Dr Johnson replies

In the February 2007 issue of RESPIRATORY CARE, the article by Douglas Johnson MD demonstrated ingenuity in developing innovative methods for adapting aerosol devices to deliver aerosol to types of patients for whom the devices were not designed.1 I applaud Johnson for the creativity and the intent of the article. I also am impressed that he pointed out the limitations of his device adaptation system; that is, further studies need to be performed to validate certain assumptions, such as lower-respiratory-tract deposition, and to objectively monitor clinical response. Though the adaptation design he used was impressive, I am concerned about the clinical ramifications of the adaptation. As Johnson pointed out, much needs to be done prior to the commercial reproduction of a similar configuration. Over the last few years, and with the impending phase-out of chlorofluorocarbons (CFCs) and the requirement to use hydrofluoroalkane (HFA) as the propellant in metered-dose inhalers (MDIs), there may be a more widespread problem we need to be concerned with. Respiratory care staff in intensive care units throughout the country often deliver either CFC-propelled or HFApropelled MDI doses to patients on mechanicalventilators, throughvariousadaptors that were probably designed for the CFC propellant. I am not aware of any available adapter that was designed specifically for HFA MDIs. Further, I’m not aware of any study that specifically compares clinical effects of HFA-propelled and CFC-propelled medicines (when each are available in both formulations, such as albuterol) through any single adapter. Though we can see a spray come out of the MDI, we don’t know much about the consistency of the plume, the aerosol particle size, or the deposition within the patient, the ventilator circuit, or the endotracheal or tracheostomy tube. Jim Fink, an expert in aerosol therapy, indicated that the nozzle in the Ventolin (CFC) inhaler is 0.53 mm in diameter whereas the Proventil inhaler nozzle is 0.28 mm.2 My guess is that if you deliver a medicine designed to be injected through a nozzle about half the size of the one being used, you will probably get a very different aerosol, and probably a very different therapeutic effect than anticipated. Fink’s article2 pointed out many variables that need to be considered when administering any aerosol. When we start deviating from the mechanics of aerosols built into and then examined by carefully controlled clinical trials by the manufacturers of the medicines we use, we need to be concerned with how these variables might affect outcomes. In fact, we are probably altering the quality of the aerosol every time we use any adapter not designed by the manufacturer. The effect these deviations may have on patient care is unclear. Spacers or valved holding chambers that enable the use of the manufacturer-designed mouthpiece are fine. Studies have demonstrated improved efficacy with those devices. But we need to exercise caution when we do anything different than intended by the device manufacturer. My point is that, while we can make a system work to accommodate the physician’s or respiratory therapist’s desire to get a medicine into a patient despite the limitations imposed by ventilator circuitry or spontaneously breathing patients, we need to consider how the adaptations will affect the many variables of aerosol delivery, and, perhaps most importantly, define, observe, and document clinically meaningful outcomes that can be tracked or trended to our adaptations. Though we probably aren’t going to hurt any patients with our adaptations and medicines (especially if they are delivered at subtherapeutic doses), we really need to evaluate whether our time and effort are offset by our ability to actually benefit the desired patient outcome.