Heart Rate Depression during Sleep Apnea Depends on Hypoxic Chemosensitivity: A Study at High Altitude

Abstract

To clarify the heart rate (HR) slowing response during periodic breathing (PB) with apnea and its relationship to hypoxic ventilatory response (HVR), sleep studies were done in seven Japanese climbers at 5,360 m in the Kunlun mountains of China in 1986. Apnea duration (APD), arterial oxygen saturation changes (delta SaO2), and the percentage of heart rate changes (delta HR%) during PB with apnea were analyzed. The data were compared with hypoxic heart rate and ventilatory responses assessed at sea level. HR during the apneic period (APD, 10, 8 +/- 1.2 s; delta SaO2, 10.2 +/- 1.8%) was significantly smaller than that during the ventilatory period of PB (56.0 +/- 5.1/min and 74.6 +/- 6.2/min, respectively). This HR slowing or acceleration alternated in accordance with off and on activities in ventilation. The magnitude of delta HR% had a significant correlation with that of delta SaO2 (p less than 0.01). The sensitivity of HR depression to desaturation (delta HR%/delta SaO2) was smaller in low HVR climbers than in high HVR climbers. We concluded that these results can be ascribed to the fact that the primary effect of peripheral chemoreceptors on the cardiovascular center is vagotonia, and the effect is overridden by the vagal pulmonary inflation reflex.

Comparison of reducing effect on lung injury of dexamethasone and bosentan in acute lung injury: an experimental study

“…Phagocytes are known to play a key role in lung injury by a cascade effect: phagocytes release oxidants and proteases that damage the pulmonary endothelial and epithelial cells, thus disrupting the alveolar-capillary unit [24,25]. Glucocorticoids such as dexamethasone are used in the treatment of inflammatory lung injuries due to their ability to inhibit phagocyte migration to the site of injury and to partially suppress phagocyte reactivity [26]. Dexamethasone pretreatment has also reduced pulmonary elastase activity and chloramine levels, further supporting the anti-inflammatory effectiveness of dexamethasone.…”

Heart rate variability during sleep at high altitude: effect of periodic breathing

“…This rise is largely the result of increased sympathetic activity triggered by stimulation of peripheral chemoreceptors contained within the carotid bodies [9]. During sleep, heart rate (HR) was found to decrease during the respiratory pause of periodic breathing cycles with SaO 2 fall [10][11][12]. These studies showed HR fluctuations during the periodic breathing cycles with the lowest values reached during apnea and the highest during hyperpnea.…”

Effects of breathing control on cardiocirculatory modulation in Caucasian lowlanders and Himalayan Sherpas

“…This phenomenon may be related to the fact that we studied awake subjects. During sleep, a more marked in¯uence of unstable breathing control on LF¯uctuations of heart rate has been noticed (Masuyama et al 1990;Ward et al 1995). However, we observed a signi®cantly increased VLF -R intervals (normalized units) in the frequency component between 0.01 and 0.08 Hz.…”