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Biomedical subjects

E A Nardell

Publications and source records attributed to E A Nardell.

9 recordsLinked to original sources
PubMed1991

Airborne infection. Theoretical limits of protection achievable by building ventilation.

Of 67 office workers 27 (40%) had documented tuberculin skin test conversions after an estimated 4-wk exposure to a coworker with cavitary tuberculosis. Worker complaints for more than 2 yr before the tuberculosis exposure prompted investigations of air quality in the building before and after the tuberculosis exposure. Carbon dioxide concentrations in many parts of the building were found to be above recommended levels, indicating suboptimal ventilation with outdoor air. We applied a mathematical model of airborne transmission to the data to assess the role of building ventilation and other transmission factors. We estimated that ventilation with outside air averaged about 15 feet 3/min (cfm) per occupant, the low end of acceptable ventilation, corresponding to CO2 levels of about 1,000 ppm. The model predicted that at 25 cfm per person 18 workers would have been infected (a 33% reduction) and at 35 cfm, a level considered optimal for comfort, that 13 workers would have been infected (an additional 19% reduction). Further increases in outdoor air ventilation would be impractical and would have resulted in progressively smaller increments in protection. According to the model, the index case added approximately 13 infectious doses (quanta) per hour (qph) to the office air during the exposure period, 10 times the average infectiousness reported in a large series of tuberculosis cases. Further modeling predicted that as infectiousness rises, ventilation would offer progressively less protection. We conclude that outdoor air ventilation that is inadequate for comfort may contribute to airborne infection but that the protection afforded to building occupants by ventilation above comfort levels may be inherently limited, especially when the level of exposure to infection is high.

Adult↗
PubMed1991

Treating hard-to-treat tuberculosis patients in Massachusetts.

For most patients with tuberculosis (TB), treatment has never been shorter or cure more certain than with current drug regimens. However, in Massachusetts and elsewhere in the United States there is a growing minority of patients who are not easily cured with the best available outpatient regimens. Close treatment supervision through culturally appropriate outreach workers has been successful for some foreign-born TB patients in whom therapy might otherwise fail. Full supervision of outpatient therapy, sometimes with incentives, has also been used successfully to treat selected homeless patients. However, a growing number of hard-to-treat homeless patients are addicted to illicit drugs, human immunodeficiency virus (HIV) infected, or have major behavioral problems. These patients often do not cooperate with fully supervised therapy and acquire drug resistance as a result of erratic drug taking. They can then transmit these dangerous organisms to others, especially to other HIV-infected persons within shelters, jails, prisons, detoxification centers, clinics, and hospitals, infecting institutional workers at the same time. In Massachusetts these hard-to-treat TB patients are increasingly being legally committed to involuntary, long-term, inpatient therapy. Although long-term inpatient TB treatment is expensive, it is likely to be cost effective when it successfully breaks the chain of transmission within institutions, and achieves cures not otherwise possible. A new model of lower-cost inpatient care that incorporates psychosocial rehabilitation techniques to modify the behavior of the hardest-to-treat patients is briefly described. Ultimately, however, the reversal of the current upsurge in hard-to-treat TB cases in Massachusetts and elsewhere depends not on inpatient care but on substantial changes in the socioeconomic order that perpetuates homelessness, substance abuse, crime, and the transmission of both TB and HIV infections.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Tuberculosis in homeless, residential care facilities, prisons, nursing homes, and other close communities.

Tuberculosis (TB) is a problem in some institutions, but not in others. Six factors may be used to assess the risk of TB in an institution: the entrance-point prevalence of infection among institutional residents and staff, the potential for reactivation, the role of transmission within the institution, the potential for detection of infection and disease, the potential for prevention and treatment of disease, and the potential of the building environment to favor transmission. The aging of the population, the crowding of prisons and the high prevalence of human immunodeficiency virus (HIV) infection are factors currently increasing the likelihood of TB in nursing homes, prisons, drug detoxification centers, and acute hospitals. Entrance-point skin testing, contact testing, periodic retesting, supervised preventive therapy, effective treatment of disease, and the selective application of ultraviolet air disinfection for certain high-risk areas are the suggested control strategies for hospitals, nursing homes, prisons, and chronic care facilities. However, for inner-city shelters and jails skin testing and preventive treatment are usually not possible, and the control strategy shifts to disease detection, isolation, effective long-term treatment, reduced crowding, ultraviolet air disinfection, and periodic testing and treatment of staff.

Cross Infection↗
PubMed1979

Role of PCO2 as determinant of CSF [HCO-3] in metabolic acidosis.

To study regulation of CSF [HCO-3] in metabolic acidosis and in particular the role of CSF PCO2 in establishing CSF bicarbonate level, acute metabolic acidosis was induced by the intravenous infusion of HCl in three groups of anesthetized dogs for six hours when PaCO2 was changed at different rates. Plasma [HCO-3] was lowered to 12 +/- 2 meq/L within one hour and maintained at that level thereafter in all groups. (I) Seven dogs were kept isocapnic while metabolic acidosis was induced. The cisternal CSF [HCO-3] fell by only 2.6 meq/L after six hours and was not significantly different from control. (II) In 11 dogs metabolic acidosis was induced while the dogs breathed spontaneously. There was a gradual drop in PaCO2 accompanied by a similar drop in CSF PCO2 of 14.5 torr. CSF [HCO-3] fell significantly by 6.1 meq/L at 6 hours and in parallel with the fall in CSF PCO2. (III) In order to show interdependence of the rate of fall in CSF [HCO-3] with rate of fall in cisternal PCO2 six dogs were mechanically hyperventilated and PaCO2 reduced to 21 torr rapidly and maintained there for six hours. CSF PCO2 followed PaCO. CSF bicarbonate fell rapidly and by 5 meq/L. In groups II and III the fall in cisternal [HCO-3] paralleled the drop in PCO2. Therefore, in metabolic acidosis the rate of the fall in cisternal bicarbonate appears to be a function of the rate of fall in CSF PCO2. It is speculated that the coupling of CSF [HCO-3] reduction in metabolic acidosis to CSF PCO2 fall is primarily for the benefit of CNS H+ homeostasis.

Acidosis↗
PubMedDate not supplied

Nosocomial tuberculosis in the AIDS era: strategies for interrupting transmission in developed countries.

In developed countries where tuberculosis is increasing in association with HIV infection, nosocomial transmission among patients and from patients to health care workers is being increasingly reported. Nosocomial tuberculosis among HIV-infected patients is difficult to prevent by conventional control measures because the clinical presentation of the disease may be atypical and confused with other respiratory infections, because the tuberculin skin test is less reliable, because cough generating procedures may increase the probability of transmission, because HIV-infected patients may progress rapidly from infection to disease, and because the organisms are increasingly drug resistant, making preventive therapy difficult. Substandard ventilation and the recirculation of air in many contemporary buildings has also been implicated in widespread nosocomial transmission. Source control through isolation and effective treatment of known or suspected cases remains the most effective strategy for preventing transmission. Dilution of infectious droplet nuclei through ventilation with outside air is important, but incompletely protective. Like ventilation with outside air, filtration of recirculated air may reduce the chance of infection by dilution, but it is expensive. Traditional surgical masks offer the wearer little or no protection. Finally, ultraviolet air disinfection may augment ventilation by inactivating organisms in the upper room air, or in ventilation ducts.

Communicable Disease Control↗