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Biomedical subjects

V Hampl

Publications and source records attributed to V Hampl.

45 records · Page 3Linked to original sources
PubMed1990

Perinatal hypoxia increases hypoxic pulmonary vasoconstriction in adult rats recovering from chronic exposure to hypoxia.

The possibility that perinatal exposure to hypoxia influences the pulmonary vasculature in adults was tested. Rats born in a hypoxic environment were kept in hypoxia for an additional week after birth. The rats were then raised in atmospheric air, and when adult, they were compared with the rats born and raised in air. Rats (10 wk old) of both groups were exposed to 10% O2 for 2 wk. They were then studied immediately after the exposure and after 2 wk of recovery from the sojourn in the hypoxic environment. The experience of perinatal hypoxia did not affect mean pulmonary arterial blood pressure, right ventricle weight, or the number of muscularized peripheral pulmonary vessels. During exposure to chronic hypoxia in adulthood, both groups developed pulmonary hypertension, which was not affected by previous perinatal hypoxia. The pulmonary vascular responses to acute hypoxic challenges were studied in the preparation of isolated perfused lungs. In both groups of rats, perinatally hypoxic and normoxic, the acute hypoxic vasoconstriction was attenuated immediately after the exposure of adult animals to chronic hypoxia. However, during the recovery from this hypoxic sojourn, the rats born in hypoxia were significantly more reactive to acute lung hypoxia than all other groups of rats studied. It is concluded that the experience of a short period of perinatal hypoxia did not affect the development of hypoxic pulmonary hypertension induced in adulthood. It increased, however, the pulmonary vascular reactivity to acute hypoxic stimuli during the period of recovery from a sojourn in the hypoxic environment in adulthood.

Age Factors↗
PubMed1986

Improved local exhaust control by directed push-pull ventilation system.

Experiments using the directed push-pull ventilation technique were conducted on a general type of local exhaust ventilation installation. The exhaust (pull) system consisted of a square hood, while the push system consisted of one or two slot jets or two round jets. The two slot or round jets were located behind and beside a mannequin (the mannequin simulated the worker's position). The one slot jet was located between the smoke source and the mannequin. Under experimental conditions, the push-pull system reduced the amount of smoke in the mannequin's breathing zone even when the exhaust system volume flow rate necessary for capture of the smoke decreased approximately 50%. Generally, no difference between the slot and round jet control performance was found. The experiments showed that the directed push-pull ventilation system can be used effectively to reduce the contaminant emission into a workroom, if the jets are located so that the eddy currents induced by the worker or other obstructions are minimized or eliminated.

Humans↗
PubMed1986

Use of tracer gas technique for industrial exhaust hood efficiency evaluation--where to sample?

A tracer gas technique using sulfur hexafluoride (SF6) was developed for the evaluation of industrial exhaust hood efficiency. In addition to other parameters, accuracy of this method depends on proper location of the sampling probe. The sampling probe should be located in the duct at a minimum distance from the investigated hood where the SF6 is dispersed uniformly across the duct cross section. To determine the minimum sampling distance, the SF6 dispersion in the duct in fully developed turbulent flow was studied at four duct configurations frequently found in industry: straight duct, straight duct-side branch, straight duct-one elbow, and straight duct-two elbows combinations. Based on the established SF6 dispersion factor, the minimum sampling distances were determined as follows: for straight duct, at least 50 duct diameters; for straight duct-side branch combination, at least 25 duct diameters; for straight duct-one elbow combination, 7 duct diameters; and for straight duct-two elbow combination, 4 duct diameters. Sampling at (or beyond) these distances minimizes the error caused by the non-homogeneous dispersion of SF6 in the duct and contributes to the accuracy of the tracer gas technique.

Air Pollutants, Occupational↗
PubMed1985

Control of wood dust from horizontal belt sanding.

An auxiliary ventilation system has been developed to reduce the wood dust emission from horizontal belt sanders. This system consists of two devices: a hood and a jet stripper. The hood is a narrow low-volume, high-velocity slot hood located between a belt surface and a worktable; the push device is a jet stripper located inside a driven pulley hood opposite the operator site. In combination with a standard sander hood, both devices significantly reduced the wood dust emission into the workroom. Laboratory data were confirmed by field tests conducted at an oscillating edge belt sander at a wood furniture manufacturing plant. These devices work independently of each other and do not interfere with the operator's sanding activity. They do not require special maintenance and are economically feasible.

Dust↗
PubMed1984

Evaluation of industrial local exhaust hood efficiency by a tracer gas technique.

Efficiency of industrial local exhaust ventilation is defined as the ratio of air contaminant quantity captured by the system per unit time to the total contaminant quantity produced by the process per unit time. To date, no direct method exists for this evaluation. This paper describes a tracer gas technique, using sulfur hexafluoride (SF6), which has been developed for the evaluation of local exhaust system efficiency. SF6 was discharged at a known rate into the industrial process generation area. Then, by comparing this quantity to that captured by the exhaust system, as measured in the exhaust duct, hood efficiency is determined. Major advantages of this technique are: The tracer gas technique is able to evaluate directly the hood efficiency. The tracer gas technique is not affected by cross-contamination from nearby industrial processes. The tracer gas technique can be conducted "on site" with minimal interruption of industrial process or interference with workers' duties. The tracer gas, using SF6 is non-toxic. Since SF6 is a gas, this technique may be limited to efficiency evaluation of hoods associated with gases, fumes, vapors, or fine particles.

Evaluation Studies as Topic↗