Surgery – Respiratory method or device – Including body or head supported means covering user's scalp
Patent
1998-02-26
2000-08-15
Weiss, John G.
Surgery
Respiratory method or device
Including body or head supported means covering user's scalp
12820113, 12820517, 12820525, 12820527, A62B 702
Patent
active
061020346
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to breathing equipment of the kind which includes a breathing hood which is intended to cover the head of the wearer, an inner mask which covers at least the wearer's mouth and nose, a breathing gas supply conduit, means for enabling gas to flow from the hood to the mask, and check valve means for releasing gas from the mask to the surroundings when the overpressure in the mask has reached a given value.
Breathing equipment of this kind may include, for instance, a so-called escape or evacuation hood used temporarily when evacuating a building or a location filled with smoke or some other gas, possibly a toxic gas.
Breathing equipment of this kind which includes a breathing hood and an inner mask is described in U.S. Pat. No. 4,926,855. The breathing gas is passed directly to the mask in the case of this equipment. This means that unused breathing gas is able to flow into the surrounding hood together with exhalation gas and from there out to the surroundings via intentional leakage connections of the mask with the wearer's neck. When the breathing gas is delivered from a container of limited volume, this means that the gas consumption time can be seriously shortened in otherwise comparable conditions.
The U.S. patent specification proposes the use of a further valve means for overcoming this problem. This further valve means is operated, e.g., electrically and further complicates the equipment besides representing a further potential fault source.
WO 94/19055 describes another embodiment of breathing equipment which includes an outer hood and an inner mask. In the case of this equipment, breathing gas is delivered to the hood and as the wearer inhales is drawn into the mask via a check valve fitted in the wall between the mask and the hood. The exhalation gas exits to the surroundings via another check valve.
Although this equipment eliminates the risk of discharging unused breathing gas directly to the surroundings, problems can arise when the volume of breathing gas inhaled by the wearer exceeds the volume of breathing gas delivered to the hood. When the hood is made of a flexible material, this can result in the hood collapsing around the wearer's head at the same time as the amount of breathing gas delivered is insufficient to meet the wearer's need.
Furthermore, this equipment does not enable part of the exhaled gas to be breathed-in together with fresh gas, as does the equipment described in the aforesaid U.S. Pat. Specification No. 4,926,855. This restricts maximum ventilation.
The main object of the present invention is to provide breathing equipment of the aforediscussed general kind with which the aforesaid problems are eliminated, among other things, and which enables optimal use of the delivered breathing gas.
To this end, breathing equipment of the kind defined in the first paragraph is characterized in accordance with the invention by a combination whereby breathing gas is delivered to the hood and whereby means are provided for enabling gas to pass between the hood and the mask in both directions, wherein said means requires a lower overpressure in the mask for gas to pass from the mask to the hood than the over-pressure required by said check valve to allow gas to exit to the surroundings.
This equipment enables a certain volume of exhaled gas to be breathed and eliminates the risk of unused or fresh breathing gas passing directly to the surroundings.
In one particular advantageous embodiment of the invention, said means includes a gas passageway of given volume.
Among other things, this means that in each case the breathing gas last exhaled will not mix with the gas present in the hood, and that all gas present in the hood must flow through said passage in order to reach the mask. In the case of large ventilation equal to or greater than the volumetric flow of delivered breathing gas, all fresh gas will be delivered to the lungs of the wearer.
The aforesaid passageway is suitably formed by a conduit, preferably a flexible hose, having a volume in the magnitud
REFERENCES:
patent: 4440163 (1984-04-01), Spergel
patent: 4926855 (1990-05-01), Hellquist et al.
patent: 4998529 (1991-03-01), Werjefelt
patent: 5526804 (1996-06-01), Ottestad
Interspiro AB
Srivastava V.
Weiss John G.
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