The invention relates to a medical respiratory assistance apparatus for delivering a respiratory gas such as air, which may or may not be enriched with oxygen, to a patient during cardiopulmonary resuscitation (CPR), having a source (1) of respiratory gas, for example a micro-blower, for delivering a respiratory gas to said patient during cardiopulmonary resuscitation (CPR), and means (4) for measuring the CO2 content, signal-processing and control means (5), and at least one graphical user interface (7). According to the invention, the signal-processing and control means (5) process the CO2 content measurement signals, to select the maximum CO2 content value (Vmax) during a given time period (dt), and to transmit this maximum value (Vmax) to the graphical user interface (7), which displays this maximum CO2 content value (Vmax).
