How to Use Metered-Dose Inhaler for Asthma with a spacer device (CDC Guide) Download this pdf on metered-dose-inhaler-spacer with more detailed instructions on how to use the MDI with spacer. This PDF is from the American Lung Association How to use a metered-dose inhaler with spacer device (aerochamber) for asthma in children. This video was created by the CDC and is in English. Below is the Spanish version of the same video.