Sassoon C S
University of California, Irvine.
Respir Care. 1992 Sep;37(9):1056-69.
Because of the design characteristics, flow-triggering appears to offer measurable advantages over pressure-triggering, particularly during spontaneous breathing. During the trigger phase, flow-triggering provides a relatively shorter time delay than pressure-triggering. A trigger sensitivity that does not cause autocycling can be set while a short time delay is maintained. It remains to be determined whether flow-triggering has less effect on the pressure-time product than pressure-triggering. During the post-trigger phase, the relatively optimal flow delivery with flow-by results in the maintenance of airway pressure at or above the end-expiratory airway pressure level. This accounts for the lower level of inspiratory muscle work observed with flow-by over that observed with demand-flow. Whether inspiratory muscle work on a demand-flow system with optimal flow delivery will be similar to that on flow-by is not known. With a flow-by or demand-flow system, the circuit pressure-sensing site influences the flow-pressure control algorithm in the post-trigger phase only. In microprocessor-based ventilators, the shortcomings seen with pressure-triggering during the post-trigger phase can unquestionably be overcome with a better ventilator algorithm design or the application of a small amount of pressure support. However, during the trigger phase, the impact of this effort is less clear.
由于其设计特点，流量触发相较于压力触发似乎具有明显优势，尤其是在自主呼吸期间。在触发阶段，流量触发比压力触发提供的时间延迟相对更短。可以设置不会导致自动循环的触发敏感度，同时保持较短的时间延迟。流量触发对压力 - 时间乘积的影响是否小于压力触发仍有待确定。在触发后阶段，持续气流带来的相对优化的气流输送可使气道压力维持在呼气末气道压力水平或以上。这就解释了与按需气流相比，持续气流观察到的吸气肌做功水平更低的原因。具有优化气流输送的按需气流系统上的吸气肌做功是否会与持续气流时相似尚不清楚。对于持续气流或按需气流系统，回路压力传感部位仅在触发后阶段影响气流 - 压力控制算法。在基于微处理器的呼吸机中，通过更好的呼吸机算法设计或应用少量压力支持，无疑可以克服触发后阶段压力触发所出现的缺点。然而，在触发阶段，这种努力的影响尚不清楚。
