Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using direct contact with electrical or electromagnetic...
Reexamination Certificate
1993-11-08
2002-12-24
Knode, Marian C. (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using direct contact with electrical or electromagnetic...
C422S004000, C422S005000, C422S117000, C422S121000, C422S186300, C250S43200R, C250S436000, C250S437000, C250S438000, C096S223000, C096S224000
Reexamination Certificate
active
06497840
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of germicidal systems employing bacteria-destroying ultraviolet lights. In particular, the present invention relates to a system for producing an air flow through a baffled ultraviolet sterilization chamber, wherein the ultraviolet light intensity, the air residency time, and the air exchange rate for the air volume in a given space, are such that a percentage of tuberculosis bacteria are destroyed that effectively prevents transmission of such disease by airborne sputum.
BACKGROUND OF THE INVENTION
Tuberculosis is the most common cause of death from infectious disease in the world today. It infects millions of people each year and causes hundreds of thousands of fatalities. The disease is particularly prevalent in less-industrialized countries where high population densities, poor sanitary conditions and a high percentage of individuals in poor health contribute to the spread of infectious diseases.
After a long period of declining rates of tuberculosis infection in the United Sates, it is believed that the infection rate is now increasing. The increasing rate is apparently due to a combination of factors. One factor is undoubtedly increased immigration from parts of the world with high rates of infection. For example, in the United States the case rate of tuberculosis per 100,000 population was 9.3 in 1985, resulting in over 22,000 cases and over 1,200 deaths. In Southeast Asia, both the case rate and the death rate are believed to be many times that, and immigrants from that part of the world now constitute 3 to 5% of new cases in the United States.
Another factor related to increased rates of tuberculosis infection appears to be the use of living quarters with high population densities and less-than-ideal sanitary conditions for persons in ill health who are susceptible to the disease. Such conditions are commonly found in shelters for the homeless, prisons and some nursing homes. Another important factor in the increased rate of infection is infections among patients with Acquired Immune Deficiency Syndrome (AIDS) and intravenous drug users.
Another reason for the recent increased incidence of tuberculosis is probably the failure of many medical professionals to diagnose and treat the disease early and properly. The relative rareness of the disease in the United States since the early epidemics resulted in an entire generation of health care workers without much experience in the disease. Further, diagnosing the disease is not always easy, for the symptoms are similar to the symptoms of many other disorders. Therefore, the disease is often misdiagnosed and mistreated, and the degree of infectiousness of the disease is underappreciated.
Even after it is recognized that a set of symptoms may indicate tuberculosis, the tests for the disease are somewhat imprecise and tend to require judgment by an experienced professional. For example, one diagnostic tool is chest x-rays which typically show apical-posterior segment cavitary changes in tuberculosis infected patients. However, in elderly individuals—who comprise a relatively large proportion of tuberculosis patients—lobar or patchy lower-zone shadows may simulate bacterial or aspiration pneumonia. Also, x-rays in the elderly may mislead the physician by showing a solitary pulmonary nodule or a pleural effusion. Another important tuberculosis test is the tuberculosis skin test, but a major disadvantage to the tuberculosis skin test is that it generates a high number of both false-positive and false-negative results. The most precise test is microscopic examination of a sputum sample, but this test may require the use of at least three separate samples of sufficient volume, which may require gastric aspiration or bronchoscopy in patients with low sputum production.
The normal body reaction to infection by tuberculosis bacteria is to build a fibrous wall around each bacterium. Initially, a person may be unaware of any infection, but over a period of months or even years the infection produces inflammation and eventually destruction of tissue. The manifestations as the disease progresses generally include cough, fever, night sweats, hemoptysis, chest pain, weight loss and malaise. The usual treatment for tuberculosis is administration of drugs over a period of many months such as isoniazid, rifampin and pyrazinamide and ethambutol. Persons recently infected but with no active disease are usually given isoniazid preventive therapy, particularly if they have other risks such as malnutrition, gastrectomy, diabetes mellitus, pneumoconiosis, malignancy or if for some reason they have immunosuppression such as from corticosteroid therapy, renal impairment or HIV infection. In short, tuberculosis in a normal healthy patient is typically a disease that is curable by drugs, although the drug therapy is quite prolonged.
A serious concern—and yet another reason for the recent increase in tuberculosis—is the development of drug-resistant tuberculosis. It is estimated that at least 5% of new cases are resistant to the usual drug therapy, and that the percentage in some areas of the United States is as high as 20%. While non-drug-resistant tuberculosis is typically 99% curable in patients with normal immune responses, drug-resistant tuberculosis is only about 50-60% curable. A related concern is drug therapy on non-drug-resistant tuberculosis for patients who are intolerant of the drugs. In those cases, drug therapy is complicated because the drug is effective against the infection but has serious adverse effects on the patient such as hepatitis or serious rashes.
Another concern is raised by the increasing incidence of non-tuberculosis mycobacterial pulmonary infections. Many such infections produce symptoms similar to those of tuberculosis infections, but may be more difficult to identify and treat. Moreover, they may be transmitted through the same means as tuberculosis and tend to infect the same types of susceptible individuals.
The transmission of the tuberculosis bacteria is accomplished almost exclusively by infected individuals expectorating microdroplets of bacteria-containing sputum by coughing or sneezing. These microdroplets are suspended in the air and are inhaled by other individuals in the vicinity. The bacteria typically lodges in the lower lung where it proliferates, and may be disseminated to other organs as well. The microdroplets of sputum which contain the bacteria may be very small—on the order of 0.01 microns. In fact, it appears that the smallest droplets are the most effective in communicating the disease since the smallest droplets stay airborne indefinitely and are easily inhaled to the lower lung where they are not readily removed. Studies have shown that aerosol droplets on the order of 1-5 microns are highly effective vehicles for transmitting the disease.
One controversial approach to combatting the disease has been the use of vaccines. However, the efficacy of tuberculosis vaccines is debatable. Even the trials which seemed to show some efficacy have shown less efficacy among adults than among infants and children. An additional objection to widespread vaccinations is that by inducing tuberculin reactivity in the population they would confound the detection and measurement of infections through the use of skin tests, since skin tests in vaccinated individuals would presumably result in a false-positives. This would severely curtail the practice of preventive drug therapy among infected patients who have not yet developed outward symptoms.
The airborne aspect of the disease has led toward systems for preventing the transmission of the disease which focus on filtration and sterilizing devices. One approach is the use of masks. Simple surgical masks are thought to be insufficient in view of the very small size of the sputum microdroplets which are effective in communicating the bacteria. Instead, disposable particulate respirators are recommended. The use of masks is fraught with practical difficulties; they are physically uncomfortable, they impai
Iseman Michael Dee
Morgan Dale R.
Palestro Richard P.
Rosier Donald P.
Gibson Dunn & Crutcher, LLP
Knode Marian C.
Ridley Basia
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