Oxygenator

A method of treating blood in an oxygenator, comprising the steps of:

• providing a flow of blood to an inlet of an oxygenator housing;
• directing the flow of blood to a bubble-removing hollow fiber membrane layer disposed in the housing and configured to remove bubbles from the blood;
• directing the flow of blood to a gas-exchanging hollow fiber membrane layer disposed in the housing and configured to exchange a gas with the blood;
• directing the bubbles removed by the bubble-removing hollow fiber membrane layer through a gas permeable member which is disposed at an end portion of the bubble-removing hollow fiber membrane layer, wherein the gas permeable member allows passage of the bubbles removed by the bubble-removing hollow fiber membrane layer without allowing passage of a plasma leaking through the bubble-removing hollow fiber membrane layer;
• removing the bubbles passing through the gas permeable member via a discharge port which is formed in the housing;
• and
• capturing the plasma leaking through the bubble-removing hollow fiber membrane layer in a plasma capture chamber which is a partition between the end portion of the bubble-removing hollow fiber membrane layer and the gas permeable member.