〔日 生 気 誌 、20(1)38-15,1983〕 Original Hyperbaric Diuresis at a Thermoneutral 31 ATA He-O2 Environment K. SHIRAKI*, S. SAGAWA*, N. KONDA* and H. NAKAYAMA** * Department of Physiology , University of Occupational and Environmental Health, Japan School of Medicine ** Department of Hyperbaric Medicine , University of Occupational and Environmental Health, Japan School of Medicine (Yahatanishi-ku, kitakyushu-shi, 807 JAPAN) Abstract The basic pattern of body water exchange was studied in four Japanese male divers during exposure to a thermoneutral 31 ATA (He-O2) environment for 3 days (Seadragon V). The hyperbaric chamber temperature was raised from 25•}0.5•Ž at 1 ATA (air) pre-dive to 31.5 f 0.3•Ž at 31 ATA. Both rectal and mean skin temperatures were measured every hour (including during sleep) and were maintained at the same level at both pressures. The exposure to 31 ATA induced an increase in the daily urine flow, and a corresponding reduction in the insensible (and evaporative) water loss without changing the total daily water output. However, the daily fluid intake decreased by 600 ml at 31 ATA, and hence the divers developed a state of negative fluid balance, as reflected by a reduction in body weight and an increase in hematocrit. All changes in the pattern of body water exchange observed at 31 ATA were gradually reversed during subsequent decompression. As observed in a previous dive to 31 ATA (Seadragon IV) in which there was a subtle cold stress (as indicated by the 1•Ž reduction in mean skin temperature at 31 ATA), the increase in daily urine flow at pressure was almost entirely due to the increase in overnight urine flow. However, the hyperbaric nocturia observed in the present dive was a water diuresis in nature what in the previous dive was an osmotic diuresis. These results indicate that the hyperbaric diuresis at 31 ATA is due to an increase in overnight urine flow, and that the hyperbaric nocturia is not in any way related to the subtle cold stress attendant to many hyperbaric environments. [Jpn. J. Biometeor. 20(1) : 8-15, 1983] 高気圧環境 におけ る尿量増 加の成 因 白 木 啓 三*・ 佐 川 寿 栄 子* 今 田 育 秀*・ 中 山 英 明** 高 気 圧 環 境 では 伝 導 及 び 伝 達 性 の 体 温 喪 失 が 増 加 し1気 圧 で の 中 性 温域(28～30℃)で は体 温 の 下 降 が認 め られ る。 特 に飽 和 潜 水 に お いて 用 い られ るヘ リウ ム加 圧 に お い て は そ の 傾 向は 著 しい 。 高 気 圧 環 境 に お い て尿 量 の増 加 す る こ とが 最 近 知 られ る よ うに な った が,そ の 機 序 に つ い て は 不 明 で あ る。 今 回31気 圧 ヘ リウムー 酸 素 環 境 を シ ミュ レー トし気 温 を31.5±0.3℃ に保 ち,3日 間 に わ た り4人 の 被 験 者 の水 分 出納 を測 定 した 。 睡 眠 時 も含 め 連 続 測 定 を行 った 直 腸 温 及 び 皮 膚 温 は この よ うな 室 温 条 件 で は31気 圧 で も低 下 しなか った 。31気 圧 で は1日 尿 量 の有 意 な 増 加 と,こ れ に 見 合 うだ け の 蒸 散 量 の減 少 が み られ た。31気 圧 で は全 水 分 摂 取量 は、1日600ml減 少 し水 分 バ ラン スは 負 で あ り,こ れ が 体 *産業医科大学生理学教室 **産 業医科大 学高気圧治療部(〒807北九州市八幡西区医生 ケ丘1-1) 〔昭和58年2月1日 受付〕 HYPERBARIC DIURESIS AT 31 ATA (9) 重 減 少及 び 血液 濃 縮 に反 映 した。 こ の よ うな負 の水 分 バ ラ ソ スは1気 圧 へ の減 圧 終 了 と共 に 消 失 した 。 1日 尿量 の増 加 はす べ て夜 間(2200～0700h)の 尿量 の増 加 に よる も ので あ った 。 糸球 体 炉 過 量 や 浸 透 圧 ク リア ラソ ス に は変 化 は み られ ず,こ の よ うな 尿量 の増 加 は尿 細管 に お け る水 再 吸 収 の 低 下 に よ る もの で あ る こ とが判 明 した。 各 被 験 者 の睡 眠 中 の ベ ヅ ドサ イ ドの気 温 は31.7。Cに 保 たれ,又 睡 眠 中 の 皮 膚 温 の 連 続 測 定 の 結 果 か ら も夜 間 の 尿量 の 増 加 の原 因 は 寒 冷 刺 激 に は よ らな い こ とが 判 明 した。 INTRODUCTION The present investigation was undertaken to Significant increases in daily urine flow have reassess the characteristics of hyperbaric diu - been observed in human divers during multi- resis at 31 ATA in which the chamber temper- day exposure to high pressure. Although ature was raised to 31.5 C to avoid any redu - this hyperbaric diuresis may be clearly due ction in the skin temperature. to the subtle cold stress in some dives, it was observed even in the complete absence METHODS of cold stress1). Moreover, neither the total Four Japanese male divers were selected on body fluid volume nor the daily fluid intake the basis of rigorous physical and psychological changes significantly during the steady state examinations. On the average, they were 35 exposure to high pressure despite the presence (31-41) years old, 171.2 (162.0-182.6) cm in of sustained diuresis1). In general, the in- height, 68.9 (62.1-85.9) kg in weight, and crease in urine flow is accompanied by a 1.83 (1.68-2.10) m2 in body surface area. reduction in urine osmolality, urinary excretion All subjects were trained professional divers of antidiuretic hormone (ADH), and the in- and were involved in earier saturation dives sensible water loss1). However, in a more carriedout at the Japan Marine Science and recent saturation diving experiment carried out Technology Center (JAMSTEC). at 31 ATA (Seadragon IV), Nakayama et al. 2) Dive Profile and Environmental Variables: observed that the hyperbaric diuresis is also The dive (code-named •gSeadragon V•h) was associated with an increase in the fractional carried out at the JAMSTEC from November excretion of filtered osmotic substances (e. g., 22 through December 13, 1982. The charac- Na, K, and urea), and that the major portion teristics of the hyperbaric chamber facilities of the increased urine flow at high pressure at JAMSTEC have been described elswhere4). is attributable to the increased overnight urine The overall dive profile and some of the envi- output. Although the chamber temperature ronmental variables are shown in FIG. 1. in the latter dive was maintained at a subjec- Following a 3-day predive(1 ATA air) control tively comfortable level of 31.0 •} 0.2 •Ž at 31 period, the chamber pressure was raised with ATA, the mean skin temperature was lowered He to 31 ATA in 12 h and maintained at this by approximately 1 •Ž at 31 ATA as compared pressure for 3 days. Subsequently, the cham- with that at the predive level. It was thus ber was decompressed to 1 ATA over 12 days felt that a subtle cold stress may have been using the standard U. SNavy decompression present during the hyperbaric exposure period schedule. Following the completion of de- in that dive, which through some heretofore compression, the divers remained inside the unknown mechanism(s) resulted in hyperbaric chamber for 3 days (postdive 1 ATA air con- nocturia. In fact, we earlier observed an trol). The chamber temperature (Ta) was inverse relationship between daily urine flow maintained at 25•}0. 5 •Ž at predive 1 ATA, and the mean skin temperature during a 4 31, 5•}0.3•Ž at 31 ATA, and 28•}0.5•Ž at ATA He-O2 dive3). postdive 1 ATA. (10) K. SHIRAKI et al FIG. 1 Dive profile and chamber gas partial pressures. Energy Balance : Meals were provided three data were recorded in a data logger every 2.5 times a day, and the actual intake of each food min(7V07, Sanei-Sokki Co., Japan) and an- item was determined as described previously2). alyzed by a computer (Type 243, Sord, Japan). The caloric intake as well as the carbohydrate, The average mean skin temperature for fat and protein intake were estimated by using each day was calculated from these hourly the Standard Table of Food Composition in measurements. The average chamber temper- Japans). The body weight was measured using ature in the day time was calculated from a platform scale (Type K-5, Kobekoki Co., temperatures obtained using 9 thermistors set sensitivity 1.0g) at 0700, 1000, 1300, 1600, at various places in the chamber, and ambi- 1900 and 2200 h, in order to determine the ent temperatures during sleep for individual insensible water loss. Reported weights at subjects were calulated from temperatures 31 ATA have been corrected for changes in measured with 2 thermistors each placed near the buoyancy due to the increased density of the sleeping subject. the chamber gas, as described earlier2). Fluid Balance : The total fluid intake The body temperature was measured using (drinks, water contained in food, and water thermistors (ZL-64, Takara Co., Japan). of oxidation) was estimated on a daily basis. The mean skin temperature (Tsk) was calcu- Each subject kept a complete record of all liquid lated from 7 point measurements according consumption (other than that contained in to the formula of Hardy and DuBois6).