| 摘要 |
Vacuum in a non-invasive medical probe having a source of vacuum interconnected with a suction cup by a resilient walled tube, is reduced in a controlled manner by creating a valve aperture in the wall of the tube at a desired location through which aperture no appreciable leakage will occur when vacuum is applied and the tube is in a relaxed state, whereby with the suction cup secured by vacuum on a patient's skin, application of a force to the tube wall will open the aperture and permit a controlled reduction of vacuum in the suction cup to a specified amount. Releasing the force permits the aperture to close so that lower vacuum is maintained and the suction cup continues to be secured on the patient's skin. In a preferred application there is provided a probe adapted for application to the scalp of a fetus with the rim of the suction cup in sealing contact with the surface of the scalp. There is also provided a method of enabling a controlled flow into a resilient walled tube inside which the pressure is lower than outside the tube, by creating a valve aperture in the wall of the tube in a desired location through which no appreciable leakage will occur when the tube is in a relaxed state. The aperture opens on application of a force to the tube wall and permits a controlled flow therethrough into the tube, and the aperture closes when the force is released.
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