Liquid warming device

• US 20070084936A1
• Filed: 09/27/2006
• Published: 04/19/2007
• Est. Priority Date: 08/24/2004
• Status: Active Grant

• Current Assignee: C Change Surgical LLC
• Original Assignee: C Change Surgical LLC
• Inventors: Kammer, Patrick, Rackers, Kevin Joseph
• Granted Patent: US 7,441,714 B2
• Time in Patent Office: Days
• US Class Current: 236/1.C
• CPC Class Codes: A61B 2050/0018 Electric heating
• CPC Class Codes: A61B 46/10 specially adapted for instruments, e.g. microscopes
• CPC Class Codes: G05D 23/1909 whose output amplitude can only take two discrete values
• CPC Class Codes: G05D 23/1931 to control the temperature of one space
• CPC Class Codes: G05D 23/20 with sensing elements having variation of electric or magnetic properties with change of temperature G05D23/13 takes precedence
• CPC Class Codes: G05D 23/22 the sensing element being a thermocouple

Abstract

A liquid warming device for heating sterile fluids in a removable basin is described with emphasis on the properties of the basin interaction with the liquid warming device and with a drape that works with the basin to maintain a sterile field above the drape and the top of the basin. The interactions between a temperature sensor and a temperature well integrated in the removable basin are disclosed. Also disclosed are various desirable aspects for a control system for a liquid warming device are provided.

Claims

1. A liquid warming device comprising:

a removable basin having a bottom, a set of at least one side wall connected to the bottom of the removable basin so that the set of at least one side wall forms a walled perimeter around the bottom of the removable basin to form a container suitable for holding a fluid, and having an exterior of the removable basin;

a cavity in a top surface of the liquid warming device, the cavity having a bottom, the cavity adapted to receive a portion of the removable basin;

a heater adapted to provide heat via a heated surface to the at least a portion of the exterior of the removable basin; and

a surgical drape for covering at least a portion of the top surface of the liquid warming device, the surgical drape having an opening of sufficient size so that at least a portion of the removable basin can be inserted through the opening in the surgical drape such that a removable basin inserted through the opening in the surgical drape and inserted into the cavity has a least a portion of the exterior of the removable basin adjacent to the heated surface so that thermal energy can pass from the heated surface to at least the portion of the exterior of the removable basin without passing through the surgical drape.

2. The liquid warming device of claim 1 wherein the liquid warming device also includes a control system comprising:

a fluid temperature controller;

a fluid temperature sensor placed in thermal contact with the removable basin for the purpose of measuring a temperature representative of a fluid placed in the removable basin, the temperature obtained by the fluid temperature sensor provided as input to the fluid temperature controller; and

a heater temperature detector positioned in thermal contact with the heater and providing a heater temperature as input to the fluid temperature controller; and

wherein the fluid temperature controller operates to control a flow of electric energy provided to the heater so as to regulate the heater temperature based on the temperature measured by the fluid temperature sensor.

3. The liquid warming device of claim 2 wherein the fluid temperature sensor placed in thermal contact with the removable basin is movable relative to the cavity in the liquid warming device.

4. The liquid warming device of claim 3 wherein contact between the removable basin and the fluid temperature sensor causes the fluid temperature sensor to move through the transfer of energy to a spring.

5. The liquid warming device of claim 2 wherein:

the fluid temperature controller accepts a liquid target temperature input and calculates a temperature underage value based on the liquid target temperature minus the temperature obtained by the fluid temperature sensor; and

the fluid temperature controller seeks to maintain a heater set point temperature selected based on the temperature underage value.

6. The liquid warming device of claim 5 wherein the fluid temperature controller accepts a liquid target temperature from an input device located on an exterior surface of the liquid warming device.

7. The liquid warming device of claim 2 wherein:

the fluid temperature controller has a liquid target temperature and calculates a temperature underage value based on the liquid target temperature minus the temperature obtained by the fluid temperature sensor; and

the fluid temperature controller seeks to maintain the heater temperature at a heater set point temperature selected based on the temperature underage value.

8. The liquid warming device of claim 5 wherein the heater set point temperature is fixed at a maximum value for temperature underage values in excess of a first value.

9. The liquid warming device of claim 8 wherein the heater set point temperature is controlled by the fluid temperature controller through the use of a proportional integral derivative control scheme when the temperature underage is less than the first value.

10. The liquid warming device of claim 1 further including a sensor adapted to detect the presence of a particular radio frequency identification tag on the removable basin so that the liquid warming device can prevent the use of a removable basin without the particular radio frequency identification tag.

11. The liquid warming device of claim 1 further including at least one indicator to indicate whether the fluid in the removable basin is within a prescribed range of a target temperature.

12. The liquid warming device of claim 11 wherein the at least one indicator includes at least one indicator light that is adapted for use below a surgical drape so that the light from the at least one indicator light can be seen through the surgical drape but the surgical drape can be in proximity to a lit indicator light for at least 24 hours without damaging the surgical drape.

13. The liquid warming device of claim 1 further including a display that may display the current temperature representative of the fluid in the removable basin.

14. The liquid warming device of claim 13 wherein the display is located on a portion of an exterior of the liquid warming device normally covered by a surgical drape during surgery and the display can be read through the surgical drape.

15. A liquid warming device comprising:

a cavity in a top surface of the liquid warming device, the cavity having a bottom, the cavity adapted to receive at least a portion of a removable basin having a bottom, a set of at least one side wall connected to the bottom of the removable basin so that the set of at least one side wall forms a walled perimeter around the bottom of the removable basin to form a container suitable for holding a fluid, the removable basin having an exterior;

a heater adapted to provide heat via a heated surface to at least a portion of the exterior of the removable basin; and

the top surface of the liquid warming device requiring a surgical drape for covering at least a portion of the top surface of the liquid warming device in order to maintain a sterile barrier to isolate the portion of the top surface of the liquid warming device from a sterile field, the surgical drape having an opening of sufficient size so that at least a portion of the removable basin can be inserted through the opening in the surgical drape such that a removable basin inserted through the opening in the surgical drape and inserted into the cavity has a least a portion of the exterior of the removable basin adjacent to the heated surface so that thermal energy can pass from the heated surface to at least the portion of the removable basin without passing through the surgical drape.

16. The liquid warming device of claim 15 wherein the liquid warming device also includes a control system comprising:

a fluid temperature controller;

a fluid temperature sensor adapted to establish thermal contact with the removable basin for the purpose of measuring a temperature representative of a fluid placed in the removable basin, the temperature obtained by the fluid temperature sensor provided as input to the fluid temperature controller; and

a heater temperature detector positioned in thermal contact with the heater and providing a heater temperature as input to the fluid temperature controller;

wherein the fluid temperature controller controls a flow of electric energy provided to the heater so as to regulate the heater temperature based on the temperature obtained by the fluid temperature sensor.

17. The liquid warming device of claim 15 wherein the fluid temperature sensor adapted to establish thermal contact with the removable basin is movable relative to the cavity in the liquid warming device.

18. The liquid warming device of claim 16 wherein:

the fluid temperature controller accepts a liquid target temperature input and calculates a temperature underage value based on the liquid target temperature minus the temperature obtained by the fluid temperature sensor; and

the fluid temperature controller seeks to maintain a heater set point temperature selected based on the temperature underage value.

19. The liquid warming device of claim 18 wherein the fluid temperature controller accepts a liquid target temperature from an input device located on an exterior surface of the liquid warming device.

20. The liquid warming device of claim 15 further including a sensor adapted to detect the presence of a particular radio frequency identification tag on the removable basin so that the liquid warming device can prevent the use of a removable basin without the particular radio frequency identification tag.

21. The liquid warming device of claim 15 further including at least one indicator to indicate whether the fluid in the removable basin is within a prescribed range of a target temperature.

22. The liquid warming device of claim 15 further including a display that may display the current temperature representative of the fluid in the removable basin.

23. The liquid warming device of claim 22 wherein the display is located on a portion of an exterior of the liquid warming device normally covered by a surgical drape during surgery and the display can be read through the surgical drape.

24. A liquid warming device comprising:

a cavity adapted to receive a portion of a removable basin, the removable basin having a bottom, a set of at least one side wall connected to the bottom of the removable basin so that the set of at least one side wall forms a walled perimeter around the bottom of the removable basin to form a container suitable for holding a fluid;

a fluid temperature sensor placed such that placement of the removable basin in the cavity though an opening in a surgical drape places the fluid temperature sensor in direct contact with the removable basin for a purpose of measuring a temperature of a portion of an exterior of the removable basin as reflective of a temperature of a fluid placed in the removable basin, the temperature obtained by the fluid temperature sensor provided as input to a fluid temperature controller;

a heater adapted to provide heat to the at least a portion of the exterior of the removable basin that extends into the cavity through the opening in the surgical drape; and

the fluid temperature controller controlling a flow of energy provided to the heater so as to regulate the temperature measured by the fluid temperature sensor.

25. A liquid warming device comprising:

a cavity adapted to receive a portion of a removable basin, the removable basin having a bottom, a set of at least one side wall connected to the bottom of the removable basin so that the set of at least one side wall forms a walled perimeter around the bottom of the removable basin to form a container suitable for holding a fluid;

a heater adapted to provide heat through a thermally conductive path to the fluid placed in the removable basin; and

a fluid temperature controller controlling a flow of energy provided to the heater so as to prevent the heater from operating without a positive indication of the presence of an appropriate removable basin.

26. The liquid warming device of claim 25 wherein the positive indication is received from a limit switch that is actuated by the insertion of an appropriate removable basin into the cavity.

27. The liquid warming device of claim 26 wherein the limit switch is implemented with an actuator that moves in a horizontal manner as an appropriate removable basin of varying width moves up and down.

28. The liquid warming device of claim 26 wherein the limit switch is implemented to interact with a known geometry of an appropriate removable basin so that the limit switch is closed when an appropriate removable basin is placed into the cavity.

29. The liquid warming device of claim 28 wherein the limit switch is open:

A) if there is not a removable basin in the cavity;

or

B) if a removable basin is placed over the limit switch but the known geometry of the appropriate removable basin is not placed adjacent to the limit switch.

30. The liquid warming device of claim 29 wherein an appropriate removable basin with a thermocouple well placed in the cavity so that the thermocouple well is not in its intended position will cause the limit switch to be in an open state as the known geometry of the bottom of the appropriate removable basin in the vicinity of the thermocouple well is not positioned adjacent to the limit switch.

31. The liquid warming device of claim 28 wherein the liquid warming device provides an indication to users when the limit switch detects an object but the limit switch is not interacting with the known geometry of an appropriate removable basin and thus the limit switch is open.

32. The liquid warming device of claim 26 wherein a distal end of a fluid temperature sensor used to obtain a temperature from a surface of an appropriate removable basin moves when contacted by the appropriate basin so as to close the limit switch.

33. The liquid warming device of claim 26 wherein a limit switch actuator is placed adjacent to a portion of a fixed fluid temperature sensor used to obtain a temperature from a surface of an appropriate removable basin.

34. The liquid warming device of claim 26 wherein the limit switch has an actuator positioned so as to surround a portion of the fluid temperature sensor so as to insulate the fluid temperature sensor from heat flowing from the heater to the fluid temperature sensor without passing into the fluid in the appropriate removable basin.

35. The liquid warming device of claim 26 wherein the limit switch has an actuator placed so that interaction between the limit switch actuator and the appropriate removable basin is remote from the interaction between a fluid temperature sensor and a portion of the surface of an appropriate removable basin.

36. The liquid warming device of claim 25 wherein the fluid temperature controller prevents the heater from operating without a positive indication from a radio frequency identification sensor that an appropriate radio frequency identification tag is in proximity to the radio frequency identification sensor.

37. The liquid warming device of claim 25 wherein the fluid temperature controller prevents the heater from operating unless the fluid temperature controller has both:

A) a positive indication from a radio frequency identification sensor that an appropriate radio frequency identification tag is in proximity to the radio frequency identification sensor; and

B) a positive indication received from a limit switch that is actuated by the insertion of an appropriate removable basin into the cavity.

38. The liquid warming device of claim 25 wherein the positive indication of the presence of an appropriate removable basin is detection of a downward force that may indicate the weight of an appropriate removable basin containing at least a particular minimum volume of a fluid expected to be placed in the removable basin.

39. The liquid warming device of claim 25 wherein the fluid temperature controller controlling the flow of energy provided to the heater so as to prevent the heater from operating without a positive indication of the presence of an appropriate removable basin is adapted to stop preventing the flow of energy to the heater:

while receiving a positive indication of the presence of a downward force that may indicate the weight of an appropriate removable basin with at least a particular minimum volume of a fluid expected to be placed in the removable basin;

until the volume of fluid in the removable basin is decreased sufficiently so that the fluid temperature controller ceases to receive a positive indication of the downward force that may indicate the weight of an appropriate removable basin with at least a particular minimum volume of a fluid expected to be placed in the removable basin.

40. The liquid warming device of claim 25 wherein the lack of a positive indication of the presence of a downward force that may indicate the weight of an appropriate removable basin with at least a particular minimum volume of a fluid expected to be placed in the removable basin activates an alarm to note the fluid temperature controller is preventing the flow of energy to the heater.

41. The liquid warming device of claim 25 wherein the positive indication of the presence of an appropriate removable basin is an affirmation provided by a user through an input device in communication with the liquid warming device that a removable basin and an adequate level of fluid are present.

42. A method of maintaining a sterile liquid near a target temperature using a liquid warming device, the method comprising the steps of:

placing a surgical drape with an opening over a cavity in the liquid warming device, the opening having a perimeter;

placing a portion of a sterile removable basin in the cavity, an exterior of the sterile removable basin in contact with the perimeter of the opening in the surgical drape such that a portion of the sterile removable basin extending into the cavity through the opening of the surgical drape is placed into thermal contact with a temperature sensing device, the combination of the surgical drape and the sterile removable basin forming a sterile barrier for at least a top surface of the liquid warming device;

placing a sterile liquid in the sterile removable basin;

providing an indication of the temperature sensed by the temperature sensing device to a fluid temperature controller;

controlling a heater to provide thermal energy to a portion of the sterile removable basin where a least a portion of the thermal energy travels through a path from the heater to the sterile removable basin that does not include the surgical drape;

the heater controlled to avoid applying additional thermal energy when the indication of the temperature sensed by the temperature sensing device exceeds a desired indication of temperature so that the sterile liquid is maintained near the target temperature.

43. The method of claim 42 wherein the sterile removable basin includes a rim that is connected to an open end of the basin and extends over a portion of the surgical drape as part of the combination of the surgical drape and the sterile removable basin forming the sterile barrier for at least the top surface of the liquid warming device.

44. The method of claim 42 wherein the surgical drape is bonded to the exterior of the sterile removable basin such that the steps of placing the surgical drape with the opening over the cavity in the liquid warming device and placing the sterile removable basin in the cavity are accomplished together.

45. The method of claim 42 wherein the step of placing the surgical drape with an opening over the cavity in the liquid warming device includes attaching the surgical drape to the liquid warming device before the insertion of the portion of the sterile removable basin through the opening in the surgical drape and into the cavity.

46. The method of claim 45 wherein the surgical drape is attached to a portion of the top surface that defines the cavity.

47. The method of claim 42 wherein the surgical drape is stretched by the insertion of the sterile removable basin through the opening in the surgical drape to form an interference fit so that the sterile removable basin and surgical drape can be lifted without the surgical drape falling off the sterile removable basin.

48. The method of claim 47 wherein the insertion of the sterile removable basin through the opening in the surgical drape is performed before placing the sterile removable basin in the cavity such that the steps of placing the surgical drape with the opening over the cavity in the liquid warming device and placing the sterile removable basin in the cavity are accomplished together.

49. The method of claim 42 wherein the portion of the sterile removable basin extends through the opening in the surgical drape to move a spring loaded temperature sensing device.

50. The method of claim 42 wherein the placement of the surgical drape over the liquid warming device covers a set of at least one indicator light that can be seen through the surgical drape to indicate that the sterile fluid is near the target temperature.

51. The method of claim 42 wherein a user can provide the target temperature to the liquid warming device.

52. The method of claim 42 wherein the step of controlling the heater to provide thermal energy to the portion of the sterile removable basin includes measuring a temperature of the heater and controlling the heater to converge on a heater set point that is a fixed value when the difference between the indication of temperature sensed by the temperature sensing device and the desired indication of temperature exceeds a first value.

53. The method of claim 52 wherein the heater set point is set using a proportional integral derivative control scheme when the temperature difference is below the first value.

54. A method of maintaining a sterile liquid near a target temperature using a liquid warming device, the method comprising the steps of:

placing a surgical drape with an opening over a cavity in the liquid warming device, the opening having a perimeter;

placing a portion of a sterile removable basin in the cavity and in contact with the perimeter of the opening in the surgical drape such that a portion of an exterior surface of the removable basin extending through the opening in the surgical drape is placed in proximity to a temperature sensing device;

placing the sterile liquid in the sterile removable basin; and

controlling a flow of thermal energy provided to the sterile liquid in order to maintain the sterile liquid near the target temperature, at least some of the thermal energy flowing to the sterile liquid passing through the portion of the exterior surface of the sterile removable basin extending through the opening in the surgical drape.

55. The method of claim 54 wherein a portion of the sterile removable basin is extended through the opening in the surgical drape before placing the surgical drape with the opening over the cavity in the liquid warming device and placing the portion of the sterile removable basin in the cavity.

56. The method of claim 54 wherein the step of placing the sterile removable basin includes aligning a portion of a bottom of the basin with a basin detector that interacts with a control system so that energy is not applied to send a flow of thermal energy when a basin is not present.

57. The method of claim 54 wherein the step of controlling the flow of thermal energy provided to the sterile liquid in order to maintain the sterile liquid near the target temperature includes controlling an amount of current provided to a set of at least one resistive heater.

58. The method of claim 54 wherein the step of controlling the flow of thermal energy provided to the sterile liquid in order to maintain the sterile liquid near the target temperature includes controlling an infra-red heat source.

59. The method of claim 54 wherein the step of controlling the flow of thermal energy provided to the sterile liquid in order to maintain the sterile liquid near the target temperature includes controlling a microwave heat source.

60. The method of claim 54 wherein the step of controlling the flow of thermal energy provided to the sterile liquid in order to maintain the sterile liquid near the target temperature includes controlling an ultrasonic heat source.

61. The method of claim 54 wherein the step of controlling the flow of thermal energy provided to the sterile liquid in order to maintain the sterile liquid near the target temperature includes controlling an induction heating heat source.