Assembly for measuring the flow rate of patient during mechanical ventilation, having: - a Y-shaped piece for connecting an inspiration branch from a ventilation machine and an expiration branch to a tube connector; - a first pneumatic resistance element in the inspiration branch and a second pneumatic resistance element in the expiration branch, and - a differential pressure sensor , characterised in that - the first pneumatic resistance element and the second pneumatic resistance element are monolithically integrated into the Y-shaped piece ; - the Y-shaped piece contains, for each of its monolithically integrated pneumatic resistance elements , a fluid measurement outlet near the patient and a fluid measurement outlet remote from the patient, which are in fluidic connection with said Y-shaped piece, and additionally a centrally arranged fifth fluid measurement outlet , which each have a germ barrier device ; - the Y-shaped piece is designed as a disposable unit; - the assembly has a separate electronics module which comprises the differential pressure sensor , a second differential pressure sensor , a pressure sensor , an evaluation unit connected to the pressure sensor and the differential pressure sensors , and pneumatic connecting lines , wherein the pneumatic connecting lines connect the pressure sensor and the differential pressure sensors in each case to fluid measurement inlets incorporated in a housing of the electronics module ; - the electronics module is detachably connectable to the Y-shaped piece , wherein in the connected state a gas-tight connection is formed between the fluid measurement inlets of the electronics module and the fluid measurement outlets of the Y-shaped piece ; and - the electronics module is designed as a reusable unit. - a Y-shaped piece for connecting an inspiration branch from a ventilation machine and an expiration branch to a tube connector; - a first pneumatic resistance element in the inspiration branch and a second pneumatic resistance element in the expiration branch, and - a differential pressure sensor , characterised in that - the first pneumatic resistance element and the second pneumatic resistance element are monolithically integrated into the Y-shaped piece ; - the Y-shaped piece contains, for each of its monolithically integrated pneumatic resistance elements , a fluid measurement outlet near the patient and a fluid measurement outlet remote from the patient, which are in fluidic connection with said Y-shaped piece, and additionally a centrally arranged fifth fluid measurement outlet , which each have a germ barrier device ; - the Y-shaped piece is designed as a disposable unit; - the assembly has a separate electronics module which comprises the differential pressure sensor , a second differential pressure sensor , a pressure sensor , an evaluation unit connected to the pressure sensor and the differential pressure sensors , and pneumatic connecting lines , wherein the pneumatic connecting lines connect the pressure sensor and the differential pressure sensors in each case to fluid measurement inlets incorporated in a housing of the electronics module ; - the electronics module is detachably connectable to the Y-shaped piece , wherein in the connected state a gas-tight connection is formed between the fluid measurement inlets of the electronics module and the fluid measurement outlets of the Y-shaped piece ; and - the electronics module is designed as a reusable unit. <EOS>