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Biomedical subjects

W M Foster

Publications and source records attributed to W M Foster.

42 records · Page 3Linked to original sources
PubMed1976

Effect of adrenergic agents and their mode of action on mucociliary clearance in man.

The aerosolized adrenergic (ADR) agent, isoproterenol (ISO), was found markedly to accelerate mucus clearance within the human tracheobronchial tree. Mucus transport was measured by external gamma counting of aerosolized Fe2O3 particles deposited on the mucous membrane during inhalation. Aerosolized epinephrine (EPI), despite its alpha-ADR bronchial vasoconstrictor activity, increased mucus clearance to the same degree as did aerosolized ISO, with its beta-ADR bronchial vasodilator activity. The vehicle used for delivery of the ADR agents, i.e., a H2O aerosol by intermittent positive-pressure breathing (IPPB), itself increased mucus clearance slightly, but did not elicit the enormous increases produced by the ADR agents. Parenteral ISO caused increases in clearances similar to aerosolized ISO and EPI (consistent with different tissue drug levels achieved). Oral atropine delayed clearance, but atropine prior to an ADR aerosol did not alter the mucus transport effect of the ADR agent. ISO and atropine, despite opposite effects on mucus clearance, caused equal bronchodilation. Thus, increased clearance following aerosolized ISO was not dependent on bronchial vasodilation, aqueous aerosol droplets, reflex parasympathetic activation, or bronchodilation, and seems best attributable to increased ciliary beat rate.

Adult↗
PubMed1975

Tracheobronchial particle deposition and clearance. A study of the effects of cigarette smoking in monozygotic twins.

Particle deposition and tracheobronchial clearance were measured in six pairs of male monozygotic twins, four of which were discordant for cigarette smoking. The fraction of an inhaled aerosol that deposited on the ciliated airways showed variations within twin pairs comparable with variations in repeated tests on a single subject, and significantly smaller (P less than .001) than among tests on different subjects. Variations that did occur were consistent with differences in forced expiratory volume (FEV1.0) values. The proximal shift of aerosol deposition and reduced FEV1.0 values in smokers indicated that they had some degree of bronchoconstriction. Mucociliary clearance characteristics are qualitatively and quantitatively similar for nonsmoking and smoking concordant monozygotic twins, ie, comparable with repeated tests on a single individual, reflecting their constitutional similarity. With one exception, clearance curves for twin pairs discordant with respect to smoking were also qualitatively indistinguishable. Nonsmokers, however, had greater upper bronchial clearance rates than their smoking twins.

Aerosols↗
PubMed1975

Factors affecting tracheobronchial mucociliary transport.

In vivo mucus transport rates were studied in humans and donkeys by external measurement of the rate of clearance of insoluble monodisperse gamma-tagged aerosols. The influence of temperature, environmental toxicants and drugs which affect the autonomic nervous system were studied by determining the changes in clearance produced by them in individual subjects. In donkeys, increased pretest ambient temperature accelerated clearance by greater than 1.7%/ degrees C. Smoking 2-7 cigarettes reduced the duration of bronchial clearance by approximately 50% in both humans and donkeys. Donkeys were exposed to higher doses; with progressive slowing of tracheal and bronchial clearance for greater than 10 cigarettes. HCN, at concentrations up to 1230 ppm, produced only a mild transient slowing of clearance. In man, atropine slowed clearance, while the adrenergic stimulating drugs, isoproterenol and epinephrine, both accelerated it by greater than or equal to 4 times, as did isoproterenol when given subsequent to atropine. The cholinergic stimulating drug methacholine increased mucociliary transport in the the donkey. Administration of a tap water aerosol for 10-15 min in humans increased bronchial clearance rates by approximately 25%.

Aerosols↗
PubMedDate not supplied

Relationship between tracheobronchial particle clearance rates and sites of initial deposition in man.

Mucociliary clearance was compared in three groups of normal subjects; each group inhaled a different type of aerosol (sebecate, iron oxide, and aqueous) labelled with 99Tc, to determine the relationship between deposition pattern and the subsequent total lung clearance. Standardization for deposition was accomplished by measuring a central to peripheral ratio (C/P) of deposited radioactivity in the thorax. Lung particle retention at 30, 60, 90, 120 min, and 24 h was measured, and compared at each time period to the C/P ratio. A linear relationship between the retention of aerosol at each time period and the C/P ratio was seen among all aerosols, e.g., aerosol with high C/P ratios had less retention of aerosol at a given time period than aerosols with more diffuse deposition patterns and lower C/P ratios. Furthermore, the relationship was similar to that of the more traditional measurement of regional deposition, the 24-h percentage retention. Lung particle retention was compared among aerosols, using analysis of covariance to standardize for C/P ratio. The intersubject variability was similar among all three aerosol groups. Thus, mucociliary clearance can be standardized in healthy subjects by using an initial deposition index, the C/P ratio, with similar accuracy to the 24-h percentage retention, as an index of aerosol deposition. The use of the C/P ratio, however, has distinct advantages over the 24-h retention, in that studies can be conveniently shortened, used with short lived isotopes, and be adapted to techniques investigating lung permeability instead of tracheobronchial clearance. An unexpected finding was the more rapid clearance of sebecate particles, compared with iron oxide or aqueous particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Smoking cessation and acute airway response to ozone.

Pulmonary function and symptom responses of asymptomatic smokers were measured during chamber exposures to ozone or filtered air. Subjects were evaluated while habituated to smoking and after 6 mo of smoking abstinence. At the onset of treatment, subjects (n = 18) who had a history of smoking 33.4 +/- 15.6 packs/y and who had almost normal pulmonary function (forced vital capacity [FVC], forced expiratory volume in 1 s [FEV1.0], and mid-maximal flow [MMF] were greater than 82% of predicted) were unresponsive to ozone exposure (0.4 ppm for 2 h). A matched group of control smokers (n = 16) did not respond to filtered air exposure. After 6 mo of smoking cessation, baseline MMF rates improved significantly (p less than .02); exsmokers (n = 15) raised this index from 3.32 to 4.11 l/s. All 9 subjects who abstained from smoking cigarettes for 6 mo and who were re-exposed to 0.4 ppm ozone had significant (p less than .01) reductions in MMF (from a mean of 3.86 +/- 1.32 [standard deviation] to 2.99 +/- 0.94 l/s, i.e., 22.5% reduction) and marginally significant reductions in comfort, as evidenced by an increase in the incidence of dry cough (p less than .10). The FVC was not reduced during ozone exposure. Control exsmokers (n = 6) remained unresponsive to filtered air exposure. The exsmokers' responses to ozone and their improved MMF during the period of smoking abstinence were correlated (coefficient = .88), i.e., subjects with the largest baseline gains in MMF after withdrawal experienced the largest acute decrements in MMF during ozone exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗