Basal respiratory volume

It may occur that the exposure route of the dose descriptor does not correspond to the exposure route of the DNEL. Therefore, the dose descriptor needs to be corrected in terms of a route-to-route-extrapolation. For example, if an inhalatory dose descriptor (expressed in mg/m ) serves as starting point for the derivation of an oral DNEL (expressed in mg/kg body weight), the basal respiratory volume for the relevant species (e.g., in rats 1.15 mVkg body weight/24 h) is used to correct the dose descriptor in terms of the estimated total daily... 

Airway cross-sections have the nominal anatomy shown in Fig. 5.16. Airway surface liquid (AST), primarily composed of mucus gel and water, surrounds the airway lumen with a thickness thought to vary from 5 to 10 mm. AST lies on the apical surface of airway epithelial cells (mostly columnar ciliated epithelium). This layer of cells, roughly two to three cells thick in proximal airways and eventually thinning to a single cell thickness in distal airways, rests along a basement membrane on its basal surface. Connective tissue (collagen fibers, basement membranes, elastin, and water) lies between the basement membrane and airway smooth muscle. Edema occurs when the volume of water within the connective tissue increases considerably. Interspersed within the smooth muscle are respiratory supply vessels (capillaries, arteriovenous anastomoses), nerves, and lymphatic vessels. 

The power required to sustain physiological processes can be calculated by using the above equation. If a pressure-volume loop for a respiratory cycle is plotted, the work of breathing may be found. If the respiratory rate is now measured then the power may be calculated. The power required for respiration is only approximately 700-1000 mW, compared with approximately 80 W needed at basal metabolic rate. 

Basal metabolism O2 consumption CO2 production Respiratory quotient Blood volume Resting cardiac output Systemic blood pressure Heart rate at rest General cardiac output... 

The effect of stavudine-based HAART on mitochondrial respiratory transport chain function in CD4-I- peripheral blood lymphocytes has been studied in HTV-positive patients in Australia [73. CD4-I-lymphocytes isolated from asymptomatic stavudine-treated patients had reduced basal mitochondrial oxygen consumption compared with untreated HIV-infected patients and uninfected controls. Cells from the stavudine-treated patients also had reduced maximal oxygen consumption. There were no significant differences in citrate synthase activities, mitochondrial volume, or mitochondrial DNA copy numbers per cell between the groups. These findings support an association between stavudine and mitochondrial dysfunction and suggest that the alteration in function does not solely result from the... 

Since HORD was used to feed animals, its toxicity was investigated in several animal species. In rats and dogs, HORD showed a positive inotropic effect, increased systolic and diastolic pressures, enhanced peripheral blood volume, and inhibited gut movement. All effects are short and only observable at high doses [43]. HORD administered at an oral dose of 2.0 mg/kg body weight to horses did not change heart rate, respiratory rate, basal body temperature, and behavior. But when HORD was injected by rapid i.v. route to horses, defecation within 60 s, substantial respiratory distress, approximately 250% increase in heart rate, and profuse sweating were observed [44]. These effects were transient and abolished within 30 min. 

Daily intakes of lead through inhalation by human or experimental populations are the product of ventilation rate and air Pb concentration, further adjusted for lead deposition rates of the inhaled volumes in the respiratory tract. The ventilation rate, i.e., total volumes of inhaled air per unit time, typically 24 hours, can be determined by either direct measurement or via food-energy intakes. The latter may also be employed to arrive at the ratios of total energy expendimre to basal metabolic rate (BMR). 

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