WO2011030088A1

WO2011030088A1 - Breathing apparatus

Info

Publication number: WO2011030088A1
Application number: PCT/GB2010/001642
Authority: WO
Inventors: Kwame Menah-Bonsu
Original assignee: Smiths Medical International Limited
Priority date: 2009-09-10
Filing date: 2010-08-31
Publication date: 2011-03-17
Also published as: GB0915816D0

Abstract

Patient breathing apparatus includes a hood enclosure (1) having a rigid hat portion (10) that rests on the top of the user's head and supports around its edge (12) a flexible curtain portion (13) that hangs down and drapes below a tube (18) attached at its lower end that sits around the neck on the user's shoulders. The curtain portion (13) has an inner and outer layer (14) and (13) separated by a cavity (16). Gas is supplied to the interior of the enclosure from a recirculating heliox gas supply carried as a backpack (3). Gas from the outlet of the supply (3) is fed through both layers (13) and (14) to the inside of the enclosure towards its upper end. Openings in the tube (18) allow stale gas towards the lower end of the enclosure (1) to flow into the cavity (16) to an outlet tube (22) and back to the inlet of the gas supply (3).

Description

BREATHING APPARATUS

This invention relates to breathing apparatus of the kind for enclosing the head.

The invention is more particularly concerned with apparatus for providing breathing gas to patients having respiratory problems.

It is known that patients with respiratory problems can benefit from a gas mixture of oxygen and helium, the latter gas reducing the patient's work of breathing. Helium, however, is relatively scarce and expensive so conventional ventilation techniques where exhaled gas is exhausted to atmosphere are very wasteful and costly. The high cost is such that treatment with helium can only usually be provided to patients with severe respiratory problems.

Various ways are used to supply breathing gas to a patient, such as face masks, nasal masks or mouthpieces. These can be uncomfortable in prolonged use, often causing damage to the skin around the mouth or nose; they usually prevent the patient talking and often make it difficult to wear spectacles. Alternatively, a hood may be used to enclose the entire head. One problem with hoods lies in the difficulty of making an effective seal with the patient. This may not be a problem where low cost gases are used and leakage is not of concern but when an expensive gas, such as a helium mixture is used, it is necessary to minimise leakage so that the maximum proportion of gas can be recovered and reduce the entrainment of ambient air, which would otherwise dilute the breathing gas.

It is an object of the present invention to provide alternative breathing apparatus.

According to one aspect of the present invention there is provided breathing apparatus of the above-specified kind, characterised in that the apparatus includes a substantially rigid hat portion and a more flexible curtain portion depending from the hat portion and attached at its lower end with a body-engaging portion, such that the hat portion is adapted to rest on the top of the wearer's head with the curtain portion spaced from the head around its circumference and with the body-engaging portion adapted to engage the wearer's body below the head to restrict flow of gas between the body and the body- engaging portion.

The curtain is preferably formed around a part at least of its circumference with an inner layer and an outer layer separated by a cavity. The apparatus preferably includes a first gas channel opening into the enclosure through the inner layer and a second gas channel opening into the cavity between the two layers. The apparatus preferably includes a tube extending around the lower end of the inner and outer layers by which gas flows between the cavity and the interior of the enclosure. The apparatus is preferably arranged such that the hat portion can be lifted above the head by gas supplied to the apparatus. The apparatus may include a gas supply including a source of helium gas and the apparatus may include a recirculating gas supply. The curtain portion may drape below the body-engaging portion when the hat portion rests on the head. The apparatus may have a gas inlet towards an upper end of the enclosure and a gas outlet towards a lower end of the enclosure. The apparatus may include a gas supply in a backpack supported on the user's back. The body-engaging portion may be adapted to rest on the user's shoulders or be adapted to extend around the chest of the user.

Breathing apparatus including a hood arrangement will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows the apparatus schematically;

Figure 2 is an enlarged sectional side elevation through the wall of the hood; Figure 3 is an enlarged sectional view of the lower end of the hood;

Figure 4 shows the apparatus schematically in an elevated state;

Figure 5 shows a modification of the apparatus; and Figure 6 is a sectional side elevation through the wall of the hood showing an alternative to the tube arrangement in Figure 2.

With reference to Figure 1, the apparatus includes an enclosure in the form of a hood arrangement 1 enclosing the patient's head and connected by tubing 2 to a gas supply 3, which, as shown, is carried by the patient in the form of a backpack supported on his shoulders.

At its upper end, the hood 1 includes a substantially rigid hat portion 10 of a shallow conical shape and generally circular section arranged such that the convex side 1 1 is uppermost and the lower side rests on the top of the patient's head. The diameter of the hat portion 10 exceeds the lateral dimensions of the patient's head so that its rim 12 projects well beyond the head. The stiffness of the hat portion 10 is such that it retains its conical shape and can support the wall or curtain portion 13 of the hood 1 hanging down around the rim 12. The height of the wall 13 is such that it drapes and folds towards its lower end.

Figure 2 shows most clearly the wall 13 of the hood 1. The wall 13 is formed by an inner and outer layer 14 and 15 separated from one another by a gas cavity 16. Some form of spacers (such as internal ribs or projections (not shown) on the layers 14 and 15) may be necessary to maintain the spacing between the layers and ensure free passage of gas within the cavity 16. Both layers 14 and 15 are made of a gas-impermeable, flexible, transparent plastics material. As shown in Figure 3, the layers 14 and 15 join at their lower end with an annular, resilient tube 18, such as of a rubber or rubber-like material. The tube 18 has a series of orifices 1 around it that open into the lower end of the cavity 16 between the layers 14 and 15. These internal orifices 19 communicate via gas passages within the tube 18 with a corresponding set of orifices 20 arranged along the tube on the inside of the hood 1 so that gas can flow freely from the inside of the hood 1 at its lower end into the cavity 16. It will be appreciated that there are other arrangements by which gas could flow into the cavity from the lower end of the hood. The weight and diameter of the tube 18 are such that it sits on the user's shoulders around his neck forming a body-engaging portion that restricts flow of gas between the user's body and the tube. The wall 13 drapes below the level of the tube 18 when the hood sits on the user's head. The elastic nature of the tube 18 makes it easy for the user to pull the lower end of the hood 1 over his head, both for putting the hood on and for taking it off.

Gas connection to the hood is made by the tubing 2, which takes the form of a length of double tubing joined together along the major part of its length but separated into two separate gas channels in the form of tubes 21 and 22 at the end connected with the hood 1. One tube, the inlet tube 21, extends in a sealing fashion through the outer layer 15 and opens via an opening 23 in the inner layer 14 into the interior of the hood 1. The other tube, the outlet tube 22, opens via an opening 24 in the outer layer 15 into the cavity 16. Both these connections are made towards the upper end of the hood 1. Figure 6 shows an alternative to the tubing arrangement of Figure 2 where corresponding parts have been given the same reference numeral with the addition of a prime. In this arrangement, the inlet tube 21 ' extends coaxially within the outlet tube 22' instead of side-by-side with it. This alternative arrangement avoids the need to form a seal between the outer layer 13' and the inlet tube 2Γ.

The gas supply 3 preferably, although not essentially, takes the form of a heliox rebreather supply arranged to provide a helium and oxygen mixture within the hood 1 by recirculating gas from the hood. More particularly, the supply 3 includes canisters of helium and oxygen gas, a filter and a scrubber for removing unwanted substances and carbon dioxide, and some form of gas flow means, such as a pump. The supply 3 creates a slight negative pressure in tube 22 so that gas in the cavity 16 is sucked along the tubing 2, is filtered and scrubbed, with fresh helium and oxygen being added as necessary before it is returned via tube 21 to the interior of the hood 1. As the fresh gas enters the upper end of the interior of the hood 1 , it displaces the older gas downwards towards the orifices 20 in the tube 18 where it is drawn into the tube and out into the cavity 16 via the orifices 19 for removal. The gas supply 3 need not be in a backpack but could be floor-mounted, or mounted on a stand or trolley.

Figure 5 shows a modification of the apparatus with a smaller hat portion 10' ' and a wall 13" that is joined at its lower end with a shirt 40 around the chest region to give an improved seal. This apparatus shows a trolley-mounted gas supply 3". The available volume of gas in the hood 1 can be varied readily by increasing the pressure of inlet gas supplied to the hood. An increase in pressure causes a slight ballooning of the hood 1 and may be sufficient to cause the hat portion 10 to lift off the user's head in the manner shown in Figure 4. The flexible nature of the wall 13 and its length ensure that the hat portion 10 can lift while the tube 18 remains sitting on the user's shoulders, thereby limiting the escape of gas. The ring-shape tube 18 could be attached to the backpack shoulder straps 3' to ensure that the tube remains on the shoulders. The varying effective volume of the hood helps accommodate pressure changes within the hood, thereby minimizing the pressure variations within the hood and reducing the risk that pressure rise within the hood would increase leakage. A second tube similar to the lower tube 18 could be incorporated into the hood at a higher position, such as around the rim 12 of the hat 10, to remove stale air in the upper part of the hood. This may be necessary if the carbon dioxide is pushed upwards in the hood by the helium. The added weight of such an arrangement would reduce lifting of the hat.

This rebreathing arrangement enables the heat and moisture in the exhaled breath to be conserved. It also reduces wastage of gas, which is especially important in the case of helium, which is relatively expensive. The gas supply arrangement within the hood enables efficient removal of stale gases to ensure an ideal patient environment. The hood

arrangement avoids the discomfort and problems often associated with masks.

The tube around the lower end of the hood could be of an inflatable construction such that any fall in pressure within the hood would cause the tube to collapse. This would have the effect of reducing the effectiveness of the gas seal with the user's shoulders, thereby allowing ambient air to flow into the hood more freely. This would act as a safety feature in the event of a fall in the gas supply pressure.

It will be appreciated that the hood arrangement could include conventional safety valves to vent gas from the hood in the event that pressure rises above an upper threshold level and to allow ambient air to flow into the hood in the event of pressure within the hood falling below a lower threshold level.

Claims

1. Breathing apparatus including an enclosure (1 ) for enclosing the head, characterised in that the apparatus includes a substantially rigid hat portion (10, 10") and a more flexible curtain portion (13, 13', 13") depending from the hat portion and attached at its lower end with a body-engaging portion (18, 40), such that the hat portion (10, 10') is adapted to rest on the top of the wearer's head with the curtain portion (13, 13', 13") spaced from the head around its circumference and with the body-engaging portion (18, 40) adapted to engage the wearer's body below the head to restrict flow of gas between the body and the body-engaging portion.

2. Breathing apparatus according to Claim 1 , characterised in that the curtain portion (13, 13', 13") is formed around a part at least of its circumference with an inner layer (14, 14') and an outer layer (13, 13') separated by a cavity (16, 16').

3. Breathing apparatus according to Claim 2, characterised in that the apparatus

includes a first gas channel (21, 21 ') opening into the enclosure through the inner layer (14, 14') and a second gas channel (22, 22') opening into the cavity (16, 16') between the two layers (13, 13' and 14, 14').

4. Breathing apparatus according to any one of the preceding claims, characterised in that the apparatus includes a tube (18) extending around the lower end of the inner and outer layers (13 and 14) by which gas flows between the cavity (16) and the interior of the enclosure.

5. Breathing apparatus according to any one of the preceding claims, characterised in that the apparatus is arranged such that the hat portion (10) can be lifted above the head by gas supplied to the apparatus.

6. Breathing apparatus according to any one of the preceding claims, characterised in that the apparatus includes a gas supply (3, 3") including a source of helium gas.

7. Breathing apparatus according to any one of the preceding claims, characterised in that the apparatus includes a recirculating gas supply (3, 3").

8. Breathing apparatus according to any one of the preceding claims, characterised in that the curtain portion (13) drapes below the body-engaging portion (18) when the hat portion (10) rests on the head.

9. Breathing apparatus according to any one of the preceding claims, characterised in that the apparatus has a gas inlet (23) towards an upper end of the enclosure (1) and a gas outlet (20) towards a lower end of the enclosure.

10. Breathing apparatus according to any one of the preceding claims, characterised in that the apparatus includes a gas supply in a backpack (3) supported on the user's back.

11. Breathing apparatus according to any one of the preceding claims, characterised in that the body-engaging portion (18) is adapted to rest of the user's shoulders.

12. Breathing apparatus according to any one of Claims 1 to 10, characterised in that the body-engaging portion is adapted to extend around the chest of the user.