Lung surface area

Doses calculated in animals are converted to equivalent doses in humans on the basis of comparative physiological considerations (c.g., ventilatory parameters and regional lung surface areas). Additionally, if the e.xposure period was discontinuous, it is adjusted to reflect continuous e.xposure. 

Symptoms Initial symptoms include malaise, dizziness, nausea, abdominal pain, and dyspnea which may develop within several hours of exposure to three parts-per-million to arsine. Children exposed to the same levels as adults may get a higher dose because they have a greater lung surface area and they are closer to ground level. 

Human equivalent concentration (HEC). The HEC is used to describe the dose of an agent to which humans are exposed through inhalation. The HEC is the estimated concentration that is equivalent to that used in an experimental animal species. The HEC is estimated using adjustment factors that account for such species-dosimetric differences as ventilatory parameters and lung surface areas, as well as factors related to the gas, aerosol, or particulate nature of the agent. 

The likely maximum exposure from a metered-dose inhaler is 33 ppm hr/ m3 lung surface area/d (Alexander et al. 1996). 

Lung Surface Area Surface area, organics, and metals are important metrics for potential for lung response of inflammation, toxicity, and apoptosis (16, 17), and the surface area of particles between 50 nm and 1000 nm is expected to be the most influential in causing lung injury. 

What is the lung surface area required for a conversion of 20% ... 

According to Pick s law of diffusion, the amount of gas that moves across the blood-gas interface is proportional to the surface area of the interface and inversely proportional to thickness of the interface. In other words, gas exchange in the lungs is promoted when the surface area for diffusion is... 

The volumes and surface areas of airways in each generation that result from scaling the Weibel A, Yeh-Schum and UCI lung models to the standard FRC (Yu and Diu, 1982), are shown in Figure 3. The residual differences in airway size are appreciable, but there is no overriding reason to prefer a particular model. Dosimetric results are therefore evaluated below for all three. 

Figure 3. Volumes and surface areas of airways in each bronchial generation of the Weibel A, Yeh-Schum and UCI lung models, with total volumes 2V and areas 2A.

Figure 9. Diameters and surface areas of bronchial airways as a function of age, according to the UCI lung model.

Insoluble metallic oxides will be retained with half-times of clearance of hundreds of days (2.5). If the particle is of intermediate solubility or contains a mixture of soluble and insoluble components, the clearance of the particle or its soluble fraction will be influenced by the surface area available for dissolution. The larger the surface area per unit mass, the higher the rate of dissolution of the soluble components of the particles, and the greater the potential for those components to interact with lung tissue. 

The respiratory system is divided into two areas the upper and the lower respiratory system. The upper respiratory system is composed of the nose, sinuses, mouth, pharynx (section between the mouth and esophagus), larynx (the voice box), and the trachea or windpipe. The lower respiratory system is composed of the lungs and its smaller structures, including the bronchi and the alveoli. The bronchial tubes carry fresh air from the trachea through a series of branching tubes to the alveoli. The alveoli are small blind air sacs where the gas exchange with the blood occurs. An estimated 300 million alveoli are found in a normal lung. These alveoli contribute a total surface area of approximately 70 m2. Small capillaries found in the walls of the alveoli transport the blood an estimated 100 ml of blood is in the capillaries at any moment. 

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