems, the sensitivity of pressure and flow triggered pressure support ventilation (PSV) was adjusted to be equal by observing the triggering time at 0 cmH2O PEEP and 16 cmH2O of pressure support (PS) with no air leak. No auto-PEEP was developed. In the measurement of trigger delay, the PS level ranged from 16 to 22 cmH2O to attain a set tidal volume (V(T)) of 470 ml at a R(aw) of 5, 20 and 50 cmH2O/l/s. The PEEP level was then changed from 0, 5 and 10 cmH2O at a PS level of 17 cmH2O and R(aw) of 5 and 20 cmH2O/l/s, and the trigger delay was determined. The effect of various levels of air leak and inspiratory effort on triggering capability was also evaluated. Inspiratory effort during triggering delay was estimated by measurements of pressure differentials of airway pressure (Paw) and driving pressure in the diaphragm bellows (Pdriv) in both systems.
There were no significant differences in trigger delay between the two triggering systems at the various PEEP and R(aw) levels. At the matched sensitivity level, air leak decreased trigger delay in both systems, and additional PEEP caused auto-cycling. A low inspiratory drive increased trigger delay in the pressure sensing system, while trigger delay was not affected in the flow sensing system. The Paw and Pdriv differentials were lower in flow triggering than in pressure triggering.
With respect to triggering delay, the triggering capabilities of the pressure and flow sensing systems were comparable with and without PEEP and/or high airway resistance at the same sensitivity level, unless low inspiratory drive and air leak were present. In terms of pressure differentials, the flow triggering system may require less inspiratory effort to trigger the ventilator than that of the pressure triggering system with a comparable triggering time. However, this difference may be extremely small.
使用机械肺模型，比较Servo 300呼吸机（瑞典西门子-伊莱玛公司）的压力触发系统和流量触发系统在不同水平的呼气末正压（PEEP）、气道阻力（R(aw)）、吸气努力和漏气情况下的触发能力。
将呼吸机连接到具有不同机械特性的双串联波纹管式肺模型。肺顺应性和胸壁顺应性分别为0.03和0.12 l/cmH₂O。R(aw)为5、20和50 cmH₂O/l/s。呼吸频率为15次/分钟。为比较两种系统的触发能力，通过在0 cmH₂O PEEP和16 cmH₂O压力支持（PS）且无漏气的情况下观察触发时间，将压力触发和流量触发压力支持通气（PSV）的灵敏度调整为相等。未产生自动PEEP。在触发延迟测量中，PS水平范围为16至22 cmH₂O，以在5、20和50 cmH₂O/l/s的R(aw)下达到470 ml的设定潮气量（V(T)）。然后在17 cmH₂O的PS水平和5及20 cmH₂O/l/s的R(aw)下，将PEEP水平从0、5和10 cmH₂O改变，并确定触发延迟。还评估了不同水平的漏气和吸气努力对触发能力的影响。通过测量两种系统中气道压力（Paw）和膈肌波纹管驱动压力（Pdriv）的压差来估计触发延迟期间的吸气努力。
在不同的PEEP和R(aw)水平下，两种触发系统的触发延迟无显著差异。在匹配的灵敏度水平下，漏气减少了两种系统的触发延迟，额外的PEEP导致自动循环。低吸气驱动力增加了压力传感系统的触发延迟，而流量传感系统的触发延迟不受影响。流量触发时的Paw和Pdriv压差低于压力触发时的压差。
关于触发延迟，在相同灵敏度水平下，无论有无PEEP和/或高气道阻力，压力传感系统和流量传感系统的触发能力相当，除非存在低吸气驱动力和漏气。就压差而言，在触发时间相当的情况下，流量触发系统触发呼吸机所需的吸气努力可能比压力触发系统少。然而，这种差异可能极小。
