Low pressure hyperbaric chamber

A portable chamber for enclosing a portion of the body, such as the lower leg, for treatment with oxygen or other gas at pressures above atmospheric, the chamber having a closed end and a limb-receiving sleeve in its entrance end, the sleeve being inflatable to ensure effective closing off of the chamber from ambient air, for maintaining desired pressure in the chamber and preventing uncontrolled escape of the gas while eliminating the danger of too tight binding of the limb. Simple means for controlling pressure and humidity may be provided.

This invention relates to a portable hyperbaric chamber for enclosing a 
portion of the body such as the lower leg, for treatment with oxygen or 
other gas at somewhat elevated pressures, the chamber having a closed end 
and an open, limb-receiving end, the latter being provided with an 
entrance sleeve and means, preferably inflatable, to hold the sleeve 
sealingly but resiliently against the limb. The treatment gas may 
conveniently be used also for inflation and humidification. This chamber 
is an improvement over the chamber disclosed in applicant's U.S. Pat. No. 
3,744,491, July 10, 1973, which patent sets forth the background of the 
invention. 
It is an object of the invention to provide a chamber with simple and 
effective means for sealing the entrance sleeve against the skin surface 
of the limb during treatment. 
It is another object of the invention to provide a sectional chamber having 
adequate sealing means at all points to prevent the leakage of gas from 
the chamber, thus ensuring maintenance of the described pressure. 
It is a further object of the invention to provide entrance sealing means 
which is self-adjusting to have a close fit against the skin surface 
without being tight enough to cut off or significantly impair the 
circulation of blood. 
It is yet another object of the invention to provide a chamber and sealing 
means therefor which are simple in construction and operation, for 
handling by relatively untrained personnel with complete safety of the 
patient. 
It is a further object of the invention to provide simple and efficient 
humidifying means, in series with the gas supply. 
It is a still further object to provide certain improvements in the form, 
construction and arrangement of the several parts whereby the above named 
and other objects may effectively be obtained. 
The invention accordingly comprises the features of construction, 
combination of elements, and arrangement of parts which will be 
exemplified in the construction hereinafter set forth, and the scope of 
the invention will be indicated in the claims.

Referring to the drawings, and particularly FIGS. 1 to 5, the chamber 
comprises two main parts, a lower flat bottomed tray portion 11 and an 
upper hood portion 12. The tray portion has vertical side walls 13 which 
diverge somewhat from the entrance end to the closed end, a vertical 
closed end wall 14, and a vertical entrance end wall 15 in which is 
installed the lower semicircular half 16 of the entrance assembly mounting 
socket. The upper edges of the walls 13 and 14, and of the socket half are 
provided with an upwardly facing groove 17 in which is fitted a resilient 
sealing strip or gasket 18. The socket half includes radially inwardly 
projecting semi-annular ridges 19, 20 which define a generally V-shaped 
groove 21 having a flat bottom 22. 
The hood portion 12 is preferably of transparent rigid plastic material, 
having a semi-cylindrical body portion 25 and an integral closed end wall 
26, the body portion flaring upward and laterally so that its sides 27 
conform to the side walls 13 of the lower portion. At its entrance end the 
body portion 25 merges with the upper semi-circular half 28 of the 
entrance assembly mounting socket, which socket half is complementary to 
the lower socket half 16 and is provided with matching ridges 29, 30 
defining a matching groove 31. 
The lower edges of the wall 26, sides 27 and socket half 28 are so disposed 
that they can rest evenly on the gasket 18, and they are held in sealing 
engagement therewith by clips 32. Such clips may be of metal or plastic, 
of various types, but a suitable all-plastic toggle clip is shown in 
detail in FIG. 5, the clips being disposed three on each side and one on 
the closed end (FIGS. 2 and 4). Each clip comprises a fixed part in the 
form of a square block 35 having its upper edge beveled to form a lip 36 
and being fixed at selected points to the outer surfaces of the sides 27 
and end wall 26, adjacent the lower edges thereof. The blocks 35 may be 
secured by cementing and/or by means of screws 37. The movable part 38 of 
the clip is of a flexible but relatively inextensible plastic material 
having a mounting tab 39 at one end, a toggle link 40 connected to the tab 
39 by a hinge 41 and a latch bar 42, connected to link 40 by the hinge 43. 
The outer wall of the groove 17 is cut away at each clip position and the 
mounting tabs 39 are secured in the recesses 44 thus formed by cementing 
and/or by means of screws 45. Each latch bar 42 is provided with a hook 46 
at its free end, adapted to engage securely over the lip 36, and at its 
hinge end the latch bar is bent at an angle sufficient to place the hinge 
43 inwardly (toward the link 40) from the plane of the latch bar. From 
observation of FIG. 5 it will be understood that the tight latching can be 
effected by engaging the hook 46 over the lip 36 (as indicated in broken 
lines) and pressing inward the hinge end of the latch bar so that the 
hinge 43 snaps past the center line defined by the point of hook-lip 
engagement (46-36) and the first hinge 41. 
The parts referred to as the entrance assembly comprise the circular hub 50 
and the cylindrical sleeve 51 of foldable plastic material. The hub 50 is 
formed with an annular grooved ridge 52 having a compressible gasket 53 
fitted in its groove, and with an annular axially projecting collar 54. 
The sleeve 51 is or may be mounted on a ferrule 55 (FIGS. 6 and 7) adapted 
to have a tight friction fit on the collar 54 (FIG. 3). If the ferrule is 
omitted, the sleeve may be fixed directly on the collar 54, as in FIGS. 8 
and 10. The free end of the sleeve is preferably cut on a slant, having a 
high side 56 and a low side 57, as shown in FIG. 6. A special means for 
constraining the sleeve is shown in FIGS. 6, 7 and 8 as comprising a strap 
60 having double walls 61, 62 of gas-impermeable flexible material 
throughout most of its length, with internal dividers 63 (three being 
shown) arranged to provide a continuous tortuous channel from a gas inlet 
64 to a gas outlet 65. The strap 60 is somewhat arcuate in plan and is 
secured, adjacent one end, to the outer surface of the sleeve in a 
position aligned with the slanting edge of the sleeve (FIGS. 6 and 8). 
Closure of the strap 60, in any adjusted position, is effected by means of 
a "Velcro" fabric area 66 on the inner surface of the strap near its free 
end and another Velcro fabric area 67 on the outer surface of the strap 
adjacent its point of attachment to the sleeve. A substantially gas-tight 
sealing engagement with the skin of the patient may be assured by the 
provision of a layer of latex 70, preferably expanded, on the inner face 
of the strap throughout the area not occupied by the Velcro fabric 66, as 
shown in FIGS. 6, 7 and 9. This achieves complete adhesion of the sleeve 
along the irregular curve of the limb surface. 
While an inflatable strap with latex facing is preferred a plain strap 71, 
with Velcro fabric attaching panels 72, 73 may be substituted, as shown in 
FIG. 10, particularly where the required gas pressure is low. The strap 71 
may be an elastic fabric, plastic web or other suitable material. 
Oxygen (or other gas) is supplied to the system from a source (not shown) 
through an inlet fitting 75 in the wall 13 of the lower portion 11 of the 
chamber. The fitting 75 is connected by a short flexible tube 76 to the 
gas inlet 64 in the strap 60. The gas outlet 65 may open freely to the 
interior of the chamber but is preferably connected by a tube 77 to a 
humidifier or nebulizer 78, which may be of any suitable and convenient 
type. From the humidifier 78 the gas diffuses into the interior of the 
chamber, from which it is vented through the exit fitting 79 in the wall 
13 diagonally opposite the inlet fitting. As a safety precaution, a 
blow-out plug 81 may be provided in a wall 13 of the lower tray. The 
pressure of gas in the chamber is controlled by a pressure-responsive 
valve of any suitable type, not shown, connected to the fitting 79, the 
range of pressures contemplated, for oxygen, being from 5 to 30 mm. Hg at 
a flow rate of 2 to 4 liters/min. 
The operation and manner of use of the chamber are clear from the foregoing 
but may be summarized as including the steps of: fitting the hub 50 and 
sleeve 51 (the unit of FIG. 8) over the patient's limb to a point which 
may be, for instance, just below the knee, as shown in FIG. 2; taking a 
tuck 80 in the longer side 56 of the sleeve and closing the strap 60 
around the sleeve in sealing engagement with the limb; placing the lower 
portion 11 of the chamber under the limb and fitting the hub 50 into the 
groove 21; connecting the hoses 76 and 77; placing the upper portion 12 of 
the chamber on the lower portion with its edge on the gasket 18; closing 
the clips 32 to hold the upper and lower portions in closed, sealed, 
position; starting the flow of oxygen or other gas. 
The flow resistance in tube 77 and humidifier 78, though small, is 
sufficient to cause inflation of the strap 60 so that the sleeve 51 is 
held gently but firmly against the skin of the patient's limb and the 
exposed areas within the chamber are subjected to a gas treatment at the 
desired pressure for any needed period of time. 
In the system described above there is the possibility that the patient's 
calf, if not otherwise supported, may compress the bottom portion of the 
strap against the floor of the chamber, thus restricting the passage of 
gas through the tortuous channel from inlet 64 to outlet 65. If gas supply 
pressure is increased to maintain the required flow to the interior of the 
chamber, undersirable tightening of the strap against the patient's limb 
may result, with possibly serious adverse effects. The alternative 
arrangement shown in FIGS. 11 to 14 is designed to obviate the difficulty 
just mentioned. 
In FIGS. 11 and 12 the lower and upper chamber portions 85, 86 correspond 
to the portions 11 and 12 in FIGS. 1 to 4, and the sleeve 87 is mounted in 
a hub assembly 88 which also correspond to the sleeve 51 and hub 50. 
The inflatable strap 90 is formed of two strips of gas-impervious plastic, 
somewhat arcuate in shape, sealed along their edges, across one end 91 and 
transversely also at 92 near the other end to form a closed compartment, 
which may be longitudinally sub-devided by the seal line 93 from the end 
91 to a point 94 near the seal 92. A gas inlet 95 is provided also near 
the seal 92, but there is no outlet, the compartments separated by the 
seal line 93 constituting dead end inflatable pockets. The strap 90 may 
conveniently be attached to the beveled end of the sleeve 87, 
corresponding to the strap attachments shown in FIGS. 6 and 8, and the 
strap is equipped with Velcro fastening areas 96, on the outside adjacent 
the sleeve, and 97 on the inside at the free end. 
The strap 98 shown in FIG. 14 is the same as strap 90 except that the 
inflatable pockets are closed by a seal line 99 to leave a flat 
non-inflatable area 98' opposite the longer Velcro fastener at the 
attached end. The gas inlet is shown at 100. 
The gas supply enters the lower chamber portion 85 through a T fitting 101, 
having a tube 102 leading to the gas inlet 95 (or 100) and a tube 103 
leading to the humidifier 105, corresponding to humidifier 78 in FIGS. 3 
and 4. The humidifier is of the bubbler type, or its equivalent, and is 
designed to maintain the humidity in the chamber, when in operation, at a 
level of 60 to 90%. This feature is of substantial importance since the 
oxygen atmosphere in the chamber tends to have a drying effect on the 
exposed skin of the patient's limb, with harmful results if not 
counteracted. Additionally, adequate humidity is needed to prevent the 
build-up of static electric charges which could cause explosions and 
fires. The humidifier could, if desired, be provided with a separate gas 
supply line. 
The straps 90 or 98 are applied to the patient's limb in such a position 
that little, if any, of the inflated area is beneath the limb, the 
inflation of the strap taking place for the most part in an arc of 
180.degree., more or less, extending across the top of the limb and down 
one or both sides. A low but adequate sealing pressure can thus be 
maintained without danger of undue tightening. 
The chamber, as shown, is designed to accommodate most conveniently a 
patient's foot and lower leg, but the same chamber could receive as well 
(with or without installing a smaller sleeve) the hand and lower arm. 
Similar parts could, however, be designed on a larger scale to receive the 
lower half of the body, with a sleeve sealing around the patient's waist. 
Even on such an enlarged scale, a chamber constructed as disclosed herein 
would be substantially less expensive than the "total containment" 
chambers discussed in applicant's prior U.S. Pat. No. 3,744,491, but the 
greatest utility of the present chamber probably lies in the limb 
treatment field. 
It may thus be seen that the objects of the invention set forth, as well as 
those made apparent from the preceding description, are efficiently 
attained and, since certain changes may be made in the above construction 
without departing from the spirit and scope of the invention, it is 
intended that all matter contained in the above description or shown in 
the accompanying drawings shall be interpreted as illustrative and not in 
a limiting sense.