Effects of Volume-Targeted Synchronized Intermittent Mandatory Ventilation on Spontaneous Episodes of Hypoxemia in Preterm Infants

Abstract

Background: Hypoxemic episodes in ventilated preterm infants are frequently caused by reduced ventilation due to a decrease in lung volume and acute worsening of respiratory mechanics. Objective: To compare the efficacy of conventional time-cycled, pressure-limited flow synchronized intermittent mandatory ventilation (SIMV) and volume-targeted SIMV (VT-SIMV) in reducing the frequency and severity of these episodes. Methods: SIMV and VT-SIMV were compared in preterm infants with frequent spontaneous episodes of hypoxemia. VT-SIMV was provided with the Draeger Babylog 8000plus ventilator in volume-guarantee mode. Results: In all, 32 infants (birth weight 668 ± 126 g, gestational age 24.8 ± 1.1 weeks, age 37.5 ± 17.3 days) were studied during 2-hour periods of SIMV and VT-SIMV in random sequence. In an initial phase, a group of 12 infants was supported during VT-SIMV with a target tidal volume of 4.5 ml/kg (VT-SIMV 4.5). A planned interim analysis did not show differences in frequency and duration of hypoxemia between VT-SIMV 4.5 and SIMV, and the initial phase was stopped. In a second phase of the study, 20 infants were studied while supported with a target tidal volume of 6.0 ml/kg during VT-SIMV (VT-SIMV 6.0). In the second phase of the study, the frequency of the hypoxemic episodes did not change but the mean episode duration was shorter during VT-SIMV compared to SIMV. The proportion of mechanical breaths with small tidal volumes (≤3 ml/kg) was reduced during VT-SIMV 6.0 versus SIMV, while the peak inspiratory pressure and mean airway pressure were increased. Conclusion: VT-SIMV did not reduce the frequency of hypoxemic episodes, but VT-SIMV 6.0 was effective in reducing the duration of the hypoxemic episodes.

Role of automation in neonatal respiratory support

“…These adjustments, which generally occur in response to changes in respiratory system mechanics and the infant ' s own inspiratory effort, maintain more stable ventilation and hence gas exchange. There is evidence that volume-targeted ventilation can reduce V T variability, the occurrence of hypocapnia, and fl uctuations in oxygenation when compared with conventional pressure-limited ventilation [4,5,18,19,23] .…”

A practical guide to neonatal volume guarantee ventilation

“…The use of a higher target V T (6.0 ml kg À1 ) only slightly reduced hypoxemic episodes in studies with other VTV modes. 55,56 Diaphragmatic braking Diaphragmatic braking causes an early interruption in expiratory flow ( Figure 7) and is sometimes associated with a small inspiration as the diaphragm contracts. 15,54 If this occurs within the 0.2 s refractory period of the ventilator an inflation is not triggered.…”

What is new in ventilation strategies for the neonate?

“…Greater lung inflammation was demonstrated when a volume of 3 rather than 5 ml/kg was used with SIPPV during the acute phase of respiratory distress syndrome (RDS) [25]. A level of 6 but not 4.5 ml/kg reduced the duration of hypoxemic episodes during SIMV in one study [34], and in another study, 6 ml/kg compared to 4 or 5 m/kg was associated with the lowest work of breathing [42].…”