The nasal distribution of metered dose inhalers

The intranasal distribution of aerosol from a metered dose inhaler has been assessed using a radiotracer technique. Inhalers were prepared by adding 99Tcm-labelled Teflon particles (simulating the drug particles) to chlorofluorocarbon propellants, and scans of the head (and chest) taken with a gamma camera. Ten healthy subjects (age range 19-29 years) each performed two radioaerosol studies with the inhaler held in two different ways: either in a single position (vial pointing upwards) or in two positions (vial pointing upwards and then tilted by 30 degrees in the sagittal plane). The vast majority of the dose (82.5 +/- 2.8 (mean +/- SEM) per cent and 80.7 +/- 3.1 per cent respectively for one-position and two-position studies) was deposited on a single localized area in the anterior one-third of the nose, the initial distribution pattern being identical for each study. No significant radioaerosol was detected in the lungs. Only 18.0 +/- 4.7 per cent and 15.4 +/- 4.1 per cent of the dose had been removed by mucociliary action after 30 minutes, and it is probable that the remainder had not penetrated initially beyond the vestibule. Since the deposition pattern was highly localized and more than half the dose probably failed to reach the turbinates it is possible that the overall effect of nasal MDIs is suboptimal for the treatment of generalized nasal disorders.

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.

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.

Choice of nebulisers and compressors for delivery of carbenicillin aerosol

Although aerosol antibiotics have been used successfully to treat respiratory tract infection in patients with cystic fibrosis, little information exists concerning the correct nebulisation technique for antibiotic solutions. We have measured aerosol output, droplet size and nebulisation time for 1 g carbenicillin (Pyopen, Beechams) diluted with 3 ml or 4 ml water for injection and delivered from six brands of jet nebuliser (Cirrus, DeVilbiss, Inspiron, Turret, Unicorn and Upmist). Three relatively weak compressors (Medix Traveller, Medic-Aid PortaNeb 50 and Inspiron) and three more powerful compressors (Medix WOBL, Medix Maxi mark I and Gast) were used as driving sources. Maxi and Gast compressors increased the quantity of "respirable" (less than 5 micron diameter) carbenicillin aerosol, and reduced nebulisation times; with the weaker compressors, nebulisation times (up to 50 min) were unacceptably long. The Turret nebuliser proved to be the most efficient, but several other brands would also be acceptable if used with a powerful compressor.

Sensory mechanisms in the upper respiratory tract affect the inhalation of cigarette smoke in man

Cigarette puffing parameters (puff volume, puff duration, number of puffs, total smoking time) and inhaled smoke volume (by a radiotracer technique) have been measured in a group of 11 asymptomatic smokers, once after topical anaesthesia of the upper airways and once without anaesthesia. Topical anaesthesia significantly reduced the mean inhaled smoke volume per puff for the group from 41.1 ml to 30.6 ml (P less than 0.05) and the total inhaled smoke volume from 575 ml to 528 ml (P = 0.05), but cigarette puffing parameters were unchanged. It is concluded that stimulation of upper airway sensory receptors, probably sensitive to nicotine, may be an important mechanism in determining the amount of cigarette smoke inhaled by smokers.

Droplet size distributions of nebulised aerosols for inhalation therapy

Jet nebulisers are used commonly for aerosol therapy in patients with asthma and bronchitis, but the manufacturers' information regarding aerosol droplet size is often inadequate. In this study, mass median diameter, geometric standard deviation and the percentage of the aerosol mass contained within 'respirable' (less than 5 micron diameter) droplets have been measured for 11 brands of jet nebuliser with a solution of hypertonic (7%) saline at compressed gas flow rates between 6 and 121 min-1 using a laser light scattering device (Malvern Instruments 2600 HSD analyser). There was a considerable variation in droplet size between the nebuliser brands and among nebulisers of the same brand. Droplet size decreased with increasing compressed gas flow rate. These findings suggest that the quantity of drug available to the patient depends on the individual nebuliser used, and upon the pressure and flow of the compressed gas.

Cerebral consequences of cardiopulmonary bypass

55 patients undergoing coronary-artery bypass surgery (CABS) and a comparison group of 20 patients having thoracic or major vascular surgery were investigated preoperatively and 8 days and 8 weeks postoperatively for changes in neuropsychological status, psychiatric state, cerebral blood flow, and neurological signs, this last being assessed also at 24 h. Major persisting neurological changes were rare, but minor abnormalities were significantly more common after CABS than after thoracic or vascular surgery. Neuropsychological deficits were common at 8 days in both CABS and comparison groups, and in about a third of all patients persisted at 8 weeks. Cerebral blood flow was reduced at 8 days in some CABS patients, but this was not significant for the group. Pre-existing cerebrovascular disease was not predictive, but low perfusion pressure and long bypass time were associated with postoperative deficits.

Effect of InspirEase on the deposition of metered-dose aerosols in the human respiratory tract

A radiotracer technique has been used to assess the effects of a 700-ml collapsible holding chamber (InspirEase, Key Pharmaceuticals Inc.) on the deposition of metered-dose aerosols in ten patients with obstructive airways disease (mean forced expiratory volume in one second [FEV1], 64.5 percent of predicted). Patterns of deposition obtained by patients' usual techniques with the metered-dose inhaler (MDI) were compared with those by correct MDI technique (actuation coordinated with slow deep inhalation and followed by ten seconds of breath-holding) and with those by InspirEase. Deposition of aerosol was assessed by placing Teflon particles labelled with 99mTc inside placebo canisters, and inhaling maneuvers were monitored by respiratory inductive plethysmography (Respitrace). Nine of the ten patients had imperfect technique with the MDI, the most prevalent errors being rapid inhalation and failure to hold their breath adequately. With patients' usual MDI techniques, 6.5 +/- 1.2 percent (mean +/- SE) of the dose reached the lungs. This was increased to 11.2 +/- 1.3 percent (p less than 0.02) with correct technique and increased further to 14.8 +/- 1.4 percent (p less than 0.05) with InspirEase. Oropharyngeal deposition exceeded 80 percent of the dose for the MDI alone but was only 9.5 +/- 0.9 percent with InspirEase (p less than 0.01); 59.2 +/- 2.1 percent of the dose was retained within InspirEase itself. It is concluded that InspirEase gives whole lung deposition of metered-dose aerosols greater than that from a correctly used MDI, while oropharyngeal deposition is reduced approximately nine times.

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.

Evaluation of jet nebulisers for use with gentamicin solution

Recently nebulised antibiotics (gentamicin and carbenicillin) have been used successfully to treat respiratory tract infection in patients with cystic fibrosis. No information exists, however, on the choice of nebuliser or the ideal mode of operation with antibiotic solutions, which are often viscous. The aerosol output, droplet size, and nebulisation time were assessed for four common brands of jet nebuliser (Bird, DeVilbiss, Inspiron, and Upmist) used to nebulise 2 ml (80 mg) and 4 ml (160 mg) of gentamicin solution (Garamycin, Kirby-Warrick) at four compressed gas flow rates (6, 8, 10, and 12 1 . min-1). There were considerable variations between the nebulisers, DeVilbiss and Upmist being most efficient in the release of respirable (less than 5 micron diameter) droplets. Droplet size and nebulisation time were inversely proportional to gas flow rate. Aerosol output and nebulisation time were increased by raising the volume fill from 2 to 4 ml, although nebulisation time could still be restricted to 12 minutes or less with DeVilbiss and Upmist at 12 1 . min-1. The output of drug in droplets of below 5 micron diameter ranged from 7.2 (SE 0.4) to 71.4 (4.3) mg, according to the type of nebuliser, flow rate, and volume fill. These studies suggest that for optimal drug delivery 4 ml gentamicin solution should be nebulised either at a fixed flow rate of 10-12 1 . min-1 or with a high flow compressor. Previous unsatisfactory clinical results with antibiotic aerosols may have been due in part to incorrect choice of nebuliser or inappropriate operating conditions, or both.

Aerosol deposition considerations in inhalation therapy

Successful aerosol therapy generally depends on the small percentage (typically 10 percent) of the drug dose delivered to the lungs from metered-dose inhalers (MDIs), nebulizers, and dry powder inhalers. Deposition of therapeutic aerosols occurs by inertial impaction (in the oropharynx and large conducting airways) and by gravitational sedimentation (in the small conducting airways and alveoli) and is determined by the mode of inhalation, particle or droplet size, and the degree of airway obstruction. Deposition of metered-dose aerosols in the lungs can be enhanced by using MDIs correctly (aerosol release coordinated with slow, deep inhalation, followed by a period of breath-holding); many patients have poor inhaler technique. Extension devices (spacers and holding chambers) make MDIs easier to use and may increase lung deposition to levels achieved by a correctly used MDI while substantially reducing oropharyngeal deposition. Optimal use of air-driven (jet) nebulizers depends primarily on the choice of nebulizers with relatively small droplet size and on the volume fill and compressed gas flow rate.

Ocular dominance, reading, and spelling ability in schoolchildren

The association of reading disability with perceptuomotor problems has had a chequered history. This study examines the relationship between a new test of ocular dominance and reading and spelling ability in a group of 298 schoolchildren. Similar rates for unstable ocular dominance were found for poor readers as in comparable studies. The rates of unstable ocular dominance did not differ between the 'dyslexics' and the controls. These findings in a blind study question the role of this test as a diagnosis of 'dyslexia.'

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.

Improvement of pressurised aerosol deposition with Nebuhaler spacer device

The effect on aerosol deposition from a pressurised metered dose inhaler of a 750 cm3 spacer device with a one way inhalation valve (Nebuhaler, Astra Pharmaceuticals) was assessed by means of an in vivo radiotracer technique. Nine patients with obstructive lung disease took part in the study. The pattern of deposition associated with use of a metered dose inhaler alone was compared with that achieved with the spacer used both for inhalation of single puffs of aerosol and for inhalation of four puffs actuated in rapid succession and then inhaled simultaneously. On each occasion there was a delay of 1 s between aerosol release and inhalation, simulating poor inhaler technique. With the metered dose inhaler alone, a mean (SEM) 8.7 (1.8)% of the dose reached the lungs and 80.9 (1.9)% was deposited in the oropharynx. With single puffs from the spacer 20.9 (1.6)% of the dose (p less than 0.01) reached the lungs, only 16.5 (2.3)% (p less than 0.01) was deposited in the oropharynx, and 55.8 (3.1)% was retained within the spacer itself. With four puffs from the spacer 15.2 (1.5)% reached the lungs (p = 0.02 compared with the metered dose inhaler alone, p less than 0.01 compared with single puffs from the spacer), 11.4 (1.2)% was deposited in the oropharynx, and 67.5 (1.8)% in the device itself. It is concluded that the spacer device gives lung deposition of metered dose aerosols comparable to or greater than a correctly used inhaler and oropharyngeal deposition is greatly reduced. The spacer should be used preferably for the inhalation of single puffs of aerosol but may also be used for the inhalation of up to four puffs actuated in rapid succession and then inhaled simultaneously.

Therapeutic inhalation agents and devices. Effectiveness in asthma and bronchitis

Although a variety of therapeutic agents can be given as aerosols, the physical problems involved in delivering the drug to the peripheral airways have often been ignored. Therapeutic aerosols are deposited in the respiratory tract by two chief mechanisms--inertial impaction (in the oropharynx and in large conducting airways) and gravitational sedimentation (in small conducting airways and in alveoli). In practice, only about 10% of the aerosol dose reaches the lungs from metered-dose inhalers (MDIs) and nebulizers, and rather less from dry-powder inhalers. Changes in either aerosol particle size or inhalation mode can optimize the amount of aerosol delivered to the peripheral lung regions by each device. The inhaled route has several advantages over oral and intravenous administration for the treatment of asthma and bronchitis, ie, a rapid onset of drug action, a small drug dose, and a low incidence of systemic side effects. Although various disadvantages or problems have been proposed for the inhaled route, these seem to be of minor importance. Drugs inhaled from MDIs, dry-powder inhalers, or nebulizers are thought to be safe if used in the recommended manner.

Dissociation between calcium and phosphate absorption in nephrotic syndrome

Intestinal calcium and phosphate absorption have been measured in nine patients with nephrotic syndrome and normal renal function, by a combined radioisotope technique which allows simultaneous measurement of both quantities. The values obtained were compared with those obtained in 20 normal controls. Calcium absorption in the nephrotic group was significantly lower than in the control group (P less than 0.01), but phosphate absorption in the nephrotic group did not differ from controls. This dissociation between calcium and phosphate absorption provides further evidence for independent mechanisms governing the two absorption processes.

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.

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.