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The response of flow-triggered infant ventilators
M Nishimura1, D Hess, R M Kacmarek
1Respiratory Care Department Laboratory, Massachusetts General Hospital, Boston 02114, USA.
Insights
New infant ventilators with flow triggering may not be suitable for patient-triggered ventilation (PTV) in infants due to prolonged delay times and high trigger work, especially with smaller endotracheal tubes.
Area of Science:
- Pediatric critical care
- Respiratory physiology
- Mechanical ventilation
Background:
- Patient-triggered ventilation (PTV) has been limited in infants due to issues with pressure-triggered systems.
- Recent advancements include four infant ventilators utilizing flow triggering technology.
Purpose of the Study:
- To evaluate the feasibility of PTV in infants using new flow-triggered ventilators.
- To assess delay times, trigger pressures, and trigger work across various conditions.
Main Methods:
- Four infant ventilators with flow triggering were tested.
- Simulated infant lungs were connected via 3-, 4-, and 5-mm endotracheal tubes.
- Measurements included delay time, trigger pressure, and trigger work under varying ventilatory demands and PEEP levels.
Main Results:
- Significant differences in delay time, trigger pressure, and trigger work were observed based on endotracheal tube size, measurement site, ventilatory demand, and ventilator brand (p < 0.001).
- The 3-mm endotracheal tube showed the longest delay time (up to 138.2 ms) at high ventilatory drive.
- Trigger pressure and work increased with smaller tubes, higher demand, PEEP use, and measurement at the alveolus.
Conclusions:
- Flow-triggered PTV may be inappropriate for infants experiencing high ventilatory drive or requiring small endotracheal tubes.
- Further research is needed to optimize PTV settings for vulnerable infant populations.
Abstract:
Patient-triggered ventilation (PTV) has not been feasible for infants because of large trigger pressures and long delay times with pressure-triggered systems. Recently, four infant ventilators with flow triggering have become available. We questioned if delay times, trigger pressures, and trigger work with these ventilators would be acceptable for PTV in infants. All ventilators were attached via 3-, 4-, and 5-mm endotracheal tubes to a spontaneously breathing infant lung model. The lung simulator was set at an inspiratory time of 0.65 s, tidal volume of 15, 30, and 45 ml, and 0 and 5 cm H2O positive end-expiratory pressure (PEEP). Delay time, trigger pressure, and trigger work were determined from pressure measured at the proximal airway, trachea, and alveolus. There were significant differences between the endotracheal tube sizes, sites of measurement, ventilatory demand and ventilator brand at each PEEP level for delay time, trigger pressure, and trigger work (p < 0.001). Delay time was greatest with the 3-mm endotracheal tube at high ventilatory drive (maximum 138.2 +/- 2.1 ms). Both trigger pressure (minimum 0.23 +/- 0.02 cm H2O) and trigger work (minimum 0.05 +/- 0.01 g.ml) increased with decreasing endotracheal tube size, increasing ventilatory demand, use of PEEP, and site of measurement: alveolus > trachea > airway (maximum: trigger pressure 5.04 +/- 0.02 cm H2O; trigger work 114.48 +/- 0.88 g.ml). PTV may not be appropriate under conditions of increased ventilatory drive and small endotracheal tube size in infants.