Editor-In-Chief: C. Michael Gibson, M.S., M.D. 
An asthmatic spacer or commercially referred to as a "Valved Holding Chamber" (VHC), is a device used by an asthmatic person to increase the effectiveness of an asthma inhaler. Spacers are specially designed plastic or metal tubes that fit an inhaler on one end, while the patient breathes normally on the other end. Some spacers utilize a collapsing bag design to provide visual feedback that successful inspiration is taking place.
Benefits of a spacer
In order to properly use an inhaler without a spacer, one has to coordinate a certain number of actions in a set order (pressing down on the inhaler, breathing in deeply as soon as the medication is released, holding your breath, exhaling), and not all patients are able to master this sequence. Use of a spacer avoids such timing issues. Spacers slow down the speed of the aerosol coming from the inhaler, meaning that less of the asthma drug impacts on the back of the mouth and more gets into the lungs. Because of this, less medication is needed for an effective dose to reach the lungs, and there are fewer side effects from corticosteroid residue in the mouth.
Valves on the spacers cause the patient to breathe the contents of the spacer, but exhalation goes out into the air. The problem of co-ordinating an inspiration with a press of an inhaler is avoided, making use easier for children under 5 and the elderly. It also makes asthma medication easier to deliver during an attack.
Large plastic bottles or polystyrene cups can be used as spacers for children in an emergency.
Disadvantages of a spacer
The first disadvantage of a spacer is it adds to the bulk, when portability is needed.
Another disadvantage is with the new HFA inhalers. The medication is dryer, and the propellant is slightly weaker, when the dose is discharged. The result is that the devices along the chain may cause the medication to cling to it. Obviously, the patient receives less than the optimal dose.
- ↑ Merck Manual 18th ed. p. 405