Inflation time in mechanical ventilation of preterm neonates.

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.