The effect of a new breath actuated dry powder inhaler, the Turbuhaler*, was found to be reduced at inhalations slower than 28 I/minute. This flow rate could be generated by virtually all children aged >6 years, by 42 of 57 children <6 years (74%), and by six of 15 preschool children with acute wheeze (40%).Many children with asthma cannot use a pressurised aerosol correctly and therefore gain little benefit from inhalation treatment with this device. In such cases dry powder inhalers may be a valuable treatment alternative. However, powder inhalers require a certain minimum inspiratory flow rate from the patient to work effectively.' 2 This limits the use of powder inhalers in children, whose inspiratory flow rate varies, both with age and expiratory pulmonary function.Dry powder inhalers are designed in different ways and vary substantially in resistance to air flow. It is important, therefore, for physicians prescribing inhalation treatment for children to know in detail the peak inspiratory flow rate (PIFR) that various age groups can generate through an inhaler as well as the lowest inspiratory flow rate at which the inhaler will work effectively.We conducted the present studies to answer these questions with regard to a new multidose powder inhaler, terbutaline Turbuhaler (Astra), which delivers pure freeze dried drug without any carrier substance or additives.

The bronchodilator response after four different modes of inhalation of 0.25 mg terbutaline from a Turbuhaler was assessed, in a double-blind cross-over study, of 14 asthmatic children aged 8-14 yrs (mean 11.6 yrs). The children inhaled as fast as possible (mean peak inspiratory flow rate = 53 l.min-1), because fast inhalations have been found to be more efficient than slow inhalations when the Turbuhaler is used. Tilting the head back during inhalation and a breath-holding pause of 10 s after the inhalation had no significant effect upon bronchodilation. Furthermore, the response was the same whether the children inhaled from residual volume (RV) or functional residual capacity (FRC). These results suggest that this new inhaler can be used with a very simple inhalation technique without any loss of effect. A simple inhalation technique is likely to facilitate teaching and improve compliance.