A valved holding chamber (VHC) is a commercially manufactured device that is designed to be used in con-junction with MDIs. VHCs make it easier to inhale asthma medicines from MDIs, increase the amount of medicine delivered directly to the lungs, and reduce potential side effects such as voice hoarseness and thrush. Purchasing a VHC in the United States requires a prescription.
Examples of VHCs are the AeroChamber, AeroChamber Max, OptiChamber, ProChamber, and the Pari Vortex. VHCs are recommended for all children with asthma who use MDIs, but VHCs are useful for adults as well. Most valved holding chambers are rigid and shaped like a tube, with a mouthpiece (or face mask) on one end and an opening at the other. The end with a mouthpiece is also manufactured with a face mask for use by children under 5 years of age. The opening at the opposite end accepts the mouthpiece of the MDI containing your medicine. The VHC is designed with a one-way valve that allows the actuation (puff ) released from the MDI to enter the chamber and from there be inhaled.
The one-way valve prevents you from breathing into the device; you can only inhale from it. Of the VHCs men-tioned, the AeroChamber, OptiChamber, and ProChamber are made of a transparent plastic material that allows you to actually see the plume of medication as it is released from the MDI. That can be useful if you are helping a child with his or her inhaler since the visual cue may help you with timing as you instruct the youngster to inhale the medicine.
The Pari Vortex is a valved holding chamber made of aluminum, which has the advantages of being nonelectrostatic as well as dishwasher safe, although you obviously cannot see the medication as it is released from the MDI. Nonelectrostatic chambers (such as the aluminum Vortex and the AeroChamber Max) have, in laboratory experiments, been shown to absorb less of the medicine, making more drug available for inhalation. The chambers made of plastic require monthly rinsing in diluted dishwasher detergent (1 part detergent to 5,000 parts water, or 1–2 drops per cup of water) followed by air-drying to counteract electrostatic charges (think static cling!) that can interfere with the VHC’s effectiveness.
Do not rub or towel dry a VHC. Although there are many studies of VHC use with asthma medicines in persons with asthma that show benefit, the latest Expert Panel Report (EPR-3) points out that “no specific combination of MDI and VHC currently has been specifically approved by the FDA for use together.” The EPR further suggests “it may be preferable to use the same combination of MDI and VHC reported” in the published study of a particular asthma medication.
Your doctor should be able to advise you on which specific holding chamber is best for the MDI you have been prescribed. If your treating physician has advised that you use a VHC with your MDI, make sure to read the instructions applicable to the particular VHC that you have purchased. You should understand how to use your VHC and how to clean it. Perhaps your doctor will directly demonstrate how to use the chamber with an MDI. It is also a good idea to bring the device with you to your appointment so that your technique can be observed in action!
VHCs are different from spacers. Spacers is a general term used to describe any simple open tube, without a one-way valve, that extends from the mouthpiece of an MDI. Some MDIs are manufactured with incorporated spacers. Azmacort MDI (the brand of triamcinolone manufactured by Kos Pharmaceuticals), a daily-use, maintenance inhaled corticosteroid medication, is an example of a medication furnished with an incorporated spacer.
Valved holding chambers (VHCs):
- Are indicated for any person who has difficulty performing adequate MDI technique
- Are advised for children
- Decrease deposition of medicine in the mouth and throat
- Decrease the risk of some side effects, such as hoarseness and thrush
- If not non-electrostatic, must be rinsed monthly with dilute dishwashing detergent and air dried
- Differ from spacers as VHCs have a one-way valve that allows only inhaling from the device
- Are preferred to spacers, which do not contain a one-way valve
You should always inhale your Azmacort brand of triamcinolone through the spacer that comes with it. Some spacers are homemade devices, such as plastic bottles or cardboard tubes. Some physicians use the terms spacer and valved holding chamber interchangeably. They are not synonymous, as you now know! The benefits of using a valved holding chamber are at least threefold (Table 42). The VHC enhances the deliv-ery of the MDI’s medication into the lung passages. It reduces potential side effects such as cough, hoarseness, thrush, and throat irritation related to asthma medicine landing in the throat. More medicine goes where it is needed, the lung airways, and less where it is not. VHCs also greatly simplify the hardest step for most MDI users: having to coordinate and precisely time inhalation with activation and pumping of the canister.
You use a valved holding chamber by inserting the mouthpiece of the MDI at the far end of the tube and placing your lips around the VHC’s mouthpiece at the opposite end. First, depress the MDI canister to release one (not more!) puff of medicine into the VHC, and then inhale deeply and steadily before holding your breath for 10 seconds or more. Some VHCs make a whistling sound if you breathe in too fast. Learn to inhale so that the spacer remains silent. What is a one-step procedure with MDIs becomes a two-step process with the MDI+VHC combination.
Kerrin’s comment: Now that my son is getting a bit older, his allergy specialist prescribed an albuterol MDI with a holding chamber for him to use when he needs it. The inhaler fits right into one end of the tube, and there is a soft, rubber-rimmed mask that fits over the nose and mouth on the other end. And rather than sitting for 15–20 minutes with the nebulizer, this delivers the medicine in twelve breaths (six breaths for each of two pushes on the MDI canister). It’s much more convenient to use because I don’t have to look for an electrical socket and a place to sit comfortably for 15–20 minutes with a squirmy child.