A manual resuscitator assembly for measuring the carbon dioxide (CO2) concentration in breathing gas of a person being ventilated, includes:a selective colorimetric CO2 detector having a detector surface adapted to change color rapidly and reversibly with CO2 concentration,a detector holding part for receiving and attaching the colorimetric detector,a manual resuscitator including a bi-directional gas conduit between an expiratory and an inspiratory part of a breathing circuit, the conduit configured such that a clinically predetermined fraction of breathing gas enters the holding part and contacts the surface during ventilation,a docking part for receiving and attaching a mobile unit, including image capturing, processing and a display elements, the processing element adapted to execute an application program to measure CO2 concentration changes in the breathing gas by identifying changes in the optical property of the detector surface captured by the image capturing element.
