Whole Body Calorimeter

The present invention relates to improved means and techniques useful in the treatment and/or observation of conditions in patients, animals and other living things by measuring metabolic heat releases.

An object of the present invention is to provide an improved calorimeter for these purposes involving the concept of using good heat conducting panels for imparting structural strength and also for providing a heat sink into which substantially all the heat from a source within the calorimeter box flows after being measured by heat flow measuring means.

Another object of the present invention is to provide a calorimeter as set forth in the preceding paragraph with the addition of a transparent window together with means and techniques whereby heat losses from such window are accounted for.

Another object of the present invention is to provide an improved calorimeter of this character in which the person's or patient's head is within a transparent duct system that allows him or her to see and talk to attendants and through which there is an air flow past the person's head and neck and then into the calorimeter box.

Another object of the present invention is to provide new teachings and arrangements for accounting for heat losses through a transparent window.

Another object of the present invention is to provide an improved calorimeter of this character in which thermopile panels are mounted in a novel manner with respect to structural elements that function also as a heat sink.

Another object of the present invention is to provide an improved calorimeter of this character involving improved sealing means between the door and calorimeter box itself.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. This invention itself, both as to its organization and manner of operation are set forth with particularity later herein with further objects and advantages thereof being best understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of a calorimeter emboding features of the present invention with some parts broken away for purpose of illustrating internal structure.

FIGS. 2 and 4 are sectional views taken substantially on lines 2--2 and 4--4 of FIG. 1 and FIG. 3 is a sectional view taken along a line perpendicular to line 3--3 of FIG. 2.

FIG. 5 is a sectional view taken substantially as indicated by line 5--5 in FIG. 1 with however, the door in closed position.

FIG. 6 is a sectional view taken substantially on line 6--6 of FIG. 5.

FIG. 7 is a perspective view illustrating thermopile constructions used in the calorimeter.

FIG. 8 illustrates a modification of the present invention in which a transparent window surrounded by a heat insulating frame is used to observe persons or animals inside a calorimeter and the association of heat flux sensors for accounting for heat losses through the window-insulating material combination.

The calorimeter as illustrated is generally in the form of a rectangular box 10 sufficiently large to accommodate a human being, and it is made portable in the sense that it includes four ground engaging wheels 12 rotatably mounted on the lower end of an open rectangular framework 14 which supports the box 10 at a convenient height above the surface of the floor or ground.

Access to the interior of the box 10 is had through a hinged door 16 forming one end of the box 10, the other end of the box being closed except that it is formed with a transparent protuberance 18A in the form of a box-shaped duct system 18B into which the person's or patient's head is disposed at 18E to allow him to see and communicate with the attendants outside the box 10.

Air enters the box-shaped double wall duct system 18B and flows past the person's head and neck as indicated by arrows 18C into the interior chamber 20 of the calorimeter box where the rest of the person's body is disposed.

This box-shaped duct system 18B includes an outer transparent rectangular box 18M which is secured to wall 18 at 18H (FIG. 2), and as seen in FIGS. 1 and 2 has a top opening 18J and a side opening 18K through which ambient air may flow from the outside to the inside of box 10. Disposed within and spaced from and secured to the outer box 18M as, for example, by screws or glue is an inner transparent rectangular box 18N which like the outer box 18M has a top opening 18P. The boxes 18M and 18N are maintained in spaced relationship by a series of spaced blocks 18S (FIGS. 2 and 3). The boxes 18M, 18N thus spaced provide a double wall transparent structure which is mounted on one end of box 10 in good heat conducting relationship to heavy metal side plates 80 (FIG. 2). This good heat conducting relationship is provided by the following interconnected elements: angle member 19A, screws 19B, 19C, element 181, metal skin material 70 and screws 132A, 19D. Air is permitted to flow in the space 18W between the spaced sides of boxes 18M, 18N from the corresponding top openings 18J, 18P. The wall of the inner box 18N adjacent opening 18K is open.

This inner box 18N within which the subject's head is disposed serves as an internal transparent shield, i.e., a radiation shield. Almost all the radiant energy from the person's head is absorbed by the walls of the inner radiation shield, i.e., inner box 18N which is removed by convection by the air flow contacting box 18N in its passage through the duct system and into the calorimeter box. Only a small fraction of the radiant heat loss from the person's head is lost through the flow opening in the transparent duct system. It is noted that the outer box 18M is exposed to the ambient air and thus has substantially the same temperature as the ambient air and consequently there is substantially no heat radiated from the ambient air to the outer box 18M.

The air flow whose presence and direction is indicated by the various arrows 18C in FIGS. 1 and 2 is generally in the following path. The air flow enters the top openings 18J, 18P of the outer and inner boxes 18M, 18N respectively and continues its flow as indicated by the various arrows 18C (FIGS. 1 an 2). The air entering the opening 18J flows through the space 18W between the two boxes 18M, 18N and then into the chamber 20. The air entering the opening 18P flows through the inner box 18N and then into the calorimeter chamber. Should such air flow, which, for example, may be produced by any of various conventional means illustrated generally in FIG. 1 as air flow producing means 8, be interrupted, i.e. become non-existent, it, of course, is no longer present and effective to carry the person's head heat releases into the chamber but the person is still able to breath ambient air without being suffocated. Applicant makes no claim for any exclusivity in any of such conventional air flow producing means 8.

The box 10 floor portion 22 has U-shaped parallel extending rail members 24, 26 are mounted for receiving and guiding the movement of wheels (not shown) of a wheeled stretcher, bed or cot (not shown) upon which a human being or other live being may rest while being within and being subjected to the environment inside the box 10 for performance of metabolic tests.

The ends, sides, floor and the rest of the box 10 are constructed to prevent heat flow therethrough to or from the room environment and to achieve that purpose, as seen in FIG. 4, the box side 28, roof 30 and floor 22 each includes heat insulating material 36. Likewise, such heat insulation material 36 as seen in FIG. 5 is included also in the door 16. The other end 18 to which the open outer box 18M is secured likewise includes insulation 36.

The outside surface of box 10 is formed in general of thin aluminum or sheet steel or skin material 70 as illustrated in FIGS. 2 and 4 except where there is a transparent air conduit means 18M, 18N at one end of the calorimeter.

Insulating material 36 is retained in pockts 36A using outwardly extending flange portions 80A (FIG. 2) of metal panels 80 and skin material 70 which together with fastening means 19D provides a means for fastening the skin material to the panels 80 to retain insulation 36 in the pockets 36A which are defined essentially by the flanged panels 80 and skin material 70.

The door 16 is as indicated in FIG. 1 hinged at 90, 91, 92 to wall 37. In the closed condition of the door, it is sealed with respect to the side walls, the roof and also to the floor, using a construction shown in FIG. 5 involving a generally rectangular elastic or "O" ring seal 94, of for example, rubber and also a so called grease seal 96.

Thus in FIG. 5 the aluminum roof portion 82 has a flanged portion 82A with a recessed portion 82B to accommodate the upper horizontal leg of the rectangular seal 94. Such flanged portion 82 also has a projecting portion 82C extending along its entire width and into a grooved portion 98A of the aluminum door panel 98 which is formed also with flanged portion 98B. This construction illustrated in FIG. 5 serves also to illustrate the manner in which the door cooperates with the two sides 28, 37 as well as the floor 22. In each of these there is a like projecting portion 82C which enters like continuous grooved portion 98A filled with sealing grease 99.

Structural strength is imparted by the wall constructions using 5/16 inch aluminum sheeting which is also used as a form of heat sink as described hereinafter. Thus in FIG. 4 the side wall 28 (typical also of the construction of the other side wall 37) includes a heavy aluminum plate 80 joined to a like aluminum floor plate 81 and ceiling plate 82. One end of plate 80 as seen in FIG. 2 has a flanged portion 80A and a recessed portion 80B in which a generally rectangular seal member 83 of, for example, rubber is disposed.

The heavy aluminum walls, roof, floor, and door panel, as indicated previously, serve in the nature of a heat sink from which heat developed inside the calorimeter is conducted away as rapidly as it reaches the aluminum. This is accomplished by maintaining the aluminum panels at a substantially constant temperature. This is done by circulating water through grids of tubing 100 of copper or other good heat conducting material which is secured to the aluminum panels in good heat conducting relationship as, for example, by soldering.

The heat flow to this form of heat sink is effectively measured and/or indicated using a plurality of thermopile sandwich panels which form the inner surfaces of the walls.

This thermopile construction 110 is illustrated in FIGS. 6 and 7 and their positions in, for example, the roof are illustrated in FIG. 1. Basically, each of the thermopiles, one of which is shown in FIG. 7 may be constantin wire 112 wrapped around a bakelite strip 113 having, for example, a thickness of 0.020 inch. This strip 113 may be of bakelite or a plastic of low thermal conductivity whose characteristics do not appreciably change. The wire 112 after wrapping may be coated along selected portions with a silver or copper coating 114 as indicated by the stripling in FIG. 7 to provide a series of hot junctions 116 along one face of the strip 113 and correspondingly, a series of cold junctions 118 (FIG. 6) is spaced along the other side of strip 113. The thermopiles thus constructed are sandwiched between the electrically insulating sheets 120, 121, such sheets 120, 121 being spaced by intervening electrically insulating sheets 114. The outer surface of these sheets 120, 121 may be clad with the copper coating or layer 126, 127 respectively. The purpose of such copper cladding is for temperature stabilization. The copper cladding is in good direct heat conducting relationship with the aluminum panel illustrated as the roof panel 82, it being understood, however, that like thermopile sandwich constructions are in good heat conducting relationship to the aluminum panels forming the structural elements of the walls, floor and door of the calorimeter box. The outer copper cladding 126 is covered with a protective sheet 130. The individual panels so constructed may be secured mechanically to the combination aluminum frame and heat sink members using screws of insulating material as, for example, nylon screws 132.

The individual thermocouples may be spaced somewhat as indicated in FIG. 1 wherein as shown in FIGS. 1 and 6 the thermopiles 110 and their mounting strips 113 lie in planes substantially parallel with the plane of the metal panel 82 and with the spacing between adjacent strips 113 being greater than the width of one of such strips and with the spacing, however, not being too large so that, in any event, the group of thermopiles serve to sense all the heat flow from the interior of the calorimeter box to the surrounding heat sink. Thermocouples or thermopiles 180 (FIG. 2) are also advantageously located continuously all the way around the rectangular opening R behind the L-shaped plastic sheet liner L which defines opening R. Here again these thermopiles 180 are in the path of heat flow from the interior of the calorimeter chamber to the heavy metal heat sink which as seen in FIG. 2 includes the flanged L-shaped heavy metal cap 181 that is secured to the heavy metal panel 80 by screws 132A. The thermopiles are connected electrically in additive relationship with all of the series connected thermopiles in the roof being connected in series with all of the thermopiles of the walls and of the floor and also of the door so that there is one electrical output in the form of a voltage or current which serves as a measure of the heat flow from the interior of the calorimeter box to the heat sink.

The output of the thermopiles appears at a jack 140 in FIG. 1. Such output may be displayed in conventional manner on a conventional output meter 140A connected to jack 140. A jack 142 having multiple conductors may have connected thereto various electrical inputs and/or outputs such as, for example, calibration circuits, power circuits. Auxillary temperature sensor circuits may be connected to the connector of jack 144. Jack 145 is an optional spare jack. Conduits may also be provided with, for example, intravenous flow connections 146, 148 for use with a patient in the calorimeter box.

Conduit connections 150, 152 are ventilating air outlets and optional air inlet connections respectively so that the heat added to such ventilating air introduced through the top opening 18J (FIG. 1) and also in some cases introduced through the inlet opening 152 together with the heat present in moisture accompanying such air may be measured and analyzed. Other conduits 156, 158 may be provided, for example, for connection to an oxygen mask system and for conducting gases expelled by a patient. Preferably all air is introduced by convential means 8 through the top opening 18J to produce air circulation past the person's head and neck.

The two lower conduits 160 and 162 are the water inlet and outlet openings through which constsnt temperature water is circulated for purpose of maintaining the heat sink at a substantially constant temperature.

At times researchers using a metabolic calorimeter wish to observe the animal under study and thus a thermal window is added to the calorimeter wall or door as in this modification of the invention as described below.

In the case of a small calorimeter, it can be too difficult and expensive to cut a hole into a heat flux sensor plate that normally covers the calorimeter walls and door. Therefore, the wall or door where the window is to be inserted is made of an insulating frame, as for example foam material 200 as illustrated in FIG. 8. A thermal window 202 is fitted in the insulating frame 200. The frame 200 may be mounted in either the door or a side wall of the calorimeter described above to allow viewing of the inside of the calorimeter from the outside thereof.

In order to account for the small amount of heat loss that takes place through the insulating frame and thermal window there is provided in accordance with features of the present invention, a heat flux sensor system that will allow this smaller heat flux term to be determined.

One heat flux sensor 204 having a constant K.sub.w Btu/hr ft.sup.2 millivolt is placed over the thermal window 202. Several heat flux sensors 206, connected electrically in series, combined to have a combined Constant, K.sub.in Btu/hr ft.sup.2 millivolt are placed in the insulating area surrounding the window. The total heat loss from the window system is q.sub.t : ##EQU1## where: q.sub.window is the heat flow through the window in Btu/hr.

q.sub.in is the heat flow through the insulation in Btu/hr.

(q/A).sub.w is the heat flux through the window in Btu/hr ft.sup.2.

(q/A).sub.in is the heat flux through the insulation in Btu/hr ft.sup.2.

A.sub.w and A.sub.in are the window and frame insulation areas respectively ft.sup.2.

The relationship between the heat flux through a heatmeter and its millivolt output signal, E, and calibration constant K is:

Thus equation (1) becomes,

Preferably, as in accordance with features of the present invention, the window flux sensors 206 on the insulation are connected electrically in series. In such case, in order that the millivolt signals E.sub.W and E.sub.IN can be meaningfully added, the following requirements must be met,

or

One uses sensors with constants such that equation (4) above is satisfied.

While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.