abstract |
A syringe for sampling blood has a handle driven plunger in which is mounted an air permeable filter in communication with a valve chamber. In the chamber is mounted a gravity driven steel ball that is heavy enough to enable the syringe to be used in aspiration, with the ball remaining seated to block the air flow through the valve, and yet light enough to be used in taking of a normal pressure arterial blood sample during which air flow through the filter will drive the ball from its seat. |