ABSTRACT
Research on respiratory protection against biologic agents is important to address major concerns such as occupational safety and terrorist attack. This review describes the literature on respiratory protection against bioaerosols and identifies research gaps. Respiratory protection is a complex field involving a number of factors, such as the efficiency of respirator filter material; face-piece fitting; and maintenance, storage, and reuse of respirators. Several studies used nonpathogenic microorganisms having physical characteristics similar to that of Mycobacterium tuberculosis to analyze microbial penetration through respirators. Some studies showed that high-efficiency particulate air (HEPA) and N95 filters provided a higher level of protection than dust/mist (DM) and dust/mist/fume (DMF) filters. Flow rate and relative humidity appear to alter the level of penetration of microorganisms through respirator filters. The relationship between microbial penetration through respirator filters and the aerodynamic diameter, length, or other physical characteristics of microorganisms remains controversial. Whether reaerosolization of bioaerosol particles should be a concern is unclear, given the fact that one study has demonstrated significant reaerosolization of 1- to 5-microm particles loaded onto respirator filters. Respirator maintenance, storage, and decontamination are important factors to be considered when reusing respirators. The respiratory protection against biologic warfare agents such as anthrax in military and civilian situations is described.
Subject(s)
Aerosols/adverse effects , Communicable Disease Control/methods , Occupational Health , Respiratory Protective Devices/standards , Air Microbiology , Decontamination , Equipment Contamination , Female , Humans , Infectious Disease Transmission, Patient-to-Professional , Male , Needs Assessment , Occupational Exposure/adverse effects , Particle Size , Research , Respiratory Protective Devices/trends , Risk Assessment , Sensitivity and Specificity , Tuberculosis, Pulmonary/prevention & control , Tuberculosis, Pulmonary/transmissionABSTRACT
Osmotic challenge of airways alters the bioelectric properties of the airway epithelium and induces the release of factors that modulate smooth muscle tone. Recent studies in our laboratory suggested that methacholine-contracted airways relax in response to incremental increases in osmolarity, rather than from cell shrinkage or absolute solute concentration. In the present study, guinea pig tracheae were mounted in Ussing chambers to elucidate the bioelectric effects of challenge of the epithelium with hyperosmolar and isosmolar solutions. Transepithelial short-circuit current (Isc) across tracheae stimulated with basolateral methacholine was inhibited by apical amiloride, apical 5-nitro-2-(3-phenylpropylamino)benzoic acid, basolateral bumetanide, basolateral ouabain, and Cl(-)-free solution, but not by basolateral iberiotoxin. Apical hyperosmolar challenge with NaCl variably decreased or increased Isc, but D-mannitol (D-M) always inhibited Isc; bumetanide attenuated decreases in Isc. The effects of the transport blockers depended upon whether Isc was initially decreased or increased. Unique concentration-dependent changes in Isc and transepithelial resistance (Rt) were observed when ionic (NaCl and KCl), nonionic impermeant (D-M and sucrose), and nonionic permeant (urea) osmolytes were added to the apical and basolateral baths. At concentrations that doubled the osmolarity of the apical bath, D-M, urea, and N-methyl-D-glucamine-gluconate (NMDG-Glu) decreased Isc. Apical isosmolar NMDG-Glu solution decreased Isc, and additional NMDG-Glu caused a further decrease in Isc. Inclusion of one permeant ion, either Na+,K+, or Cl-, reversed the response to apical isosmolar and hyperosmolar solutions. Thus, bioelectric responses of the airway epithelium to hyperosmolar solution are induced by incremental increases in osmolarity.
