Apparatus and method for monitoring vent line vacuum

In an apparatus for automatically drawing a blood sample from a sealed container having an internal pressure below atmospheric pressure, said container being sealed by a pierceable cap, said apparatus comprising:

• (a) an aspirating needle for both piercing said cap to aspirate blood from said container, and venting the interior of the container to the surrounding atmosphere through venting means operatively connected to said aspirating needle;
• and (b) a vacuum pump for aspirating the blood from the container, said vacuum pump being connected to said aspirating needle through an aspiration line, the improvement comprising:
• means for sensing a failure of the venting means, said failure-sensing means comprising:
• (i) means for producing a first signal indicative of the negative pressure associated with said vacuum pump;
• (ii) means for producing a second signal indicative of said internal pressure within said sealed container after said cap has been pierced by said aspirating needle;
• and (iii) logic and control means for comparing said first and second signals and producing a third signal in the event the comparison of said first and second signals indicates said internal pressure is less than said negative pressure.

In an apparatus for automatically drawing a blood sample from a sealed container having an internal pressure below atmospheric pressure, said container being sealed by a pierceable cap, said apparatus comprising:

• (a) an aspirating needle for both piercing said cap to aspirate blood from said container, and venting the interior of the container to the surrounding atmosphere through venting means operatively connected to said aspirating needle;
• and (b) a syringe for aspirating the blood from the container, said syringe being connected to said aspirating needle through an aspiration line, the improvement comprising:
• means for sensing a failure of the venting means, said failure-sensing means comprising:
• (i) means for producing a first signal indicative of said internal pressure within said sealed container after said cap has been pierced by said aspirating needle;
• and (ii) logic and control means for:
• (a) storing a predetermined nominal value;
• (b) comparing said first signal and said predetermined nominal value;
• and (c) producing a third signal in the event the comparison of said first signal and said predetermined nominal value indicates said internal pressure is less than said predetermined nominal value.

In a method for aspirating a liquid from a sealed container having an internal pressure that may be less than a nominal vacuum pressure applied to a needle used to aspirate such liquid from the container, the improvement comprising a method for detecting and signaling such condition, said method comprising the steps of:

• (a) producing a first signal indicative of the nominal vacuum pressure;
• (b) producing a second signal indicative of the vacuum pressure within the sealed container;
• (c) comparing said first and second signals;
• and
• (d) producing a third signal in the event the comparison of said first and second signals indicates that the container vacuum pressure is less than that of said nominal vacuum pressure.