Breathing circuit with slidable gas sampling tube

A tubular adapter is formed by a wall, the wall having a hole formed therein, and a gas sampling tube extends through the hole. The respective diameters of the hole and the tube are sized to produce a tight sealed connection therebetween but permit adjustment of the tube in the hole. The sampling tube has a sampling end thereof located within the tubular adapter, and the sampling end has a radially enlarged or flanged portion which is larger than the hole, whereby the sampling tube may be adjusted in the hole but may not be withdrawn.

FIELD AND BACKGROUND OF THE INVENTION 
This invention relates to a breathing circuit for a patient, and more 
particularly to a gas sampling tube of a respirator or anesthesia system. 
Respiratory therapy and anesthesia systems include an inhalation tube for 
conducting fresh gas to a patient and an exhalation tube for conducting 
gas away from the patient. The two tubes are usually joined to a Y-piece 
which in turn is coupled to a face mask or a trach tube. Such a system may 
also include a gas sampling tube which removes samples of the gas and 
feeds the samples to a gas analyzer. In a respiratory therapy system, the 
CO.sub.2 in the gas is analyzed, and in an anesthesia system a number of 
gases may be analyzed. 
Numerous prior art patents show such systems, and the following is a list 
of U.S. Pat. Nos. relating to breathing systems: 
______________________________________ 
U.S. Pat. No. 
Patentee Date 
______________________________________ 
4,914,720 KNODLE ET AL. 04-03-90 
4,852,563 GROSS 08-01-89 
4,850,371 BROADHURST ET AL. 07-25-89 
4,846,167 TIBBALS 07-11-89 
4,840,172 AUGUSTINE ET AL. 06-20-89 
4,827,921 RUGHEIMER 05-09-89 
4,821,736 WATSON 04-18-89 
4,815,459 BERAN 03-28-89 
4,774,940 LINDER 10-04-88 
4,677,987 CHOKSI 07-07-87 
4,637,384 SCHROEDER 01-20-87 
4,621,634 NOWACKI ET AL. 11-11-86 
4,558,709 AIDA ET AL. 12-17-85 
4,558,708 LABUDA 12-17-85 
4,456,014 BUCK ET AL. 06-26-84 
4,346,584 BOEHRINGER 08-31-82 
4,297,871 WRIGHT ET AL. 11-03-81 
4,221,130 BURROWS 09-09-80 
4,202,352 OSBORN 05-13-80 
4,197,858 OSBORN 04-15-80 
4,178,919 HALL 12-18-79 
3,927,670 TURNEY ET AL. 12-23-75 
3,910,261 RAGSDALE ET AL. 10-07-75 
______________________________________ 
The P.V. Choksi U.S. Pat. No. 4,677,987, for example, shows a variety of 
structures including a sampling tube, wherein the sampling tube extends 
through the wall of a gas tube of a breathing circuit. FIG. 2 of this 
patent shows a sampling tube pressed through a hole formed in an elbow and 
extending along the axis of one arm of the elbow. 
In such a system it is an advantage to be able to adjust the position of 
the sampling tube to obtain an accurate measurement or analysis of both 
the inhaled and exhaled gases. It is also important that the system be 
inexpensive and have a minimum risk of harming the patient. 
It is therefore a general object of the present invention to provide an 
improved arrangement of a gas sampling tube in a breathing system. 
SUMMARY OF THE INVENTION 
Apparatus in accordance with this invention comprises a tubular adapter 
formed by a wall, the wall having a hole formed therein, and a gas 
sampling tube extending through the hole. The respective diameters of the 
hole and the sampling tube are sized to produce a tight sealed connection 
therebetween but to permit adjustment of the tube in the hole. The 
sampling tube has a sampling end thereof located within the tubular 
adapter, and the sampling end has a radially enlarged or flanged portion 
which is larger than the hole, whereby the sampling tube may be adjusted 
in the hole but may not be withdrawn. 
DETAILED DESCRIPTION OF THE DRAWINGS 
The invention will be better understood from the following detailed 
description taken in conjunction with the accompanying FIGURES of the 
drawing, wherein: 
FIG. 1 is a perspective view of apparatus incorporation the present 
invention; and 
FIG. 2 is an enlarged sectional view of a fragment of the apparatus of FIG. 
1.

DETAILED DESCRIPTION OF THE DRAWINGS 
FIG. 1 illustrates the construction and use of the apparatus with a patient 
10. A face mask 11 is in position over the mouth and nose of the patient, 
although it should be understood that a trach tube could be used instead. 
An adapter 12 is connected to the face mask 11, the adapter being formed by 
a Y-piece which includes two legs 13 and 14 and a center leg 15. The 
center leg 15 is coupled to the face mask 11 and carries both inhaled and 
exhaled gases, whereas flexible corrugated tubes 17 and 18 are connected 
to the two legs 13 and 14. In the present specific example, the tube 18 is 
connected to a source of inhaled gas and the tube 17 is connected to a 
receptacle or receiver of exhaled gas. 
In the specific example illustrated and described herein, the three legs 
13-15 are formed by thin walled circular tubes, the walls being indicated 
by the numerals 13a, 14a and 15a respectively. The axes of the three legs 
may be parallel or the two legs 13 and 14 may be swiveled on the center 
leg 15. Flow openings 21 are formed on opposite sides of the wall 15a, and 
the legs 13 and 14 are mounted on flanges 22 surrounding the openings 21, 
such that the legs 13 and 14 may be swiveled on the axes of the openings 
21. 
The center leg 15 further includes a semispherical end wall 23 on its end 
which is opposite to the open end 24 connected to the face mask 11. A hole 
26 is formed through the wall 23 at substantially its center, the hole 24 
preferably being coaxial with the wall 15a in the specific example 
illustrated wherein the adapter comprises a Y-piece. 
A gas sampling tube 27 having a relatively small diameter (for example, the 
O.D. is typically 0.125 inch and the I.D. is typically 0.025 to 0.06 inch) 
is positioned in the hole 26, and has an inner or sampling end 28 which is 
within the interior of the center leg 24. The outer end of the tube 27 has 
a coupler 29 fastened to it which is connected to a tube 31 that leads to 
a gas analyzer 32. 
The sampling tube 27 is made of a flexible somewhat pliable material such 
as plastic, and its outer diameter is sized relative to the size of the 
hole 26 such that the margin of the hole tightly pinches the tube 27. This 
pinching engagement serves both to hold the tube 27 in a selected or 
adjusted position relative to the leg 15 and to form a gas seal between 
the wall 23 and the tube 27. 
The hole 26 may have a straight or constant diameter bore or the bore may 
be cone shaped to produce a relatively thin annular line of contact 
between the tube 27 and the wall 23. 
While there is a tight pinch engagement between the wall 23 and the tube 
27, the plastic parts are pliable to permit the position of the tube 27 to 
be adjusted within the center leg 15. FIG. 2 shows one position in solid 
lines and another position in dash-dot lines, and it will be obvious that 
the tube 27 may be located between these two positions or the sampling end 
28 may be located closer to the end 24 and the patient. As shown in FIG. 
2, the axes of the hole 26 and the tube 27 are on the axis of the tubular 
wall 15a. 
To prevent the sampling tube 27 from being accidentally pulled out of the 
hole 26, a flange or radially enlarged portion 33 is formed on the 
sampling end 28. The flange 33 is integral with the tube 27 and has a 
larger diameter than the hole 26, thereby retaining the tube connected 
with the leg 15. The flange may be formed by briefly heating the plastic 
end 28 to soften it and cause the end to form the flange. 
The sampling tube 27 and the Y-piece adapter 12 are made of molded plastic 
which is sufficiently rigid to maintain their shape but pliable enough 
that the tube 27 forms a pinch seal with the adapter 12 but that the tube 
position may be adjusted. A suitable plastic for the Y-piece is a low 
density polyethylene. The sampling tube 27 may be made of PVC having a 
hardness of 90-100 Durometer on the Shore A scale. The tube 27 should be 
pliable enough that it may be bent and pinched at the margin of the hole 
26, but at the same time not so pliable that the flange 33 may be pulled 
or extruded through the hole 26. The end of a PVC tube naturally flairs 
outwardly (not inwardly) when heated without pressure being applied to the 
end. 
It will be apparent from the foregoing that a novel, useful and improved 
gas sampling arrangement has been provided. The sampling tube 27 is 
connected directly to the Y-piece 12 which is normally provided in such a 
circuit and not to a special adapter designed for use only with a sampling 
tube, and therefore a part is eliminated. This is advantageous because of 
the cost savings and because a point of potential leakage (at the ends of 
a special adapter) is avoided. Further, the absence of a special adapter 
reduces the amount of dead air space. 
The location of the sampling end 28 may be adjusted in the Y-piece to 
obtain the optimum location for an accurate sample of the gases flowing to 
and from the patient, and to reduce the amount of dead space between the 
patient and the sampling end 28 to obtain an accurate gas sample. Since 
the tube 27 slides along the axis of the leg 15, it is equidistant from 
both openings 21, thereby attaining a balance between the gases in the two 
legs 13 and 14. 
While the tube 27 may be slid through the hole 26, it cannot accidentally 
be pulled out of the hole 26 because the flange 33 prevents withdrawal. 
The flange 33 is integral with the tube 27 and is not a separate part 
which would have the potential danger of coming loose and harming a 
patient.