Comparison of Flowmetric Plethysmography and Forced Oscillatory Mechanics to Measure Airway Hyperresponsiveness in Horses

Abstract

Airway hyperresponsiveness (AHR) is linked to airway inflammation and is considered a key manifestation of mild/moderate equine asthma (EA). The study purpose was to determine whether two modalities of non-invasive lung function testing (FOM—forced oscillatory mechanics vs. FP—flowmetric plethysmography) establish the same clinical diagnosis of AHR in horses, using histamine bronchoprovocation. Nineteen horses (3–25 years, 335–650 kg) with clinical signs suggestive of mild/moderate equine asthma were enrolled. FOM and FP testing was performed in each horse on two consecutive days, using a randomized cross-over design. AHR was defined by the histamine dose needed to double FOM baseline resistance, or to achieve a 35% increase in FP delta flow. Bronchoalveolar lavage fluid (BALF) was subsequently collected and stained with modified Wright's and toluidine blue stains. Binary statistical tests (related samples T-test, Mann-Whitney U, Chi-square analyses) were performed to compare study groups, with P < 0.05 considered significant. Abnormal BALF cytology confirmed EA in 14/19 (73.7%) horses. Both FOM and FP revealed AHR in 7/14 (50%) of these EA horses. An additional 4/19 (21.1%) horses showed AHR based on FP but not FOM, including two horses with normal BALF cytology. A diagnosis of AHR was more often associated with FP than FOM (P = 0.013), although the prevalence of AHR was significantly higher in EA vs. non-EA horses, regardless of testing methodology. The phase angle between thoracic and abdominal components of breathing did not differ between test groups. In conclusion, FP diagnosed AHR more frequently than did FOM, including horses with no other diagnostic evidence of EA. Without further evaluation, these two testing modalities of AHR cannot be used interchangeably.

Effects of Bedding Material on Equine Lower Airway Inflammation: A Comparison of Two Peat Beddings, Wood Pellet, and Straw Pellet

“…Even more detailed clinical scoring systems than the one that was used in our study have failed to differentiate healthy horses from the ones affected with mild equine asthma (30). Lung function testing would offer more information about the airway hyperresponsiveness than mere BALF in some cases (31). We were not able to perform lung function tests to the horses used in this study for practical reasons, as the horses were examined in their own stable.…”

Use of human airway smooth muscle in vitro and ex vivo to investigate drugs for the treatment of chronic obstructive respiratory disorders

“…For example equines affected by heaves, currently improperly called equine asthma, may be a potential model of pathophysiological conditions overlapping between human asthma and COPD. In this respect, airways obtained from horses with heaves are characterised by persistent and not fully reversible airflow limitation, AHR, mucus hypersecretion, prevalent neutrophilic inflammation with concomitant signs of eosinophilic inflammation, allergic responses to aeroallergens, airway remodelling and emphysema in the more severe forms of disease (Bullone & Lavoie, 2017; Couëtil et al, 2016; Dixon et al, 2021; Hunter et al, 2020; Leclere et al, 2011). Indeed, this is a condition characterised by several features associated with asthma and several features associated with COPD, suggestive of asthma–COPD overlap (ACO) as already reported in humans (Miravitlles, 2017).…”

Decision Making in Severe Equine Asthma—Diagnosis and Monitoring

“…This system, which has been specifically developed for equines and was suited for field testing [104], is no longer commercially available. It had a sensitivity similar to that of pleural pressure but, when combined with histamine bronchoprovocation, allowed the detection of horses in disease remission [18,46,105,106].…”