Heat exchanger for an oxygenator, comprising a. a 5 base body (11), b. a heat exchanger body (1) disposed in the base body (11) with a mat (8) with several sections of flexible plastic tube (3) each having a longitudinal axis (5), i. which are connected to each other by means of fasteners (6) that run transversely to the longitudinal axis (5), ii. presenting an inlet opening (17) for the entry of the heat exchanger means, iii. presenting an outlet opening (18) for the output of the heat exchanger medium and iv. presenting polyurethane, c. wherein the heat exchanger body (1) has adjacent to the plastic flexible tube sections (3) blood flow channels (13) each with a blood inlet flow opening (14) and a blood outlet flow opening (15), d. wherein by means of the arrangement of the inlet openings (17) and outlet openings (18) in the heat exchanger (9) a flow direction of the heat exchanger means (19) is defined, e. wherein by disposing the blood inlet flow openings (14) at one end of the blood flow channels (13) and the blood outflow openings (15) at one end of the blood supply channels blood flow (13) opposite this end defines a direction of blood flow (16), characterized in that f. The base body (11) is made in the form of a tube and has a central longitudinal axis (10), g. the mat (8) of the heat exchanger body (1) is rolled into a roll (12), h. The longitudinal axes (5) of the plastic hose sections (3) are oriented parallel to the central longitudinal axis (10), i. The flow direction of the heat exchanger means (19) is oriented against the flow direction of the blood (16), j. The blood flow direction (16) is oriented along the central longitudinal axis (10) of the base body (11).Intercambiador de calor para un oxigenador, que comprende a. un 5 cuerpo base (11), b. un cuerpo intercambiador de calor (1) dispuesto en el cuerpo base (11) con una estera (8) con varias secciones de tubo flexible de plástico (3) que presentan en cada caso un eje longitudinal (5), i. que está
