Abstract: A mask insert to provide conformal support for the reflective seal of an oxygen mask comprising a formed rim made of a resiliently deformable material which is held in place beneath the reflective seal by a supporting framework which conforms to the contours of the interior surface of the mask. The formed rim applies constant pressure on the face-engaging surface of the reflective seal, adjusting for variations in the user's facial structure, thereby eliminating leaks.

Abstract: A method and apparatus for determining a number of important physiologic characteristics of a patient based on a end tidal determinations taken from a single respiratory waveform. In the preferred embodiment, breath detection, end-tidal occurrence, and respiratory information is determined using only the expired CO.sub.2 gas concentration waveform. The system of the present invention is capable of performing the following basic functions: (1) identification of breath-by-breath inspired/expired end-tidal gas concentrations of three or more other expired gases (i.e., O.sub.2, NO.sub.2, and a volatile anesthetic); (2) calculation of the respiratory, inspiratory, and expiratory periods; (3) calculation of the respiratory rate and inspiratory/expiratory ratio; and (4) calculation of the multi-breath and time-trend averages.The preferred embodiment of the invention system comprises a breath detection algorithm which is implemented in two phases--initialization and normal.