The invention relates to a breathing apparatus comprising an internal compartment (9) comprising an upper wall (9a), a motorized turbine (1, 10) comprising an electric motor (1) driving a motor shaft (10) carrying a at least one impeller (2), a volute (4, 5) surmounting said motorized turbine (1, 10) and surrounding at least a portion of said at least one impeller (2), said volute (4, 5) comprising a gas inlet (11) and an outlet (12) of gas, and a roof (7) overlying said volute (4, 5), said roof (7) comprising a gas passage (13) located opposite the inlet (11) of the volute (4, 5) so as to allow fluid communication between said gas passage (13) of the horn (7) and said inlet orifice (11) of the volute (4, 5), and said horn (7) being spaced from the upper wall (9a) of the inner compartment (9) so as to create a circulation gap (15) between them gas supply. According to the invention, a plurality of abutments (14) having a longitudinally rectilinear or curved wall shape are arranged in the spacing (15) between the horn (7) and the upper wall (9a) of the inner compartment (9).L'invention concerne une appareil d'assistance respiratoire comprenant uncompartimentinterne (9) comportant une paroi supérieure (9a), une turbine motorisée (1,10) comprenantun moteur électrique (1) entraînant un arbre-moteur (10) portant au moins uneroue à ailettes(2), une volute (4, 5) surmontant ladite turbine motorisée (1, 10) etentourant au moins unepartie de ladite au moins une roue à ailettes (2), ladite volute (4, 5)comprenant un orificed'entrée (11) de gaz et un orifice de sortie (12) de gaz, et un pavillon (7)surmontant laditevolute (4, 5), ledit pavillon (7) comprenant un passage de gaz (13) situé enregard de l'orificed'entrée (11) de la volute (4, 5) de manière permettre une communicationfluidique entreledit passage de gaz (13) du pavillon (7) et ledit orifice d'entrée (11) de lavolute (4, 5), etledit pavillon (7) étant espacé de la paroi sup
