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PubMed1981

Renal salt and water handling in water immersion in the nephrotic syndrome.

1. Eleven nephrotic patients were immersed up to the neck in 1.3 m of water at 34 degrees C for 4 h. 2. A diuresis began, within the first hour of, and continued throughout, immersion. The urine osmolality fell significantly and decreased to hypotonic levels in the first hour of immersion and increased gradually during the remainder of immersion and postimmersion. 3. Throughout immersion there was a steady increase in urinary sodium and chloride excretion and a sharp fall in the postimmersion hour. 4. Overall fractional excretion of sodium and of chloride increased steadily throughout immersion and fell during the post-immersion hour. 5. There was an increase in urinary potassium excretion on immersion but no change in fractional excretion of potassium. There was an initial increase in distally reabsorbed sodium/chloride on immersion, as expressed by positive values of CH2O in the first hour of immersion. 6. Plasma aldosterone levels were initially elevated in only two out of nine patients. There was a significant fall in plasma aldosterone levels on immersion, but there was no correlation between sodium/chloride handling and aldosterone levels on immersion.

Adolescent↗

PubMed2006

Breath-hold performance during cold water immersion: effects of psychological skills training.

INTRODUCTION: Accidental cold water immersion (CWI) is a significant cause of death, particularly in those who are immersed in rough water or forcibly submerged such as in a ditched and inverted helicopter. The marked reduction in maximal breath-hold time associated with CWI, part of the 'cold shock' response, significantly increases the risk of drowning. However, the response is highly variable between subjects. This experiment tested the hypothesis that part of this variability is due to psychological factors. METHODS: There were 32 subjects who completed 2 2.5-min, head-out immersions in 11 degrees C water, separated by 7 d. Between immersions, subjects were matched on initial maximum breath-hold time on immersion (BHwater) and allocated to either a psychological intervention group (PIG) or control group (CG). PIG (n=16) subjects each undertook a psychological skills intervention comprising 4 interlinked training sessions covering goal-setting, arousal regulation, mental imagery, and positive self-talk; CG (n=16) continued normal daily activity. RESULTS: Psychological intervention significantly increased BHwater on immersion in the PIG vs. the CG [mean (SD); CG BHwater immersion 1:24.01 (6.72) s; immersion 2: 21.34 (16.31) s; PIG: BHwater immersion 1: 24.66 (14.60) s; immersion 2: 44.25 (31.63) s]. The difference in maximum voluntary BHwater between immersion 1 and 2 in the PIG averaged 19.59 s, equating to an 80% increase following psychological intervention. CONCLUSION: Psychological influences may account for a significant amount of the variability in the respiratory responses during CWI, and may be a key factor in determining the chances of survival following accidental immersion.

Adolescent↗

PubMed2000

Arterial pulse pressure and vasopressin release during graded water immersion in humans.

Previous results indicate that arterial pulse pressure modulates release of arginine vasopressin (AVP) in humans. The hypothesis was therefore tested that an increase in arterial pulse pressure is the stimulus for suppression of AVP release during central blood volume expansion by water immersion. A two-step immersion model (n = 8) to the xiphoid process and neck, respectively, was used to attain two different levels of augmented cardiac distension. Left atrial diameter (echocardiography) increased from 28 +/- 1 to 34 +/- 1 mm (P < 0.05) during immersion to the xiphoid process and more so (P < 0.05), to 36 +/- 1 mm, during immersion to the neck. During immersion to the xiphoid process, arterial pulse pressure (invasively measured in a brachial artery) increased (P < 0.05) from 44 +/- 1 to 51 +/- 2 mmHg and to the same extent from 42 +/- 1 to 52 +/- 2 mmHg during immersion to the neck. Mean arterial pressure was unchanged during immersion to the xiphoid process and increased during immersion to the neck by 7 +/- 1 mmHg (P < 0.05). Arterial plasma AVP decreased from 2.5 +/- 0.7 to 1.8 +/- 0.5 pg/ml (P < 0. 05) during immersion to the xiphoid process and significantly more so (P < 0.05), to 1.4 +/- 0.5 pg/ml, during immersion to the neck. In conclusion, other factors besides the increase in arterial pulse pressure must have participated in the graded suppression of AVP release, comparing immersion to the xiphoid process with immersion to the neck. We suggest that when arterial pulse pressure is increased, graded distension of cardiopulmonary receptors modulate AVP release.

Adult↗

PubMed1997

Relationship between mechano-receptive fields of dorsal horn convergent neurons and the response to noxious immersion of the ipsilateral hindpaw in rats.

This study examines the relationship between mechano-receptive fields (inhibitory and excitatory, located on the ipsilateral hindpaw) of convergent dorsal horn neurons, and the responses of the neurons to noxious immersion of an entire paw in noxious hot water. In pentobarbital anesthetized rats with intact spinal cords and in unanesthetized decerebrate-spinalized rats, rat hindpaws were immersed in 50 degrees C water for 10 s after the mechano-receptive fields had been delineated using 5-s noxious pinches. Convergent neurons were either excited or inhibited by noxious immersion of the hindpaw. In both groups, a significant association (chi2, P < 0.01) was found between the make-up of the mechano-receptive field and the response of the neuron to immersion. Immersion-inhibited neurons (intact = 27, spinalized = 13), always had both an excitatory and an inhibitory mechano-receptive field on the same hindpaw. Additionally, when the hindpaw was removed from the noxious water, these immersion-inhibited cells displayed a strong afterdischarge which was immediately inhibited once the paw was reimmersed. Pinch-induced and immersion-induced inhibition were found in both spinalized and intact rats suggesting spinal mechanisms were sufficient to mediate this effect. The majority of immersion-excited cells showed only an excitatory mechano-receptive field on the hindpaw (intact rats = 18/23 or 78.3%, spinalized rats = 24/36 or 66.7%). However, other immersion-excited cells had both an inhibitory and an excitatory mechano-receptive field on the hindpaw (intact rats = 5/23 or 21.7%, spinalized rats = 12/36 or 33.3%). The response of a convergent neuron, which has its excitatory receptive field located on a paw, to noxious immersion of the entire paw can be predicted by the make-up of the mechano-receptive fields. Additionally, since noxious paw immersion affects ipsilateral convergent neurons in two opposite manners, it suggests that other effects, such as heterotopic actions, might also not be uniform.

Animals↗

PubMed1996

Effects of body immersion on postural adjustments to voluntary arm movements in humans: role of load receptor input.

1. The effect of body immersion on postural adjustments was studied in ten healthy subjects. Reaction times, for pushing or pulling a rigid handle, in response to a visual stimulus were measured. In addition EMG recordings were taken from upper arm and lower leg muscles during three levels of body immersion while standing on a platform (immersed to spinal levels: lumbar nerve root 2 (L2); thoracic nerve root 4 (T4); and cervical nerve root 7 (C7)), while floating and while standing or sitting out of water. 2. With increasing levels of body immersion there was a near linear reduction in the amplitude of the gastrocnemius (GM) EMG activity before (200 ms) the onset of a force signal from pulling, but immersion had a significantly weaker effect on the amplitude of the tibialis anterior (TA) EMG during pushing movements. There was no significant difference in the effect of body immersion on biceps femoris (BF) and rectus femoris (RF). Under free-floating conditions postural adjustments did not occur in response to pull or push movements. There were no adaptational changes of EMG adjustments during successive trials at a given immersion level. 3. Under non-immersed conditions reaction times were significantly shorter during sitting than during standing. This difference is assumed to be due to the postural adjustments required while standing before the onset of a voluntary arm movement. While standing, reaction times were significantly longer for pull compared with push movements. Under all conditions of body immersion the reaction times remained longer compared with the sitting condition, even when no leg muscle EMG adjustments were present. 4. It is assumed that the differential effect of body immersion on the antagonistic leg muscles is due to the differential neuronal control of antagonistic leg muscles with a strong influence from proprioceptive input (most probably from load receptors) on the leg extensors. The longer reaction times seen during body immersion, where no postural adjustments were evident, suggests that a supraspinal command to the leg muscles precedes the voluntary arm movement. However, because of the changed/decreased afferent input no postural adjustments are generated.

Arm↗

PubMed1992

Influence of self-induced hypnosis on thermal responses during immersion in 25 degrees C water.

The efficacy of self-induced post-hypnotic suggestion to improve thermogenic responses to head-out immersion in 25 degrees C water was evaluated in 12 males. An on-line computerized system permitted the change in body heat storage to be used as the independent variable and immersion time as the dependent variable. Test-retest reliability was good, exhibiting a coefficient of variation of less than 5% for exposure time. Immersion profiles consisted of the following: rest until 200 kJ of heat were lost, leg exercise at VO2 approximately 1.5 L.min-1 to regain 200 kJ, rest until 100 kJ were lost, and repeat the exercise to regain 100 kJ. A control immersion was done prior to two 1-h hypnotic training sessions. A second immersion (hypnotic) occurred within 24 h after training. There were no differences in rates of heat production, heat loss, mean skin temperature, or rectal temperature between control and hypnotic immersions. Individual hypnotic susceptibility scores did not correlate with changes in thermal status. Ratings of perceived exertion during exercise were similar for both immersions, but perceived sensation of cold was lower during the second rest period of the hypnotic immersion. Three subjects used images of warm environments during their hypnotic immersion and lost heat at a faster rate than during control immersions. These results indicate that brief hypnotic training did not enhance the thermogenic response to cool water immersion.

Adult↗

PubMed1978

Physiological responses to head-out immersion in water at 11 ATA.

Cardiorespiratory, thermal, and renal responses to a 30-min head-out immersion in 15 degree C water were studied at 1-ATA air and 11-ATA helium-oxygne environments in four male subjects wearing dry suits. Cardiorespiratory responses to immersion (reductions in heart rate, expiratory reserve volume, vital capacity, and thoracic impedance; and increases in stroke volume, cardiac output, and inspiratory capacity) were comparable at both pressures. However, thermal responses to immersion (a reduction in mean skin temperature and increases in skin heat flux and suit conductance) were significantly greater at 11 ATA compared to those at 1 ATA. The rate of urinary excretion of norepinephrine increased significantly during and after immersion at 11 ATA but not at 1 ATA. In contrast, the urinary excretion of epinephrine was not altered by pressure or immersion. The immersion diuresis was greater and lasted longer at 11 ATA than at 1 ATA although there was no difference in the endogenous creatinine excretion . This diuresis was accompanied by a significant natriuresis which was more marked at 1 ATA than at 11 ATA. At 1 ATA, the urinary excretion of both aldosterone and antidiuretic hormone (ADH) decreased during immersion. At 11 ATA, the rate of excretion of these hormones before immersion was lower compared to that at 1 ATA and did not change significantly during immersion. These results indicate that immersion in a hyperbaric helium-oxygen environment presents a greater cold stress than at 1-ATA air, and also that immersion diuresis and natriuresis at high pressure may be induced by a factor other than inhibition of aldosterone and ADH.

Adult↗

PubMed2001

Thermoregulatory responses to repeated warm water immersion in subjects who are paraplegic.

OBJECTIVE: To compare thermoregulatory responses to repeated warm water immersion (39 degrees C) between physically active subjects who are paraplegic or able-bodied in order to gain insight into rehabilitative and adaptive processes. METHODS: Five paraplegic (P) and six able-bodied (AB) males participated. VO2 peak was determined by open-circuit spirometry using a cycle ergometer (AB) and propelling a wheelchair on a motor driven treadmill (P). Subjects sat immersed to the nipple line in 39 degrees C water for 60 min for 5 consecutive days. Pre- and post-test measurements included heart rate (HR), oesophageal temperature (Tes), sweat onset and rate (dew point hygrometry). Venous blood was obtained before, and during immersion to estimate changes in plasma volume. RESULTS: The P group was older and lighter than AB group (P<0.05). VO2max, VCO2max and VE(max) were significantly greater in AB group. HR at rest and after 60 min immersion was not significantly different between the groups pre- or post-test. Tes significantly increased after 60 min immersion in both groups, at both pre- and post-testing sessions. Post-test Tes after 60 min immersion (AB) was significantly less than Tes after 60 min of immersion pre-test. The DeltaTes (Tes 60 min-Tes 0 min) was significantly higher in AB group than the P group at pre- but not post-testing. No significant changes in sweat onset or rate were found for the AB or P groups during the pre- or post testing sessions. Significant expansion of plasma volume occurred during immersion in both groups, pre- and post-immersion sessions. CONCLUSIONS: Repeated warm water immersion (39 degrees C) for 60 min per day for a total of 5 days did not produce a significant adaptive response in P group. In the AB group, Tes at the end of 60 min immersion was significantly lower after the adaptation period.

Adult↗

PubMed1996

Effects of immersion in water on survival of preimaginal stages of Haematobia irritans (Diptera: Muscidae).

Laboratory studies on effects of immersion and immersion duration on all Haematobia irritans (L.) preimaginal stages revealed a significant disparity in tolerance limits among different developmental stages and in tolerance to different immersion durations (0, 1, 6, 18, and 30 h). Of the 4 preimaginal stages, 2nd instars were most susceptible to immersion of any duration, whereas eggs and pupae were most resistant. All instars were intolerant of immersion durations >6 h, with <10% survival at 6-, 18-, and 30-h immersion durations. Survival of 2nd instars was reduced to 38% by 0-h immersion, when compared with the control group. Adult eclosion was reduced by immersion durations of 18 and 30 h during the pupal stage. Life stage survival was dependent upon immersion duration, with survival generally decreasing as a negative linear function of increasing immersion duration. Immersion durations of 0, 1, 6, 18, and 30 h resulted in overall mortality rates of approximately 30, 37, 53, 61, and 82%, respectively. In wet regions with low elevations, water accumulation may significantly affect horn fly distribution and abundance. In drier regions, where flooding events are sporadic and water accumulation variable, the effect on horn fly populations is uncertain.

Animals↗

PubMed1990

[Renal, hemodynamic and hormonal effects of repeated water immersion in liver cirrhosis].

In patients with cirrhosis of the liver sodium retention plays an important role in fluid and salt disturbances. We performed a study in 3 groups of 12 compensated and 7 decompensated cirrhotic patients and 11 controls to determine the renal, hemodynamic and hormonal effect of repeated water immersion (6 immersions in 3 weeks). In all groups immersion resulted in a marked acute natriuresis and diuresis combined with acute reduction of blood pressure. In both cirrhotic groups we found decreased salt excretion except the acute effect of immersion in comparison with controls. The natriuresis of the immersion day were in decompensated patients significantly elevated in comparison with a control day. This was not due to the acute, but the prolonged immersion effect on renal excretion. During the study the immersion effects increased in both groups of cirrhotic subjects. The controls showed decreased responses. The immersion response shall be caused at least, in part by the Atrial Natriuretic Peptide (ANP): all groups had a significant elevation of ANP during the immersion which was like the renal natriuresis prolonged in the 6th immersion in cirrhotics. A repeated water immersion may improve the natriuretic responsiveness of cirrhotics, especially those of decompensated patients.

Adult↗

PubMed2004

Immersion in water in pregnancy, labour and birth.

BACKGROUND: Enthusiasts for immersion in water during labour, and birth have advocated its use to increase maternal relaxation, reduce analgesia requirements and promote a midwifery model of supportive care. Sceptics are concerned that there may be greater harm to women and/or babies, for example, a perceived risk associated with neonatal inhalation of water and maternal/neonatal infection. OBJECTIVES: To assess the evidence from randomised controlled trials about the effects of immersion in water during pregnancy, labour, or birth on maternal, fetal, neonatal and caregiver outcomes. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group trials register (September 2003). SELECTION CRITERIA: All randomised controlled trials comparing any kind of bath tub/pool with no immersion during pregnancy, labour or birth. DATA COLLECTION AND ANALYSIS: We assessed trial eligibility and quality and extracted data independently. One reviewer entered the data and another checked them for accuracy. MAIN RESULTS: : Eight trials are included (2939 women). No trials were identified that evaluated immersion versus no immersion during pregnancy, considered different types of baths/pools, or considered the management of third stage of labour. There was a statistically significant reduction in the use of epidural/spinal/paracervical analgesia/anaesthesia amongst women allocated to water immersion water during the first stage of labour compared to those not allocated to water immersion (odds ratio (OR) 0.84, 95% confidence interval (CI) 0.71 to 0.99, four trials). There was no significant difference in vaginal operative deliveries (OR 0.83, 95% CI 0.66 to 1.05, six trials), or caesarean sections (OR 1.33, 95% CI 0.92 to 1.91). Women who used water immersion during the first stage of labour reported statistically significantly less pain than those not labouring in water (40/59 versus 55/61) (OR 0.23, 95% CI 0.08 to 0.63, one trial). There were no significant differences in incidence of an Apgar score less than 7 at five minutes (OR 1.59, 95% CI 0.63 to 4.01), neonatal unit admissions (OR 1.05, 95% CI 0.68 to 1.61), or neonatal infection rates (OR 2.01, 95% CI 0.50 to 8.07). REVIEWERS' CONCLUSIONS: There is evidence that water immersion during the first stage of labour reduces the use of analgesia and reported maternal pain, without adverse outcomes on labour duration, operative delivery or neonatal outcomes. The effects of immersion in water during pregnancy or in the third stage are unclear. One trial explores birth in water, but is too small to determine the outcomes for women or neonates.

Analgesia, Obstetrical↗

PubMed2002

Thermoregulatory responses to exercise and warm water immersion in physically trained men with tetraplegia.

OBJECTIVE: To compare thermoregulatory responses of highly trained men who are tetraplegic during 40 min exercise at 65% [Vdot]O(2) peak and 60 min immersion in 39 degrees C water. METHODS: Four physically trained men who are tetraplegic participated in three laboratory visits. The first visit involved familiarisation and then determination of [Vdot]O(2) peak using open circuit spirometry during an incremental test to exhaustion with each man propelling his sport wheelchair on a motor driven treadmill. The order of second and third visits was randomly allocated. Visit 2 involved 40 min of exercise at 65% [Vdot]O(2) peak propelling each man's sport wheelchair on treadmill. Visit 3 involved sitting immersed to nipple line in 39 degrees C water for 60 min. Venous blood was obtained pre, during and after each intervention and analyzed for haemoglobin, haematocrit and changes in plasma volume were calculated. Separated plasma was analyzed for noradrenalin and adrenalin (high performance liquid chromatography). Heart rate, rectal temperature, and sweat rate estimated from a sweat capsule placed on forehead (dew point hygrometry) were recorded throughout. RESULTS: [Vdot]O(2) peak and HR max of these subjects were 1.14+/-0.16 l.min(-1) and 99+/-4 b.min(-1) respectively. Heart rate preimmersion was 67+/-4 b.min(-1) rising to 75+/-4 b.min(-1) after 40 min and 87+/-3 b.min(-1) after 60 min immersion. Heart rate was 68+/-3 b.min(-1) pre-exercise rising to 91+/-5 b.min(-1) after 40 min exercise. Rectal temperature rose from 35.97+/-0.30 degrees C pre immersion to 37.32+/-0.51 degrees C after 60 min immersion, and from 36.42+/-0.20 degrees C pre-exercise to 36.67+/-0.19 degrees C after 40 min exercise. Haemoconcentration occurred during 40 min of exercise and haemodilution occurred throughout 60 min of water immersion. Three participants demonstrated no sweating on the forehead during immersion or exercise. One subject commenced sweating after 20 min exercise and after 5 min of immersion. CONCLUSION: Compared to exercise, immersion was associated with a lower heart rate, a lower plasma noradrenalin concentration and an expanded plasma volume. When considering exercise or warm water immersion as therapeutic modalities in men who are tetraplegic, attention should be paid to heat gain and changes in plasma volume.

Adult↗

PubMed1991

Role of prostaglandins in the natriuresis of head-out water immersion in humans.

1. Prostaglandins may play a role in the natriuresis seen after acute circulatory challenges. To assess this role in head-out water immersion, we compared, in clearance studies, the effects of acute (24 h) and chronic (7 days) administration of indomethacin, an inhibitor of prostaglandin synthesis, on the renal response to head-out water immersion in six healthy subjects on a 200 mmol of sodium/day diet and on a 40 mmol of sodium/day diet. 2. Indomethacin caused a similar degree of sodium retention on each of these two diets. 3. During the 40 mmol of sodium/day diet, acute administration of indomethacin decreased sodium excretion before, as well as during, head-out water immersion; however, the relative increase caused by head-out water immersion was normal. After chronic administration of indomethacin, both baseline sodium excretion and the natriuresis induced by head-out water immersion were similar to those in control studies. 4. During the 200 mmol of sodium/day diet, indomethacin had no effect on baseline sodium excretion, nor on the natriuretic effect of head-out water immersion. 5. Head-out water immersion decreased tubular lithium reabsorption and increased diluting segment delivery. Despite opposite effects of indomethacin on these parameters, indomethacin did not prevent the tubular effects of head-out water immersion on either diet. However, indomethacin did prevent the marked increase in estimated renal plasma flow and the fall in filtration fraction that were observed during head-out water immersion in the absence of indomethacin (control). 6. Head-out water immersion was not associated with an increase in urinary excretion of prostaglandins.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Respiratory, blood-gas transport, and acid-base response of Leptograpsus variegatus to long-term immersion and hyposaline exposure.

The respiratory and acid-base responses of the supratidal crab Leptograpsus variegatus to immersion in either 100% or 50% seawater were measured over a 3-wk period. Leptograpsus maintained haemolymph PO2 and CO2 during immersion, owing partly to elevated cardiac output and without recourse to hyperventilation. Both haemolymph PCO2 and CCO2 were reduced following 3 wk of immersion, and L-lactate remained low, but nonetheless Leptograpsus exhibited a marked metabolic acidosis. Specific responses to 50% seawater exposure were observed in Leptograpsus when compared with control crabs immersed in 100% seawater. Improved O2 delivery concomitant with elevated perfusion and ventilation maintained haemolymph oxygenation. In hyposaline-exposed Leptograpsus, both PCO2 and CCO2 were reduced after 24 h, while pH was elevated after 15 min and remained so during the 3-wk immersion. The marked acidosis exhibited in Leptograpsus exposed to 100% seawater was partially reduced in those in 50% seawater, presumably because of net acid excretion associated with elevated Na+ uptake. Immersion of Leptograpsus reduced Hc-O2 affinity to a greater extent in hyposaline-immersed individuals, while the cooperativity of O2 binding by Leptograpsus Hc decreased at low pH in both salinities. When immersed, the respiratory status of Leptograpsus resembles that of water-breathing crabs. Exposure to 50% seawater causes a twofold increase in energetic cost but does not perturb the immersed condition. The metabolic acidosis induced by chronic immersion is partially compensated at the lower salinity. Leptograpsus thus has the ability to take advantage of habitats ranging from supratidal through brackish to fully marine.

Acid-Base Equilibrium↗

PubMed1975

Suppression of ADH during water immersion in normal man.

Since previous studies from this laboratory have demonstrated that the redistribution of blood volume and concomitant relative central hypervolemia induced by water immersion to the neck causes a profound natriuresis and a suppression of the renin-aldosterone system, it was of interest to assess whether the diuresis induced by immersion was mediated by an analogous inhibition of ADH. The effects of water immersion on renal water handling and urinary ADH excretion were assessed in 10 normal male subjects studied following 14 h of overnight dehydration on two occasions, control and immersion. The conditions of seated posture and time of day were identical. During control ADH persisted at or above prestudy values. Immersion resulted in a progressive decrease in ADH excretion from 80.1 plus or minus 7 (SEM) to 37.3 plus or minus 6.3 muU/min (P smaller than 0.025). Cessation of immersion was associated with a marked increase in ADH from 37.3 +/- 6.3 muU/min to 176.6 +/- 72.6 muU/min during the recovery hour (P smaller than 0.05). Concomitant with these changes urine osmolality decreased significantly beginning as early as the initial hour of immersion from 1044 +/- 36 to 542 +/- 66 mosmol/kg H2O during the final hour of immersion (P smaller than 0.001). Recovery was associated with a significant mean increase in Uosm of 190 +/- 40 mosmol/kg H2O over the final hour of immersion (P smaller than 0.001). The suppression of ADH occurred without concomitant changes in plasma tonicity. These studies are consistent with the suggestion that in hydrated subjects undergoing immersion suppression of ADH release contributes to the enhanced free water clearance, which has been previously documented.

Adult↗

PubMed1991

Human initial responses to immersion in cold water at three temperatures and after hyperventilation.

The present investigation was designed to examine the influence of water temperature and prior hyperventilation on some of the potentially hazardous responses evoked by immersion in cold water. Eight naked subjects performed headout immersions of 2-min duration into stirred water at 5, 10, and 15 degrees C and at 10 degrees C after 1 min of voluntary hyperventilation. Analysis of the respiratory and cardiac data collected during consecutive 10-s periods showed that, at the 0.18-m/s rate of immersion employed, differences between the variables recorded on immersion in water at 5 and 10 degrees C were due to the duration of the responses evoked rather than their magnitude during the first 20 s. The exception to this was the tidal volume of subjects, which was higher on immersion in water at 15 degrees C than at 5 or 10 degrees C. The results suggested that the respiratory drive evoked during the first seconds of immersion was more closely reflected in the rate rather than the depth of breathing at this time. Hyperventilation before immersion in water at 10 degrees C did not attenuate the respiratory responses seen on immersion. It is concluded that, during the first critical seconds of immersion, the initial responses evoked by immersion in water at 10 degrees C can represent as great a threat as those in water at 5 degrees C; also, in water at 10 degrees C, the respiratory component of this threat is not influenced by the biochemical alterations associated with prior hyperventilation.

Adult↗

PubMed1997

Effect of physical exercise on renal response to head-out water immersion.

Head-out water immersion (HOI) induces various renal functional changes, such as diuresis, natriuresis, and kaliuresis. The present study was undertaken 1) to characterize the renal response to HOI in Koreans who routinely ingest high salt diet and 2) to evaluate the impact of exercise on the renal response to HOI. Six healthy male subjects (average Na+ intake of 232 mEq.day-1) were immersed upto the neck in 34.5 degrees C water and rested in a seated position or exercised on a bicycle ergometer for 3 hours. In resting subjects, we observed a reversible increase in urine flow and a decrease in urine osmolality, with no changes in creatinine clearance. The peak urine flow observed during the second hour of immersion was 4-fold greater than the pre-immersion level. The excretion of total osmotic substances rose progressively during the 3-hour immersion, which was accompanied by a similar change in Na+ excretion. The K+ excretion was slightly elevated. The major component of the immersion diuresis was a water diuresis in the early phase and an osmotic diuresis in the late phase of immersion. In exercising subjects, the diuretic and natriuretic responses to HOI were attenuated and the kaliuretic response was potentiated. Blood hemoglobin concentration and plasma levels of renin, ADH, and aldosterone decreased during immersion-rest, but they remained unchanged or increased during immersion-exercise. These results suggest that 1) the cardiac mechanoreceptor-mediated renal responses to HOI are not changed by chronic high salt diet, and 2) excessive urinary sodium and water losses are prevented by exercise during immersion.

Adult↗

PubMed1987

Effect of head-out immersion on plasma atrial natriuretic factor in man.

This study was conducted to examine the role of atrial natriuretic factor (ANF) in the development of diuresis and natriuresis in response to the head-out immersion in 35 degrees C water. Six male subjects were hydrated (0.5% body wt), sat for 1 hr in air (preimmersion), were immersed in water to the neck for 3 hr, and then sat for 1 hr in air (postimmersion). In another series they were similarly hydrated and then sat for 5 hr in air for the time control. Urine and venous blood samples were collected hourly for creatinine and electrolyte measurements. In addition, the concentration of ANF was determined in unextracted plasma by a radioimmunoassay. The pattern of electrolyte excretion was evaluated on the basis of fractional excretion of filtered load. In the time control series, urine flow and fractional excretion of Na and K remained low throughout the 5-hr experimental period. On the other hand, urine flow increased significantly from the preimmersion level of approximately 2 to approximately 7 ml/min during the first hour of immersion (P less than 0.05), after which it decreased to approximately 5 ml/min during the second hour of immersion (P less than 0.05) and to approximately 2 ml/min during the third hour of immersion. Fractional excretion of Na increased continuously from preimmersion level of approximately 1.0 to approximately 1.8% during the second and third hours of immersion (P less than 0.05) and then decreased to 1.2% during the 1-hr postimmersion period. The plasma ANF remained low (approximately 75 pg/ml) during the 5-hr time control period. In the immersion series, plasma ANF increased significantly from the preimmersion level of approximately 80 to approximately 120 pg/ml during the entire 3-hr immersion period and then returned to the preimmersion level during 1 hr postimmersion. These results indicate that the immersion diuresis and natriuresis are indeed associated with the increased ANF release. However, it can not be ascertained from the present study if the increased ANF contributes directly to these renal responses to immersion or in concert with other mediators.

Atrial Natriuretic Factor↗