Page 601 - Clinical Application of Mechanical Ventilation

Neonatal Mechanical Ventilation 567

Machine Volume

Machine Volume in AVEA (CareFusion) uses the desirable features of both volume-
controlled and pressure-controlled ventilation. The clinician sets a target tidal vol-
ume and inspiratory time (volume-controlled), and the ventilator will deliver the
tidal volume using variable flow to meet the patient’s resistance, compliance, and
flow demands (pressure-controlled). The inspiratory pressure used to generate the
flow is determined within the breath (while the breath is being delivered).
Machine Volume for neonatal application requires a proximal flow sensor. The
initial Machine Volume may be set in three steps: (1) In pressure-controlled mode,
adjust the peak inspiratory pressure to reach the desired tidal volume (or V /Kg),
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(2) Select V (uncorrected tidal volume during PCV) as a monitoring parameter,
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and (3) Set the Machine Volume to the V (or slightly below the V to anticipate
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any slight decrease in compliance).
Volume Guarantee

Volume Guarantee in Babalog 8000 plus (Dräger) can be described as pressure-
limited ventilation with tidal volume targeting. It is not pressure-controlled because
the inspiratory pressure for each breath in Volume Guarantee is variable (or limited),
depending on the preceding expired tidal volume.
In Volume Guarantee, the clinician sets the tidal volume and maximal peak inspi-
ratory pressure. Immediately before delivery of tidal volume breaths, the ventilator
monitors the preceding expired tidal volume and makes breath-by-breath adjust-
ments of the peak inspiratory pressure to deliver the set tidal volume. This method
of breath delivery allows the lowest peak inspiratory pressure needed to deliver the
set tidal volume.
Volume Guarantee is active in the PSV, SIMV, or SIPPV (synchronized inter-
mittent positive pressure ventilation [same as assist/control]) mode. In PSV, the
inspiratory time is limited by the mechanics of the baby’s lungs. It is more natural
because the inspiration will be terminated once the baby’s lungs are full. In SIMV
and SIPPV, the inspiratory time is set by the clinician. Should the set inspiratory
time be longer than the baby needs to fill the lung, the inspiratory pressure is limited
to the set maximum peak inspiratory pressure.
The goal of Volume Guarantee is to reduce volutrauma and barotrauma to the
baby’s lungs. The underlying premise is that using the lowest inspiratory pressure to
deliver a target tidal volume will result in a lower incidence of lung injury.

Liquid Ventilation

Although not a new concept, the ability to successfully utilize this technology has
been developed over the past several years. The concept behind liquid ventilation is
to use liquid rather than gas to inflate the lungs, resulting in more equal distribu-
tion of ventilation. Mechanical inflation could then occur at pressures low enough
to prevent damage to lung tissues.

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