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The distribution of deposited dust between the alveolar and tracheobronchial regions of the lung has been measured for 2 µm (12 subjects) and 5 µm (50 subjects) unit relative density particle diameters by the radioisotope tracer technique. For the 2 and 5 µm particles 31 ± 6.6% and 54 ± 1.9% of the initial lung burden were deposited in the tracheobronchial region: the mean difference was highly significant ( < 0.001). Standardization of these and other published values for particle size and density, tidal volume and flow rate of inhalation and interval between inhalation and assessment of retention resulted in a considerable reduction in the scatter. The regression of the square of aerodynamic particle diameter ( on percentage tracheobronchial deposition (%TB) after standardization was %TB = 20.7 + 0.6 . [ABSTRACT FROM PUBLISHER]

The method using radioactive tracer particles has been applied to study the effect of the mode of inhalation of aerosols on the depth of deposition in the lungs of 50 patients with airways obstruction. The findings show that the penetration of particles is directly related to: (1) volume inspired per breath (VI); (2) forced expiratory volume in one second (FEV1); and inversely related to (3) flow rate during inhalation (V). In mathematical terms, alveolar deposition (%) = 40-3 (VI)+10-98 (FEV1)--0-75 (V)+40-4; for this regression F = 4-41 and P less than 0-01. [ABSTRACT FROM PUBLISHER]

The mucolytic efficacy of S-carboxymethylcysteine has been assessed in a double-blind crossover trial in 16 patients with chronic obstructive bronchitis. No significant difference was found between drug and placebo after four or seven days' treatment in the rate of clearance of secretions from the lung. This was measured by external counting of previously inhaled polystyrene tracer particles tagged with technetium-99m (99mTc). Lateral scans across the right chest after inhaling the aerosol showed equal penetration of particles towards the periphery of the lung in drug and placebo runs; this indicated that the airways had not been cleared of mucus by the drug. There was no significant difference between drug and placebo runs in the number of coughs or the weight and radioactive content of sputum voided or raised at the end of the run by chest percussion and postural drainage. Ventilatory capacity was not significantly changed nor was there any subjective improvement in the patients as a result of taking the drug. [ABSTRACT FROM PUBLISHER]

, , 742-747. The effect of guaiphenesin (administered as Robitussin) on mucociliary clearance has been assessed in 15 subjects from the rate of removal from the lung of previously inhaled radioactive tracer particles. The guaiphenesin was compared with a positive control preparation consisting of the guaiphenesin vehicle only in two double-blind crossover trials. The first trial examined eight aged `healthy' volunteer subjects and the second trial examined seven chronic bronchitic patients. Sequential gamma counts were made from the whole lung by scintillation counters for 6 hours after inhalation and the chest was also scanned rectilinearly. In the first 5 hours after inhalation the mean rate of removal of particles and therefore of secretions was faster after guaiphenesin than after the control preparation. This difference was not statistically significant in the healthy volunteers but achieved significance (P <0·05) in the chronic bronchitic patients. Lung scans after inhaling the tracer aerosol indicated that on average the initial penetration of the particles into the lung was similar in the guaiphenesin and control runs. The faster clearance after guaiphenesin was unlikely to be due to bulk movements of mucus caused by coughing since the mean frequency of coughing during the experiment was somewhat less after the drug. [ABSTRACT FROM PUBLISHER]