Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
2000-05-18
2003-03-04
Buiz, Michael Powell (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S846000, C137S908000, C128S203110, C128S205240
Reexamination Certificate
active
06527011
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to valve devices and, more particularly, to a valve adapted for use in breathing apparatus such as respiration assistance apparatus or anesthesia administration equipment.
FIELD OF THE INVENTION
Non-rebreathing valves, or NRVs, are commonly used in an assortment of anesthesia administration equipment and respiration assistance apparatus including, inter alia, ventilators, resuscitators and sleep apnea treatment devices. The NRV is typically situated in the breathing apparatus gas flow circuit between a source of respiratory gas (e.g., ambient or pressurized air, pressurized oxygen and/or anesthetic gas) and a patient interface means such as a nasal or oral
asal mask, an endotracheal (intubation) tube or nasal prongs. The function of the NRV is to act essentially as a two-way check valve. More particularly, when it is desired to deliver respiratory gas to the patient, the NRV permits such flow. When the patient exhales, however, the NRV vents the patient's expiratory gases while temporarily stopping the flow of respiratory gas responsive to back pressure created by the patient's expiratory efforts. In this manner, the NRV effectively prevents mixing of the patient's expiratory gases with the delivered respiratory gas whereby the patient does not “rebreathe” his expiratory gases.
Although their functions are essentially the same, NRVs assume a broad variety of structural configurations and levels of functional sophistication. Because of its relative simplicity in construction and low resistance to administered respiratory gas flow, a commercially popular NRV is the type commonly known as a “duck-bill” valve. A duck-bill valve derives its name from the peculiar shape of its valve element. That is to say, a duck-bill valve element typically comprises a thin, resilient diaphragm that is secured at its periphery to a valve housing and from which projects, in the direction of administered respiratory gas flow, a hollow, wedge-like extension that terminates in a small slot and generally resembles the shape of a duck bill.
The duck-bill valve element is constructed such that its slot is normally closed. However, in response to a flow of respiratory gas, which may arise from negative pressure associated with a patient's inspiration and/or delivery of respiratory gas under positive pressure, the slot opens to permit the respiratory gas to flow to the patient's airway. When the patient thereafter exhales, the back pressure exerted by the patient's expiratory gases closes the slot and displaces the valve element from the valve housing seat whereupon the expiratory gases are diverted to and discharged from suitable exhaust port means provided in the valve housing.
Examples of presently known duck-bill valves are provided in U.S. Pat. Nos. 3,363,833, 3,556,122, 4,774,941, 5,109,840 and 5,279,289. Ironically, the primary feature which renders duck-bill valves particularly desirable for use in breathing apparatus, namely, a thin, flexible valve element that offers minimal resistance to respiratory gas flow, is a source of potentially serious malfunctions in such valves. Specifically, should the exhalation efforts of the patient be extremely forceful, such as, for example, when the patient coughs, the sudden imposition of high-level impulses of back pressure on the valve element may cause the duck-bill portion of the valve element diaphragm to invert. Under these circumstances, the duck-bill would point in the direction of the administered respiratory gas flow and the slot thereof would be caused to close under the influence of the applied respiratory gas. As a consequence, the supply of respiratory gas to the patient would become effectively occluded whereby the patient may experience harmful or even fatal respiratory distress, particularly if the patient is unconscious or is not being closely monitored by medical personnel.
Perhaps recognizing, although not specifically identifying, the need to prevent inversion of the duck-bill portions of their valve elements, the valves disclosed in U.S. Pat. Nos. 3,363,833, 3,556,122 and 5,109,840 disclose valve housings which incorporate various and sometimes elaborate structures upstream of the duck-bill which permit respiratory gas to flow through the duck-bill but, by virtue of their location, would appear to prevent the duck-bill from inverting. U.S. Pat. No. 5,279,289, on the other hand, expressly provides for a retainer ring upstream of the duck-bill valve element to “support” the valve element.
The retainer ring disclosed in U.S. Pat. No. 5,279,289 is designed to stay in a fixed position. Whereas, the present invention provides a flexible retainer ring having a center portion that can deflect in response to the duck-bill valve being moved by the flow of the expiratory gas. This movement of the flexible retainer ring of the present invention allows the duck-bill valve to unseat further from the valve housing seat thereby increasing the flow of the expiratory gas through the exhaust port of the valve housing. This increase in flow of expiratory gas to the exhaust port of the valve housing allows the valve housing to be made smaller than a conventional valve housing while maintaining the necessary flow rate for expiratory gas through the exhaust port of the valve housing. This smaller housing can be extremely useful in the care of infants and neonatal patients.
In addition, the flexible retainer ring of the present invention is able to provide better protection against inversion and distortion of the duck-bill valve. Since the flexible retainer ring is able to deflect in response to movement of the duck-bill valve, the flexible retainer ring is able to act as a shock absorber. This shock absorbing capability helps to prevent inversion and deformation of the duck-bill valve.
The flexible retainer ring of the present invention can also be employed in any industry needing to control the flow of two fluids in opposing directions.
An advantage exists, therefore, for a flexible retainer ring which is simple in design, economical to manufacture, and increases the flow of expiratory gas while preventing the inversion and distortion of the duck-bill valve element.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an improved duck-bill non-rebreathing valve (NRV) adapted for use in breathing apparatus such as anesthesia administration equipment and respiratory assistance apparatus. The duck-bill NRV may be situated in the breathing circuit between a source of respiratory gas (e.g., ambient or pressurized air, pressurized oxygen and/or anesthesia gas) and a patient interface means such as a nasal or oral
asal mask, an endotracheal tube or nasal prongs.
The duck-bill NRV of the present invention comprises a thin, resilient valve element in the form of a diaphragm adapted to be secured at its periphery to a valve housing and from which projects, in the direction of administered respiratory gas flow, a hollow, wedge-shaped formation that terminates in a small slot and generally resembles the shape of a duck bill. The improvement in the NRV is the inclusion of a flexible retainer ring which has a center portion that that can deflect in response to the duck-bill valve being moved by the flow of the expiratory gas. This movement of the flexible retainer ring of the present invention allows the duck-bill valve to unseat further from the valve housing seat thereby increasing the flow of the expiratory gas through the exhaust port of the valve housing. This increase in flow of expiratory gas to the exhaust port of the valve housing allows the valve housing to be made smaller than a conventional valve housing while maintaining the necessary flow rate for expiratory gas through the exhaust port of the valve housing. This smaller housing can be extremely useful in the care of infants and neonatal patients.
In addition, the flexible retainer ring of the present invention is able to provide better protection against inversion and distortion
Buiz Michael Powell
Holland & Knight LLP
Krishnamurthy Ramesh
LandOfFree
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