Table 2.

Factors affecting dry powder inhaler use

Drug delivery	Consistent dose delivery throughout device life
	Dose reproducibility across range of temperatures and humidities
	High proportion of dose available for inhalation over a range of inspiratory flow rates
	Large fine particle mass in relation to total emitted dose (see section Drug delivery)
	Low resistance of device to airflow during inhalation
Ease of use	Small number of steps required to actuate device
	Low inhaler technique training requirements
	Low degree of manual dexterity required to use device
Patient preference	Appropriate size and low obtrusiveness
	Incorporation of a dose counter
	Positive reinforcement of dose delivery