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At least 469 records · Page 26Linked to original sources
PubMed1998

Hypothermia and physiological control: the respiratory system.

1. Ventilation (VE) in unanaesthetized hypothermic animals remains tightly coupled to oxygen consumption (VO2) such that VE/VO2 remains constant despite changes in body temperature. 2. Ventilatory responses to hypoxia would suggest that, relative to metabolic rate, the gain of the respiratory system is unaltered in hypothermic animals. 3. Future studies should exercise care to ensure that the method applied in inducing hypothermia does not complicate ventilatory control and that the ability of the species to hibernate is taken into consideration.

Animals↗
PubMed2006

Virtual respiratory system for education and research: simulation of expiratory flow limitation for spirometry.

BACKGROUND: Due to economic and ethical problems, virtual organs may appear more convenient than experiments on animals or limited investigations on patients. In particular, a virtual respiratory system (VRS) may be useful for tasks such as respirators and support methods testing, education, staff (medical and technical) training, (initial) testing of scientific hypotheses. METHODS: A comparative study of simulated and real spirometric results for different patient states (healthy lungs, restrictive lung disease, and obstructive lung disease of different localization and degree) was performed. The volume-flow curve and such standard parameters as FEV1, FEV1%VC, MEF75 etc. were analyzed. RESULTS: A mathematical description of collapsing bronchi was proposed. All fundamental phenomena present during spirometry also appeared in VRS, especially characteristic dependence between lung volume and air flow for forced expiration. In particular, both airway resistance and the flow limitation were described with one formula derived from commonly known dependence of the resistance on lung volume. Generally there were no significant differences between simulated results and those seen in clinical practice. Only simulation of obstruction in upper airways gave incorrect results, which suggested a different flow limitation mechanism (perhaps wave-speed limitation). CONCLUSIONS: Our VRS can already be used in medical education, e.g. courses of spirometry, and in some other applications. It seems that the significance of the wave-speed criterion has been overestimated.

Computer Simulation↗
PubMed1984

Immunohistochemical techniques and their applications in the histopathology of the respiratory system.

Subsequent to the first report in the 1940s on incubation of tissue sections with fluorescein-conjugated antibodies for localization of antigens, a great number of modifications were introduced to improve the validity of immunohistochemistry which has become a growingly popular tool. The use of immunoenzymatic techniques eliminates the need for expensive fluorescence microscopy equipment, the lack of permanency of preparations and the lack of electron density required in ultrastructural localization of antigens. Regardless of the technique, it is also important to choose a correct fixation which allows the proper preservation of antigens and morphology and the penetration of antibodies through the entire thickness of the preparation. A variety of immunohistochemical techniques have been applied to study several components of the lung, such as collagen, surface active material, lung specific antigens, and enzymes and the detection of tumor markers, immunoglobulins and infectious agents in the respiratory system which is reviewed. The large surface area and the multiplicity of cell types provided by the respiratory tract epithelium of humans for exposure to microbial as well as toxic substances in the environment make this organ system very vulnerable but a good early indicator of adverse health effects. Immunohistochemistry provides valuable information complementary to the immunochemical and biochemical characterization of this barrier.

Animals↗
PubMed1992

Effects of acute oligohydramnios on respiratory system of fetal sheep.

Prolonged oligohydramnios, or a lack of amniotic fluid, is associated with pulmonary hypoplasia and subsequent perinatal morbidity, but it is unclear whether short-term or acute oligohydramnios has any effect on the fetal respiratory system. To investigate the acute effects of removal of amniotic fluid, we studied nine chronically catheterized fetal sheep at 122-127 days gestation. During a control period, we measured the volume of fluid in the fetal potential airways and air spaces (VL), production rate of that fluid, incidence and amplitude of fetal breathing movements, tracheal pressures, and fetal plasma concentrations of cortisol, epinephrine, and norepinephrine. We then drained the amniotic fluid for a short period of time [24-48 h, 30.0 +/- 4.0 (SE) h] and repeated the above measurements. The volume of fluid drained for the initial studies was 1,004 +/- 236 ml. Acute oligohydramnios decreased VL from 35.4 +/- 2.9 ml/kg during control to 22.0 +/- 1.6 after oligohydramnios (P less than 0.004). Acute oligohydramnios did not affect the fetal lung fluid production rate, fetal breathing movements, or any of the other measured variables. Seven repeat studies were performed in six of the fetuses after reaccumulation of the amniotic fluid at 130-138 days, and in four of these studies the lung volume also decreased, although the overall mean for the repeat studies was not significantly different (27.0 +/- 5.2 ml/kg for control vs. 25.5 +/- 5.5 ml/kg for oligohydramnios). Again, none of the other measured variables were altered by oligohydramnios in the repeat studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1989

Evaluating the penetration of Cladosporium spores into the human respiratory system on the basis of aerobiological sampling results.

The penetration of Cladosporium spores and spore aggregates into human airways was studied using three different spore sampling methods: 1) a Burkard spore trap for determining the aggregation degree of Cladosporium; two samplers, simulating the human respiratory system, 2) a 6-stage Andersen 2000 sampler, and 3) a new size-selective bioaerosol sampler (SSBAS), designed specifically for immunochemical and chemical analyses. The aggregation degree of Cladosporium spores varied between 1.0 and 1.3 spores per dispersal unit. Grouping seems to be of little if any importance to the penetration ability of Cladosporium spores into the respiratory tract. The distribution of spores in the Andersen and SSBAS differed significantly in the largest size class (spores greater than 7 microns in diameter); with the Andersen sampler only 10.8% of the spores were detected in stage 1, compared with 43% with the SSBAS. On the Andersen culture plates 95% of all colonies were detected in stages 1-4, where particles greater than 2.1 microns in diameter are trapped. In the SSBAS altogether 99.4% of spores were found in the first two filter stages (cutoff point approx. 2.5 microns in diameter). Conclusions regarding the penetration of spores to the lungs on the basis of aerobiological results should always be based on the use of properly calibrated spore traps.

Cladosporium↗
PubMed1991

Low-frequency respiratory system resistance in the normal dog during mechanical ventilation.

The low-frequency resistances of the respiratory system, lung, and chest wall were investigated in four anesthetized paralyzed dogs mechanically ventilated at various frequencies between 0.08 and 0.83 Hz. The resistances were calculated by three different methods: 1) as the real part of the complex impedance obtained from regular ventilation data, 2) as the effective resistance of a two-compartment model fitted to the same data, and 3) as the resistance of a single-compartment model fitted to data obtained during sinusoidal ventilation at various frequencies. Alveolar pressures were measured by a closed-chest alveolar capsule technique and afforded a direct measure of airways resistance. All three resistance estimates were very similar and decreased markedly with frequency between 0 and 1 Hz. The real part of lung impedance at the higher frequencies investigated (around 5 Hz) closely approximated airways resistance, as predicted by the eight-parameter viscoelastic model of respiratory mechanics proposed by Bates et al. (J. Appl. Physiol. 67:2276-2285, 1989).

Airway Resistance↗