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Shared MDIs: Can Cross-Contamination be Avoided?

As a cost-savings measure, some respiratory therapy departments have been using a single metered dose inhaler (MDI) canister to administer medication to multiple patients. MDI with spacerThis practice, first described more than a decade ago,1-3 employs a protocol in which the MDI nozzle (mouthpiece) is wiped with an alcohol prep pad and then inserted into a patient-specific aerosol cloud enhancer (ACE) spacer with a one-way valve before delivering the medication (see Figure 1). Most protocols also call for disinfecting the nozzle using an alcohol prep pad after the medication has been delivered. The MDI remains with the respiratory therapist and is used to deliver subsequent doses to other patients prescribed the same drug. The spacer remains with each patient and is not shared. This process, referred to as a common MDI canister protocol, is not used for patients on isolation precautions and is rarely used for patients being mechanically ventilated.

Proponents of this practice cite significant cost savings, staff efficiency, and fewer treatment delays, while advocating that cross-contamination among multiple users of the MDI is unlikely if the above-cited protocol is followed. Eliminating the need to retrieve and return each patient’s MDI from patient-specific or unit medication supplies—particularly automated dispensing cabinets—has increased staff efficiency. Annual cost savings up to 55% have been documented, and the shared MDIs allow patients to be charged per puff of medication.1-3 Treatment delays associated with pharmacy distribution of MDIs have been eliminated in many cases, and improvements in patient education have also been reported due to one-on-one time with respiratory therapists.  

Opponents of allowing multiple patients to use the same MDI canister are not convinced that these benefits outweigh even a minimal risk of cross-contamination, particularly if the protocol for disinfecting the nozzle is not followed. Early findings from several hospitals that adopted the practice showed varying results. In one hospital, microbiological sampling of the canisters used to administer treatments showed no growth of organisms cultured from the mouthpiece after being swabbed with alcohol.1 But cross-contamination was documented in two other cases.2-3

In one case, cultures were taken of the MDI nozzle before and after disinfection with an alcohol prep pad, as well as after treatments were administered. Growth of Staphylo-coccus epidermidis occurred in at least 5% of the cultures with all three types of specimens, including those taken after the nozzle was disinfected with an alcohol prep pad.2 In another case, the hospital assessed the failure to wipe the canister nozzle with an alcohol prep pad prior to patient use; 1 of 18 (5.5%) cultures resulted in growth of Streptococci Group D (Enterococci).3   

Two more recent studies showed no adverse effects after implementing a common MDI canister protocol.4-5 In 2000, a study of 17 patients showed no contamination at 24, 48, or 72 hours when cultures were taken from the MDI mouthpiece after swabbing with an alcohol pad, after actuation and removal from the spacer, and after removing it from the spacer and swabbing it with alcohol.4 A similarly designed 2001 study also showed no growth in cultured samples from the MDIs after use with 50 patients.5

Contamination that might occur from a common MDI canister protocol would seem to come from the surface of the canister, not the medication itself. This risk could be mitigated by good hand washing, along with wiping down the canisters with alcohol swabs. But if staff are not compliant with hand hygiene between patients—and many are not—how compliant will they be with cleaning the mouthpiece after every patient use? The problem is less with the common MDI canister protocol itself and more so with the potential lack of carrying out proper infection control practices.

Hospitals that have successfully implemented the common MDI canister protocol state that compliance with disinfecting the MDI nozzle is key. But we know practitioners don’t always follow proper procedures. In one of our recent newsletters, we mentioned reports of transmitting blood-borne infections after reusing insulin pens, even after the needle was changed between patients.6 In 2008, the Centers for Disease Control and Prevention (CDC) found that more than 60,000 patients in the US during the last decade were at risk for blood-borne diseases due to multiple lapses in infection control practices, including the failure to clean shared glucometers.7 More than 400 patients acquired Hepatitis B or C infections in patient-to-patient transmission due to a failure to follow fundamental infection control principles.7 Failure to properly disinfect stethoscopes between patient use has also been linked to nosocomial infections.8 The CDC and the American Medical Association recommend disinfecting stethoscopes between patient use,8 but as a practical matter, it does not happen.

Deciding whether to implement a common MDI canister protocol requires thoughtful analysis and deliberation. If the results of earlier studies2-3 hold true, a 5% rate of potential cross-contamination may not be acceptable given the high-volume use of MDIs, frequency of repeated exposure to patients who use MDIs several times a day, and the heightened risk to immunocompromised patients. With shrinking reimbursements for care associated with nosocomial infections, cost-containment gains from employing a common MDI canister protocol may be quickly lost if an infection occurs. If a decision is made to move forward with a common MDI canister protocol, the Association for Professionals in Infection Control and Epidemiology (APIC) recommends carefully analyzing your processes to ensure handoffs between patients are not inadvertent sources of contact transmission, and emphasizing in the protocol the importance of hand hygiene and canister disinfection with alcohol after each use and prior to the next use.9 For hospitals that choose to dispense individual MDIs to patients, we encourage all manufacturers to provide smaller “institutional” containers of MDIs to prevent unnecessary costs and waste.

ISMP also suggests further research involving larger and more diverse patient samples from varied settings to better demonstrate any risks associated with cross-contamination among patients. Studies that show the level of staff compliance with the common MDI canister protocol over time and describe facilitators and detractors related to compliance would also be useful. 


  1. Filippelli A, Gregory G. Multiple patient metered dose inhaler (MDI) program. Abstract presented at the December 1997 ASHP Midyear Meeting, Atlanta, GA.
  2. Dunlew CL, Rau JL, Roman SB. Surveillance of reservoir cross-contamination with multiple patient MDI use. Abstract presented at the December 1997 ASHP Midyear Meeting, Atlanta, GA.
  3. Hinson D, Rau JL. Incidence of contamination of metered dose inhaler canisters when used with multiple patients using spacer devices. Abstract presented at the December 1997 AHSP Midyear Meeting, Atlanta, GA.
  4. Duncan JL, Sheils SG, Wojciechowski WV. The common canister protocol using the Monaghan AeroChamber reveals no cross-contamination and potential cost savings. Respir Care August 2000;45(8):981.
  5. Wojciechowski WV, Maddox HC, Moseley AL. Analysis of cross-contamination of metered dose inhalers when using the Respironics Optichamber under the common canister protocol. Abstract presented at the 2004 AARC International Congress, New Orleans, LA.
  6. ISMP. Hazard Alert! Reuse of insulin pen for multiple patients risks transmission of bloodborne disease. ISMP Medication Safety Alert! February 12, 2009;14(3):1-2.
  7. Thompson ND, Perz JF, et al. Nonhospital health care-associated Hepatitis B and C virus transmission: United States, 1998-2008. Ann Intern Med 2009;150:33-39.
  8. Wurtzberger I. Stethoscope friend or foe. June 2004.
  9. Fisher A. Personal communication on APIC Community APICList. Association for Professionals in Infection Control and Epidemiology (APIC). Posted 1/16/2009