Comparison of Flowmetric Plethysmography and Forced Oscillatory Mechanics to Measure Airway Hyperresponsiveness in Horses.
Authors: Dixon Claire E, Bedenice Daniela, Mazan Melissa R
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: Comparing Lung Function Tests for Equine Asthma Diagnosis Airway hyperresponsiveness (AHR) serves as a hallmark of mild to moderate equine asthma (EA), and identifying it reliably is crucial for early intervention and management planning. Dixon and colleagues compared two non-invasive lung function testing methods—forced oscillatory mechanics (FOM) and flowmetric plethysmography (FP)—to determine whether they produce equivalent diagnoses of AHR in 19 horses with suspected EA, using histamine bronchoprovocation followed by bronchoalveolar lavage to confirm inflammation. Both tests identified AHR in 50% of the 14 horses with cytologically confirmed EA, but FP diagnosed an additional four horses with AHR (21% of the total population), including two without inflammatory evidence on bronchoalveolar lavage fluid analysis, making FP significantly more sensitive overall (P = 0.013). The two modalities cannot be used interchangeably in clinical practice, and practitioners should be aware that flowmetric plethysmography may identify airway dysfunction in horses that other diagnostic markers—including inflammatory cytology—would not flag as asthmatic. This discrepancy warrants further investigation into whether FP-positive, cytology-negative horses represent early-stage disease, alternative airway pathology, or false positives, since diagnostic precision directly impacts treatment decisions and prognosis.
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Practical Takeaways
- •When using non-invasive lung function testing to screen for equine asthma, clinicians should be aware that FP and FOM may yield different AHR diagnoses in the same horse—do not assume results are comparable
- •FP appears more sensitive for detecting AHR but may identify airway changes in horses without other diagnostic confirmation of EA; use alongside clinical signs and BALF cytology for confident diagnosis
- •Standardize your diagnostic approach: choose one testing modality and combine it with BALF analysis rather than switching between FOM and FP, as this causes interpretation inconsistency
Key Findings
- •Flowmetric plethysmography (FP) diagnosed AHR in 11/19 horses (57.9%) while forced oscillatory mechanics (FOM) diagnosed AHR in only 7/14 horses with EA (50%), showing FP is more sensitive (P = 0.013)
- •Both FOM and FP correctly identified AHR in 7/14 horses with confirmed EA based on abnormal BALF cytology (50%)
- •FP alone identified 4 additional horses with AHR, including 2 with normal BALF cytology, suggesting FP may detect subclinical airway changes
- •The two testing modalities cannot be used interchangeably for diagnosing AHR in horses