Oxygenator

An oxygenator comprising:

• a housing having a cylindrical shape and including a blood inflow port and a blood outflow port;
• and
• a hollow fiber membrane layer having a stacked structure obtained by winding hollow fiber membranes, the hollow fiber membrane layer being accommodated in the housing, the oxygenator in which blood flowing in from the blood inflow port flows from one end toward an other end in a longitudinal direction of the housing and flows out from the blood outflow port, wherein, in the hollow fiber membrane layer, a winding interval of the hollow fiber membranes wound in an outermost layer in the stacked structure is wider than a winding interval of the hollow fiber membranes in other layers;
• and
• wherein, in the hollow fiber membrane layer, the number of windings of the hollow fiber membranes in the outermost layer in the stacked structure is fewer than the number of windings of the hollow fiber membranes in the other layers.

An oxygenator comprising:

• a housing having a cylindrical shape and including a blood inflow port and a blood outflow port;
• and
• a hollow fiber membrane layer having a stacked structure obtained by winding hollow fiber membranes, the hollow fiber membrane layer being accommodated in the housing, the oxygenator in which blood flowing in from the blood inflow port flows from one end toward an other end in a longitudinal direction of the housing and flows out from the blood outflow port, wherein, in the hollow fiber membrane layer, a winding interval of the hollow fiber membranes wound in an outermost layer in the stacked structure is wider than a winding interval of the hollow fiber membranes in other layers;
• and
• wherein, in the hollow fiber membrane layer, the winding interval of the hollow fiber membranes in the stacked structure is discontinuous, and an interval difference between the winding interval of the hollow fiber membranes in the outermost layer and the winding interval of the hollow fiber membranes in the other layers is larger than the interval difference between the winding intervals between any other layers.