spacer

A spacer is a hollow chamber you attach between a pressurized inhaler and your mouth. You fire the inhaler into the chamber, then breathe the aerosol from it over a few breaths — so you no longer have to perfectly time the press with the inhale. It is essentially a holding tank that buys time and tames the spray.

Two things happen inside the chamber. First, the high-speed jet from the inhaler slows down and the propellant evaporates, so the fast-moving large droplets that would otherwise smack into the throat fall out or shrink, leaving a higher proportion of fine, lung-sized particles. Second, the aerosol simply waits in the chamber for a moment, removing the need for split-second coordination between actuation and breath. Spacers fitted with a one-way valve (valved holding chambers) only release the aerosol when the patient inhales.

The benefits are real: more drug reaches the lung, much less deposits in the mouth and throat (reducing local side effects like oral thrush from inhaled steroids), and use becomes far easier for children, the elderly, and anyone who struggles with technique. The trade-offs are bulk and the need to keep the spacer clean and free of static charge, which can otherwise make drug cling to the walls. Spacers are used with metered-dose inhalers, not with dry-powder inhalers, which rely on the patient's own inhalation to disperse the powder.