Distribution Of Radioaerosol Research Articles

Domiciliary humidification improves lung mucociliary clearance in patients with bronchiectasis

Inspired air humidification has been reported to show some benefit in bronchiectatic patients. We have investigated the possibility that one effect might be to enhance mucociliary clearance. Such enhancement might, if it occurs, help to lessen the risks of recurrent infective episodes. Using a radioaerosol technique, we measured lung mucociliary clearance before and after 7 days of domiciliary humidification. Patients inhaled high flow saturated air at 37 degrees C via a patient-operated humidification nasal inhalation system for 3 h per day. We assessed tracheobronchial mucociliary clearance from the retention of (99m)Tc-labelled polystyrene tracer particles monitored for 6 h, with a follow-up 24-h reading. Ten out of 14 initially recruited patients (age 37-75 years; seven females) completed the study (two withdrew after their initial screening and two prior to the initial clearance test). Seven patients studied were non-smokers; three were ex-smokers (1-9 pack-years). Initial tracer radioaerosol distribution was closely similar between pre- and post-treatment. Following humidification, lung mucociliary clearance significantly improved, the area under the tracheobronchial retention curve decreased from 319 +/- 50 to 271 +/- 46%h (p < 0.07). Warm air humidification treatment improved lung mucociliary clearance in our bronchiectatic patients. Given this finding plus increasing laboratory and clinical interest in humidification mechanisms and effects, we believe further clinical trials of humidification therapy are desirable, coupled with analysis of humidification effects on mucus properties and transport.

The effects of one-week fluticasone propionate inhalation therapy for Tc-99m DTPA radioaerosol distribution in asthma of children: a preliminary report.

This study evaluated the effects of fluticasone propionate inhalation therapy for the distribution pattern of Tc-99m DTPA radioaerosols in 10 children with asthma. The homogeneous degree of depositing Tc-99m DTPA radioaerosol was evaluated using a modified standard score system over the bilateral lungs. The baseline scores were calculated from Tc-99m DTPA radioaerosol inhalation lung scintigraphy before inhalation therapy (100 microg fluticasone propionate two times daily for one week), and the scores were recalculated after inhalation therapy to evaluate the effects of one-week of fluticasone propionate inhalation therapy for Tc-99m DTPA radioaerosol distribution patterns. After one week of fluticasone propionate inhalation therapy, the scores were decreased in all of the 10 children, which may mean that the bronchial constriction degree due to asthma is decreased. In addition, there was a significantly statistical difference in the scores before and after one-week fluticasone propionate inhalation therapy (p < 0.05). In conclusion, one-week fluticasone propionate inhalation therapy could significantly improve the bronchial constriction due to asthma in children based on the evidence of Tc-99m DTPA radioaerosol inhalation lung scintigraphic findings.

Fractal analysis of nuclear medicine images for the diagnosis of pulmonary emphysema: interpretations, implications, and limitations.

The purpose of this study was to investigate, on images obtained in nuclear medicine examinations, the physical meanings and consequent implications of fractal analysis developed in a recent study that was reported to be effective in quantifying the heterogeneous distribution of carbon particle radioaerosol in the lungs. Fractal dimensions were computed for 108 sets of radionuclide imaging data from 28 patients according to the methods in a previous report, and were then correlated with the ratio of tissue areas segmented at two thresholds (15% and 35% of maximal radioactivity). Fractal dimension was found to linearly correlate with the ratio natural logarithm of tissue areas segmented at two different threshold levels (n = 108, r = 0.999), with regression slope accurately predicted (error = 0.06%). Bland-Altman analysis showed that fractal dimensions ranging from 0.2 to 1.9 can be explained by this area ratio with disagreement of only 5.13% at two standard deviations; thus, fractal dimension seems to be an over-simplified parameter unrelated to spatial heterogeneity of radioaerosol distribution. The analysis of this study suggested that the fractal dimension defined in a previous report was limited to the indication of the percentage area of low-radioactivity regions with respect to total tissue area in the image. Because the fractal dimension partially reflects, but is not specific to, a certain degree of focal spots of low radioactivity, we suggest using fractal analysis in clinical practice only with careful control and thorough understanding of the physical meanings.

Using 99mTc-DTPA Radioaerosol Inhalation Lung Scintigraphies to Detect the Lung Injury Induced by Consuming Sauropus androgynus Vegetable and Comparison with Conventional Pulmonary Function Tests

Consuming Sauropus androgynus, a Malaysian plant, to reduce body weight began to become fashionable in Taiwan in 1994. According to some reports, people consuming this vegetable developed lung injuries. From July to November 1995, there were 81 nonsmoking women admitted to our hospital. Thirty-six cases had respiratory symptoms/signs and the remaining 45 had no symptoms/signs. We investigated these patients with pulmonary function tests (PFT) and technetium-99m DTPA radioaerosol inhalation lung scintigraphies (DTPA lung scan), a test to evaluate the lung ventilation and alveolar epithelial permeability. Eighteen patients had abnormal results in PFT, including obstructive type (n = 17), restrictive type (n = 5), and both (n = 4). There were 33 patients with abnormalities in DTPA lung scans, including unhomogeneous deposition of DTPA radioaerosols (n = 19), faster clearance of radioaerosols from lung (n = 26), and both (n = 12). Analyzing the results, we found that the patients with respiratory symptoms had a higher incidence of abnormal results of PFT and DTPA lung scans than the patients without respiratory symptoms (p < 0.05). Besides, we found that the DTPA lung scan was more sensitive than chest x-ray and PFT in detecting the lung injuries related to the consumption of S. androgynus (p < 0.05). Consuming S. androgynus can result in symptomatic or asymptomatic lung injuries, manifested as obstructive or restrictive ventilatory impairment, unhomogeneous radioaerosol distribution, and increased alveolar epithelial permeability. In addition, measurement of the ^99mTc-DTPA clearance is the most sensitive test to detect the lung injuries caused by consuming S. androgynus.

No effect of gender on lung mucociliary clearance in young healthy adults

Lung mucociliary clearance (LMC) depends on age and it is adversely affected by cigarette smoking. When using the radioaerosol technique for measuring LMC the initial site of deposition of the radioaerosol within the lungs affects its rate of removal. Whether there is a difference in gender for LMC is still an open question. Forty-one (20 female, 21 male) healthy, non-smoking subjects had their lung mucociliary clearance measured using an objective, non-invasive radioaerosol technique. The male and female groups were closely matched for initial distribution of the radioaerosol. There was no statistical significant difference between males and females in the rate of clearance of inhaled radioaerosol over a 6 h observation period. When comparing the LMC of two groups although it is important to match them for age, smoking habits and initial topographical distribution of the tracer radioaerosol it does not seem essential to also match the two groups for gender.

Inhaled frusemide does not affect lung mucociliary clearance in healthy and asthmatic subjects

Inhaled frusemide has been shown to protect against the bronchoconstrictor effect of several inhaled agents in asthmatic subjects by mechanism(s) that are unclear. Since loop diuretics can modulate Cl- transport in the airway epithelium, frusemide may alter the quality and/or the quantity of the periciliary layer, which in turn may affect lung mucociliary transport. We investigated the effect of a single inhalation of nebulized frusemide (40 mg) on lung mucociliary clearance in four healthy subjects and in seven stable, mild asthmatics using an objective radioaerosol technique. Frusemide or placebo was inhaled in a double-blind, randomized, cross-over manner half an hour after the inhalation of 5 microns polystyrene particles labelled with 99mTc, used for assessing mucociliary clearance. The pulmonary function and initial radioaerosol distribution were similar between frusemide and placebo runs within each of the two study groups. The areas under the tracheobronchial retention curves over the 6 h observation period were similar between frusemide and placebo runs for both groups. Our findings show inhaled frusemide, at a dose known to inhibit bronchoconstrictor responses, does not affect lung mucociliary clearance.

Distribution of radioactive aerosol in the airways of children and adolescents with bronchial hyper-responsiveness.

The purpose of this study was to examine the relationship between the pulmonary distribution of inhaled radioaerosol, bronchial responsiveness, and lung function in children and adolescents. The participating subjects (n = 39) were divided into three groups: (1) 14 asthmatics with bronchial hyper-responsiveness (BHR), (2) five non-asthmatic subjects with BHR, and (3) 20 controls without BHR. Pulmonary distribution of [99Tcm) albumin radioaerosol, maximal expiratory flow when 25% of forced vital capacity remain to be exhaled (MEF25), and bronchial responsiveness to inhaled histamine were measured. Twenty subjects (52%) had irregular central distribution and 19 subjects (48%) had regular distribution of radioaerosol in their lungs. No difference in distribution of radioaerosol was found between the three groups of children. The median MEF25 among non-asthmatic subjects (80% predicted) was lower than that found in controls (92% predicted) but higher than that found in asthmatic subjects (55% predicted). A relationship was found between reduced flow at the peripheral airways, as indicated by MEF25 and the degree of central distribution of radioaerosol. Furthermore, subjects with irregular central distribution of radioaerosol had an increased degree of bronchial responsiveness. In conclusion, children and adolescents who have flow rates in the peripheral airways or increased degree of bronchial responsiveness tend to have abnormal distribution of radioaerosols.

Influence of breathing pattern on lung deposition and bronchodilator response to nebulised salbutamol in patients with stable asthma.

The influence of breathing pattern on lung deposition and bronchodilator response to nebulised salbutamol is uncertain. Three different breathing patterns were assessed in eight patients with chronic stable asthma. Salbutamol solution (2.5 mg in 4 ml) mixed with technetium-99m labelled human serum albumin was nebulised by an Acorn nebuliser at a flow rate of 6 litres a minute. Particles with a mass median aerodynamic diameter of 4.8 microns were produced for inhalation by (a) tidal breathing, (b) six tidal breaths followed by three deep breaths, and (c) six tidal breaths followed by three deep breaths with a five second breath hold after each breath. Each breathing pattern was continued for four minutes. There was no significant difference in the percentage of radioaerosol deposited in the lung or in the distribution of radioaerosol within the lung as assessed by gamma camera imaging. Changes in bronchodilator responses as measured by peak expiratory flow rate (PEF), forced expiratory volume in one second (FEV1), and forced vital capacity (FVC) 30, 45, and 60 minutes after inhalation were similar for the three studies. The mean (SEM) maximum percentage change in FEV1 was 44 (7.1), 47 (9.2), and 51 (8.4) for studies 1, 2, and 3 respectively. The percentage of nebulised solution deposited in the body was also similar for the three breathing patterns--that is, 11-13%, of which 98% entered the lung. This study shows that inhaling a nebulised aerosol by tidal breathing, the simplest method, is as effective as tidal breathing with deep breaths with or without a breath hold.

Regional mucociliary removal of inhaled particles in smokers with small airways disease.

Quantitative radioaerosol lung imaging was performed in 30 asymptomatic smokers selected on the basis of abnormal findings in pulmonary function tests of small airways. Regional clearance rates of inhaled 99mTc-labelled human serum albumin minimicrospheres (HAMM) were determined over upper, middle, lower, central, and peripheral anterior lung zones. In contrast with the findings in 20 nonsmokers without evidence of small airways dysfunction significant mucociliary clearance delay occurred in the peripheral and upper pulmonary regions. An aerosol distribution index (ADI) measures the homogeneity of distribution of inhaled particles in the lung. A significant difference in the mean values of ADI was found, indicating an abnormal uneven radioaerosol distribution pattern in the smokers with small airways disease.

Deposition of pressurized suspension aerosols inhaled through extension devices.

Only a small fraction of the dose from a pressurized aerosol inhaler reaches the lung, because most is deposited on the upper airways by inertial impaction. We have investigated the effects on aerosol deposition of two spacer devices (a 10-cm tube and a 22-cm cone) by incorporating teflon particles (mass median aerodynamic diameter, 3.2 micrometer) labeled with 99mTc into pressurized canisters. Ten subjects with obstructive airway disease inhaled the aerosol in a controlled manner from a conventional actuator alone or in combination with the tube or the cone. Radioaerosol distribution was measured using a shadowshield whole body counter. Deposition on the conducting airways was significantly improved by both spacers, but alveolar deposition was unchanged. Initial oropharyngeal deposition was reduced by both spacers in all 10 patients. We conclude that the spacer devices may have a role to play in aerosol therapy by increasing drug availability to the lung, while at the same time decreasing unwanted drug deposition in the oropharynx.