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Background -Several factors have been identified which improve nebulised aerosol delivery in vitro. One of these is the addition ofa spacer to the ventilator circuit which improves aerosol delivery from a jet nebuliser to a model lung by approximately 30%. The current study was designed to demonstrate whether similar improvements could be demonstrated in vivo. Methods -Ten patients (seven men) were studied during mechanical ventilation (Siemens Servo 900C) after open heart surgery. Aerosol was delivered using a Siemens Servo 945 nebuliser system (high setting) driving a System 22 Acorn jet nebuliser (Medic-Aid) containing 3 ml technetium-99m labeliled human serum albumin (9Tc-HSA (50 tg); activity in the first nebulisation, 90 MBq; in the second nebulisation, 185 MBq). Central and peripheral lung aerosol deposition and the time to complete deposition were measured using a gamma camera and compared when the nebuliser was connected to the inspiratory limb using a simple Tpiece or a 600 ml spacer. Results -The addition of the spacer increased total lung deposition (mean (SD) percentage initial nebuliser activity) from 2-2 (0-7)% to 3 (0.8)%. There was no difference in the time required to complete nebulisation (18-2 min v 18-3 min respectively for T-piece and spacer) or in the retention of activity in the nebuliser (46-2% v 47-1% respectively). Conclusions -The combination ofa spacer with a jet nebuliser increased lung deposition by 36% in mechanically ventilated patients and is a simple way of increasing drug deposition or reducing the amount of an expensive drug required for nebulisation. (Thorax 1995;50:50-53)

In practices where the proportion of Asian patients is high, both antidepressant and anxiolytic prescribing is low. This is important for understanding interpractice prescribing variation and for setting levels of drug budgets. This study confirms that the low rates of non-psychotic disorders presented by Asian populations is not a selective feature of access to secondary care, but is evident in the prescribing behaviour of GPs. Uncertainty remains as to how much this is due to a lower prevalence rate, "culture-bound syndromes" or practical difficulties in diagnosis and management within the general practice setting.