FLUID WARMING APPARATUS

Abstract

The invention provides forced air warming apparatus for providing air to a patient temperature regulation tool for regulating the temperature of a patient, the forced air warming apparatus comprising: a housing; an air pressurising device provided within the housing, the air pressurising device being configured to receive an air intake and to pressurise air from the air intake; and a suspension configured to restrict transfer to the housing of vibrations caused by the air pressurising device pressurising the said air from the air intake.

Claims

1. Forced air warming apparatus for providing air to a patient temperature regulation tool for regulating the temperature of a patient, the forced air warming apparatus comprising: a housing; an air pressurising device provided within the housing, the air pressurising device being configured to receive an air intake and to pressurise air from the air intake; and a suspension configured to restrict transfer to the housing of vibrations caused by the air pressurising device pressurising the said air from the air intake.

2. The forced air warming apparatus according to claim 1 wherein the air pressurising device is mechanically coupled to the housing by way of the said suspension, and wherein the said suspension enables movement of the air pressurising device relative to the housing to thereby restrict transfer of vibrations from the air pressurising device to the housing.

3. The forced air warming apparatus according to claim 1 wherein the air pressurising device is configured to generate pressurised air in a pressure chamber provided within the housing.

4. The forced air warmer according to claim 3 wherein the pressure chamber is mechanically coupled to the housing by way of the said suspension to thereby restrict transfer of vibrations from the pressure chamber to the housing.

5. The forced air warming apparatus according to claim 4 wherein at least a portion of the suspension is configured to damp movement of the pressure chamber relative to the housing to thereby restrict transfer of vibrations from the pressure chamber to the housing.

6. The forced air warmer according to claim 3 wherein the air pressurising device is mechanically coupled to the pressure chamber by way of the said suspension to thereby restrict transfer of vibrations from the air pressurising device to the pressure chamber.

7. The forced air warmer according to claim 3 wherein the air pressurising device is mechanically coupled to the housing by way of the pressure chamber.

8. The forced air warming apparatus according to claim 3 wherein the air pressurising device comprises one or more blades rotatable about an axis of rotation to thereby generate the said pressurised air from the air intake, wherein at least a portion of each of the said one or more blades is provided within the pressure chamber.

9. The forced air warming apparatus according to claim 3 wherein the pressure chamber comprises an air outlet port and the housing comprises an air outlet port, wherein the air outlet port of the pressure chamber is in fluid communication with the air outlet port of the housing by way of a coupler, the said coupler enabling movement of the pressure chamber relative to the housing to thereby restrict transfer of vibrations from the pressure chamber to the housing.

10. The forced air warming apparatus according to claim 1 wherein at least a portion of the suspension is resilient.

11. The forced air warming apparatus according to claim 1 wherein the said suspension comprises a plurality of suspension mountings, wherein each of the suspension mountings comprises one or more of the group comprising: a damper; a resilient element; a resiliently deformable element; an elastic element; an elastically deformable element; an energy storage element; an elastomeric element; a spring; and a hinge.

12. The forced air warming apparatus according to claim 1 further comprising a hose connector, wherein the hose connector is coupled to the housing by way of a coupler which enables movement of the hose connector relative to the housing to thereby restrict transfer of vibrations from the hose connector to the housing.

13. A patient temperature regulation system comprising: a forced air warming apparatus according to claim 1; and a patient temperature regulation tool configured to receive heated air from the forced air warming apparatus by way of a hose.

14. The patient temperature regulation system according to claim 13 wherein the forced air warming apparatus is provided adjacent to a patient or mounted to a bed frame.

15. A method of pressurising air in forced air warming apparatus for providing air to a patient temperature regulation tool for regulating the temperature of a patient, the method comprising: providing an air pressurising device within a housing; the air pressurising device receiving an air intake; the air pressurising device pressurising air from the air intake, thereby causing vibrations; and a suspension restricting transfer of said vibrations to the housing.

Description

DESCRIPTION OF THE DRAWINGS

[0112] An example embodiment of the present invention will now be illustrated with reference to the following Figures in which:

[0113] FIG. 1 is a block diagram showing the rear of a fluid warming apparatus coupled to a perforated blanket by a flexible hose;

[0114] FIG. 2 shows the fluid warming apparatus of FIG. 1, with the housing shown as being transparent to make an inner pressure chamber of the fluid warming apparatus visible;

[0115] FIG. 3 is a rear schematic view of the pressure chamber of the fluid warming apparatus of FIGS. 1 and 2;

[0116] FIG. 4 is a close up schematic view of a suspension mounting which connects the pressure chamber to the housing of the fluid warming apparatus;

[0117] FIG. 5 is a front schematic view of the pressure chamber, housing and hose of FIGS. 1-3, the pressure chamber being coupled to the housing by a first coupler and the housing being coupled to the hose connector by a second coupler;

[0118] FIG. 6 is a front sectional view of an alternative fluid warming apparatus to that shown in FIGS. 1 to 4, the inner pressure chamber being mechanically coupled to the housing by a suspension having an alternative configuration; and

[0119] FIG. 7 shows an axial fan which is an alternative to the centrifugal fan of the embodiments of FIGS. 1 to 6.

DETAILED DESCRIPTION OF AN EXAMPLE EMBODIMENT

[0120] FIG. 1 is a block diagram showing the rear of a fluid warming apparatus 1 (typically sealedly) fluidly coupled to a perforated blanket 2 by a flexible hose 3, the perforated blanket 2 being draped over a (typically human) patient (not shown) during a medical procedure or operation (typically when the patient is under a general anaesthetic). Air heated by the fluid warming apparatus 1 is delivered to the blanket 2 through the hose 3. The blanket 2 contains a plurality of perforations (not shown) through which heated air received from the fluid warming apparatus 1 is delivered to the patient to heat the patient by forced convection, thereby preventing the onset of unintentional hypothermia in the patient.

[0121] As shown in FIGS. 1 and 2, the fluid warming apparatus 1 comprises a vertically mounted (by way of a resilient mounting 7) external housing 8 having opposing first (upper) and second (lower) faces 10, 12 extending between opposing third (front) and fourth (rear) faces 14, 16 and between opposing fifth (side) and sixth (side) faces 18, 20. The third (front) and fourth (rear) faces 14, 16 also extend between the fifth (side) and sixth (side) faces 18, 20. The third (front) face 14 is removable so that the inside of the external housing 8 can be accessed for maintenance (although any one or more of the first to sixth faces could be removable for access). The second face 12 of the fluid warming apparatus 1 has an ambient air intake port 22 configured to receive ambient air from the surrounding environment into an inner volume of the housing 8. The air intake port 22 is provided with a filter 23 for filtering the incoming ambient air.

[0122] As shown most clearly in FIG. 2, within the housing 8 is provided a pressure chamber 30 in the form of an annular volute which is mechanically coupled to an internal surface of the rear face 16 of the housing 8 (although it will be understood that the pressure chamber could alternatively be mounted to any of the other faces of the housing 8) by way of a suspension comprising first, second and third suspension mountings 32, 34 and 36 respectively (the suspension mountings are most clearly shown in FIGS. 4 and 6, and are not shown in detail in FIG. 2). The suspension mountings 32, 34, 36 extend from an outer perimeter of the pressure chamber 30 and are spaced from each other around the said perimeter in a plane perpendicular to the axis of rotation, the second and third suspension mountings 34, 36 extending from upper and lower portions of the perimeter respectively and the first suspension mounting 32 extending from a portion of the perimeter intermediate the second and third mountings 34, 36. This is illustrated most clearly in FIG. 3.

[0123] The suspension mountings 32, 34, 36 are identical so only suspension mounting 32 will be described in detail, it being understood that suspension mountings 34, 36 comprise the same features. As shown in FIG. 4, suspension mounting 32 comprises: an n-shaped bracket 37 having first and second sides 37a, 37b extending outwardly from the outer perimeter of the pressure chamber 30 and a third side 37c extending (and coupling) the first and second sides 37a, 37b; and an elastomeric damper 38, the damper 38 comprising a base 38a, a boss 38b and an intermediate portion 38c extending between the base 38a and the boss 38b. The base 38a (and part of the intermediate portion 38c adjacent the base 38a) of the damper is received by an aperture (not shown) in (and retained by) the third face 37c of the bracket 37, the said aperture having a smaller width than the base 38a. A bracket 39 extends from an inner surface of the rear face 16 of the housing 8 for coupling the housing 8 to the damper 38 (and thus for retaining the pressure chamber 30 on the said rear surface of the housing 8). The bracket 39 comprises a recess 39a into which a portion of the suspension mounting 32 (including a portion of the n-shaped bracket 37 and a portion of the damper 38) is received. The bracket 39 further comprises protrusions 39b which are received by a recess 38d in the damper 38 between the intermediate portion 38c and the boss 38b and the engagement of the protrusions 39b and inner walls of the recess 38d inhibit relative radial movement of the damper 38 and the bracket 39 (in either radial direction). Vibrational movement of the pressure chamber 30 relative to the housing 8 is enabled and damped by movement and/or resilient deformation of the damper 38 relative to the bracket 39. The bracket 39 is however configured to restrict larger movements of the pressure chamber 30 relative to the housing 8 (e.g. beyond the elastic deformation limit of the damper 38), for example in the event of large accelerations (e.g. due to external impacts on the fluid warming apparatus).

[0124] In order to design the suspension mountings 32, 34, 36, it is necessary to consider the natural frequency, stroke and mass of the system which is to be damped (in this case, the pressure chamber 30 and its contents) and the environmental conditions (e.g. temperature and humidity) in which it is to be used. At least the following parameters can be tuned to optimise their design: the required lifetime of the suspension mountings 32, 34, 36; the allowed stroke and maximum deflection of the damped system; the stiffness of the damper 38 (or, for embodiments comprising springs, the spring constant of the springs); the required durability of the damper 38; and the number of suspension mountings (which number is dependent on budget and space considerations).

[0125] The pressure chamber 30 houses a centrifugal fan 40 which is rigidly mounted to the pressure chamber 30 and which comprises a hub 42 and a plurality of blades 44, proximal ends of the blades 44 being mechanically connected to and extending from the hub 42. The hub 42 houses a motor which, in use, causes the hub 42 (and thus the blades 44) to rotate about an axis of rotation (represented in FIG. 2 by a dotted line extending through a centre of the hub 42). The hub 42 is provided within an annulus 46 of the annular pressure chamber 30 and is therefore surrounded by the annular pressure chamber 30 but is not provided within the annular pressure chamber 30. On the other hand, the blades 44 (or at least portions of the blades 44, typically including distal ends thereof remote from the hub 42) are provided within the pressure chamber 30.

[0126] It will be understood that, alternatively, a drive shaft may extend into the annulus from a motor positioned elsewhere (other than in the hub) in order to rotate the fan blades.

[0127] When ambient air is received into the housing 8 through the air intake port 22 and the filter 23, the air within the inner volume of the housing 8 is at underpressure (i.e. at a pressure less than the atmospheric pressure immediately surrounding the housing 8) due to a pressure drop across the filter 23. When the motor causes the hub 42 and thus the blades 44 to rotate, air from the inner volume of the housing 8 is drawn into the annulus 46 of the fan (and ambient air is drawn into the housing 8 through air intake port 22 and the filter 23). Air drawn into the annulus 46 is caused to enter the annular pressure chamber 30 through gaps between adjacent blades 44, and is pressurised (increased in pressure), by rotation of the fan blades 44. The air drawn into the annular pressure chamber 30 flows along an air flow passage extending around the annulus 46 of the pressure chamber 30 (illustrated by the dashed arrow-headed line in FIG. 5) to an outlet 48 of the pressure chamber 30. A heater 49 (see FIG. 5) is provided at the outlet 48 of the pressure chamber 30 and configured to heat the pressurised air output from the pressure chamber 30 (although the heater may alternatively be provided anywhere along the air flow path between the air intake port 22 of the housing 8 and the hose 3). In this way, a supply of heated, pressurised air is provided in the annular pressure chamber 30. In addition, the ambient air flow through the inner volume of the housing 8 cools electronics provided therein (the electronics are shown in FIG. 6 which is described below).

[0128] As the motor and the blades 44 of the fan rotate, they vibrate and generate acoustic waves (typically at human audible frequencies) in the pressure chamber 30. In addition, the pressurised air provided in and vibration of the pressure chamber 30 typically flows turbulently, thereby causing vibration of the pressure chamber 30. By providing the blades 44 of the fan (or at least portions thereof) within the pressure chamber 30, the pressure chamber 30 substantially attenuates (e.g. absorbs or reflects) the acoustic waves generated by the blades in use, to thereby reduce the amplitudes of acoustic waves which propagate to the faces of the housing 8. In addition, by coupling the pressure chamber 30 to the housing 8 by way of a suspension 32, 34, 36 which enables movement of the pressure chamber 30 relative to the housing, transfer of vibrations from the pressure chamber 30 to the housing 8 is substantially restricted. This allows the fluid warming apparatus 1 to be mounted closer to the patient (e.g. on a frame of a bed which supports the patient), and even adjacent to the patient's head, without transmitting a significant amount of noise to the patient. In addition, this enables a shorter hose 3 to be employed which improves thermal efficiency as well as the convenience and safety of the system.

[0129] In some embodiments, the mounting 7 mounts the fluid warming apparatus 1 to a patient's bed frame, the mounting 7 being resiliently (e.g. elastically) deformable so as to act as a suspension enabling vibrational movement of the housing 8 relative to the bed frame, thereby restricting transfer of vibrations from the housing 8 to the bed frame.

[0130] Heated, pressurised air is transferred from the pressure chamber 30 to the hose 3 by way of the outlet 48 of the pressure chamber 30. As most clearly shown in FIG. 5 (which omits some elements of the fluid warming apparatus for clarity), heated, pressurised air from the pressure chamber 30 is carried from the outlet 48 of the pressure chamber 30 and out of the housing 8 to the hose 3 through an outlet port 50 of the housing 8 by a coupler 52 extending (at least part of the way) between them. The hose 3 is coupled to the pressure chamber 30 by way of a (typically rigid) hose connector 54. In this embodiment, the hose connector 54 extends through the port 50 from a first end 54a outside the housing 8 to a second end 54b inside the housing 8. The first and second ends 54a, 54b of the hose connector 54 are provided with threaded portions (e.g. it may be that the hose connector 54 is threaded along its length between the first and second ends 54a, 54b). The hose 3 is threadably coupled to the first end 54a of the hose connector 54. The first coupler 52 comprises: a first end 52a having threads which threadably mate with threads at the outlet 48 of the pressure chamber 30 and a second end 52b opposite the first end 52a has threads which threadably mate with threads on the second end 54b of the hose connector 54. Between the first and second ends 52a, 52b of the coupler 52 is provided an elastic sleeve 52c which enables relative (e.g. vibrational) movement of the pressure chamber 30 and the housing 8 and which fluidly couples the hose connector 54 to the outlet of the pressure chamber 30.

[0131] By providing the coupler 52 with the elastic sleeve 52c, the transfer of vibrations from the pressure chamber 30 to the housing 3 is further restricted because the propagation of mechanical waves between the pressure chamber 30 and the housing 8 is made less efficient. This is because vibrations of the pressure chamber 30 cause elastic deformation of the sleeve 52c as they propagate away from the pressure chamber 30 towards the housing 8, thereby reducing the amplitude of any remaining vibrations which propagate into the housing by way of the coupler 52. This in turn reduces the vibration and acoustic noise output by the housing 8.

[0132] In addition (although it is optional, and indeed can be an alternative to the coupler 52 having an elastic sleeve 52c) a resilient (e.g.) elastic coupler 55 (provided in the form of a sleeve over the hose connector 54) is provided between the hose connector 54 and the housing 8 within the port 50. The elastic coupler 55 extends from the outer perimeter of the hose connector 54 to the housing 8 (i.e. from the hose connector 54 to the inner walls of the port 50), surrounding the hose connector 8 around its perimeter. The elastic coupler 55 enables relative (e.g. vibrational) movement of the hose connector 54 and the housing 55 to thereby further restrict the transfer of vibrations from the hose connector 54 to the housing 8.

[0133] FIG. 6 is a sectional view of an alternative fluid warming apparatus 100 which is identical to that shown in FIGS. 1 to 5, but for a different arrangement of the suspension mountings 32, 34, 36 and the provision of feet 102, 104 which support the housing 8 on a mounting surface 106 (typically instead of mounting 7). Suspension mounting 36 is provided in substantially the same place in the arrangement of FIG. 6 as in the arrangement of FIGS. 2-3, and the suspension mountings 32, 34 and 36 are still spaced from each other about the perimeter in a plane perpendicular to the axis of rotation of the fan. However, in a change from the arrangement of FIGS. 1 to 5, suspension mountings 32, 34 of the arrangement of FIG. 6 extend from opposite sides of the perimeter of the pressure chamber 30 at (similar) heights between the axis of rotation and the top of the pressure chamber 30.

[0134] For optimal damping, the suspension mountings 32, 34, 36 are provided in the same (typically vertical) plane and the plane comprises (i.e. is aligned with) the centre of gravity of the pressure chamber 30. Providing the suspension mountings 32, 34, 36 in the same plane helps to isolate the vibrations of the pressure chamber 30 from the housing 8. Providing the suspension mountings 32, 34, 36 in the same plane as the centre of gravity of the pressure chamber 30 also helps to limit and control the three dimensional vibrations of the pressure chamber 30. The suspension mountings 32, 34, 36 are also distributed symmetrically about the centre of gravity of the pressure chamber 30 in order to distribute the load evenly among them.

[0135] Also shown in FIG. 6 are control electronics 101 (e.g. for controlling rotation of the fan and operation of the heater) provided within the housing 8.

[0136] Feet 102, 104 can be formed from a resilient elastomer such that they enable (e.g. vibrational) movement of the housing 8 relative to the mounting surface 106. This restricts the transfer of vibrations of the housing 8 to the mounting surface 106.

[0137] The other features of the fluid warming apparatus 100 will not be described in detail in view of the fact that they are identical to corresponding features of the embodiment of FIGS. 1 to 5; identical features have been allocated the same reference numerals (where applicable) as corresponding features of the fluid warming apparatus 1 of FIGS. 1 to 5. The hose 3 and the blanket 2 have been omitted from FIG. 6.

[0138] Further variations and modifications may be made within the scope of the invention herein described. For example, it will be understood that the housing 8 does not need to be vertically mounted. It may alternatively be horizontally mounted or mounted at an angle to the horizontal and/or to the vertical.

[0139] It will also be understood that the fan 40 need not be a centrifugal fan. For example, an axial fan could alternatively be used, such as the one shown in FIG. 7. In this case, the fan comprises four blades 110 rotatable about an axis 112 and enclosed within a pressure chamber 114. The pressure chamber 114 is provided with a meshed front face 116 through which pressurised air can be output to a hose as above and typically a meshed rear face through which intake air can be received by the fan. The pressure chamber 114 is typically mounted to the housing 8 by way of suspension mountings as described above.

[0140] Although three suspension mountings are provided in each of the embodiments described above, it will be understood that any suitable number of suspension mountings may be provided (e.g. one or more, or more than three) or indeed any other suitable suspension design may be provided which enables (e.g. vibrational) movement of the pressure chamber 30 relative to the housing 8 to restrict transfer of vibrations from the pressure chamber 30 to the housing 8.

[0141] It will also be understood that the pressure chamber need not be annular, and need not have a volute (or scroll) shape.

[0142] It may be that both the hub and the blades of the fan may be provided within the pressure chamber. Alternatively, the hub may be mounted in the inlet port of the pressure chamber 30 (even when the pressure chamber is not annular and does not have a volute (scroll) shape).

[0143] In embodiments in which the housing 8 comprises feet for mounting the housing 8 to a mounting surface, any suitable number of feet may be provided.

[0144] The housing may have any suitable shape.

[0145] It may be that, instead of being rigidly coupled, the fan 40 is mechanically coupled to the pressure chamber 30 by a suspension (e.g. identical to one or more of the suspension mountings 32, 34, 36 described above) enabling relative (e.g. vibrational) movement of the fan 40 and the pressure chamber 30 to thereby restrict transfer of vibrations of the fan 40 to the housing 8.

[0146] It may be that the motor of the fan 40 is mechanically coupled to the pressure chamber 30 or to the housing 8 by a suspension (e.g. identical to one or more of the suspension mountings 32, 34, 36 described above) enabling relative vibrational movement of the motor and the pressure chamber or housing to thereby restrict transfer of vibrations therebetween.