Pulmonary ventilation

As stated earlier, inhalation is the main route of absorption for occupational exposure to chemicals. Absorption of gaseous substances depends on solubility ifi blood and tissues (as presented in Sections 2.3.3-2.3.5), blood flow, and pulmonary ventilation. Particle size has an important influence on the absorption of aerosols (see Sections 2.3.7 and 3.1.1). 

Inappropriate pulmonary ventilation In acutely ill patient" eg. Myocardial infarct Pulmonary embolus Shock... 

Adrenaline, when administered to humans at 20 ug. per min. levels, caused increases in pulmonary ventilation of 13 to 153 per cent. The percentage increases in oxygen consumption resulting from the same administration were 19 to 56 per cent.30 Noradrenaline at the same level caused increases in pulmonary ventilation of 39 to 70 per cent and changes in oxygen consumption from -23 percent up to +31 per cent. Funkenstein, et al.,31 have tabulated the differences in the pharmacological action of these two substances and have adduced good evidence that two different types of psychotic patients tend to secrete excessive amounts, respectively, of the two types of hormones. Those who appear to secrete excess epinephrine-like hormone are more likely, at better than the 0.01 level of probability, to be benefited by electric shock therapy. If there are, as indicated, wide... 

In gas-uptake experiments, Gearhart et al. (1993) demonstrated a dose-dependent decrease in core body temperature with increased inhaled concentrations of chloroform. The decrease in body temperature could account for decreased in vivo chloroform metabolism, partition coefficients, pulmonary ventilation, and cardiac output rates in mice. 

The inhaled air volume (V in L) depends on the extent of chest enlargement. During normal breathing, the inhaled and exhaled volumes (tidal volume) are only part of the total lung volume [8,21]. The different parameters that describe pulmonary ventilation are shown in Figure 3.2. Table 3.1 presents a definition of the different parameters. Normal adults have a tidal... 

Figure 3.2. Schematic diagram of the different volumes describing pulmonary ventilation.

Table 3.1. Definitions of the different parameters describing pulmonary ventilation.

Almitrine, like doxapram, increases the rate and depth of respiration. In addition, it is believed that it redistributes pulmonary blood circulation, increasing it in alveoh, which leads to relatively better pulmonary ventilation. It has a more prolonged effect than doxapram.Synonyms are vectarion, duxil, and others. 

Acute abdominal conditions Narcotics may obscure diagnosis or clinical course. Do not give SR morphine to patients with Gl obstruction, particularly paralytic ileus, as there is a risk of the product remaining in the stomach for an extended period and the subsequent release of a bolus of morphine when normal gut motility is restored. Special risk patients Exercise caution in elderly and debilitated patients and in those suffering from conditions accompanied by hypoxia or hypercapnia when even moderate therapeutic doses may dangerously decrease pulmonary ventilation. Also exercise caution in patients sensitive to CNS depressants, including those with cardiovascular disease myxedema convulsive disorders increased ocular pressure acute alcoholism delirium tremens cerebral arteriosclerosis ulcerative... 

Mechanism of Action A central nervous system stimulant that directly stimulates the respiratorycenterinthemedullaorindirectlybyeffectsonthecarotid. TfterflpeMtIc Effect Increases pulmonary ventilation by increasing resting minute ventilation, tidal volume, respiratory frequency, and inspiratory neuromuscular drive, and enhances the ventilatory response to carbon dioxide. 

The concentration of an inhaled anesthetic in a mixture of gases is proportional to its partial pressure (or tension). These terms are often used interchangeably in discussing the various transfer processes involving anesthetic gases within the body. Achievement of a brain concentration of an inhaled anesthetic necessary to provide an adequate depth of anesthesia requires transfer of the anesthetic from the alveolar air to the blood and from the blood to the brain. The rate at which a therapeutic concentration of the anesthetic is achieved in the brain depends primarily on the solubility properties of the anesthetic, its concentration in the inspired air, the volume of pulmonary ventilation, the pulmonary blood flow, and the partial pressure gradient between arterial and mixed venous blood anesthetic concentrations. 

Krypton-81m has been used to study cardiopulmonary systems from as early as 1970 (X,2). Since then other investigators have proposed its use for myocardial perfusion, (3,4, cerebral perfusion, C5, >), and venography, (.7) A Rb-81 /Kr-81m generator for pulmonary ventilation studies has been commercially available since 1980 from Medi-Physics, Inc. The present work will focus on the manufacture and testing of a Rb-81/Kr-81m generator suitable for liquid elution and use in perfusion studies. 

Grant CM. 1959. The action of nitrophenols on the pulmonary ventilation of rats. Br J Pharmacol 14 401-403. 

Kr81 13 s Pulmonary ventilation images in asthmatic patients, and for the early... 

Q3 The thyroid hormones thyroxine and triiodothyronine have many metabolic effects. In adults they increase metabolic rate, oxygen and calorie consumption, stimulate carbohydrate metabolism and turnover of protein, deplete fat stores and increase catabolism of free fatty acids. Thyroid hormones stimulate heart rate and force and increase pulmonary ventilation, gastrointestinal motility and central nervous system (CNS) activity. Actions on the heart can result in an increased incidence of dysrhythmias. Thyroid hormones are critical for the normal growth and development of the infant, particularly in respect of skeletal growth and maturation of the CNS. 

Here Qaiveoiar is pulmonary ventilation rate, Cfnhah,d is the chemical concentration inhaled, and PMo0d air is the partition coefficient between the blood and air, and Clh l PiM.-mr is the concentration exhaled. 

The structure of PBPK models is fairly well defined and does not need to be changed, except for some particular chemicals, for which in vitro data would indicate unusual ADME properties. The major problem in PBPK modeling is thus the setting of parameter values. A first set of parameters is purely physiological and anatomical (e.g., organ volumes, blood flows, pulmonary ventilation, glomerular filtration rate). They can be specifically measured on... 

Animal experiments provide supporting evidence that inhaled 1,1,1-trichloroethane is rapidly and extensively absorbed and that the absorption, during short-term exposures, is influenced by ventilation rate. In rats exposed to 50 or 500 ppm, percentage uptake decreased from - 80% at the onset of exposure to - 50% after 2 hours of exposure to 50 or 500 ppm. 1,1,1-Trichloroethane was detected in arterial blood within 2 minutes ofthe onset of exposure and approached steady-state concentrations within 2 hours (Dallas et al. 1989). In anesthetized dogs under regulated respiration conditions, 1,1,1-trichloroethane was detected in arterial blood within 2 minutes of the onset of exposure to 700, 1,500, or 3,000 ppm. Arterial blood concentrations approached steady-state levels within 1 hour at 700 ppm, but not at 1,500 or 3,000 ppm absorption increased with increases in pulmonary ventilation rate (Hobara et al. 1982, 1983). 

Polycythemia is characterized by an increase in the number, and in the hemoglobin content, of circulating red cells. In patients who have chronic anoxia from impaired pulmonary ventilation or congenital or acquired heart disease, the increase in plasma erythropoietin leads to secondary polycythemia. Some renal cell carcinomas, hepatocarcinomas, and other tumors, which produce physiologically inappropriate amounts of erythropoietin, may also cause secondary polycythemia. Conversely, anemia can result from renal insufficiency and from chronic disorders that depress erythropoietin production. In polycythemia vera (primary polycythemia), which is a malignancy of erythrocyte stem cells of unknown cause, erythropoietin levels are normal or depressed. 

Respiratory Effects. Volunteers were exposed to 98, 113, or 195 ppm 2-butoxyethanol for 4-8 hours (Carpenter et al. 1956). The recorded responses of those exposed to 195 ppm included immediate irritation of the nose and throat. The subjects exposed to 113 ppm also experienced nasal irritation and a slight increase in nasal mucus discharge. In another study, no effects on pulmonary ventilation or respiratory frequency were found in seven male volunteers exposed to 2-butoxyethanol for 2 hours at the Swedish occupational exposure limit (20 ppm) during light physical exercise on a bicycle ergometer (Johanson et al. 1986a). 

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