| 摘要 |
An air introduction system for a medical needle assembly is provided and includes a flexible bladder, and a male luer assembly with an air valve which is biased to allow air to enter the air introduction system but not to exit. The air introduction system is coupled to a needle assembly which is to be introduced into the epidural space. As the needle traverses the tissue layers overlying the epidural space, and the practitioner applies pressure to the bladder, the practitioner experiences resistance to the forcing of air through the needle assembly. If air is lost from the bladder, the bladder may be refilled by releasing the pressure on it and allowing outside air to enter via the air valve. Once the epidural space is penetrated, air is quickly forced from the bladder through the needle assembly and the practitioner can feel a sudden drop in pressure. To aid in detection, the air introduction system is provided with an air activated sound device situated so as to be exposed to the air flow pushed out of the bladder. With the sound device, an audible warning is provided as the air rushes from the bladder through the needle assembly and into the epidural space.
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