ASV mode

Q: Ventilator determines which of the following parameter to calculate the respiratory rate in Adaptive Support Ventilation (ASV) mode? (select one)

A) inspiratory time constant
B) expiratory time constant


Answer: B

ASV is a mode of ventilator in which respiratory mechanics of a patient dictate adjustments to the respiratory rate and inspiratory pressure to achieve the desired minute ventilation. Ventilator calculates these parameters depending on an expiratory time constant obtained from the expiratory limb of the flow volume loop on a breath by breath basis. So patients with a long expiratory time constant like in COPD receives a lower respiratory rate in comparison to patients with stiff lungs.

Although ASV  failed to show any benefit in mortality it may shorten the time to weaning initiation and weaning duration.

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References: 

1. Arnal JM, Wysocki M, Nafati C, et al. Automatic selection of breathing pattern using adaptive support ventilation. Intensive Care Med 2008; 34:75. 

2. Kirakli C, Naz I, Ediboglu O, et al. A randomized controlled trial comparing the ventilation duration between adaptive support ventilation and pressure assist/control ventilation in medical patients in the ICU. Chest 2015; 147:1503.