Gas sampling line

Abstract

A gas sampling line having a channel for conducting respiratory gases from a patient respiratory interface to a gas monitor, the gas sampling line comprising, i.a., a gas sampling tube comprised of a polyether block amide material, the polyether segments of which comprise polyethyleneoxide. Use of a tube comprised of a polyether block amide material, the polyether segments of which comprise polyethyleneoxide, for sampling of respiratory gases; and a method for sampling of respiratory gases, the method comprising conducting respiratory gases through such a tube. A gas analysis system for analysing respiratory gases, comprising a gas sampling line as defined above and a gas monitor connectable to the gas sampling line.

Claims

1. A gas sampling line having a channel for conducting respiratory gases comprising: a gas sampling tube surrounding a portion of the channel; a drying assembly extends along the outside of the gas sampling tube, wherein the drying assembly comprises: a casing comprised of a polyether block amide material, wherein the polyether block amide material comprises polyether segments and polyamide segments, and the polyether segments comprise polyethyleneoxide; and a hydrophilic member disposed within the casing and being in fluid contact with the channel.

2. The gas sampling line according to claim 1, wherein the gas sampling tube is made by a material that is not permeable by moisture and/or water.

3. The gas sampling line according to claim 1, wherein the polyamide segments of the polyether block amide material is selected from the group consisting of polyamide-12, polyamide-11, and polyamide-12.12.

4. The gas sampling line according to claim 1, wherein the polyether segments and the polyamide segments in the polyester block amide material has a ratio from about 60:40 to about 40:60.

5. The gas sampling line according to claim 1, wherein the drying assembly further comprises a hydrophobic member disposed across the channel.

6. The gas sampling line according to claim 1, further comprising: a patient respiratory interface connector adapted to couple the gas sampling line to a patient respiratory interface; and a gas monitor connector adapted to couple the gas sampling line to a gas monitor.

7. A method for sampling of respiratory gases, the method comprising conducting respiratory gases through the gas sampling line of claim 1.

8. The method according to claim 7, wherein the polyamide segments of the polyether block amide material is selected from the group consisting of polyamide-12, polyamide-11, and polyamide-12.12.

9. The method according to claim 7, Wherein the first polyester block amide material comprises polyether segments and polyamide segments in a ratio of polyether to polyamide from about 60:40 to about 40:60.

10. The method according to claim 7, wherein the drying assembly further comprises a hydrophobic member disposed across the channel.

11. A gas analysis system for analysing respiratory gases, comprising a gas sampling line as defined in claim 6 and a gas monitor connectable to the gas sampling line.

12. The gas analysis system according to claim 11, further comprising a respiratory device connectable to the patient respiratory interface.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a schematic sectional view of a portion of a gas sampling line.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

(2) Referring to FIG. 1, some details of a an embodiment of a gas sampling line will be explained. The gas sampling line comprises a gas sampling tube 1, comprised of a material as specified above, connecting a patient respiratory interface connector (not shown) and a gas monitor connector 2. A gas monitor (not shown) may be coupled to the gas monitor connector 2. The gas sampling line further comprises a drying assembly comprising a housing 3, comprised of a material as specified above, and a hydrophilic member 4 disposed within the casing. The drying assembly 3, 4 extends along the outside of the gas sampling tube 1. The hydrophilic member is in fluid contact with a channel 5 for conducting respiratory gases traversing the gas sampling line. A hydrophobic member 6 is disposed across the channel 5.

(3) When a sample of respiratory gases is conducted through the channel 5 of the gas sampling line towards the gas monitor connector 2, moisture or water present in the sample will be adsorbed to or absorbed by the hydrophilic member 4. A wicking action of the hydrophilic member 4 will transport the moisture or water towards the housing 3. Subsequently, moisture or water will permeate the housing 3 and be removed into surrounding air. The respiratory gases will pass the hydrophobic member 6 on their way towards the gas monitor connector 2, whereas undesirable objects or substances (e.g. bacteria, body excretions) will be withheld by the hydrophobic member 6 and not reach the gas monitor. The hydrophobic member 6 also serves as an additional measure to stop water or moisture from reaching the gas monitor.

(4) It is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Examples

(5) Characteristics and advantages of the present invention are further illustrated by the following, non-limiting, examples.

(6) Preparation of Gas Sampling Tubes According to the Invention

(7) Gas sampling tubes according to the invention were prepared by extrusion of a polyether block amide material (available from Atofina under the trade name Pebax®) to form a tubing having an inner diameter of 1 mm and an outer diameter of 2.5 mm, and subsequent cutting of the tubing to obtain gas sampling tubes having a length of 2 m. The composition of the polyether block amide material is shown in Table 1.

(8) TABLE-US-00001 TABLE 1 Gas sampling tube according to the present invention Tube no. Composition 1 polyether block amide material of 55% polyethyleneoxide and 45% polyamide-12
Preparation of Comparative Gas Sampling Tubes

(9) As comparative gas sampling tubes were used 2 m lengths of four different tubings having an inner diameter of 1 mm and an outer diameter of 2.5 mm. The composition of the tubing materials and the construction of the tubings are shown in Table 2. Comparative tubes 3-5 represent well-known embodiments of gas sampling tubes used in respiratory care for the conduction of gases to gas analysis equipment.

(10) TABLE-US-00002 TABLE 2 Comparative gas sampling tubes Tube no. Composition and construction 2 polyether block amide material of 53% polytetramethylene oxide and 47% polyamide-12 (extruded) 3 polyvinylchloride (extruded) 4 polyvinylchloride/polyethylene (co-extruded; inner layer PVC, outer layer PE) 5 polyvinylchloride + Nafion ® (1.9 m PVC joined to 0.1 m Nafion ®)
Test Methods

(11) All tests were performed at room temperature of about 22° C. at a gas flow of 50 ml/min through the gas sampling tube. In the tests, tube no. 5 was arranged so that in the direction of the gas flow, the Nafion® portion was upstream of the PVC portion.

(12) A) Moisture test: A gas sample of moist air was passed from a simulated patient circuit, equipped with a heated humidifier, through a gas sampling tube to a water trap having a volume typical for disposable water traps for analysis of respiratory gases. The moist air leaving the simulated patient circuit had a relative moisture of 95-100% at 35-37° C. Water condensed in the tube was collected in the water trap and the time until the water trap had been filled with 200 μl liquid was recorded.

(13) B) Water test: A gas sample comprising dry air and drops of water was passed from a simulated patient circuit, equipped with a syringe pump for delivery of water, through a gas sampling tube to a water trap having a volume typical for disposable water traps for analysis of respiratory gases. The syringe pump was set to deliver one droplet of water per minute, corresponding to 100 μl liquid per hour. The liquid was collected in the water trap and the time until the water trap had been filled with 200 μl liquid was recorded.

(14) C) CO.sub.2 accuracy: The sampling tube was connected between an equipment providing alternating two reference gases (5% CO.sub.2 balanced N.sub.2 and synthetic air) according to EN ISO 21647:2004 (Medical electrical equipment—Particular requirements for the basic safety and essential performance of respiratory gas monitors), FIG. 102, and a gas monitor. The measuring equipment was set to alternate the reference gases at a frequency corresponding to 40 breaths per minute. The ratio of CO.sub.2 concentration measured by the gas monitor and CO.sub.2 concentration of the reference gas was recorded.

(15) D) Halothane accuracy: The sampling tube was connected between an equipment providing alternating two reference gases (5% CO.sub.2, 5% halothane balanced N.sub.2 and synthetic air) according to EN ISO 21647:2004, FIG. 102, and a gas monitor. The measuring equipment was set to alternate the reference gases at a frequency corresponding to 40 breaths per minute. The ratio of halothane concentration measured by the gas monitor and halothane concentration of the reference gas was recorded.

(16) Results

(17) The results are shown in Table 3. The gas sampling tube according to the invention (tube no. 1) provided an outstanding combination of desirable results in the moisture and water tests as well as in the CO.sub.2 accuracy and halothane accuracy tests.

(18) TABLE-US-00003 TABLE 3 Results A) B) C) D) Moisture Water CO.sub.2 Halothane Tube no. test (h) test (h) accuracy accuracy 1 >24 >24 0.98 0.98 2 2.5 2 0.98 0.98 3 2.5 2 0.98 0.73 4 2.5 2 0.98 0.98 5 >24 2 0.97 0.74