Penetration of fiber versus spherical particles through filter media and faceseal leakage of N95 filtering facepiece respirators with cyclic flow

Medidas de protección respiratoria de tuberculosis en personal de salud: revisión integrativa

Introducción: los trabajadores de la salud (TS) son vulnerables a la infección por tuberculosis. Se suma el desconocimiento de los TS de las medidas de protección respiratoria que puede aumentar el riesgo individual de adquirir tuberculosis en instituciones de salud. Objetivo: describir la producción de literatura científica en las bases de datos científicas sobre las medidas de protección respiratoria de la infección tuberculosa durante el periodo 2012-2018. Síntesis de contenido: revisión integrativa a través de: formulación de la pregunta de investigación, recolección de datos, evaluación, análisis e interpretación de datos y presentación de los resultados. 45 artículos cumplieron con los criterios de inclusión. Las características predominantes de los estudios fueron: año 2017 con mayor número de publicaciones, en el continente de África, la metodología de estudio cuantitativo cuasiexperimental. En los estudios se identificaron las características del respirador N95 y la mascarilla quirúrgica, los conocimientos, actitudes y prácticas de las medidas de protección respiratoria y programas educativos. Conclusiones: se evidenció que el respirador N95 es la medida de protección individual más eficiente para el control de la infección tuberculosa en los TS. También se identificó la necesidad del diseño de programas educativos sobre las medidas de protección de la infección tuberculosa.

Quantitative analysis of the role of fiber length on phagocytosis and inflammatory response by alveolar macrophages

BACKGROUND

In the lung, macrophages attempt to engulf inhaled high aspect ratio pathogenic materials, secreting inflammatory molecules in the process. The inability of macrophages to remove these materials leads to chronic inflammation and disease. How the biophysical and biochemical mechanisms of these effects are influenced by fiber length remains undetermined. This study evaluates the role of fiber length on phagocytosis and molecular inflammatory responses to non-cytotoxic fibers, enabling development of quantitative length-based models.

METHODS

Murine alveolar macrophages were exposed to short and long populations of JM-100 glass fibers, produced by successive sedimentation and repeated crushing, respectively. Interactions between fibers and macrophages were observed using time-lapse video microscopy, and quantified by flow cytometry. Inflammatory biomolecules (TNF-α, IL-1α, COX-2, PGE2) were measured.

RESULTS

Uptake of short fibers occurred more readily than for long, but long fibers were more potent stimulators of inflammatory molecules. Stimulation resulted in dose-dependent secretion of inflammatory biomolecules but no cytotoxicity or strong ROS production. Linear cytokine dose-response curves evaluated with length-dependent potency models, using measured fiber length distributions, resulted in identification of critical fiber lengths that cause frustrated phagocytosis and increased inflammatory biomolecule production.

CONCLUSION

Short fibers played a minor role in the inflammatory response compared to long fibers. The critical lengths at which frustrated phagocytosis occurs can be quantified by fitting dose-response curves to fiber distribution data.

GENERAL SIGNIFICANCE

The single physical parameter of length can be used to directly assess the contributions of length against other physicochemical fiber properties to disease endpoints.

The effect of simulated air conditions on N95 filtering facepiece respirators performance

The objective of this study was to determine the effect of several simulated air environmental conditions on the particle penetration and the breathing resistance of two N95 filtering facepiece respirator (FFR) models. The particle penetration and breathing resistance of the respirators were evaluated in a test system developed to mimic inhalation and exhalation breathing while relative humidity and temperature were modified. Breathing resistance was measured over 120 min using a calibrated pressure transducer under four different temperature and relative humidity conditions without aerosol loading. Particle penetration was evaluated before and after the breathing resistance test at room conditions using a sodium chloride aerosol measured with a scanning mobility particle sizer. Results demonstrated that increasing relative humidity and lowering external temperature caused significant increases in breathing resistance (p < 0.001). However, these same conditions did not influence the penetration or most penetrating particle size of the tested FFRs. The increase in breathing resistance varied by FFR model suggesting that some FFR media are less influenced by high relative humidity.