呼吸を伴う顔面浸水の自律神経活動へ及ぼす影響

Influence of Facial Immersion with Breathing on Autonomic Nerve Activity

　目的：5℃の冷水ヘシュノーケルを通じて自然な呼吸を行いながら顔面浸水を行った（Facial Immersion Breathing through a Snorkel：FIBS）時とその回復時の心拍変動，カテコラミン（CA）および血圧（BP）の変動の解析から，FIBSの自律神経活動へ及ぼす影響を検討した．対象と方法：健康成人男女14名を対象に，各5.5分の安静時，FIBS時および回復時に心電図，CAおよびBPを計測した．心拍変動は高速フーリエ変換を施すとともにCVRR,MSDおよびRR50を求め心臓の迷走神経活動の指標とした．結果：安静時と比較してFIBS時にはノルアドレナリン（NA），収縮期血圧（SBP），拡張期血圧（DBP），LogHF（高速フーリエ変換より算出された心臓の迷走神経活動の指標），MSDおよびRR50は有意に増加した．一方，FIBS時と比較して回復時にはアドレナリン（A），SBP,DBP，LogHF,CVRR,MSDおよびRR50は有意に低下した．高速フーリエ変換より算出された心臓の交感神経活動の指標（LF／HF）は有意に増加した．しかし，LF／HFとCAの変動量の間の相関性は，安静時からFIBS時ではLF／HFとAでr＝−0.045,LF／HFとNAでr＝0.177であり，FIBS時から回復時ではLF／HFとAでr＝−0.300, LF／HFとNAでr＝−0.154であり，いずれも有意な水準はなかった．考察：FIBS時には心臓の迷走神経と交感神経の活動はともに亢進し，その回復時には両自律神経活動とも抑制することが示唆された．しかし，LF／HFとCAの変動の間の相関性は低く，交感神経の活動の動態についてはさらに検討を要するであろう．

This study investigated variations in autonomic nerve activity during and after facial immersion breathing through a snorkel (FIBS) in water at 5℃. Fourteen healthy adults of both genders served as subjects. Elec-trocardiogram, catecholamine (CA). and blood pressure were measured during rest, FIBS, and recovery. After analysis of successive RR intervals using methods in-cluding fast Fourier transformation, CVRR, MSD, RR50, and LogHF were used as indices of cardiac vagus nerve activity, and LF/HF was used as an index of cardiac sympathetic nerve activity. MSD, RR50, LogHF, nor-adrenaline, systolic blood pressure (SBP), and diastolic blood pressure (DBP) increased significantly during FIBS. In contrast, CVRR, MSD, RR50, LogHF, adrenaline, SBP, and DBP decreased but LF/HF in-creased significantly during recovery. From these results, it was suggested that cardiac vagus and sympa-thetic nerve activities were accelerated simultaneously during FIBS, and both activities were depressed during recovery. However, because the correlation between the variations of LF/HF and CA was low, further study is indicated.