What is Assist Control Ventilation (ACV)?
Assist Control Ventilation (ACV) is a mode of mechanical ventilation used in
neonatal intensive care units (NICUs) to support infants with respiratory distress. In ACV, each breath is either initiated by the infant’s spontaneous effort or by the ventilator if the infant fails to initiate a breath within a set time interval. Once a breath is initiated, the ventilator delivers a preset tidal volume or pressure.
How Does ACV Work?
In ACV mode, the ventilator is set to deliver a specific volume (volume control) or pressure (pressure control) with each breath. The infant's spontaneous breaths are supported by the ventilator, which ensures that each breath reaches the preset parameters. If the infant does not initiate a breath within a certain period, the ventilator automatically delivers a breath, ensuring a minimum breathing rate is maintained.
Consistent Ventilation: Ensures stable and consistent ventilation, crucial for infants with underdeveloped lungs.
Reduced Work of Breathing: Helps to prevent respiratory muscle fatigue by reducing the effort required to breathe.
Improved Oxygenation: Maintains adequate oxygen levels and reduces the risk of
hypoxemia.
Synchrony with Spontaneous Breaths: Supports the infant's spontaneous breathing efforts, promoting natural respiratory patterns.
Barotrauma: The risk of lung injury due to excessive pressure, particularly in infants with fragile lungs.
Volutrauma: Lung injury caused by overdistension from high tidal volumes.
Dependence: Prolonged use may lead to ventilator dependence, making weaning more challenging.
Asynchrony: Mismatches between the ventilator and the infant’s spontaneous efforts can lead to discomfort and ineffective ventilation.
How is ACV Different from Other Ventilation Modes?
ACV is different from other ventilation modes like
CPAP and
SIMV. In CPAP, continuous positive pressure is provided to keep the airways open, but it does not deliver breaths. In SIMV, the ventilator provides a set number of mandatory breaths and allows spontaneous breathing between these breaths without support. ACV, on the other hand, supports both mandatory and spontaneous breaths, ensuring each breath meets the preset parameters.
Have severe respiratory distress or failure.
Require precise control over tidal volumes or pressures.
Are at risk of fatigue from spontaneous breathing efforts.
How is ACV Managed and Monitored?
Effective management and monitoring of ACV in neonates require a multidisciplinary approach involving neonatologists, respiratory therapists, and nursing staff. Key aspects include:
Regularly assessing the infant's respiratory status and adjusting ventilator settings as needed.
Monitoring for signs of
ventilator-induced lung injury and making adjustments to minimize risks.
Ensuring proper humidification and temperature control of the inspired air.
Gradually weaning the infant from the ventilator as their respiratory function improves.
Conclusion
Assist Control Ventilation (ACV) is a vital tool in the management of neonatal respiratory disorders. It provides controlled and consistent ventilation, supporting the infant’s breathing efforts and ensuring adequate oxygenation. While it has its risks, careful monitoring and management can help mitigate these, making ACV a crucial component in neonatal intensive care.
