Filter Device

Parenteral liquids such as normal saline, 5% dextrose, etc. are frequently administered to a patient from a bottle hanging above the patient which is connected to a flexible tube having at its lower end a needle penetrating the patient's vein. This is frequently referred to as intravenous (I.V.) administration or feeding.

During this administration it is important not to inject any air into the patient's vein as this could cause a serious embolism. One proposal for eliminating any air bubbles or other entrapped air from the administered liquid is described in the Riely U.S. Pat. No. 3,631,654 in which a Y type connector has two dissimilar filters, one passing air, but not liquid, to the atmosphere through one branch; and the other filter passing liquid, but not air, to the patient delivery line. Such type filters sometimes encounter problems with large head pressures created by the hanging bottle causing the air venting filter to seep liquid to the atmosphere.

To provide a more positive control over extraction of the gas, it has been proposed by others, O'Leary et al U.S. Pat. No. 3,905,905 to use a single filter which passes liquid, but not gas, to separate out the gas into a gas collection chamber. Such filter would also filter out any particulate matter that may be in the administration liquid. Rather than automatically venting the collected air or gas to the atmosphere, O'Leary et al periodically extracts it with a hypodermic syringe that pierces a puncturable diaphragm into the gas collecting chamber. In the O'Leary et al device the extraction needle is inserted in very close relationship to the filter membrane so substantially all of the air or gas collected directly above the membrane can be extracted through the syringe needle. Great care must be taken to prevent cocking of the extraction needle and thereby gouging and damaging the filter membrane which could allow both gas and particulate matter to flow through the filter membrane.

The present invention prevents any damage to the filter membrane and very closely controls the angle of entry of the extraction syringe needle. This invention has a housing with a gas collection chamber and an extraction port on this chamber that includes a substantially nonpuncturable tubular guide for the extraction needle that prevents any contact between the extraction needle and the filter membrane. There is also a nonpuncturable abutting wall surface spaced from the filter membrane that limits the depth of penetration of the extraction needle.

FIG. 1 is a top plan view of the filter unit shown connected in series with the parenteral liquid administration line;

FIG. 2 is a sectional view taken along line 2--2 of FIG. 1; and

FIG. 3 is a sectional view taken along line 3--3 of FIG. 1.

In FIG. 1 the filter unit includes a housing shown generally as 1 with an inlet 2 connected to an upstream portion 3 of a parenteral liquid administration line leading from the parenteral liquid bottle (not shown). An outlet 4 of the housing connects to a portion 5 of the administration line leading to a patient (not shown). A gas collection portion 6 of the housing includes therein a gas collecting chamber 7. A port 8 into chamber 7 has a tubular nonpierceable structure that joins to a tubular nonpierceable adapter 9. At an outer end of adapter 9 is a pierceable resealable rubber diaphragm 10. Adapter 9 and a tubular substantially nonpierceable section 10 of the housing combine to define a tubular guide for a hypodermic needle 11 with a hub 12 and a cannula 13. This needle 11 is attached to a conventional hypodermic syringe 14. A substantially nonpuncturable forward wall 15 of the housing limits the penetration depth of cannula 13.

The housing 1 is separated into an upper chamber containing an unfiltered liquid 16 and a lower chamber containing a filtered liquid 17. This chamber separation is caused by a transverse filter member 18 that is previous to liquid but impervious to gas once wetted and at normal I.V. systems pressures. Preferably a series of supporting ribs such as 19 or 20, support membrane 18 and prevent its inadvertent rupture.

As shown in FIG. 2, gas collecting chamber has collected a volume of gas which will not pass through membrane 18. Hypodermic needle 11 has been inserted through the tubular substantially nonpuncturable guide structure form by adapter 9 and tubular section 10. The cannula 13 has been cocked to the fullest extreme in FIG. 2 and is still a safe distance from delicate membrane 18. Its depth of penetration is controlled by wall 15. The accumulated gas in gas collecting chamber 7 can be extracted into syringe 14 and needle 11 then removed. Rubber diaphragm 10 then reseals and prevents any liquid seepage from unfiltered liquid in the upper chamber of the housing.

In FIG. 2 the adapter 9 and tubular section 10 are shown in a two-piece construction that is either wedge fitted together or bonded together. It is understood that adapter 9 could be integrally molded with tubular section 10. The important thing is to provide a nonpuncturable guide channel of sufficient length and cross-sectional area relationship to prevent contact between cannula 13 and membrane 18. In FIG. 2 the length of the tubular guide channel is substantially greater than its cross-sectional dimension.

To provide a very firm sealing connection between filter membrane 18 and the housing, the housing is made in separate upper and lower portions which have respectively wide outwardly extending flanges 21 and 22 about their perimeters. These flanges tightly grip and seal the filter membrane 18 therebetween over a wide lateral area. A snap-in or heated sealed edge section 23 on one flange reliably blocks the two flanges together and forms the housing.

In the foregoing description, a specific example has been used to describe the invention. However, it is understood by those skilled in the art that certain modifications can be made to this example without departing from the spirit and scope of the invention.