Inflation time in mechanical ventilation of preterm neonates

Abstract

The importance of the preterm infant's inspiratory time in determining the optimum inflation time during mechanical ventilation was investigated. The optimum inflation time was defined as that which was most commonly associated with synchronous respiration and maximum minute volume. Twelve preterm infants were studied on 14 occasions. They were ventilated at rates of 60, 75, 90, 105 and 120 breaths/min, with an inspiratory: expiratory ratio of 1:1.2. These rates were chosen as they resulted in inflation times approximating to the spontaneous inspiratory time measured during a brief period of disconnection, on continuous positive airways pressure (CPAP), and greater than that measured on CPAP. Inspiratory time during disconnection was always shorter than that measured on CPAP (P less than 0.01). Synchrony was most commonly provoked and minute volume greatest at the shortest inflation time (P less than 0.01). We conclude fast ventilator rates are most efficacious for preterm neonates. As previously shown, this rate can be estimated by examining the standard reference range of rates in relation to gestational age.

In vitro assessment of proportional assist ventilation

“…It is also assumed that there would be no delay between the onset of the Ppl change and the onset of increase in airway pressure, but we have shown there was a delay of 100 ms for elastic unloading and 60 ms for resistive unloading. The effect of the delay is that during elastic unloading, no support would be provided for up to 33% of the infant's inspiratory effort assuming this to be 0.3 s in duration 10. It has been demonstrated that the longer the ‘trigger’ delay the greater the increase in the work of breathing,11 which is undesirable as an increased work of breathing can lead to muscle fatigue and has been associated with failed extubation in prematurely born infants 12.…”

A practical guide to neonatal volume guarantee ventilation

“…In an AC mode we recommend setting the T i B0.3 s for babies with RDS; similar to their spontaneous T i . [42][43][44] Infants with other lung pathologies may need a longer T i . The appropriateness of the T i can be evaluated by observing the ventilator graphics ( Figure 3).…”