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Biomedical subjects

D Pavia

Publications and source records attributed to D Pavia.

At least 55 records · Page 3Linked to original sources
PubMed1986

Inhaled smoke volume, puffing indices and carbon monoxide uptake in asymptomatic cigarette smokers.

Nine asymptomatic smokers each smoked one cigarette of their usual brand on four separate occasions. The inhaled smoke volume was measured by tracing the smoke with the inert gas 81Krm. Puffing indices were recorded by using an electronic smoking analyser and flowhead/cigarette holder. The expired air carbon monoxide concentration was measured immediately before and within 5 min of finishing smoking. The inhaled smoke percentage (total inhaled smoke volume/total puff volume) averaged 46% to 85% in different subjects. Neither the mean inhaled smoke volume per puff nor the total inhaled smoke volume per cigarette was significantly correlated with any of the puffing indices. Smokers took significantly smaller and shorter puffs, left longer between puffs and inhaled less smoke as the cigarette was smoked (P less than 0.01), although the proportion of the puff which was subsequently inhaled did not change significantly. There was no significant intra-subject difference in any index from one visit to another.

Adolescent↗
PubMed1986

Comparison of nasal and tracheobronchial clearance by similar techniques in normal subjects.

Nasal and tracheobronchial mucociliary clearance have been compared in 10 healthy subjects. Nasal clearance was measured by monitoring the rate of removal of 2 microns diameter Teflon particles, labelled with 99mTc, which had been placed in the anterior part of the nose. Tracheobronchial clearance was measured with an objective radioaerosol technique, 5 microns diameter polystyrene particles being used. With these comparable techniques there was a close correlation between the nasal mucociliary clearance rate and both the area under the tracheobronchial clearance curve from 0 to 6 hours after radioaerosol inhalation (rs = -0.94, p less than 0.001) and the area under the tracheobronchial clearance curve from 0 to 2.5 hours after inhalation (rs = -0.79, p less than 0.01). The rate of clearance of small particles from the nose may thus be a useful guide to tracheobronchial clearance in healthy individuals.

Adult↗
PubMed1986

Effect of four weeks' high dose ipratropium bromide treatment on lung mucociliary clearance.

In a randomised, double blind crossover study the effect of high dose ipratropium bromide (200 micrograms three times daily given by metered dose inhaler for four weeks) on lung mucociliary clearance and on the wet weight and mean apparent viscosity of sputum was compared with that of placebo. Six smokers, six ex-smokers, and three non-smokers (12 men and three women, median age 60 years) were studied. Eight subjects had chronic obstructive lung disease (median FEV1 46% predicted) and seven had asthma (FEV1 70% predicted). Seven subjects produced sputum regularly, two of whom had asthma. Clearance of secretions was measured by an inhaled radioaerosol technique. The number of coughs and the wet weight, radioactive content, and mean apparent viscosity of sputum produced during the six hour observation period were recorded, as was the mean wet weight of sputum produced during the last two 24 hour periods ending each treatment. Comparison with placebo showed that treatment with high dose ipratropium bromide was associated with a significant increase in the penetration index of inhaled particles, but there was no significant change in alveolar deposition of particles or in tracheobronchial clearance, uncorrected or corrected for sputum expectorated. The wet weight of sputum produced, its radioactive content, and mean apparent viscosity were similar after treatment with ipratropium bromide and placebo. These results show that high dose inhaled treatment with the synthetic anticholinergic bronchodilator ipratropium bromide for four weeks is not associated with detectable modification of the clearance of secretions from the lungs, or of sputum volume or viscosity.

Adult↗
PubMed1986

Effect of selective and non-selective beta blockade on pulmonary function and tracheobronchial mucociliary clearance in healthy subjects.

A controlled, double blind, crossover study was carried out to ascertain the effect of single doses of selective (100 mg atenolol) and non-selective (160 mg propranolol) beta blocker on pulmonary function and tracheobronchial mucociliary clearance. The study group comprised 12 healthy, young subjects. Adequate and comparable blockade was achieved with both drugs, the administration of which resulted in significantly lower pulse rates (at least up to eight hours after administration of the drug) and systolic blood pressures (three hours after drug administration) than were found with placebo. Small (of the order of 5%) but nevertheless statistically significant falls in FEV1 and forced vital capacity accompanied the administration of both beta blockers (but not the placebo) and were measurable up to eight hours after administration of the drug. Indices of pulmonary function had returned to normal by the next day. Peak expiratory flow and indices of small airways function remained unaltered after beta blockade. Mean tracheobronchial mucociliary clearance was depressed after administration of both beta blocking drugs, although the reduction was significant (p less than 0.05) only when propranolol was compared with placebo.

Adult↗
PubMed1986

Effect of aerosol particle size on bronchodilatation with nebulised terbutaline in asthmatic subjects.

The bronchodilatation achieved by the beta 2 agonist terbutaline sulphate given as nebulised aerosol from different devices has been measured in seven patients with mild asthma (mean FEV1 76% predicted) over two hours after inhalation. The subjects were studied on four occasions. On three visits they received 2.5 mg terbutaline delivered from three different types of nebuliser, selected on the basis of the size distribution of the aerosols generated; and on a fourth (control) visit no aerosol was given. The size distributions of the aerosols expressed in terms of their mass median diameter (MMD) were: A: MMD 1.8 microns; B: 4.6 microns; C: 10.3 microns. The aerosols were given under controlled conditions of respiratory rate and tidal volume to minimise intertreatment variation. Bronchodilator response was assessed by changes in FEV1, forced vital capacity (FVC), peak expiratory flow (PEF), and maximal flow after expiration of 50% and 75% FVC (Vmax50, Vmax25) from baseline (before aerosol) and control run values. For each pulmonary function index all three aerosols gave significantly better improvement over baseline than was seen in the control (p less than 0.05) and had an equipotent effect on FEV1, FVC, and PEF. Aerosol A (MMD 1.8 microns) produced significantly greater improvements in Vmax50 and Vmax25 than did B or C (p less than 0.05). These results suggest that for beta 2 agonists small aerosols (MMD less than 2 microns) might be advantageous in the treatment of asthma.

Adult↗
PubMed1986

Functional small airways defence in symptomless cigarette smokers.

Smoking induced changes in the secretory cells of bronchiolar epithelium by facilitating secretion of cross linked glycoprotein mucus may influence the efficiency of mucus-cilia coupling. The functional impact on mucociliary transport in small (peripheral) airways has been studied by comparing data on aerosol deposition and clearance from symptomless cigarette smokers (30 tests, 18 subjects) with data from age matched non-smokers (30 tests, 19 subjects). Gamma camera images, assessed in terms of a penetration index comparing peripheral with inner zone deposition, indicated closely similar initial deposition in the two groups. Alveolar deposition, however, assessed in terms of particle retention at 24 hours, was significantly (p less than 0.01) less in the smokers. Given the similarity of initial deposition, this implies that an increased proportion of small conducting airways are protected by mucociliary defence in the smokers' lungs. Clearance from conducting airways of the peripheral zone in tests with relatively high peripheral deposition (14 tests on smokers, and 12 on non-smokers) nevertheless proceeded at the same rate in smokers as in non-smokers.

Adult↗
PubMed1986

Radioaerosol assessment of mucociliary clearance: towards definition of a normal range.

Radioaerosol measurements of mucociliary clearance have been assessed in relationship to depth of particle penetration into the lung. The tests analysed were performed with 5 microns diameter 99Tcm particles inhaled under standardised conditions but at varying inhalation flow rates. Aerosol lung penetration was assessed by (i) penetration index (PI), a ratio of outer to inner zone radioactivity determined from a gamma camera image; and (ii) alveolar deposition (AD), a measure of activity retained at 24 hours and taken to represent deposition distal to the ciliated airways. Clearance rates in 30 tests on 19 normal non-smokers under the age of 50 varied significantly with aerosol inhalation flow rate, PI and AD. A normal range varying with PI is proposed although normal inter-subject variability remains high even after allowance for PI. Nevertheless 8 out of 12 patients with stable asthma and 21 out of 24 patients with chronic bronchitis demonstrated slow clearance lying outside the PI-based normal range.

Adult↗
PubMed1985

Factors affecting the 'alveolar deposition' of 5 microns inhaled particles in healthy subjects.

The long-term lung retention fraction of insoluble inhaled aerosols--'alveolar deposition' (AD)--may be assessed in healthy subjects from lung retention at 24 h. For persons inhaling long-lived hazardous particles this represents their long-term dose commitment; in clinical tests of mucociliary function with inert particles it represents the fraction of particles not available to act as tracers of mucus transport. AD (24 h retention) was measured with 99Tcm-labelled, 5 microns diameter polystyrene particles which were inhaled at various flow rates; a post-inspiratory breath-hold of 3 s maximised AD efficiency. In 32 tests on young non-smokers (age less than or equal to 30 y), AD was significantly related to flow rate (r = 0.61, p less than 0.001). Intersubject variability about the regression line was not related to variability of airway calibre as detected by conventional spirometry. Significant dependence of AD on flow rate but not lung function was found in young asymptomatic cigarette smokers and in older non-smokers. In older smokers (age greater than 30 y) dependence on flow rate was significant but dependence on lung function equivocal. Smoking was associated with decreased AD. A considerable intersubject variability of AD could not be attributed to variability of inhalation conditions or lung function. AD should therefore be directly measured whenever possible in occupational hygiene assessments and clinical aerosol applications.

Adult↗
PubMed1985

Tracheobronchial mucociliary clearance in asthma: impairment during remission.

Tracheobronchial mucociliary clearance was measured in eight non-smoking patients with asthma in complete remission. The patients were symptom free and required no medication whatsoever for one to six months before assessment. Mucociliary clearance was measured with an objective, radioaerosol technique. For comparison, mucociliary clearance of eight non-smoking, healthy subjects with physical characteristics and pulmonary function similar to those of the asthmatics was also measured on two occasions. In their first assessment the healthy subjects inhaled the tracer radioaerosol under experimental conditions similar to those used for the asthmatics; in the second assessment they inhaled the radioaerosol rapidly to simulate the asthmatic pattern of deposition. Under similar experimental conditions the radioaerosol was deposited more proximally in the asthmatic subjects than in the normal subjects and the difference was statistically significant (p less than 0.01). When, however, the depth of radioaerosol lung penetration was similar in the two groups, there was evidence of a significantly (p less than 0.01) poorer mucociliary clearance six hours after radioaerosol inhalation in the asthmatic than in the healthy group. These findings raise the question whether asthma ever remits completely.

Adult↗
PubMed1985

Increase in mucociliary clearance in normal man induced by oral high frequency oscillation.

Data on the effect on mucociliary clearance of oral high frequency oscillation is conflicting. By means of a technique to superimpose high frequency oscillation on tidal breathing, changes in mucociliary clearance during high frequency oscillation were studied in seven normal non-smokers by monitoring the clearance of inhaled radiolabelled aerosol from the lungs. After inhalation of 5 microns technetium 99m labelled particles under controlled conditions, whole lung clearance was monitored by scintillation counters half hourly for six hours with a final count at 24 hours, from which tracheobronchial deposition and clearance could be calculated. Control and high frequency oscillation studies were performed on separate days in random order. Oral high frequency oscillation was applied by a bass loudspeaker through a mouthpiece to superimpose sinewave oscillations (RMS input pressure 1.2 cm H2O, mean pressure zero) on normal breaths. On high frequency oscillation days 30 minutes of oscillation alternated with 30 min of rest. Between 3 and 4.5 hours mucociliary clearance with high frequency oscillation exceeded control by about 10% (p less than 0.05). The mean time taken to eliminate 90% of deposited radioaerosol from the tracheobronchial tree fell from 4 hours 50 minutes (range 1 h 52 min-6 h 50 min) during control to 3 hours 43 minutes (range 2 hr 28 min-5 hr 54 min) during the high frequency oscillation run (p less than 0.05). Possibly this comfortable, simple technique would be of therapeutic benefit to patients with chronic sputum retention and merits further investigation.

Adult↗
PubMed1985

Assessment of percussion, vibratory-shaking and breathing exercises in chest physiotherapy.

While gravity-assisted positions (postural drainage) and the forced expiratory technique are known to promote sputum clearance, the additional value of percussion, vibratory-shaking and breathing exercises individually in chest physiotherapy is uncertain. These modalities have been evaluated in 8 patients with copious sputum production (mean: 44 g/day), using an inhaled radioaerosol technique. Tracheobronchial clearance was unaffected by the addition of either vibratory-shaking or percussion with and without breathing exercises to postural drainage. There was however a significant (p less than 0.01) increase in the dry weight of sputum produced during each of these treatments. The combination of postural drainage used in conjunction with the forced expiration technique is responsible for the majority of mucus mobilisation and should form the basis of routine chest physiotherapy programmes; the other modes appear to be of lesser value.

Breathing Exercises↗
PubMed1985

Effect of oral N-acetylcysteine on mucus clearance.

Oral N-acetylcysteine has been advocated as a mucolytic agent for use in chronic bronchitis. We have investigated the effects of regular use of this drug at a dose of 200 mg thrice daily for 4 weeks in nine patients with chronic bronchitis on lung function, lung mucociliary clearance and sputum viscosity in a controlled, double-blind, crossover study. No significant differences were found in lung function, mucociliary clearance curves or sputum viscosity following treatment with N-acetylcysteine compared to control or placebo measurements.

Acetylcysteine↗
PubMed1985

Effects of iodopropylidene glycerol on tracheobronchial clearance in stable, chronic bronchitic patients.

We carried out a randomised, double-blind, two-period crossover study in 15 stable, chronic bronchitics to ascertain the effect on tracheobronchial clearance (TBC) of 1 week's treatment with iodopropylidene glycerol (IPG-Organidin), two tablets four times daily compared to matched placebo. TBC was measured by radioaerosol technique. The drug did not significantly alter TBC in the group as a whole but did significantly enhance TBC in 6 patients who expectorated during both placebo and IPG 6-h observation periods. In 4 patients who did not expectorate in either period no change in TBC occurred. In 10 patients who expectorated in either one or both observation periods, a significant positive correlation was found between an index of the patients' sputum produced and improvement in TBC following IPG treatment. IPG can be an effective expectorant in patients with mucus hypersecretion and particularly so in patients with copious sputum production.

Aged↗
PubMed1984

Krypton-81m and 5-micron radioaerosol images in asymptomatic asthma: a blind marking assessment.

Gamma camera images recorded during tidal breathing of krypton-81m (81mKr) and after slow inhalation of 99mTc-labelled monodisperse 5-micron polystyrene particles were assessed by three independent observers. Results from 20 symptom-free asthmatic subjects, all with a forced expiratory volume in 1 s (FEV1) at least equal to 75% of the predicted value, were compared with those from 16 healthy non-smoking volunteers. Blind marking scores for the 81mKr images of the asthmatic subjects related significantly to small airways function. Radioaerosol abnormalities in the asthmatic subjects included excessive deposition of the radioaerosol in the central airways and related significantly to small airways function. Radioaerosol imaging performed better than 81mKr imaging at differentiating asthmatic from normal subjects. Radioaerosol abnormalities in patients with poor small airways function probably reflect (1) uneven distribution of ventilation to different regions of the lung periphery and (2) changed patterns of airflow in the bronchial tree. Image abnormalities detected in routine clinical ventilation imaging - with 81mKr or radioaerosol - may sometimes be caused by small airways dysfunction even when the patient's FEV1 is normal.

Adult↗
PubMed1984

Radionuclide demonstration of ventilatory abnormalities in mild asthma.

The distribution of 5 microns 99mTc aerosol particles deposited in the lungs was compared with that of 81mKr gas in 20 asthmatic subjects (FEV1.0 greater than or equal to 75% predicted) whose asthma was mild or in remission. Sixteen normal non-smokers and 14 'normal' cigarette smokers were studied as control subjects. Radioaerosol lung penetration in the 'normal' smokers was the same as in the normal non-smokers but was reduced in the asthmatic subjects. Radioaerosol penetrated better than 81mKr to the lung apices of normal non-smokers and asthmatic subjects; it penetrated better than 81mKr to the lung bases of the asthmatic subjects. Uneven distribution of aerosol relative to 81mKr related strongly to maximal mid-expiratory flow rate (MMFR) in the asthmatic subjects. Aerosol deposition abnormalities in symptom-free asthmatic subjects may reflect basal airways closure at functional residual capacity and abnormal patterns of lung filling.

Adult↗