Typical pressure-time curves during forced expiration against an occluded airway in cystic fibrosis (CF) patients and healthy controls. Typical pressure-time curves during forced expiration against an occluded airway in cystic fibrosis (CF) patients and healthy controls. The increased maximal relaxation rate during the maximal expiratory pressure in CF, compared to healthy controls, is represented by the steeper pressure fall during the first half of the relaxation curve. Theodore G Dassios et al. Respir Care 2013;58:474-481 (c) 2012 by Daedalus Enterprises, Inc.