Surgery – Respiratory method or device – Means for removing substance from respiratory gas
Reexamination Certificate
2000-09-21
2002-10-08
Ruhl, Dennis (Department: 3761)
Surgery
Respiratory method or device
Means for removing substance from respiratory gas
C128S206190, C128S205290, C128S206220, C128S205120
Reexamination Certificate
active
06460539
ABSTRACT:
The present invention pertains to a respirator that has an integrally-disposed filter element in its mask body and that has an impactor element associated with its exhalation valve. The impactor element allows the respirator to remove particulate contaminants from the exhale flow stream.
BACKGROUND
Filtering face masks are typically worn over a person's breathing passages for two common purposes: (1) to prevent contaminants from entering the wearer's respiratory system; and (2) to protect other persons or items from being exposed to pathogens and other contaminants expelled by the wearer. In the first situation, the face mask is worn in an environment where the air contains substances that are harmful to the wearer—for example, in an auto body shop. In the second situation, the face mask is worn in an environment where there is a high risk of infection or contamination to another person or item—for example, in an operating room or in a clean room.
Face masks that have been certified to meet certain standards established by the National Institute for Occupational Safety and Heath (generally known as NIOSH) are commonly referred to as “respirators”; whereas masks that have been designed primarily with the second scenario in mind—namely, to protect other persons and items—are generally referred to as “face masks” or simply “masks”.
A surgical mask is a good example of a face mask that frequently does not qualify as a respirator. Surgical masks are typically loose-fitting face masks that are designed primarily to protect others from contaminants that are exhaled by a doctor or other medical person. Substances that are expelled from a wearer's mouth are commonly in the form of an aerosol, which is a suspension of fine solids and/or liquid particles in gas. Surgical masks are capable of removing these particles despite being loosely fitted to the wearer's face. U.S. Pat. No. 3,613,678 to Mayhew discloses an example of a loose fitting surgical mask.
Loose-fitting masks, typically do not possess an exhalation valve to purge exhaled air from the mask interior. The loose-fitting aspect allows exhaled air to easily escape from the mask's sides—known as blow by—so that the wearer does not feel discomfort, particularly when breathing heavily. Because these masks are loose fitting, however, they may not fully protect the wearer from inhaling contaminants or from being exposed to fluid splashes. In view of the various contaminants that are present in hospitals and the many pathogens that exist in body fluids, the loose-fitting feature is a notable drawback for loose-fitting surgical masks.
Some tightly-fitting face masks have a porous mask body that is shaped and adapted to filter inhaled air. The filter material is commonly integrally-disposed in the mask body and is made from electrically-charged melt-blown microfibers. These masks are commonly referred to as respirators and often possess an exhalation valve that opens under increased internal air pressure when the wearer exhales—see, for example, U.S. Pat. No. 4,827,924 to Japuntich. Examples of other respirators that possess exhalation valves are shown in U.S. Pat. Nos. 5,509,436 and 5,325,892 to Japuntich et. al., U.S. Pat. No. 4,537,189 to Vicenzi, U.S. Pat. No. 4,934,362 to Braun, and U.S. Pat. No. 5,505,197 to Scholey.
Known tightly-fitting respirators that possess an exhalation valve can prevent the wearer from directly inhaling harmful particles, but the masks have limitations when it comes to protecting other persons or things from being exposed to contaminants expelled by the wearer. When a wearer exhales, the exhalation valve is open to the ambient air, and this temporary opening provides a conduit from the wearer's mouth and nose to the mask exterior. The temporary opening can allow aerosol particles generated by the wearer to pass from the mask interior to the outside. Aerosol particles, such as saliva, mucous, blood, and sweat, are typically generated when the wearer sneezes, coughs, laughs, or speaks. Although sneezing and coughing tend to be avoided in environments such as an operating room—speech, a vital communication tool, is necessary for the efficient and proper functioning of the surgical team. Saliva particles are laden with bacteria. Unfortunately, aerosol particles that are generated by speaking can possibly lead to infection of a patient or contamination of a precision part.
The particles are made when saliva coated surfaces separate and bubble in response to the air pressure behind them, which commonly happens when the tongue leaves the roof of the mouth when pronouncing of the “t” consonant or when the lips separate while pronouncing the “p” consonant. Particles may also be produced by the bursting of saliva bubbles and strings near the teeth during sneezing or during pronunciation of such sounds as “cha” or “sss”. These particles are generally formed under great pressures and can have projectile velocities greater than the air speed of normal human breath.
Mouth-produced particles have a great range in size, the smallest of which may average about 3 to 4 micrometers in diameter. The projectile particles, however, which leave the mouth and travel to a nearby third party, are generally larger, probably 15 micrometers or greater.
The settling rates of these airborne particles also affect their deposition on a nearby third party, such as a patient. Because particles that are less than 5 micrometers tend to settle at a rate of less than about 0.001 m/s, they are the equivalent of a floating suspension in the air.
Respirators that employ exhalation valves currently are not recommended for use in the medical field because the open conduit that the exhalation valve temporarily provides is viewed as hazardous. See, e.g.,
Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health Care Facilities
, MORBIDITY AND MORTALITY WEEKLY REPORT, U.S. Dept. of Health & Human Services, v. 43, n. RR-13, pp. 34 & 98 (Oct. 28, 1994). The Association of Operating Room Nurses has recommended that masks be 95 percent efficient in retaining expelled viable particles.
Proposed Recommended Practice for OR Wearing Apparel
, AORN JOURNAL, v. 33, n. 1, pp. 100-104, 1 01 (January 1981); see also D. Vesley et al.,
Clinical Implications of Surgical Mask Retention Efficiencies for Viable and Total Particles
, INFECTIONS IN SURGERY, pp. 531-536, 533 (July 1983). This recommendation was published in the early 1980s, and since that time, the standards for retaining particles have increased. Some organisms, such as those that cause tuberculosis, are so highly toxic that any decrease in the number of contaminants that are expelled is highly desired.
Respirators have been produced, which are capable of protecting both the wearer and nearby persons or objects from contamination. See, for example, U.S. Pat. No. 5,307,706 to Kronzer, U.S. Pat. No. 4,807,619 to Dyrud, and U.S. Pat. No. 4,536,440 to Berg. Commercially-available products include the 1860™ and 8210™ brand masks sold by 3M. Although these respirators are relatively tightly-fitting to prevent gases and liquid contaminants from entering and exiting the interior of the mask at its perimeter, the respirators commonly lack an exhalation valve that allows exhaled air to be quickly purged from the mask interior. Thus, known respirators can remove contaminants from the inhale and exhale flow streams and can provide splash-fluid protection, but they are generally unable to maximize wearer comfort. And when an exhalation valve is placed on a respirator to provide improved comfort, the mask encounters the drawback of allowing contaminants from the mask interior to enter the surrounding environment.
SUMMARY OF THE INVENTION
In view of the above, a respirator is needed, which can (i) prevent contaminants from passing from the wearer to the ambient air; (ii) prevent contaminants from passing from the ambient air to the wearer; (iii) prevent splash-fluids from entering the mask interior; and (iv) allow warm, humid, high CO
2
-content air to be quickly p
Japuntich Daniel A.
McCullough Nicole V.
3M Innovative Properties Company
Hanson Karl G.
Mendoza Michael G.
Ruhl Dennis
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