Although the use of pressurised aerosol inhalers is widespread, little is known about the actual deposition of the aerosol in the respiratory tract, since this has previously been difficult to measure. We have incorporated Teflon particles (mean various conditions and for assessment of theracentages of the dose deposited on the conducting airways and in the alveoli are unknown. In this paper we present the first direct measurement of the deposition of pressurised inhalation aerosols, using an objective in vivo radioactive technique. MethodsIn order to study the deposition of pressurised aerosols, we have incorporated Teflon particles (density 2'1 gm cm-3), generated by the spinning disc technique,7 into metered-dose inhalers. A fine suspension of fluorocarbon resin (Teflon 120, Dupont) in a mixture of 40% ethanol and 99mtech-netium (Tc) was delivered to the centre of the rapidly rotating disc. The particles generated (mean diameter 2 ,tm, standard deviation 0 4 ,tm) were allowed to settle onto the base of a large airtight tank inside which the generator was situated. After collection, the 99mTc was firmly sealed within the particles by heating at 2400C for five minutes.The pressurised canisters and valves used in this study were those available commercially for the delivery of terbutaline sulphate (Bricanyl, Astra Pharmaceuticals). Eight mg of the Teflon particles were placed inside an open canister, and 2 ml of 52 on 9 May 2018 by guest. Protected by copyright.

Ocular microtremor (OMT) is a high frequency tremor of the eyes present during fixation and probably related to brainstem activity (Coakley, D. (1983). Minute eye movement and brain stem function. CRC Press, FL.). Published observations on the frequency of OMT have varied widely. Ocular microtremor was recorded in 105 normal healthy subjects using the Piezoelectric strain gauge technique. The dominant frequency content of a signal was determined using the peak counting method. Values recorded ranged from 70 to 103 Hz, the mean frequency being 83.68 Hz (S.D. +/- 5.78 Hz).

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The relative value of chest physiotherapy (including cough) and cough alone for the removal of excessive tracheobronchial secretions has been assessed in six patients with stable chronic obstructive lung disease. After labelling with inhaled radioactive tracer particles, clearance of secretions from selected central and peripheral lung regions was followed with a gamma camera linked to a computer. Cough alone and chest physiotherapy (including cough) were equally effective in the enhancement of central lung clearance. Physiotherapy but not cough alone accelerated peripheral lung clearance (p < 0 05). Sputum yield was greater during physiotherapy than during cough (p < 0-05). These findings confirm the value of chest physiotherapy and high-light the limitation of cough in patients with excessive tracheobronchial secretion and impaired mucociliary clearance.Since the description of simple manoeuvres in 1915,1 chest physiotherapy has become established in the treatment of chronic lung conditions associated with excessive tracheobronchial secretions. Objective evidence for its value, however, is both lacking and controversial.2 3 Using the radioaerosol tracer technique,4 we were able to establish the efficacy of the various combined manoeuvres of the chest physiotherapist with cough in aiding the removal of excessive secretions from central, intermediate and peripheral lung regions. Oldenburg et al,5 however, using similar techniques subsequently produced data suggesting that cough alone was as effective as chest physiotherapy combined with cough. We have therefore examined critically the relative roles of cough alone and chest physiotherapy with cough in enhancing regional lung clearance. MethodsSix patients (three men and three women) with stable chronic airway obstruction and regular daily expectoration took part in the study. Written informed consent from the patients and approval of the local ethics committee were obtained. Three patients had chronic obstructive bronchitis and three bronchiectasis. Three were non-smokers, two exsmokers, and one a current smoker. Their physical characteristics and ventilatory function are summarised in table 1.The labelling of tracheobronchial secretions by an aerosol containing uniform 5 ,um polystyrene particles firmly tagged with 99mTc (half-life 6 h) has been fully described previously.6 After the controlled inhalation of radioaerosol, the clearance of particles deposited throughout the tracheobronchial tree was monitored by external gamma counting using a Nuclear Enterprises Mark III gamma camera. Counts were collected from the anterior chest over five-minute periods at halfhourly intervals from 30 to 150 minutes after

ABSTRACr 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.Asthma is a disease characterised by reversible airway obstruction' caused by mucosal oedema, bronchial smooth muscle contraction, and hypersecretion of mucus.2 Death from "ciliary insufficiency" and mucus plugging of small airways in asthmatics has been known for many years.3 When the asthma is mild but variable, however, the roles of the cilia and of mucus and its clearance are ill defined. Mucociliary function in asthmatics has been examined by only a few investigators,4-9 who have confined their measurements primarily to the proximal airways of the lungs. The numbers of patients studied are small and the results are conflicting. We have therefore assessed tracheobronchial mucociliary clearance in a moderately large group of patients with mild, stable asthma and compared it with that in a group of matched healthy subjects. MethodsThe objective non-invasive radioaerosol technique'0 was used to measure whole-lung mucociliary clearance. Polystyrene particles 5 ,um in diameter tagged with the radionuclide technetium-99m (99mTc) (T112 = 6 h) were generated by means of a spinning top" generator located within an airtight tank. The radioaerosol was inhaled from the tank by each subAddress for reprint requests: Dr SW Clarke, Department of Thoracic Medicine, Royal Free Hospital, London NW3 2QG. Accepted 10 December 1982 ject or patient via a mouthpiece (a nose clip being worn) in eight discrete breaths starting from functional residual capacity and limited to 450 ml in volume by a Krogh spirometer. Inspiratory flow was measured by a pneumotachograph interposed between the spirometer and the tank. Each inhalation was followed by a three-second breath-holding pause to enable particles to deposit in the lungs by sedimentation. At the end of the inhalation procedure a water mouthwash and drink were used to clear the oropharynx and oesophagus of deposited radioaerosol.