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Volume Guarantee (VG) is a new mode, available on the Babylog 8000plus ventilator. Volume ventilation has not been available for neonatologists until recently. Recent advances have meant that the sophisticated electronics responsible for bringing information about respiratory mechanics and respiratory function monitoring can be integrated into the delivery system of the ventilator.
This means that instead of using pressure as a means of determining ventilation, expired volume (specifically tidal volume, VT) can be specified. The ventilator will try to deliver the prescribed volume with the lowest possible pressure. This is done on a breath-to-breath basis, looking at how much volume was delivered with the previous breath and adjusting the Peak Inspiratory Pressure up or down to increase or decrease the VT accordingly.
Principles behind VG
The goal of VG is to reduce volutrauma and barotrauma to the baby's lungs. It is a mode which has not been well studied in infants. However, the underyling premise is that delivering the lowest possible pressure required to deliver the volume will result in less lung injury. Studies have shown less variation in delivered VT but more variation in PIP in VG modes. Mean airway pressure is generally reduced.
Choose your patient carefully!
Patient selection is important! The key thing to consider is
Another thing to consider is what you expect to happen to the baby in their disease process. For example, if the lungs are stiff and non-compliant because the baby has RDS, then PSV+VG is a good mode to use after you give surfactant and you expect the baby's compliance to improve. The ventilator will essentially wean itself.
In our experience, it can be less successful for babies with Chronic Lung Disease.
Setting up the ventilator
The main issue is to choose an appropriate VT at the start and to give enough pressure to get it in.
Weaning from VG
Weaning (or, for that matter, increasing ventilation) should be on the basis of volume. If the baby is over-ventilated, reduce the prescribed volume by an appropriate amount.
Conversely, if you need to increase the amount of ventilation, you may need to increase the PIP so that the ventilator can deliver the set VT.