A study[9]was done to assess the accuracy of ATC in mechan-ical ventilators. It was found that ventilators with built-in ATCdon’t have expiratory tube compensation; which might be benefi-cial for COPD patients, as ATC expiratory assistance will result inclosure of the small airways[9]. However, from another point ofview it might in fact eliminate dynamic hyperinflation. Furtherclinical studies are needed to evaluate this iss