Sassoon C S, Del Rosario N, Fei R, Rheeman C H, Gruer S E, Mahutte C K
Department of Medicine, Veterans Affairs Medical Center, Long Beach, CA 90822.
Crit Care Med. 1994 Dec;22(12):1933-41.
To determine the effect of pressure- and flow-triggered synchronous intermittent mandatory ventilation on inspiratory muscle work.
Consecutive clinical, prospective, randomized trial.
Medical intensive care unit (ICU) of a U.S. Veterans Affairs Medical Center.
Eight patients recovering from acute respiratory failure of various etiologies.
Assist control, followed by randomized application of pressure- and flow-triggered synchronous intermittent mandatory ventilation at 60%, 40%, 20% of the assist-control rate, and flow-triggered continuous positive airway pressure. A total of eight settings were maintained for 10 mins each.
Total work rate (joules/min), inspiratory muscle work (joules/L), and pressure time-product per breath (cm H2O-sec) were measured. During pressure- or flow-triggered synchronous intermittent mandatory ventilation, total work rate increased as the mandatory rate was decreased. The method of ventilator triggering had a significant effect on the total work rate. With pressure-triggered synchronous intermittent mandatory ventilation, the total work rate at 60% of the assist-control rate was similar to that with assist-control; whereas with flow-triggered synchronous intermittent mandatory ventilation, this result was achieved at 40% of the assist-control rate. At a machine support level of 20%, total work rate with pressure-triggered synchronous intermittent mandatory ventilation was significantly greater than with flow-triggered synchronous intermittent mandatory ventilation. The method of ventilator triggering had no significant effect on the inspiratory muscle work of the mandatory breaths. This finding was in contrast to the effect on inspiratory muscle work of spontaneous breaths. With pressure-triggered synchronous intermittent mandatory ventilation, inspiratory muscle work of the spontaneous breaths was greater than with the flow-triggered at machine support of 40% and 20%. With either pressure- or flow-triggered synchronous intermittent mandatory ventilation, inspiratory muscle work of the mandatory breaths was not significantly different from that of the corresponding spontaneous breaths, except at the lower machine support levels with the pressure-triggered synchronous intermittent mandatory ventilation. Pressure-time product followed a trend similar to that of inspiratory muscle work.
During synchronous intermittent mandatory ventilation, the method of ventilator triggering has a significant effect on the total work rate and inspiratory muscle work of the spontaneous breaths, particularly at lower machine support levels. Conversely, the method of ventilator triggering has no significant effect on inspiratory muscle work of the mandatory breaths.
确定压力触发和流量触发的同步间歇指令通气对吸气肌做功的影响。
连续的临床前瞻性随机试验。
美国退伍军人事务医疗中心的医学重症监护病房（ICU）。
8例因各种病因从急性呼吸衰竭中恢复的患者。
辅助控制通气，随后以辅助控制通气频率的60%、40%、20%随机应用压力触发和流量触发的同步间歇指令通气，以及流量触发的持续气道正压通气。每个设置共维持10分钟。
测量总做功速率（焦耳/分钟）、吸气肌做功（焦耳/升）和每呼吸周期的压力时间乘积（厘米水柱·秒）。在压力触发或流量触发的同步间歇指令通气期间，随着指令通气频率降低，总做功速率增加。通气触发方式对总做功速率有显著影响。压力触发的同步间歇指令通气在辅助控制通气频率的60%时，总做功速率与辅助控制通气相似；而流量触发的同步间歇指令通气在辅助控制通气频率的40%时达到此结果。在机器支持水平为20%时，压力触发的同步间歇指令通气的总做功速率显著高于流量触发的同步间歇指令通气。通气触发方式对指令呼吸的吸气肌做功无显著影响。这一发现与对自主呼吸吸气肌做功的影响相反。在机器支持水平为40%和20%时，压力触发的同步间歇指令通气时自主呼吸的吸气肌做功大于流量触发时。无论压力触发还是流量触发的同步间歇指令通气，指令呼吸的吸气肌做功与相应自主呼吸的吸气肌做功无显著差异，压力触发的同步间歇指令通气在较低机器支持水平时除外。压力时间乘积呈现与吸气肌做功相似的趋势。
在同步间歇指令通气期间，通气触发方式对自主呼吸的总做功速率和吸气肌做功有显著影响，尤其是在较低机器支持水平时。相反，通气触发方式对指令呼吸的吸气肌做功无显著影响。
