Abstract: The invention concerns a process for regulating a respiratory apparatus and the respiratory apparatus itself. The apparatus permits a succession of respiratory cycles depending on patient requirements, such as frequency FR (or respiratory rate RR). The succession of respiratory cycles consists of an inspiration phase, during which the patient is supplied with a current tidal volume (VT) of respirable gaseous fluid, and an expiration phase. The patient has his/her own natural spontaneous respiration, and the pressure in the patient's respiratory passages is defined as Paw. According to the the process, a theoretical respiration volume per minute value, called Vmn optical, is established as a function of the patient's condition and natural spontaneous respiration. Other values are also set or calculated. A minimum current tidal volume (VTmin) and a maximum allowable airway passage pressure, Paw max, are established.