Respirator mechanisms

The level of design complexity and engineering needed for the critical care ventilators is higher than the ventilators used for chronic treatment. However, many of the engineering concepts employed in designing critical care ventilators can also he applied in the simpler chronic care units. Therefore, this chapter focuses on the design of intensive care ventilators. Hence, the terms respirator, mechanical ventilator, or ventilator will be used from this point to refer to the intensive care unit respirators. 

The particle size range for the respirating mechanism for each of these is shown in Table 16. 

Morphine and its salts are very valuable analgesic drugs but are highly addictive. In addition to suppression of pain, morphine causes constipation, decreases pupillary size and depresses respiration. Only the (-l-)-stereoisoraer is biologically active. They appear to produce their effects on the brain by activating neuronal mechanisms normally activated by... 

Two compounds associated with particular industrial risks are iron(III) oxide, Fe202, and iron pentacarbonyl, Fe(CO). Chronic inhalation of iron(III) oxide leads to siderosis. Adequate ventilation and mechanical filter respirators should be provided to those exposed to the oxide. Iron pentacarbonyl is volatile and highly toxic. 

Supplement "Corticosteroids Their Biological Mechanisms and AppHcation to the Treatment of Asthma", Am. Rev. Respir. Dis. 141, SI (1990). 

The places from which pollutants emanate are called sources. There are natural as well as anthropogenic sources of the permanent gases considered to be pollutants. These include plant and animal respiration and the decay of what was once living matter. Volcanoes and naturally caused forest fires are other natural sources. The places to which pollutants disappear from the air are called sinks. Sinks include the soil, vegetation, structures, and water bodies, particularly the oceans. The mechanisms whereby pollutants... 

Asbestos An lAQ investigation often includes inspection above accessible ceilings, inside shafts, and around mechanical equipment. Where material suspected of containing asbestos is not only present, but also has deposited loose debris, the investigator should take appropriate precautions. This might include disposable coveralls and a properly fitted respirator. 

Compounds that induce bronchoconstriction include tobacco smoke, formaldehyde, and diethyl ether. Several other compounds, such as acidic fumes (e.g., sulfuric acid) and gases, such as ozone and nitrogen dioxide, as well as isocyanates, can cause bronchoconstriction. Also, cellular damage in the airways induces bronchoconstriction because of the release of vasoactive compounds. Frequently, different mechanisms work at the same time, provoking bronchoconstriction and increased secretion of mucus, both of which interfere with respiration. 

Respirable particulates Particulates in the size range that can pass through the defence mechanisms in the human body and enter the lungs during inhalation. 

The body maintains blood pH by two primary mechanisms respiration and excretion. Carbonic acid concentration is controlled by respiration as we exhale, we deplete our system of CO, and hence deplete it of H2C03, too. This decrease in acid concentration raises the blood pH. Breathing faster and more deeply increases the amount of C02 exhaled and hence decreases the carbonic acid concentration in the blood, which in turn raises the blood pH. Hydrogen carbonate ion concentration is controlled by its rate of excretion in urine. 

Respiratory acidosis results when decreased respiration raises the concentration of C02 in the blood. Asthma, pneumonia, emphysema, or inhaling smoke can all cause respiratory acidosis. So can any condition that reduces a person s ability to breathe. Respiratory acidosis is usually treated with a mechanical ventilator, to assist the victim s breathing. The improved exhalation increases the excretion of C02 and raises blood pH. In many cases of asthma, chemicals can facilitate respiration by opening constricted bronchial passages. 

Exposure to fiime and the precipitated silica (amorphous silica) causes fatal bronchial response as these are respirable. Repeated exposure dries the skin and causes mechanical irritation to eyes. Sol-gel silica, as an alternative to this, ceases the floating problem and avoids unnecessary contamination. 

Kobayashi, K., Salathe, M., Pratt, M.M., Cartagena, N.J., Soloni, F., Seybold, Z.V. and Wanner, A. (1992). Mechanism of hydrogen peroxide induced inhibition of sheep airway cilia. Am. J. Respir. Cell Mol. Biol. 6, 667-673. 

Gauldie J. Inflammatory mechanisms are a minor component of the pathogenesis of idiopathic pulmonary fibrosis. Am J Respir Crit Care Med 2002 165(9) 1205-1206. 

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