Inhaler Devices for Asthma: Part 2

by Frederic Little, M.D. Health Professional

Read Part I of this series here

Inhaler devices for asthma treatment
In this second entry of this two part-series, I would like to review devices that help optimize delivery of inhaled medications to the lungs from metered dose inhalers (MDIs), including spacers/holding chambers, and some other newer features of inhalers to help patients take care of their asthma.

Proper technique is important to get the maximum amount of medication into your lungs (and not in your mouth or throat). While the devices I will discuss help, your doctor, nurse, or respiratory therapist should take you through the steps in proper inhaler technique and use of any additional devices they recommend.

Spacers and holding chambers for metered dose inhalers
As I discussed in the previous entry, the medicine in an MDI is under pressure, it comes out of the inhaler as a jet that slows down gradually after it leaves the mouthpiece opening. This fact is key to design of spacers and holding chambers, and understanding how they work.

Basic concepts
I'll start with the concept of a spacer. Any spacer puts distance between the mouthpiece of the inhaler and the mouth. This allows the small particles that are sprayed out of an MDI to slow down close to a standstill in the air. The idea is that the small particles have enough distance to slow down before hitting the back of the throat or tongue, where they stick and don't get breathed in. If they are "sitting in the air," they can be breathed into the lungs more effectively. Some physicians and nurses will recommend that patients hold their MDI three to four inches from their open mouth before activating it. This helps give particles the distance to slow down before being inhaled. But this only helps somewhat. What if our aim isn't so good, or we don't time activating the inhaler with our breathing in properly? This is where the concept of the holding chamber comes in.

A holding chamber contains the dose of medication sprayed into it. This prevents losing particles that are either not aimed perfectly or sprayed 'out of range' because of the way the MDI is designed. Essentially all inhaler devices combine the functions of holding chamber and spacer. Together, they get the dose of particles in a way that they are airborne and contained for optimal delivery to the lungs. Since the device keeps the medicine contained, timing of actuating the inhaler and breathing in at the right time are less critical.

Some spacer/holding chamber devices
The simplest inhaler device is a holding chamber/spacer such as the Aerochamber. This device (and other like it) has an additional feature which encourages breathing in slowly and gradually to optimize medication particles going into the lungs. This is a small whistle that sounds if you are breathing in too fast. A version of the Aerochamber is suitable for kids as it has a mask attachment that fits nicely over a child's mouth and nose. This has a one-way valve in the mask attachment so that when a child breathes out they breathe into the air and not back into the holding chamber. Other devices, such as the E-Z Spacer or InspirEase have a collapsible holding chamber or 'bag'. The medication from the inhaler is sprayed into the chamber when it is open, and when breathed in, the bag collapses. This has the benefit of ensuring that as much medication is breathed in from the bag. The InspirEase also has a soft whistle that will sound if you breathe in too quickly.

This is not a complete listing of available spacer devices, and I do not endorse one over the other. I can say that using a spacer, any spacer, is preferable over not using one, especially at home where they are easy to have around.


It is often hard to keep track of how much of our inhaler is left to know when we need a refill, or if we need to get a new inhaler for a trip. Some older 'tricks' to know how much medicine is left, such as floating the canister in water, are unfortunately unreliable, especially with different inhalers. Some of the newer inhalers have built in counters on the canister that count down with each actuation. This is very helpful for both planning ahead, and for you and your doctor to get a better idea of how regularly you have been taking your controller inhaler or how frequently you have needed your quick relief inhaler.

See also:

Step-By-Step Instructions for Using an Inhaler Spacer

Frederic Little, M.D.
Meet Our Writer
Frederic Little, M.D.

Frederic Little is an Assistant Professor in the Department of Medicine at Boston University. He attends on the Allergy Consultation Service as well as the Medical Intensive Care Unit and Pulmonary Consultation Service at Boston Medical Center. He wrote for HealthCentral as a health professional for Asthma and Allergy.