The invention relates to a catheter (2) permitting combined measurements and intended for a respiratory assistance device (4) used for the cardiopulmonary resuscitation of a person in cardiorespiratory arrest. At its proximal end (22), the catheter has, on the one hand, a device (20) for connection to the proximal end (6) of the respiratory assistance device and, on the other hand, a gas connector (23) for connecting the lumen (24) of the catheter to an appliance (16) for measuring the gas composition and to an appliance (15) for measuring the gas pressure, and, in the gas connector, the gas connection to the appliance for measuring the gas composition has a passage cross section (27) smaller than the passage cross section of the gas connection to the appliance for measuring the gas pressure, and the catheter is configured such that, once connected to the respiratory assistance device, its distal end (3) is positioned towards the distal end (7) of the respiratory assistance device.
