The order of the factors affects a product!

Patients receiving nebulized respiratory treatments and airway clearance therapies often combine the treatments to decrease treatment time, despite a lack of data supporting this practice. Moreover, manufacturers advertise simultaneous use in their marketing. The airway clearance devices that allow concomitant administration of aerosol can be classified as those that alter the pathway of the aerosol and those that do not. We all learn in algebra that the order of the factors does not affect a product. However, this might not be true in respiratory care practice. In this issue of RESPIRATORY CARE, Mesquita et al1 report the findings of an in vivo study of the effect of different configurations of a high-frequency