Breath of Fresh Air: Feature Articles

Chapter 32: How can I tell if my inhaler is empty?

One of the more frustrating aspects of asthma medication use is not knowing when your inhaler is empty of medication, or when it is about to become empty. Even when the medication has run out, most of the inhalers — whether they contain bronchodilator or antiinflammatory medication — will continue to make a sound when shaken (because of the remaining inactive gases still present in the cannister) and will continue to release some spray when activated. Many people often find themselves uncertain as to whether to risk using an inhaler that may have no medication in it or discard a partially empty inhaler when active (and expensive) medication is still in it.

The ideal solution would be a device that records and displays the number of "puffs" used or — even better — the number of "puffs" still remaining in the canister. Although such counters are being developed [and now exist; see information on the “Doser” in the News about Asthma section, Chapter 49], they are either limited to certain inhalers or add significantly to the cost of the inhalers.

Alternatively, two methods can be used to determine how full or empty an inhaler is. The first method involves knowing how many "puffs" are in a full canister prior to use and keeping track of how many "puffs" you have used. This technique is probably practical only if you use the same number of "puffs" each day, such as 2 puffs twice a day of a long-acting bronchodilator or 4 puffs twice a day of an inhaled steroid. It would not work well if you tend to activate the inhaler for extra "puffs" when you are uncertain as to how well you have inhaled the medication or if you use a number of different inhalers with the same medication around the house, car, and workplace.

The number of "puffs" reported to be in each canister is quite accurate; this information is provided in the package insert when you buy your inhaler. Some examples are given here:

The second method is the "float test." Take the metal canister out of its plastic holder and place it in a container of water. A full canister is heavy and either sinks or floats with its top pointing down in the water. A half-full canister is less heavy and floats at a 45 degree angle with the surface of the water. An empty canister is light and floats nearly horizontal with the surface of the water. A major shortcoming of this method is that it is not very precise and cannot accurately distinguish between nearly empty and entirely empty.

Clearly there is room for improvement and a need for some good new ideas in this area of asthma treatment.

[Since this article was written, two new devices have become available that address this particular problem in different ways. The Diskus® dry-powder inhaler has a built in counter that indicates the number of inhalations remaining. The Turbuhaler® dry-powder inhaler has a clear plastic window along its side. When 20 doses of medication are left in the device, a red plastic indicator fills half the window. When the Turbuhaler® is empty, the red indicator completely fills the window.]