spacer /spās′ər/ [L, spatium, space] , on a metered dose inhaler, a chamber between the inhaler canister and the patient’s mouth where droplets of medication can slow down and evaporate so that there is less direct impact on the oropharynx, with more medication delivered to the lower respiratory tract instead of being lost in the mouth. This is especially helpful for children. See also metered dose inhaler.
