34th Annual Scientific Meeting proceedings

Objectives:

The chronic hypoxia experienced by brachycephalic dogs that exhibit brachycephalic obstructive airway syndrome (BOAS) has been described previously, but the systemic repercussions of this hypoxia remain unclear. These dogs are used as models of sleep apnoea syndrome (SAS) in human studies because they share breathing and sleeping characteristics with human patients showing SAS. Since recent studies have shown that human patients with SAS have high serum concentrations of hypoxia-inducible factor (HIF-1α), we hypothesised that dogs with BOAS would also show the same findings.

Methods:

Fifty-two brachycephalic dogs that were clinically assessed as healthy except for clinical signs related to BOAS underwent grading of BOAS (grade 0-3) on the basis of the results of laryngeal auscultation before and after an exercise test. Their blood samples were collected subsequently, and HIF-1α quantification was performed by enzyme-linked immunosorbent assay testing. The results considered normal by Levene tests were analysed with one- and two-way analyses of variance and Tukey’s post-hoc test in RStudio. Significance was defined by a P value ≤ 0.05.

Results:

Dogs graded as 0 (no clinical signs of BOAS) had higher levels of HIF-1α (76.6 ± 28.2) than those graded as 3 (52.4 ± 26.8). Additionally, these animals also showed alterations in arterial and venous pH, lactate levels, and venous partial pressure of carbon dioxide (PCO₂).

Conclusions:

These results suggest that the regulatory mechanisms of dogs with BOAS may be different from those of human patients with SAS. The findings also imply that dogs with BOAS may have lost the sensitivity to HIF-1α due to the congenic character of the syndrome.

Financial Support: São Paulo Research Foundation 2023/12747-5