Continuous non-invasive monitoring of evolving acute severe asthma during sleep.

A spontaneous acute severe asthmatic attack was monitored non-invasively in a 27 year old sleeping female asthmatic subject. As the attack evolved there was a switch from predominant abdominal breathing (associated with inspiratory indrawing of the rib cage) to gradually increasing rib cage excursion (associated with inspiratory paradox of the abdominal wall with respect to the rib cage). Abdominal paradox increased progressively until it appeared to fill the whole of the inspiratory period of the rib cage, at which point rapid oxygen desaturation developed.