Bronchial tree

Sympathomimetics (drugs that mimic the sympathetic nervous system) are used primarily to treat reversible airway obstruction caused by bronchospasm associated with acute and chronic bronchial asthma, exercise-induced bronchospasm, bronchitis, emphysema, bronchiectasis (abnormal condition of the bronchial tree), or other obstructive pulmonary diseases. 

The authors have now reviewed in detail four cases of unexpected death following the use of neck holds in PCP-intoxicated individuals. In all of the cases, multiple carotid compression holds had been attempted, according to the history. Skin abrasions, hemorrhage into the soft tissues of the neck, and fractures of the hyoid bone and thyroid cartilage provide structural evidence of the application of substantial force to the neck. On autopsy, there has been no evidence of lethal injuries to the bronchial tree, bra in, or heart. 

The most significant information given in Table I is that the radon daughter ions do contribute to the total internal dose if only at about 3% in this study. The effect of free ions in contrast with daughters attached to aerosols is substantial when the mechanics of deposition in the bronchial tree and lungs are taken into account. The dose from "unattached" Po-218, which includes the Po-218 positive ions as a major component, can be from 3 to 40 times that of the attached Po-218 (NCRP, 1984). Current dosimetry models allow for the important role played by Po-218 in small-ion form. Hence, their effect is significantly greater than the 3% contribution to the PAEC (WL) shown in Table I. 

It is reasonable to conclude that dose to cells throughout the bronchial tree may contribute to the risk of lung cancer and not just the dose received by certain cells in the large central airways. It is probably also appropriate to evaluate the dose absorbed by cells throughout the depth of bronchial epithelium, i.e. the mean dose,... 

Figure 4. Deposition of submicrometer aerosols measured for cyclic flow through a hollow cast of the human bronchial tree, compared with calculated values.

The absorption characteristics of radon daughters remain somewhat uncertain, as do the rates of mucous clearance at various levels in the bronchial tree. Accordingly, the effect on calculated doses of a range of assumed clearance behaviour is examined below. It is considered that the following postulates determine the possible range of doses ... 

Martin, D. and W. Jacobi, Diffusion Deposition of Small-sized Particles in the Bronchial Tree, Health Phys. 23 23-29 (1972). 

Tu and Knutson (1984) also measured the particle deposition of hydrophobic and hygroscopic particles in the human respiratory tract. They showed that the hygroscopic particles grow by a factor of 3.5 to 4.5 at the saturated humidity present in the lung. For the purpose of calculating bronchial deposition for a hygroscopic aerosol we assume an increase in size by a factor of 4 upon entry into the bronchial tree. 

It is well known that enhanced deposition in the first few airways occurs due to the turbulence produced. Turbulent diffusion is accounted for by using factors (ratio of observed deposition to calculated diffusion deposition) to correct the diffusion deposition. These had formerly been measured by Martin and Jacobi (1972) in a dichotomous plastic model of the upper airways. The data used here are from measurements performed by Cohen (1986) using hollow casts of the upper bronchial tree which included a larynx. This cast was tested using cyclic flow with deposition measured for 0.03, 0.15 and 0.20 urn diameter particles. Her turbulent diffusion factors are used in the calculation here (14 for generation 0, and 2 for generations 1 to 6). 

Table II shows the nominal alpha dose factors for occupational mining exposure. Table III shows the alpha dose factors for the nominal environmental situation. Table IV shows the bronchial dose factors for the smallest sized particles, that dominated by the kerosene heater or 0.03 pm. particles. The radon daughter equilibrium was shifted to a somewhat higher value in this calculation because this source of particles generally elevates the particle concentration markedly with consequent increase in the daughter equilibrium. Table V shows the alpha dose for a 0.12 pm particle, the same as the nominal indoor aerosol particle, but for a particle which is assumed to be hygroscopic and grows by a factor of 4, to 0.5 pm, once in the bronchial tree.

Nikiforov, A. and R.B. Schlesinger, Morphometric Variability of the Human Upper Bronchial Tree, Respiration Phvsiologvf 59 289-299 (1985). 

Chronic bronchitis is associated with chronic or recurrent excess mucus secretion into the bronchial tree with cough that occurs on most days for at least 3 months of the year for at least 2 consecutive years when other causes of cough have been excluded. 

Gram stain and culture is questionable because some patients have chronic bacterial colonization of the bronchial tree between exacerbations. 

TABLE 7-3 Anatomic Model of the Bronchial Tree and Mucus Layer ... 

Altman, E. I., and P. G. Men. Aerodynamical characteristics of the bronchial tree of the right human lung. Biofizika 20 303-307, 1975. (in Russian, summary in English)... 

Phalen, R. F., H.-C. Yeh, and D. J. Velasquez. Bronchial tree structure in the human, beagle, rat, and hamster, pp. 289-292. In 1973-1974 Annual Report of the Inhalation Toxicology Research Institute. LF-49. Albuquerque. N.M. Lovelace Foundation for Medical Education and Research, 1974. 

West, J. B. Observations on gas flow in the human bronchial tree, pp. 3-7. In C. N. Davies, Ed. Inhaled Particles and Vapours. Proceedings of an International Symposium organized by the British Occupational Hygiene Society, 1960. New York Pergamon Press, 1%1. 

Mice exposed to ozone at 2.5 ppm for 120 days showed progressive metaplasia along the tracheal bronchial tree. Return of these animals to clear air resulted in a reversal of these changes after an additional 120 days. ... 

The size of the fibrous particles that appear to induce disease in the animal models is compatible with the measured respiratory range in humans (Lipp-man, 1977). Most particulate deposition takes place not in the upper or conducting portion of the airways but in the alveolar region of the pulmonary tree (the respiratory unit). Some surface deposition may occur at bifurcations in the bronchial tree, but the actual amount at each location is influenced by anatomy, specific to the species—probably to an individual—as well as the variety of fiber. A large proportion of airborne particulates are rejected as part of the normal clearance mechanisms in animals, but in humans clearance mechanisms may be compromised by smoking, for example. We are unaware of any experiments on fiber toxicity using smoking rats ... 

Bronchial asthma Increased sympathetic activity prevents broncho-spasm in patients disposed to paroxysmal constriction of the bronchial tree (bronchial asthma, bronchitis in smokers). In this condition, P2-receptor blockade will precipitate acute respiratory distress (B). 

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