# US 10,500,364 B2 · Drying expiratory limb with tailored temperature profile and multi-lumen configuration > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,500,364 B2 - Document ID: US10500364B2 - Status: Granted - Kind: B2 - Application number: 14/777,440 - Filed: 2014-03-14 - Published: 2016-02-18 - Granted: 2019-12-10 - Earliest claimed: 2013-03-15 - Assignees: Fisher & Paykel Healthcare Limited - Applicants: Fisher & Paykel Healthcare Limited - Inventors: Robert Andrew David Milne; Timothy Dee Gierke - Web page: https://patentgrep.com/patent/US10500364B2 ## CPC - A61M 16/0808: {Condensation traps} - A61M 16/0875: {Connecting tubes} - A61M 16/0883: {Circuit type} - A61M 16/1095: {in the connecting tubes} - A61M 16/161: {with means for measuring the humidity} - A61M 16/16: Devices to humidify the respiration air {(A61M16/1045 takes precedence)} - A61M 2205/0238: the material being a coating or protective layer - A61M 2205/33: Controlling, regulating or measuring - A61M 2205/3368: Temperature - A61M 2205/3633: thermally insulated - A61M 2205/3673: thermo-electric, e.g. Peltier effect, thermocouples, semi-conductors - A61M 2205/50: with microprocessors or computers - A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)} ## Abstract A drying expiratory limb of a breathing circuit is provided that is configured to increase or optimize drying of a gas to reduce or prevent condensation. The drying expiratory limb can include a wall that is at least partly made of a breathable material configured to allow transmission of water vapor but substantially prevent transmission of liquid water. The wall includes first and second openings in the wall, the openings respectively configured to receive a gas at a first temperature and a first relative humidity and to allow the gas to exit having a second temperature and a second relative humidity. The drying expiratory limb can be configured to tailor the temperature drop of the gas along the wall to maintain a relative humidity within a targeted range and/or to maintain the gas temperature above its dew point temperature. ## Claims ### Claim 1 A drying expiratory limb of a breathing circuit, the drying expiratory limb comprising: a wall having a first end and a second end separated by an expiratory limb length, the wall defining a space within and wherein at least a part of said wall comprises a breathable material configured to allow transmission of water vapor but substantially prevent transmission of liquid water; a first opening in the first end of the wall, the first opening configured to receive a gas at a first temperature and a first absolute humidity; and a second opening in the second end of the wall configured to allow the gas to exit the drying expiratory limb, the gas having a second temperature that is lower than the first temperature and a second absolute humidity that is dryer than the first absolute humidity upon exiting the drying expiratory limb, wherein the drying expiratory limb is configured such that a temperature of the gas has a temperature drop and remains above a dew point temperature of the gas along the drying expiratory limb length. ### Claim 2 (depends on 1) The drying expiratory limb of claim 1, wherein the drying expiratory limb is configured such that a difference in temperature of the gas and the dew point temperature of the gas along the drying expiratory limb length is approximately constant. ### Claim 3 (depends on 1) The drying expiratory limb of claim 1, further comprising an insulating material on an outer surface of the wall. ### Claim 4 (depends on 3) The drying expiratory limb of claim 3, wherein the insulating material is configured to control the temperature of the gas to be between about 0.9° C. and 1° C. above the dew point temperature. ### Claim 5 (depends on 3) The drying expiratory limb of claim 3, wherein an amount of the insulating material is substantially constant along the expiratory limb length. ### Claim 6 (depends on 3) The drying expiratory limb of claim 3, wherein an amount of the insulating material varies along the expiratory limb length. ### Claim 7 (depends on 1) The drying expiratory limb of claim 1, wherein a rate of temperature decrease from the first end to a distance of about 300 mm from the first end is less than or equal to about −0.01° C./mm. ### Claim 8 (depends on 1) The drying expiratory limb of claim 1, further comprising a heater wire configured to selectively receive electrical power to provide heat to the gas in the drying expiratory limb. ### Claim 9 (depends on 8) The drying expiratory limb of claim 8, wherein the heater wire is configured to control the temperature of the gas to be between about 0.9° C. and 1° C. above the dew point temperature. ### Claim 10 (depends on 8) The drying expiratory limb of claim 8, further comprising a second heater that is configured to control the rate of temperature decrease of the gas. ### Claim 11 (depends on 8) The drying expiratory limb of claim 8, wherein the heater wire has a varying pitch spacing along the expiratory limb length. ### Claim 12 (depends on 11) The drying expiratory limb of claim 11, wherein the pitch spacing increases with distance from the first end. ### Claim 13 (depends on 8) The drying expiratory limb of claim 8, wherein the heater wire comprises at least two sections, the two sections being configured to be independently controlled using control circuitry. ### Claim 14 (depends on 1) The drying expiratory limb of claim 1, wherein a flow rate of the drying expiratory limb is configured to improve breathability. ### Claim 15 (depends on 1) The drying expiratory limb of claim 1, wherein a profile of an absolute humidity of the gas is substantially parallel to a profile of a dew point temperature of the gas. ### Claim 16 (depends on 1) The drying expiratory limb of claim 1, wherein the drying expiratory limb is configured to substantially eliminate rain out at the first end of the wall and at the second end of the wall. ### Claim 17 A drying expiratory limb of a breathing circuit, the drying expiratory limb comprising: a wall having a first end and a second end separated by an expiratory limb length, the wall defining a space within and wherein at least a part of said wall comprises a breathable material configured to allow transmission of water vapor but substantially prevent transmission of liquid water; a first opening in the first end of the wall, the first opening configured to receive a gas at a first temperature and a first relative humidity; and a second opening in the second end of the wall configured to allow the gas to exit the drying expiratory limb, the gas having a second temperature that is lower than the first temperature and a second relative humidity upon exiting the drying expiratory limb, wherein the drying expiratory limb is configured such that a temperature of the gas has a temperature drop along the drying expiratory limb length and the first relative humidity and the second relative humidity are approximately between about 90% and about 99%. ### Claim 18 (depends on 17) The drying expiratory limb of claim 17, wherein the first relative humidity of the gas or the second relative humidity of the gas or both are at least about 95%. ### Claim 19 (depends on 17) The drying expiratory limb of claim 17, wherein the first relative humidity of the gas or the second relative humidity of the gas or both are at least about 99%. ### Claim 20 (depends on 17) The drying expiratory limb of claim 17, wherein the temperature drop along the expiratory limb length is controlled according to a drying rate to keep a relative humidity of the gas along the expiratory limb length within a targeted relative humidity range. ### Claim 21 (depends on 20) The drying expiratory limb of claim 20, wherein the targeted relative humidity range is between about 90% and about 99%. ### Claim 22 (depends on 1) The drying expiratory limb of claim 1, wherein the temperature drop of the gas along the drying expiratory limb length is controlled by one of more of: a) varying an amount of insulating material on an outer surface of the wall along the drying expiratory limb length; b) varying a pitch spacing of a heater wire along the drying expiratory limb length; and c) controlling at least two heater wire sections along the drying expiratory length, each of the at least two heater wire sections being configured to be independently controlled. ### Claim 23 (depends on 17) The drying expiratory limb of claim 17, wherein the temperature drop of the gas along the drying expiratory limb length is controlled by one of more of: a) varying an amount of insulating material on an outer surface of the wall along the drying expiratory limb length; b) varying a pitch spacing of a heater wire along the drying expiratory limb length; and c) controlling at least two heater wire sections along the drying expiratory length, each of the at least two heater wire sections being configured to be independently controlled.