OSCILLOMETRY IN EQUINE ASTHMA

The present project investigated the use of oscillometry as a mean for the diagnosis of equine asthma, evaluating two different Techniques: the impulse oscillometry system (IOS) and the Forced Oscillation Technique (FOT). The aim of the first study was to evaluate whether the IOS could be sensitive enough to discriminate amongst healthy and asthmatic horses in different clinical conditions. Seven severely asthmatic (SEA) horses in disease exacerbation, 7 asthmatic horses in clinical remission and 7 control horses from a cohort of experimental age-matched animals underwent IOS testing. Only data at 3, 5 and 7Hz with coherence >0.85 at 3Hz and >0.9 at 5 and 7Hz were considered in the study. Mean, inspiratory and expiratory resistance (R) and reactance (X) and the difference between inspiratory and expiratory X (ΔX) were calculated at each frequency. The three groups were compared using one-way ANOVA and Dunnett’s multiple comparison test or Kruskal-Wallis test and Dunn’s multiple comparison test. Significant differences were found between SEA horses in exacerbation and control horses for all R parameters at 3Hz. For X, significant differences were present between exacerbation horses and control horses at each frequency for mean, inspiratory and expiratory parameters. Between controls and remission horses differences were present for X7 and for inspiratory X3, X5 and X7. Regarding Delta X, values in exacerbation horses were significantly higher than remission or control horses. Results indicate that, as reported in humans during tidal expiratory flow limitation (EFL), X during the expiratory phase is more negative than during inspiration in exacerbated horses. Difference in inspiratory X appears to be promising to discriminate between healthy horse and SEA horses in clinical remission. The aim of the second study was to evaluate the application of a FOT device specially designed for horses and his ability in discriminate between healthy subjects, SEA horses in exacerbation and moderate asthmatic horses (MEA). 4 SEA horses, 4 MEA horses and 4 controls from a clinical population were selected, age-matched. Data of FOT measurement at 2, 3, 4, 5 and 6 Hz were considered in the study. Mean, inspiratory and expiratory resistance (R) and reactance (X) and the difference between inspiratory and expiratory X (ΔX) were calculated at each frequency. The three groups were compared using Kruskal-Wallis test and Dunn’s multiple comparison test. Statistical comparison showed significant differences between SEA and control group for R at 3Hz and for R at 2 Hz in expiration phase. Regarding X, several differences were found between controls and SEA horse at frequencies ranging from 2 to 6 Hz in all the phases of the breath. Finally, comparison for ΔX showed that values in SEA horses were significantly higher than MEA or control horses, indicating that in SEA horses in exacerbation the reactance during expiratory phase is worse than during inspiration. No differences were found between controls and MEA horses. Results showed that the new FOT device was able to discriminate between healthy and SEA horses. EFL in SEA horses was identified also by this system. Further studies are required in order to increase the sensitivity in discriminate between healthy and MEA horses.