Nikischin W, Gerhardt T, Everett R, Gonzalez A, Hummler H, Bancalari E
Department of Pediatrics, University of Miami School of Medicine, FL 33101, USA.
Pediatr Pulmonol. 1996 Jul;22(1):28-34. doi: 10.1002/(SICI)1099-0496(199607)22:1<28::AID-PPUL5>3.0.CO;2-G.
Patient-triggered synchronized ventilation requires reliable and early detection of the infant's inspiratory effort. Several trigger methods have been developed that frequently lack the sensitivity to detect inspiration in small preterm infants (trigger failure), or show a high rate of breaths triggered by artifacts in the respiratory signal (autotrigger). The purpose of this study was to determine the effectiveness of the following trigger signals: abdominal movement sensed by a newly developed induction technique, chestwall motion detected by changes in transthoracic impedance, and tidal volume measured by anemometry at the endotracheal tube connector. Ten preterm infants (birth weight, 580-1,424 g; median weight, 943 g; study weight, 535-1,415 g; median weight, 838 g; gestation age, 26-32 weeks, median gestational age, 28 weeks, study age, 1-50 days, median study age, 11 days) were included in the study. A Sechrist SAVI ventilator was triggered by one of three signals: chestwall or abdominal movement, or tidal volume generated by the infants. Response time between beginning of inspiratory flow, the occurrence of the trigger signal (signal delay), and the onset of the triggered breath (trigger delay) were determined for each of the three signals. The signal response time was -13.5 msec (95% CI, -33 to -2 msec) for the abdominal movement signal, indicating that it started before inspiratory flow; 0.0 msec for the volume signal; and 44.0 msec (95% CI, 29-73 msec) for the chestwall signal (P < 0.002); this long delay was secondary to chestwall distortion and a subsequent delay in outward ribcage movement in many infants. The trigger delay for the abdominal signal was 90.0 msec (95% CI, 55-104 msec), 135.5 msec (95% CI: 82-186 msec) for the volume signal, and 176.5 msec (95% CI: 165-232 msec) for the chestwall signal, indicating that there was a difference in the rise time of signal voltage between the three methods (P < 0.01). The rate of autotriggered breaths was 3.2% (95% CI, 0.3-9.3%) when using the abdominal signal, 0.55% (95% CI, 0.0-2.1%) for the tidal volume signal, and 11.25% (95% CI, 0.5-27.8%) for the chestwall signal (P < 0.05). The incidence of trigger failure was low with all three signals and was not significantly different between the techniques. In summary, the chestwall signal had a long trigger delay and was highly susceptible to false triggering. It is, therefore, not a reliable trigger signal for synchronized mechanical ventilation in preterm infants. In contrast, tidal volume and abdominal movement signals had an acceptable trigger delay and a low rate of autotriggering, making them useful clinical trigger signals.
患者触发同步通气需要可靠且早期地检测婴儿的吸气努力。已经开发了几种触发方法，但这些方法常常缺乏检测小早产儿吸气的敏感性（触发失败），或者显示出呼吸信号中由伪差触发的呼吸频率很高（自动触发）。本研究的目的是确定以下触发信号的有效性：通过一种新开发的感应技术感知的腹部运动、通过经胸阻抗变化检测的胸壁运动，以及通过气管导管接头处的风速仪测量的潮气量。十名早产儿（出生体重580 - 1424克；中位数体重943克；研究体重535 - 1415克；中位数体重838克；胎龄26 - 32周，中位数胎龄28周，研究年龄1 - 50天，中位数研究年龄11天）被纳入研究。一台Sechrist SAVI呼吸机由三种信号之一触发：胸壁或腹部运动，或婴儿产生的潮气量。针对这三种信号中的每一种，确定吸气气流开始、触发信号出现（信号延迟）以及触发呼吸开始（触发延迟）之间的响应时间。腹部运动信号的信号响应时间为 - 13.5毫秒（95%置信区间，- 33至 - 2毫秒），表明它在吸气气流之前开始；容积信号为0.0毫秒；胸壁信号为44.0毫秒（95%置信区间，29 - 73毫秒）（P < 0.002）；这种长延迟是由于许多婴儿的胸壁变形以及随后胸廓向外运动的延迟。腹部信号的触发延迟为90.0毫秒（95%置信区间，55 - 104毫秒），容积信号为135.5毫秒（95%置信区间：82 - 186毫秒），胸壁信号为176.5毫秒（95%置信区间：165 - 232毫秒），表明这三种方法之间信号电压的上升时间存在差异（P < 0.01）。使用腹部信号时自动触发呼吸的发生率为3.2%（95%置信区间，0.3 - 9.3%），潮气量信号为0.55%（95%置信区间，0.0 - 2.1%），胸壁信号为11.25%（95%置信区间，0.5 - 27.8%）（P < 0.05）。所有三种信号的触发失败发生率都很低，且各技术之间无显著差异。总之，胸壁信号具有长触发延迟且极易出现误触发。因此，它不是早产儿同步机械通气的可靠触发信号。相比之下，潮气量和腹部运动信号具有可接受的触发延迟且自动触发率低，使其成为有用的临床触发信号。
