Atelecto-trauma resulting from varying tidal volumes is the key factor
resulting in ventilation associated lung injury and thereby causing
chronic lung disease [1]. The Volume guarantee ventilation (Babylog), a
form of volume targeted ventilation, has been documented to reduce
chronic lung disease [2]. However, there is a caution while using this
form of ventilation.
Volume guarantee ventilation is a time-cycled
pressure – limited volume –targeted ventilation. The edge of Volume
guarantee over other forms of ventilation is ensuring the target tidal
volume, and auto weaning. The problem arises in this mode if the neonate
has severe metabolic acidosis. The neonate is vigorous and has high
spontaneous breath rates, due to acidosis, overshooting the back-up
rates. As a result, the tidal volumes during these spontaneous breaths
are higher or equal to the set tidal volume, and the working peak
inspiratory pressure (PIP) is closer to the positive end expiratory
pressure (PEEP) making the mode as ventilator continuous positive airway
pressure (CPAP). The general condition would not allow to extubate to
CPAP and the blood gases are also acceptable making it more difficult to
raise the tidal volumes. We try to overcome this situation by switching
off to synchronized intermittent mandatory ventilation (SIMV) mode
keeping a difference between PIP and PEEP so that the delta P is
maintained.
Allowing ventilator to auto-wean could lead to
problems, if the flow sensor is blocked or is disturbed, resulting in
higher tidal volume, VALI and inadvertent hypocarbia; hence, the flow
sensor needs to be in efficient working condition. Auto-triggering owing
to high leak may also result in hypocarbia.
Although, the Babylog recommends coupling the Volume
guarantee with SIMV, Synchronized intermittent positive pressure
ventilation (SIPPV) or Patient support ventilation (PSV); Volume
guarantee should not be coupled with SIMV as the unsupported breaths
would have varying tidal volumes, and could result in atelectotrauma.
Volume guarantee mode is a robotic mode which
operates automatically rendering us interfering least, except for
fraction inspired oxygen. The modality needs efficient understanding by
the operator, and if used cautiously is a state-of-art. However, it
could be double edged sword if the issues mentioned above are not looked
into carefully, especially in a busy unit.
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