Heart rate variability in dogs with brachycephalic obstructive airway syndrome evaluated during wakefulness and sleep.

BOAS significantly elevates HRV indices, reflecting autonomic dysregulation driven by airway obstruction rather than conformation alone.

This prospective cross-sectional study evaluated heart rate variability (HRV) in 46 client-owned dogs—34 brachycephalic (with and without BOAS) and 12 non-brachycephalic controls—using 24-hour Holter monitoring with segmented analysis during wakefulness and sleep. Key HRV indices assessed included corrected SDNN (cSDNN), corrected RMSSD (cRMSSD), the vagal tone index (VVTI), and Poincaré plot parameters. BOAS-affected dogs demonstrated significantly elevated cSDNN and cRMSSD compared to controls over 24 hours, suggesting heightened autonomic modulation, particularly enhanced parasympathetic activity. BOAS severity was moderately correlated with the longest sinus pause, cSDNN, and cRMSSD (r ≈ 0.42–0.46), indicating a meaningful relationship between upper airway obstruction and cardiac autonomic dysregulation. Sleep universally increased cSDNN, cRMSSD, and VVTI across all groups, with no significant group-by-state interaction, suggesting the sleep-related HRV augmentation is a physiological phenomenon independent of BOAS status. Notably, HRV differences between BOAS and control dogs were more pronounced during wakefulness, likely attributable to chronic respiratory effort and intermittent hypoxia characteristic of BOAS. Importantly, the presence of BOAS—rather than brachycephalic conformation alone—was the primary driver of autonomic changes, highlighting the clinical relevance of diagnosing and grading BOAS severity. These findings suggest that HRV monitoring may serve as a non-invasive biomarker for autonomic dysfunction in BOAS patients and could have implications for anesthetic and perioperative risk assessment in brachycephalic breeds.

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