Canine brachycephalic obstructive airway syndrome as a model for studying the effects of obstructive sleep apnea...

Brachycephalic obstructive airway syndrome (BOAS) in dogs shares pathophysiological features with human obstructive sleep apnea, presenting different degrees of airway obstruction. Thus, the severity of the disorder may result in negative pregnancy consequences differently. This study aimed to compare the effects of BOAS severity throughout gestation on maternal clinical status, uteroplacental hemodynamics, and fetal development. Bitches were grouped according to BOAS symptomatic manifestation as mild (n = 5), severe BOAS (n = 5), and non-BOAS groups (control; n = 5). Along gestation (early, mid, and late stage), females were examined for clinical evaluations, arterial blood acid-base balance, and obstetric B-mode and uterine and umbilical artery Doppler velocimetry. Mild and severe BOAS had lower blood pressure, considered hypotension, and remained tachycardiac. All bitches had tachypnea, but mild BOAS group had higher (p < 0.05) respiratory rate. Peripheral oximetry decreased (p < 0.05) with time in severe BOAS, in a manner that females presented severe hypoxia (87.8% ± 4.6%) and hypocapnia (30.7 ± 2.37 mmHg) in late pregnancy. Blood glucose concentration was higher (p < 0.05) in mild BOAS (123.8 ± 5.79 mg/dL), in addition to persistent hyperglycemia until mid-pregnancy (121.8 ± 7.37 mg/dL). Severe BOAS bitches had higher (p < 0.05) lactatemia and hyperlactatemia throughout gestation. Fetal abdominal diameter, femur length, and humerus length were lower (p < 0.05) in severe BOAS compared to control. Uterine artery hemodynamic indexes, indicative of vascular resistance, decreased (p < 0.05) over time only in control, whereas BOAS degree groups remained unchanged. Severe BOAS had higher (p < 0.05) umbilical artery resistance in mid and late pregnancy (0.84 ± 0.02 and 0.77 ± 0.01) compared to mild BOAS (0.76 ± 0.01 and 0.64 ± 0.04, respectively). In conclusion, the degree of respiratory impairment in BOAS dogs has an adverse impact on maternal health and the fetoplacental unit, despite tentative attempts of physiological adaptations during pregnancy to maintain gestational homeostasis.