フンザ高地住民における低酸素と副交感神経機能との関係

Abstract

低酸素の副交感神経機能に与える影響を調べるために, フンザ高地住民41名(男:女:24:17 平均年齢58.4歳)の酸素飽和度(SpO2)と心電図R-R間隔変動係数(CVR-R)を測定しこれらの関係を検討した. 酸素飽和度とCVR-Rは有意の正相関関係を示した(R=0.523, P=0.0005). 心拍数とCVR-R, 酸素飽和度と心拍数はそれぞれ有意の逆相関を示した. 低酸素における心拍数増加のCVR-R低下に及ぼす影響を除外するため, 平均心拍数に一致させた修正CVR-Rを計算した. 修正CVR-Rも酸素飽和度と有意の相関を示した(R=0.353，P=0.0235). 年齢と酸素飽和度は有意の逆相関を示したが, 年齢とCVR-Rは有意な相関関係を認めなかった. 低酸素により心拍数は増加し, それとは独立してCVR-Rは低下した. フンザ高地住民において, 低酸素それ自体が副交感神経機能を抑制すると考えられた.

We investigated oxygen saturation and coefficient variation of R-R intervals on ECG (CVR-R) in highland subjects to clarify the effects of hypoxia on the vagal activity. We examined 41 subjects (mean age; 58.4 years) living in three villages in Hunza in Pakistan at the altitude of about 2500 meter. Oxygen saturation significantly correlated with CVR-R(R=0.523, P=0.0005). There were also significant relationship between heart rate and CVR-R (R=-0.473, P=0.0018) and between oxygen saturation and heart rate (R=-0.446, P=0.0035) respectively. To exclude the effect of increase in heart rate for hypoxia on CVR-R, we calculated corrected CVR-R which was matched with mean heart rate. Corrected CVR-R hild also significant correlation with oxygen saturation (R=0.353, P=0.0235). Age was significantly correlated with oxygen saturation (R=-0.369, P=0.0174), but not with CVR-R (R=-0.207, P=0.193). Heart rate was higher and oxygen saturation was lower in women than in men (women;79/min, 90.4% vs men; 68/min, 92.3%, respectively). With hypoxia heart rate increased and CVR-R decreased independently for the increase in heart rate for hypoxia itself. In conclusion, hypoxia, per se, inhibits vagal activity in highlanders.