The "cold Freon effect," in which high-velocity aerosol hits the back of the throat, also causes patients to stop inhaling prematurely. Drug delivery varies from 7 to 20%, depending on the patient's technique, and, again, as much as 80% of the dose deposits in the oropharynx. This is seen in MDI. With use of spacer, the patient's participation is not required and thus the cold freon effect is avoided.
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