Use of a Capsaicin Cough Challenge Test to Compare Four Different Techniques for Nebulization Delivery in Cats

Successful aerosol therapy might rely more heavily on proper drug delivery than on the effectiveness of the medication. This study compared four techniques for nebulization delivery in cats. Tolerance rate (TR) was subjectively evaluated (1-3). Increasing capsaicin concentrations were nebulized for objective evaluation of efficiency. The positive response (PR) was considered when more than five coughs were induced. The following delivery methods were tested: flow-by (FB); face mask (FM); plastic-covered Elizabethan collar (EC); and plexiglass chamber (PC). The number of PRs (NPR) and the concentration of capsaicin that induced a PR (CCP) were statistically compared (p < 0.05). The PC method was the best tolerated (TR = 3.0 ± 0.0), followed by the FB (2.7 ± 0.5) and FM (2.6 ± 0.5). The EC was very stressful, and the test had to be suspended in four out of nine cats. The lowest CCP was found with the FM (91.8 ± 157.2 µM), followed by the FB (166.7 ± 190.9 µM), PC (242.6 ± 244.8 µM), and EC (350.0 ± 225.7 µM), with significant differences only between the FM and EC (p = 0.02). The highest NPR (8) corresponded to the FM, followed by the FB (7), the PC (5), and the EC (3), with significant differences between the FM and EC (p = 0.016). In conclusion, the capsaicin cough test induces reproducible and quantifiable cat responses. The FM is the most efficient for nebulization delivery, offering good compliance and the best quantitative results. FB nebulization is less efficient but may be practical if the FM is not tolerated. PC offers minor efficiency but may be useful for very stressed or aggressive cats. The EC presents low efficiency and compliance.