Hyperbaric Diuresis at a Thermoneutral 31 ATA He-O2 Environment

〔日生気誌、20(1)38-15,1983〕 Original

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). The food) in terms of type and quantity. The rectal temperature (Tre) was measured by a water content of food items was taken from similar thermistor probe sealed in polyethylene the food table. The water of oxidation was tubing inserted 10-15 cm beyond the anal calculated on the basis of 0.146 g/kcal which sphincter. The mean body temperature (Tb) represents the average value for standard Japa- was calculated by the following equation7) : nese meals. Both urinary and fecal water Tb = 0.8 Tre + 0.2 Tsk losses were determined daily. Fecal weight where the coefficients 0.8 and 0.2 are weigh- was determined by the change in body weight ting factors for the steady state (or near before and after defecation, and the water steady state) in the warm environment at rest. content of feces was taken as 80% of the The body temperatures were monitored at least mass8). The subjects collected urine at 3 h for 10 min every h during the daytime and intervals between 0700 and 2200 h, and at continuously during sleeping. All temperature night(2200-0700 h). Each urine sample was HYPERBARIC DIURESIS AT 31 ATA (11) collected in a separate container and the con- postdive period (TABLE 1). FIG. 3 shows the tainer was locked out at the end of each fluctuation of mean skin temperature measured

interval, the volume was recorded, aliquots every 3 h throughout the dive, and indicates

for various analyses were obtained, and the the normal cycle of the mean skin temperature remainder was then kept in a refrigerator. at 31 ATA.

At 0700 h, a pooled urine sample for each

subject was prepared from the 6 individual urine samples collected during the previous

24 h. Aliquots of individual and pooled samples

were then frozen for later analysis.

Venous blood samples (10 ml) were drawn

from the antecubital vein at 0700 h on selected

days. The hematocrit was measured by the capillary tube method.

Chemical and Data Analyses : Both plasma and urine samples were analyzed for osmolality, Na, K, and creatinine using conventional methods described earlier2). Statistical analyses of the data were made by the Student t tests.

RESULTS

Body Temperatures : Daily average values of rectal, mean skin, and mean body temperatures are shown in FIG. 2. There were no significant differences in these values between FIG. 2 Rectal (Tre) and mean skin (Tsk) temperatures predive (1 ATA) and 31 ATA periods. during the course of the dive. Ta represents

However, they increased significantly during the chamber temperature. Values of body tem- the postdive (1 ATA) period when the chamber peratures are means SD, * : p<0.05, and ** : p<0 . 01 from pre-dive values. temperature was 28•Ž (in contrast to 25•Ž during the predive period). Body temperatures Body weight : The average daily caloric in-

(Tre and Tsk) of the subjects at night were take was maintained at approximately 2, 500 also not different between the predive and 31 kcal throughout the entire experimental period.

ATA periods, but increased slightly (by 0.1 •Ž Despite a constant caloric intake, the body for Tre and 0.3 •Ž for Tsk, p<0. 01) during the weight decreased progressively during the sat-

TABLE.1 Ambient and body temperatures during sleeping (2200h-0700h)

Values are means •} SD of 4 subjects. ** ;p<0 . 01, *** ; p<0.001 from corresponding pre-dive value. (12) K. SHIRAKI et al

Frc. 3 Fluctuations of the mean skin temperarure of the day. Each point is the average value of 3-h measurements values are means of 4 divers. Shaded area represents hours when the divers were sleeping (2300 to 0600 h).

FIG. 4 Time course of changes in the pattern of daily water exchange and in the body weight during the dive. •gIntake•h includes drinks, water contained in foods, and metabolic water production. •gBalance•h

is calculated by subtracting total water outputs from water intake.

Dotted area below •g0 balance•h line represents water deficit and

shaded area above •g0 balance•h line water retention. •gBody weight•h is the change of the body weight from pre-dive control values.

•g pre•h, •gC•h, •gsaturat•h and •gpost•h indicate the pre-dive, compression, saturation at 31 ATA and post-dive periods, respectively. •g Decomp-1•h, •gdecomp-2•h, and •gdecomp-3•h indicate the decompres-

sion periods of 30-21 ATA, 20-11 ATA, and 10-1 ATA,

respectively. * : p<0.05, ** : p<0.01, and *** : p<0.001 from the corresponding pre-dive value. uration period (BW = -1.2 kg on 3rd day at pression and completely by the 3rd day of the 31 ATA), was restored partly during decom- postdive period (FIG. 3). HYPERBARIC DIURESIS AT 31 ATA (13) Body Water Exchange : The pattern of daily ative water balance was partially restored dur- water exchange is shown in FIG. 4. The urine ing decompression and fully restored during flow increased progressively after compression, the postdive period. The plasma estimated reaching a maximal level on the 3rd day at 31 from changes in hematocrit value9) indicated a ATA (p(0.05 as compared to predive level), reduction of 6.4% at 31 ATA and an increase which was gradually returned to normal during of 7.1% during the postdive period (TABLE2). decompression. On the other hand, the in- TABLE. 2 Hematocrit value (Hct), Osmolarity of the sensible (and evaporative) water loss decreased serum and percent change in plasma volume(%PV) significantly at 31 ATA, the magnitude of which was comparable to that of the inceease in urine flow (300 ml/day). The fecal water loss remained constant at a level of approximately 200 ml/day throughout the dive.

Therefore, the total body water loss remained Values are means •} SD. * : p<0 unchanged at 2,000 ml/day throughout the en- .05, *** : p<0.001 from corresponding pre-dive tire experimental period. However, the daily value. fluid intake decreased significantly (by 500 ml Characteristics of Diuresis : The increased on the 1st day) at 31 ATA, and then returned daily urine flow observed at 31 ATA was ac- to the predive level during decompression. As companied by reductions in the urine osmolarity a result, the divers went into a state of neg- (p<0.05) and negative free water clearance ative water balance at 31 ATA, which quan- (p<0.05) but not by changes in the glomerular titatively accounted for the reduction of the filtration rate (estimated by the endogenus body weight (see above). This state of neg- creatinine clearance), the osmolal clearance and

TABLE. 3 Characteristics of water and solute excretion at 1 and 31 ATA.

(Mean •} SD) * : denotes a significant differences (p<0 .05) from the corresponding 1 ATA (predive). (14) K. SHIRAKI et al

FIG. 5 Diurnal rhythm of urine flow at 1 and 31 ATA. * : p<0 .05 from the corresponding predive (1 ATA) level. the fractional excretion of filtered Na and K (Seadragon IV) in which the mean skin tem-

(TABLE 3). These results indicate that the perature decreased by 1 •Ž upon compression to nature of the hyperbaric diuresis observed in 31 ATA2). As clearly shown in FIG. 3, and the present dive represents a water diuresis TABLE 1, mean skin temperature did not decrease rather than an osmotic diuresis. As shown to cause a cold stress at 31 ATA. Therefore, in FIG. 5, the increase in daily urine flow obs- it may be safely assumed that the findings in erved at 31 ATA is almost entirely due to the present dive truly represent the effect of that of overnight urine flow. In fact, the the hyperbaic environment per se independent overnight urine flow was almost doubled at 31 of thermal effects.

ATA. Characteristics of overnight urine sa- The basic pattern of body water exchange mples indicated that the hyperbaric nocturia observed in the present dive is similar to that is also a water diuresis (TABLE 3). On the observed in the Hana Kai II dive (18.6 ATA)1). other hand, the results of analyses of daytime In both dives, the exposure to the hyperbaric urine samples indicate that the fractional exc- environment resulted in a diuresis accompanied retion of the filtered osmotic substances inc- by a reduction in urine osmolarity and insensi- ludiug Na and K is decreased at 31 ATA. ble water loss, but not by changes in renal

hemodynamics, and osmolal clearance. These

DISCUSSION findings lend further support to the view,

The present investigation was carried out to originally proposed by Hong et al. 1) that the study primarily the urinary response to a 3- primary mechanism for hyperbaric diuresis day exposure to a dry 31 ATA He-O2 environ- may be the suppression of ADH induced by the ment in the absence of any subtle cold stress. decreased insensible water loss. However,

To this end, the chamber temperature was there are some differences in findings between raised to 31.5±0. 3 •Ž at 31 ATA, at which the previous dive (Seadragon IV) and present both rectal, and mean skin temperatures were dive at 31 ATA. First, a significant reduction unchanged as the chamber pressure was raised in the glomerular filtration rate associated with from 1 ATA (FIG. 2). The above chamber a significant increase in the fractional excretion temperature is slightly higher (by 0.5 •Ž) than of filtered osmotic substances (including Na) the temperature employed in a previous dive was observed in the previous dive, indicating HYPERBARIC DIURESIS AT 31 ATA (15) the presence of an osmotic component (superim- in future dives. posed on a water diuresis component) in the development of hyperbaric diuresis2). In the ACKNOWLEDGEMENT present dive, however, the above parameters We thank Drs. T. Kohno and M. Matsuda of renal function were not altered. Whether for the medical check and safety control of or not these differences are entirely due to the the subjects, and all of the operating staff difference in the chamber temperature between of the hyperbaric chamber in the Japan Marine the two dives is not certain at present. Sec- Science and Technology Center for the exce- ond, the magnitude of hyperbaric diuresis (on llent cooperation. This investigation was a daily basis) in the present dive was only supported by the fund provided by the Science about one-half that of the previous dive (Sea- and Technology Agency of the Office of the dragon IV). This is most likely attributable Prime Minister, Government of Japan, and in to a greater redution in the daily fluid intake part by Grant-in Aid for Scientific Research in the present dive (by 600 ml/day on the 1st from the Ministry of Education, Science and day at 31 ATA) than in the previous dive (by Culture of Japan 56440027. 100-300ml/day). In other words, a self-im- posed dehydration (FIG. 4 and TABLE 2) ap- REFERENCES pears to have opposed the hyperbaric diuretic 1) Hong, S.K., Claybaugh, J. R., Frattali, V., et force in the present dive. Such a dehydration al.: Hana Kai II: a 17-day dry saturation dive at 18.6 ATA. III. Body fluid balance. Undersea would further activate the renin-aldosterone Biomed. Res. 4 : 246-265,1977. system and counteract the potential hyper- 2) Nakayama, H., Hong, S. K., Claybaugh, J. R., et al.: Energy and body fluid balance during a 14-day baric natriuretic effect (see above). dry saturation dive at 31 ATA (Seadragon IV). Despite the above described differences be- In: A. J. Bachrach, M. M. Matzen (eds). Under- tween the Seadragon IV and V, there is a clear water Physiology VII. Proceedings of the Sixth Symposium on Underwater Physiology, pp541-554. agreement that in both dives hyperbaric diure- Bethesda, Md : Undersea Medical Society, 1980. sis is primarily due to an increase in over- 3) Shiraki, K., Konda N., Sagawa S., et al.: Body heat balance and urine excretion during a 4-day night urine flow. The data indicate that the saturation dive at 4 ATA. Undersea Biomed. hyperbaric nocturia is not related to the subtle Res. 9 : 321-333,1982. 4) Matsuda, M., Nakayama, H.,Arita, H. , et al : Physi- cold stress to which the divers were exposed ological responses to head-out immersion in water in the previous dive, but represents the effect at 11 ATA. Undersea Biomed. Res. 5 : 37-52,1978. 5) Standard Tables of Food Composition in Japan, of non-thermal environmental factors, includ- 4th revised edition. Resources Council, Science ing pressure and gas density. Although the and Technology Agency, Japan, 1982. 6) Hardy, J. D., DuBois, E. F.: The technique of mechanism underlying the hyperbaric nocturia measuring radiation and convection. J. Nutr. is entirely unknown at present, it is interesting 15 : 461-475,1938. 7) Stolwijk, J. A. J., Hardy, J. D.: Partitional calori- to compare the characteristics of this phenom- metric studies of responses of man to thermal enon observed in the two dives. The hyperbaric transients. J. Appl. Physiol. 21 : 967-977,1966. 8) Takeuchi, H., Shidara, F., Nakayama, H.,Kirigaya, nocturia observed in the present dive is N.: Studies on the digestive power under the high basically a water diuresis in nature (TABLE 3) pressure environment. Tech. Rep. Japan Marine Science and Technology Center. 2 :135-142,1978. while that sbserved in the previous dive is 9) van Beumont, W.: Evaluation of hemoconcent- primarily an osmotic diuresis10). Again, it ration from hematocrit measurements. J. Appi. Physiol. 32 : 712-713,1972. is not certain at present whether or not the 10) Claybaugh, J. R., Hong, S. K., Matsui, N., et al.: above difference is due to the difference in the Responses of salt and water regulating hormones during a saturation dive to 31 ATA (Seadragon thermal stress. Obviously this new phenom- IV). Undersea Biomed. Res. (in press). enon should be investigated more systemically