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Patient-triggered ventilation: a comparison of tidal volume and chestwall and abdominal motion as trigger signals
W Nikischin1, T Gerhardt, R Everett
1Department of Pediatrics, University of Miami School of Medicine, FL 33101, USA.
Insights
Tidal volume and abdominal movement signals are reliable for triggering mechanical ventilation in preterm infants. Chest wall motion is less effective due to long delays and false triggering.
Area of Science:
- Neonatal critical care
- Respiratory support technologies
- Biomedical engineering
Background:
- Patient-triggered synchronized ventilation is crucial for preterm infants.
- Existing trigger methods often fail to detect weak inspiratory efforts or trigger on artifacts.
- Reliable trigger signal detection is essential for effective mechanical ventilation in neonates.
Purpose of the Study:
- To evaluate the effectiveness of three trigger signals for synchronized ventilation in preterm infants.
- To compare abdominal movement, chest wall motion, and tidal volume signals.
- To assess trigger delay, signal delay, and autotriggering rates for each method.
Main Methods:
- Ten preterm infants (gestation 26-32 weeks) were studied.
- Ventilator triggering was assessed using abdominal movement (induction), transthoracic impedance (chest wall motion), and endotracheal tube anemometry (tidal volume).
- Signal delay, trigger delay, and autotrigger rates were measured for each signal.
Main Results:
- Abdominal movement signal had a signal delay of -13.5 msec and trigger delay of 90.0 msec with 3.2% autotriggering.
- Tidal volume signal had a signal delay of 0.0 msec and trigger delay of 135.5 msec with 0.55% autotriggering.
- Chest wall signal showed a long signal delay (44.0 msec) and trigger delay (176.5 msec) with 11.25% autotriggering, indicating susceptibility to distortion and artifacts.
Conclusions:
- Chest wall motion is an unreliable trigger signal for synchronized ventilation in preterm infants due to significant delays and high autotrigger rates.
- Tidal volume and abdominal movement signals demonstrate acceptable trigger delays and low autotriggering rates.
- Both tidal volume and abdominal movement signals are suitable for clinical use in patient-triggered synchronized ventilation for preterm infants.
Abstract:
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.