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Biomedical subjects

D Pavia

Publications and source records attributed to D Pavia.

At least 73 records · Page 4Linked to original sources
PubMed1984

Aerosol particle impaction in the conducting airways.

Modelling of inhaled particle deposition in the lungs potentially offers data relevant to assessing hazards from toxic inhaled particles, to studying mucus clearance or lung permeability by aerosol techniques, and to achieving better utilisation of drugs administered as aerosols. Analysis of published modelling studies is complicated by differing approaches to the quantitative estimation of physical factors determining deposition and by differing choices of anatomical data. Published formulae for predicting aerosol particle impaction are compared by applying them to the deposition of 5 micron particles in the human conducting airways using the morphological data of Weibel together with information from other sources about airways branching angles. The results indicate the range of deposition estimates that may be obtained from currently available impaction formulae. All but one of the formulae considered agree in indicating maximum deposition by impaction in, or close to, the segmental or subsegmental bronchi. Data are presented to indicate how the principal physical determinants of deposition depend on particle size, inhalation flow rate and lung volume during inhalation.

Aerosols↗
PubMed1984

A model for assessing bronchial mucus transport.

We propose a scheme for the assessment of regional mucus transport using inhaled Tc-99m aerosol particles and quantitative analysis of serial gamma-camera images. The model treats input to inner and intermediate lung regions as the total of initial deposition there plus subsequent transport into these regions from more peripheral airways. It allows for interregional differences in the proportion of particles deposited on the mucus-bearing conducting airways, and does not require a gamma image 24 hr after particle inhalation. Instead, distribution of particles reaching the respiratory bronchioles or alveoli is determined from a Kr-81m ventilation image, while the total amount of such deposition is obtained from 24-hr Tc-99m retention measured with a sensitive counter system. The model is applicable to transport by mucociliary action or by cough, and has been tested in ten normal and ten asthmatic subjects.

Adolescent↗
PubMed1983

Assessment of jet nebulisers for lung aerosol therapy.

The effect on nebuliser output of varying the flow rate of compressed air driving the device and the volume of respirator solution used was investigated in four brands of jet nebuliser. Raising the airflow rate from 4 to 6 1/min reduced the duration of nebulisation by approximately 40%, and a rise from 6 to 8 1/min reduced the duration by a further 15%. However, this change had only a slight effect on the proportion of the solution released. The volume of respirator solution placed in the nebuliser directly influenced the volume released as aerosol. After a 2 ml fill, less than 1 ml was released (50%). With a volume fill of 4 mg 60-80% was released, and with 6 ml 70-85% was released. Nebuliser output fell during nebulisation as the temperature of the solution dropped by 8-12 degrees C. A minimum 4 ml fill and an air-flow rate of 6 l/min are advocated to optimise nebuliser output.

Aerosol Propellants↗
PubMed1983

Effects of terbutaline sulphate aerosol on bronchodilator response and lung mucociliary clearance in patients with mild stable asthma.

Ventilatory function and whole lung mucociliary clearance have been assessed in 10 patients with mild stable asthma following inhalation of 1 mg of the beta-adrenergic receptor agonist terbutaline sulphate (Bricanyl, Astra Pharmaceuticals) from a metered dose inhaler (MDI). Compared to placebo inhalation, terbutaline produced marked bronchodilatation (mean percentage increase in FEV1 14%, P less than 0.01). Mucociliary clearance (measured by the in vivo radioaerosol technique) was assessed on three occasions--control, followed by placebo or terbutaline studies in a double-blind, cross-over manner. Particles were removed from the lung at a similar rate in all three studies. The mean (+/- s.e. mean) percentage of aerosol retained in the lungs after 6 h was 58 +/- 5%, 57% +/- 5% and 57 +/- 4% for control, placebo and drug studies respectively. It is concluded that terbutaline sulphate, given as a 1 mg acute dose, does not enhance mucociliary clearance in mild stable asthmatics, although it produces marked bronchodilatation.

Adult↗
PubMed1983

Factors influencing the size distribution of aerosols from jet nebulisers.

The size distribution of saline and bronchodilator (terbutaline) aerosol droplets generated from four widely used jet nebulisers (Acorn, Upmist, Turret, and Inspiron Mini-neb) has been measured with a Malvern 2200 Laser Particle Sizer. The mass median diameter of aerosol droplets generated by each nebuliser was strongly influenced by the driving flow rate of compressed air. By increasing the flow rate from 4 to 8 1 min-1 mass median diameters were halved (p less than 0.01) and there was an increase in the mass of aerosol within the optimum respirable range (less than 5 micron). To achieve this range the following individual flow rates were required: Turret 4 1 min-1, Acorn and Upmist 6 1 min-1, and Inspiron Mini-neb 8 1 min-1. A significant inverse relation (p less than 0.001) was found between mass median diameter and the geometric standard deviation, indicating that the aerosols were smaller but more heterodisperse at high flow rates. Changes in drug concentration had little effect on aerosol size. In 72% of the nebulisations followed to dryness there was no significant change in mass median diameter during the course of nebulisation and in the remainder it was less than 1.3 micron.

Aerosol Propellants↗
PubMed1983

Impaired tracheobronchial clearance in patients with mild stable asthma.

Tracheobronchial mucociliary clearance was measured with the radioaerosol technique in 25 patients with stable, mild asthma, none of whom was taking systemic corticosteroids. The results were compared with those obtained from a control group of 25 healthy subjects matched for age and sex. All patients and healthy subjects were non-smokers. Ventilatory function was significantly impaired in the asthmatic group, which resulted in a more central initial tracheobronchial deposition of inhaled radioaerosol than in the control group. Despite the shorter transit path along the ciliated airways for the tracer radioaerosol in the asthmatic group, mucociliary clearance was found to be significantly poorer than in the healthy control group. This may be important with respect to bronchial mucus plugging.

Adult↗
PubMed1983

Drug effects on mucociliary function.

We summarize the findings of 18 clinical studies carried out over a decade to ascertain the effect of 14 pharmacological agents on lung mucociliary clearance. These studies were carried out on a total of 172 subjects/patients and amounted to 443 individual assessments. The objective, in vivo radioaerosol technique was used to measure clearance. Bromhexine, aerosolized hypertonic saline and aminophylline enhanced the clearance of lung secretions. There was some indirect evidence of a speeding up of mucociliary clearance following the administration of prednisolone and the synthetic anticholinergic bronchodilator ipratropium, while hyoscine was found to reduce clearance. There was no effect on clearance of single doses of the beta blockers propranolol and atenolol, the beta 2 adrenergic drug terbutaline, the cholonergic drug bethanecol and the expectorants 2-mercapto-ethane-sulphonate (aerosol) and glycerol guaiacolate. Long term administration (4 - 7 days) of the beta 2 adrenergic drugs terbutaline and clenbuterol also failed to show any effect on lung mucociliary function.

Adrenal Cortex Hormones↗
PubMed1983

Measurement of bronchial mucociliary clearance.

We briefly review bronchial mucociliary clearance: one of the non-specific host defence mechanisms operating in the lungs, helping to maintain cleanliness and sterility. We describe in detail the measurement in man of bronchial mucociliary clearance by means of the radioaerosol technique used in our laboratory. We report the use of the technique for detecting impairment of tracheobronchial clearance in patients with chronic bronchitis compared with healthy control subjects. We illustrate whole lung and tracheobronchial retention curves in a patient with Kartagener's syndrome - and also preliminary results on the inter-subject variability of clearance in a small group of patients (n = 5) with this syndrome. In 24 chronic bronchitics studied on three separate occasions intra-subject variability of 6 hr tracheobronchial clearance was 17%, inter-subject variability was 25% - figures commensurate with those reported by other authors.

Aerosols↗
PubMed1983

Assessment of the forced expiration technique, postural drainage and directed coughing in chest physiotherapy.

The Forced Expiration Technique (FET), postural drainage (PD) and directed coughing have been evaluated in 10 patients with copious sputum (mean value 63.3 ml/24 h) with an inhaled radioaerosol method over a 30-min treatment period. FET alone and FET + PD (but not directed coughing) cleared more radioaerosol than during the control period (P less than 0.01). The wet weight of sputum obtained following FET, FET + PD and directed coughing were all significantly greater than control (P less than 0.01). However, sputum obtained by FET + PD was significantly greater than FET alone (P less than 0.05). Both FET and particularly FET + PD have been shown to be more effective than directed coughing alone and it is suggested that these manoeuvres should be incorporated into standard chest physiotherapy.

Adult↗
PubMed1982

Inhaled aerosols: lung deposition and clinical applications.

Although aerosol deposition in the lungs is often considered in the context of industrial hygiene, aerosols also play an important clinical role. Three principal mechanisms (inertial impaction, gravitational sedimentation and Brownian diffusion) account for the majority of aerosol deposition in the lungs. Deposition depends upon the mode of inhalation, the nature of the particles and physical characteristics of the subject inhaling the particles. Radioaerosols are widely employed in measurements of total and regional deposition, and topographical distribution may also be determined. Aerosols play an important role in the treatment of various forms of respiratory disease, with bronchodilators for the therapy of asthma being particularly important. On average only 10% of the therapeutic aerosol dose actually reaches the lungs. The rate of removal of insoluble radioaerosols deposited in the lungs may be used as an index of mucociliary transport. Aerosols are also used in a variety of other diagnostic and research procedures, particularly for ventilation scanning, alveolar clearance, measurement of alveolar permeability, and for measuring the size of pulmonary air space.

Aerosols↗
PubMed1982

Quantitative comparison of 99Tcm-aerosol and 81Krm ventilation images.

Quantitative indices are described for assessing the distribution of ventilation imaging agents (radioaerosols, in particular) within the lung. They have been applied to images obtained with 99Tcm aerosol particles (0.5-2.0 micrometer diameter) and with 81Krm gas in 12 patients with a wide range of lung function. In patients with normal lung function aerosol distribution was similar to that of 81Krm. In patients with airways obstruction, the aerosol tended to penetrate less well than 81Krm to the lung periphery and to show a less homogeneous distribution there. Quantitative analysis confirms that the aerosol technique is an effective substitute for 81Krm in patients with normal lung function. When lung function is impaired aerosol images may still be valuable particularly in confirming a diagnosis of pulmonary embolism though they must be interpreted with caution in attempting to exclude that diagnosis. We conclude that small particle radioactive aerosols provide a readily available ventilation technique for clinical ventilation-perfusion imaging.

Adult↗
PubMed1982

Lung mucociliary clearance in rheumatoid disease.

Lung mucociliary clearance rates were measured in 11 patients with rheumatoid disease and found to be unaltered when compared with those of a group of matched control subjects. The results are discussed in relation to the increased incidence of respiratory infection in patients with rheumatoid disease and also to the recently reported finding of increased airways obstruction in these patients.

Aged↗
PubMed1982

Effects of various inhalation modes on the deposition of radioactive pressurized aerosols.

The deposition of aerosol consisting of Teflon particles (mass median aerodynamic diameter 3.2 micrometers) labelled with 99Tcm has been measured in patients with obstructive airways disease. Aerosol was inhaled at 30 l min-1 with 4 s breath holding (patient group A) and at 30 l min-1 with 10 s breath holding (patient group B). A further group of patients (group C) inhaled at 90 l min-1 with 10 s breath holding. Each subject was given the aerosol during inhalation at three different lung volumes (20% VC, 50% VC and 80% VC) on three different days. The greatest whole lung, tracheobronchial and alveolar depositions occurred in group B patients, irrespective of the lung volume of aerosol actuation. By comparison, deposition was similar in groups A and C only when the aerosol was actuated at 20% VC. Whole lung deposition in groups A and B was significantly correlated both with the bronchodilator response to terbutaline sulphate aerosol administered under the same inhalation conditions and with the residence time of airborne particles in the respiratory tract. The optimum inhalation technique for a beta-adrenergic aerosol indicated by these data (slow inhalation with 10 s breath holding) confirms the results of previous studies.

Aerosols↗