顔面浸水止息時の心電図応答の時刻間変動，月間変動および年間変動

Time, Month, and Year-related Variations of Electrocardiographic Responses Provoked by Apneic Facial Immersion

　目的：本研究は顔面浸水止息時の心電図応答に対する1日の時刻間変動，約1年間の月間変動および約10年間を通じた年間変動を追究することを目的としている．対象と方法：被検者は時刻間変動では健康成人男女12名，月間変動では健康成人男女4名，年間変動では健康成人男性2名であった．被検者は時刻間変動では9時30分（朝食の約2時間後），12時00分（昼食前），17時30分（夕食前）に，そして月間変動では1ヵ月間隔で13ヵ月間にわたって，年間変動では数ヵ月から数年の間隔で11年間にわたって，5℃の冷水を用いた顔面浸水止息を行った．結果：各時刻における顔面浸水止息時の最低下心拍数（HRmin）とHRminの安静時心拍数に対する相対値（％HRmin）はともに相互間に有意な差はなく，相互間の相関係数はHRminではr＝0.851〜0.953，％HRminではr＝0.845〜0.930でいずれも有意であった．また，発現した不整脈の有無にも良好な一致性が認められた．各月におけるHRminと％HRminの変動には季節に基づく規則性は認められなかったが，不整脈の発現には良好な一致性が認められた．HRminと％HRminの年間変動では，1名の被検者は34.4歳，もう1名は38.9歳を境として増加していく傾向を示した．結語：顔面浸水止息時の心電図応答は食事直後を除いた9時30分から17時30分の間であれば良好な等結果性が期待される．また，月別でも不整脈発現の再現性は良好である．さらに年間変動から30歳代中盤以降を境として加齢に伴う徐脈反応の減弱化が推察された．

This study examined the time, month, and year-related variations of electrocardiographic responsesprovoked by apneic facial immersion (API). First, therewere no significant differences among three minimumheart rates (HRmin) obtained at 9:30, 12:00, and17:30. Neither were there significant difference in theirthree values in relation to resting heart rates (%HRmin).Correlation coefficients among three HRmins weresignificant at r=0.845~0.953, and those among three%HRmins were also significant at r=0.845~0.930.Furthermore good correspondence was observed in theincidence of arrhythmias by AFI. Second, in regard tomonth-related variations, although bradycardiacresponses by AFI didn't seem to reveal seasonal varia-tions, the incidence of arrhythmias corresponded fairlywell. Third, with regard to year-related variations, theattenuated bradycardiac responses were observed in twosubjects who were over 34.4 years of age and 38.9 yearsof age respectively.

From these results, the following three points weresuggested: 1) Good electrocardiographic correspond-ence can be expected from 9:30 to 17:30 except attimes immediately after meals; 2) Month-related re-producibility of the incidence of arrhythmias corres-ponded fairly well; 3) It is probable that bradycardiacresponses start to attenuate on or after the mid thirtieswith large differences depending on the individual.