Influences of nonobstructive apneas on hemodynamic changes in anesthetized dogs

Kim, Jin Woo; Lee, Sang Haak; Choi, Young Mee; Kwon, Soon Seog; Kim, Young Kyoon; Kim, Kwan Hyoung; Song, Jeong Sup; Park, Sung Hak; Moon, Hwa Sik

Abstract

BACKGROUND: The cardiovascular dysfunction frequently accompanies sleep apnea syndrome, but the exact pathophysiology of cardiovascular dysfunction still remains uncertain. Moreover, most studies are concerned with obstructive sleep apnea syndrome and the studies of central sleep apnea syndrome are rare.
METHODS
We studied with sixteen dogs which were anesthetized with intravenous pancuronium bromide. We created nonobstructive breath hold (apnea) in anesthetized dogs by means of alternating fixed duration (30s) of apnea and mechanical ventilation (breathing). After five or seven repetitions of this apnea-breathing cycle, we measured arterial oxygen pressure, arterial carbon dioxide pressure, heart rate, cardiac output, mean femoral artery pressure and mean pulmonary artery pressure separately before apnea (baseline), 25s after apnea (apneic period), 10s (early phase of postapneic period) and 25s (late phase of postapneic period) after resumption of breathing. We analysed the impact of oxygen trial on the hemodynamic changes by comparing measures of the eight 30% oxygen breathing dogs with the other eight room air breathing dogs.
RESULTS
Heart rate decreased significantly at apneic period compared to baseline (p<0.05), and increased significantly at early and late phase of postapneic period compared to apneic period (p<0.05). After oxygen trial, this change of heart rate showed significant difference (p<0.05). Cardiac output only tended to decrease during late phase of postapneic period by comparison with baseline and apneic period. Mean femoral artery pressure of apneic period increased more than that of baseline (p<0.05), and persisted until late phase of postapneic period (p<0.05). When oxygen was supplied, this change of increase disappeared, but did not show statistical significance. Mean pulmonary artery pressure did not change according to apnea-breathing cycle and oxygen trial.
CONCLUSION
In anesthetized dogs with periodic nonobstructive apnea, the changes of heart rate, cardiac output, mean femoral artery pressure were noted and the change of heart rate was closely related with hypoxia. Through this study, indirectly, we were able to understand partially the changes of cardiovascular function in patients with central sleep apnea syndrome.