Respiratory assistance apparatus for providing respiratory gas to a patient during cardiopulmonary resuscitation comprising: - a source of respiratory gas for providing respiratory gas to said patient during cardiopulmonary resuscitation, - CO 2 content measuring means for carrying out concentration measurements of the CO 2 produced by said patient, and providing CO 2 content measurement signals to signal processing and control means, - signal processing and control means configured to process the CO 2 content measurement signals provided by the CO 2 content measuring means, - at least one graphical user interface, characterised in that: - the signal processing and control means are configured to: a) process the CO 2 content measurement signals corresponding to measurements carried out by the CO 2 content measuring means during a given time period (dt) which corresponds to several successive thoracic contractions and compression releases performed by a first-aider carrying out CPR on the patient P in a state of cardiac arrest, and to extract therefrom a plurality of values of CO 2 content peaks, b) select the maximum value (Vmax) of CO 2 content among the plurality of values of CO 2 content peaks measured during said given time period (dt), and c) transmit said maximum value (Vmax) of CO 2 content to the graphical user interface, - and the graphical user interface is configured to display the maximum value (Vmax) of CO 2 content. - a source of respiratory gas for providing respiratory gas to said patient during cardiopulmonary resuscitation, - CO 2 content measuring means for carrying out concentration measurements of the CO 2 produced by said patient, and providing CO 2 content measurement signals to signal processing and control means, - signal processing and control means configured to process the CO 2 content measurement signals provided by the CO 2 content measuring means, - at least one graphical user interface, - the signal processing and control means are configured to: a) process the CO 2 content measurement signals corresponding to measurements carried out by the CO 2 content measuring means during a given time period (dt) which corresponds to several successive thoracic contractions and compression releases performed by a first-aider carrying out CPR on the patient P in a state of cardiac arrest, and to extract therefrom a plurality of values of CO 2 content peaks, b) select the maximum value (Vmax) of CO 2 content among the plurality of values of CO 2 content peaks measured during said given time period (dt), and c) transmit said maximum value (Vmax) of CO 2 content to the graphical user interface, a) process the CO 2 content measurement signals corresponding to measurements carried out by the CO 2 content measuring means during a given time period (dt) which corresponds to several successive thoracic contractions and compression releases performed by a first-aider carrying out CPR on the patient P in a state of cardiac arrest, and to extract therefrom a plurality of values of CO 2 content peaks, b) select the maximum value (Vmax) of CO 2 content among the plurality of values of CO 2 content peaks measured during said given time period (dt), and c) transmit said maximum value (Vmax) of CO 2 content to the graphical user interface, - and the graphical user interface is configured to display the maximum value (Vmax) of CO 2 content.