Adaptive Support Ventilation

What is Adaptive Support Ventilation?

Adaptive support ventilation is one of the newer modes of mechanical ventilation. It has proven useful in several lung pathologies. Providers in critical care units will likely encounter adaptive support ventilation.

Adaptive support ventilation is also known as closed-loop ventilation because the ventilator senses when the patient is spontaneously breathing and when they’re completely passive. Depending on the reading and the patient’s breathing, the ventilator makes adjustments. Adaptive support ventilation also takes into account respiratory mechanics.

Adaptive support ventilation automatically adjusts ventilation based on the patient’s breathing.

Settings for Adaptive Support Ventilation

For adaptive support ventilation, the provider sets:

• Gender and Height: The provider inputs the patient’s gender and height into the ventilator settings to predict the ideal body weight. Next, the ventilator generates a target minute ventilation, also known as minute volume. Ideal minute ventilation is 100 mL per kg per minute. 
• Minute Ventilation (%): Based on the patient’s lung pathology, the clinician decides whether to set the minute ventilation at a higher or lower target.
• Positive End Expiratory Pressure (PEEP): PEEP is the extra pressure the ventilator delivers at the end of expiration to help keep the patient’s alveoli open. The units for PEEP are centimeters of water (cm H₂O).
• Fraction of Inspired Oxygen (FiO₂). The (FiO₂) is the concentration of oxygen in the inhaled air. Natural air has a FiO₂ of 21% oxygen. The FiO₂ is set anywhere between 30% to 100%.

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Three circles on the right side of the ventilator monitor screen display these readings:

1. 1. Minute ventilation (% MinVol)
   2. Positive end-expiratory pressure (PEEP)
   3. Fraction of inspired oxygen (FiO₂)

The provider sets the minute ventilation (%), PEEP, and (FiO₂).

For example, a patient with acute respiratory distress syndrome (ARDS), a lung disorder, has significantly decreased lung compliance. Adaptive support ventilation senses lung compliance and adjusts the tidal volume and respiratory rate. For ARDS, the minute ventilation is usually set around 120%, while an asthmatic patient with high airway resistance is set around 90%.

Set the minute ventilation based on the patient’s lung pathology factors.

Passive vs. Active Breathing

When the patient is passive, the ventilator delivers a mandatory number of respiratory breaths per minute to achieve the predetermined ideal minute ventilation. This is a pressure-controlled, volume target mode of ventilation. 

The ventilator detects when a patient is active and spontaneously breathing and switches to a pressure support mode. The ventilator ceases mandatory breaths, instead providing pressure support to reach the target minute ventilation.

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Weaning a Patient off Adaptive Support Ventilation

To wean a patient off a ventilator, providers gradually decrease the minute ventilation. For example, if the target minute ventilation is set at 120%, a clinician decreases it to 110%. The ventilator will automatically decrease the amount of pressure support being given to achieve the target minute ventilation. If the patient continues to meet the target minute ventilation and stays stable, the provider will continue decreasing the target minute ventilation. 

To ensure the patient is stable, providers should check the arterial blood gases, work of breathing, and hemodynamics.

Advantages and Disadvantages of Adaptive Support Ventilation

Adaptive support ventilation senses the lung’s resistance and compliance, the patient’s work of breathing, and the patient’s improving or worsening state while making adjustments to the tidal volume and respiratory rate, quickly relieving the patient of their need for a ventilator. 

Without the ventilator, clinicians need to check the ABG’s every day and predict what intervention might be necessary. They may even need to guess or trial different changes, such as switching the ventilator mode or decreasing the respiratory rate to see how the patient responds.

Adaptive support ventilation also supports lung protective strategies. There is less risk for breath stacking and auto-PEEP. During auto-PEEP, the ventilator attempts to maintain the preset tidal volume. There are also lung-protective strategies to prevent barotrauma and volume trauma, common complications in lung pathologies such as ARDS and COPD.

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According to some medical literature, one possible disadvantage of adaptive support ventilation is that it increases the respiratory rate as needed to meet the preset minute ventilation.

Adaptive support ventilation senses when a patient is passive or spontaneously breathing, adjusting tidal volume and respiratory rate as needed to quickly relieve the patient from ventilation. It supports clinicians because they don’t have to manually check ABGs or predict interventions. They simply set gender and height, minute ventilation, PEEP, and FiO₂.