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PubMed2001

Facial immersion bradycardia in teenagers and adults accustomed to swimming.

We compared heart rate and breath-hold duration during facial immersion in teenagers, 11-14 years (N = 6), 15-18 years (N = 6) and adults, 33-48 years (N = 11). The subjects were members of a competitive swimming club, and were familiar with facial immersion. In contrast to the results of a previous study (J. Appl. Physiol. 63 (1987) 665) in which naïve subjects were used, the 11-14 group were able to breath-hold as long as adults (mean +/- SE, 47+/-6 vs. 46+/-4 s). This allowed time for the full development of bradycardia. Pre-immersion heart rate was significantly higher in young teens than in adults (100+/-4 vs. 78+/-3 b.p.m.). Heart rate after 30 s of head immersion was statistically identical (young teens, 65+/-5 b.p.m.; adults, 64+/-3 b.p.m.). Therefore, both the percentage reduction from pre-immersion rate and rate of fall in heart rate were greater in 11-14-year-olds than in adults. Oxygen loading increased breath-hold time in all groups, and slowed the onset of bradycardia in adults and older teens, but not in the 11-14-year-old group, during the first 10 s after immersion. We conclude that breath-hold time in teenagers is influenced by familiarity with underwater breath-holding. The resulting cardiovascular adjustments in 11-14-year-olds are intrinsically at least as intense as those in adults and seem to have a faster onset.

Adolescent↗
PubMed1991

Aldosterone, atrial natriuretic factor and sodium intake as determinants of the natriuretic response to head-out water immersion in healthy subjects.

1. The effect of sodium intake on the natriuresis and hormonal changes induced by head-out water immersion was studied in seven normal subjects during head-out water immersion and on a control day while successively on 20 mmol of sodium/day and 100 mmol of sodium/day diets. The effects of head-out water immersion were compared with those seen on the control day for both diets. 2. The natriuresis on the 100 mmol of sodium/day diet was significantly greater than on the 20 mmol of sodium/day diet (natriuretic peak: 10.3 +/- 2.2 versus 3.9 +/- 1 mmol of sodium/h; P less than 0.01). The total sodium excretion during the 3 h of head-out water immersion was 26.2 +/- 2.0 mmol on the 100 mmol of sodium/day diet and 9.9 +/- 0.9 mmol on the 20 mmol of sodium/day diet (P less than 0.01). In contrast, the increase in the plasma atrial natriuretic factor level was similar on both diets (peak plasma atrial natriuretic factor level 23.1 +/- 1.9 versus 26.2 +/- 1 pg/ml; not significant). As expected, the baseline serum aldosterone level was higher on the 20 mmol of sodium/day diet and, despite a significant suppression, remained significantly higher at the end of the third hour of head-out water immersion (peak serum aldosterone level: 495 +/- 130 versus 197 +/- 26 pmol/l, P less than 0.06). Furthermore, there was an inverse relationship between the serum aldosterone level and the urinary sodium excretion at the time of peak natriuresis (r = -0.59, P less than 0.01). 3. We conclude that the effect of sodium intake on the natriuresis induced by head-out water immersion is more dependent upon anti-natriuretic agents, such as aldosterone, than on natriuretic factors, such as atrial natriuretic factor.

Adult↗
PubMed2002

Atrial distension, haemodilution, and acute control of renin release during water immersion in humans.

We tested the hypothesis that atrial distension (stimulation of cardiopulmonary baroreceptors) is not the single pivotal stimulus for the acute suppression of renin release during water immersion in humans and that immersion-induced haemodilution constitutes an important additional stimulus. In nine healthy male subjects, identical increases in atrial distension were induced by two immersion procedures (of 30 min each); one without (WI) and one with attenuation (WI + cuff) of the concomitant haemodilution (estimated from changes in plasma protein concentration) by inflating thigh cuffs during immersion. During WI, central venous pressure (CVP) and left atrial diameter (LAD) increased (P < 0.05) by 5.5 +/- 0.4 mmHg and 4.6 +/- 0.5 mm, respectively, and plasma protein concentration and plasma renin activity (PRA) progressively decreased (P < 0.05) by 4.8 +/- 0.5 g L(-1) and 1.6 +/- 0.2 ng mL(-1) h(-1) (to 49 +/- 4% of baseline values), respectively. The WI + cuff caused similar atrial distension as WI (CVP and LAD increased by 6.9 +/- 0.5 mmHg and 5.5 +/- 0.5 mm, respectively), attenuated haemodilution (plasma protein concentration decreased by 1.9 +/- 0.4 g L(-1), P < 0.05 vs. WI), and markedly inhibited suppression of PRA, which decreased by 0.4 +/- 0.1 ng mL(-1) h(-1) (to 87 +/- 4% of baseline values, P < 0.05 vs. WI). Differences in renin release could not be accounted for by differences in mean arterial pressure. In conclusion, baroreceptor stimulation induced by atrial distension is not the single pivotal stimulus for the acute suppression of renin release in response to intravascular volume expansion by water immersion in humans. Haemodilution constitutes a significant and conceivably the principal stimulus for the acute immersion-induced suppression of renin-angiotensin system activity.

Adult↗
PubMed1992

Effect of daily immersion on the edema of pregnancy.

To evaluate whether pregnant women become refractory to the effects of immersion, we studied 11 healthy women from 26 to 38 weeks' gestation, immersed in 34 degrees C shoulder-deep water for 4 or 5 consecutive days. The daily immersion diuresis showed no change throughout the study (p = 0.98: mean, 145 ml, 159 ml, 159 ml, 173 ml, 184 ml, day 1 through day 5, respectively). The range of urine volumes was broad, 35 to 675 ml, depending on the subject's degree of edema. Immersion produced a significantly larger diuresis compared with preimmersion values, 162 ml versus 110 ml. Maternal blood pressure and heart rate consistently fell during immersion, and this effect was maintained for each day studied. The subjects' hematocrit, hemoglobin, and total protein were unchanged from a preimmersion sample on day 1 to a postimmersion sample on the last day of the study. The results of this study indicate that pregnant women do not become refractory to the hemodynamic and diuretic effects of immersion.

Adult↗
PubMed2006

Micromorphological analysis of dentinal structure after irradiation with Nd:YAG laser and immersion in acidic beverages.

OBJECTIVE: The purpose of this study was to analyze dentinal surfaces that were exposed to acidic beverages, then treated with Nd:YAG laser and afterwards exposed to acidic beverages again. BACKGROUND DATA: Dentin hypersensitivity can result from surface erosion caused by acidic beverages, which exposes and enlarges the dentinal tubules. Nd:YAG laser has been used as a treatment option. METHODS: Sixty-eight dentin samples were prepared and assigned to five groups: G1, control (n = 4); G2, 3-h immersion (n = 16); G3, 3-h immersion + Nd:YAG; G4, 3-h immersion + Nd:YAG + 3-h immersion; and G5, 3-h immersion + Nd:YAG + 6-h immersion. Each group was divided into four subgroups, with different acid beverages: lemon (n = 4); passion fruit (n = 4); cola (n = 4); and wine (n = 4). Irradiation with the Nd:YAG was in contact mode, focused and perpendicular through a quartz fiber of 300 microm of diameter in scanning movements for 60 sec with a 10-sec interval and the paramenters 0.6 W, 10 Hz, 60 mJ, and 85 mJ/cm(2). Each subgroup was examined by scanning electron microscope. RESULTS: All the acidic beverages contributed to exposure and increased diameter of the dentinal tubules. CONCLUSIONS: Irradiation with Nd:YAG laser produced obliteration of and reduction in the number of dentinal tubules, thus modifying the original structure.

Adult↗
PubMed1986

Ventilatory drive during face immersion in man.

Four series of experiments have been performed in normal subjects to determine whether face immersion gives rise to a reduction in ventilatory drive. Such a response might be advantageous, like the cardiovascular components of the 'diving response', in prolonging breath-hold diving. In the first series, ventilatory drive was measured indirectly as the maximal voluntary breath-holding time, starting each breath-hold at the same alveolar partial pressures and at the same lung volume. When the face was immersed in cold water, breath-holding times were increased by 14%. The breaking point occurred at a higher alveolar PCO2 and the rate of rise of PCO2 was not affected. Control immersions in warm water had no effect. In the second and third series, subjects lay prone and breathed either air or 5% CO2 through a valve in the bottom of a bowl. Minute ventilation was measured before, during and after 5 min of face immersion in cold water. Transient hypoventilations of 13% and 10% respectively were seen, accompanied by small rises in alveolar PCO2. In control experiments, immersion of the forearm in cold water produced the opposite responses. In the fourth series, a cold wet pack was applied to the face during moderate steady-state exercise. A small irregular hypoventilation was seen, but not in control experiments when a warm pack was applied. Face temperatures fell by about 10 degrees C in these experiments. No material changes were found in the temperatures of the inspired air or of the aural canal. It is concluded that face immersion in cold water causes a modest reduction in ventilatory drive in man. This appears to be a component of the 'diving response'.

Adult↗
PubMed1988

Human adaptation to repeated cold immersions.

1. The present investigation was designed to examine human adaptation to intermittent severe cold exposure and to assess the effect of exercise on any adaptation obtained. 2. Sixteen subjects were divided into two equal groups. Each subject performed ten head-out immersions; two into thermoneutral water which was then cooled until they shivered vigorously, and eight into water at 15 degrees C for 40 min. During the majority of the 15 degrees C immersions, one group (dynamic group) exercised whilst the other (static group) rested. 3. Results showed that both groups responded to repeated cold immersions with a reduction in their initial responses to cold. The time course of these reductions varied, however, between responses. 4. Only the static group developed a reduced metabolic response to prolonged resting immersion. 5. It is concluded that repeated resting exposure to cold was the more effective way of producing an adaptation. The performance of exercise during repeated exposure to cold prevented the development of an adaptive reduction in the metabolic response to cold during a subsequent resting immersion. In addition, many of the adaptations obtained during repeated resting exposure were overridden or masked during a subsequent exercising immersion.

Adaptation, Physiological↗
PubMed1980

Effect of cold water immersion and its combination with alcohol intoxication on urine flow rate of man.

Urine flow rate was determined for man before and after immersion in either thermoneutral (33 degrees C) or cold (10 degrees C) water. The effect of alcohol intoxication of a level of approximately 80 mg dL-1 was also evaluated for the cold water immersion. Immersion and cold were additive in their effect, resulting in a mean urine flow rate of 4.25 mL min-1, approximately 3.5 times the preimmersion level. Alcohol intoxication in conjunction with cold water immersion caused a further large increase in urine flow to 8.03 mL min-1. These results permit better evaluation of the importance of volume diuresis as it relates to the reduction of insulative performance of dry-type immersion suits for cold water survival, and to the possible enhancement of "rewarming shock" during therapy for hypothermia victims. The increased urine production observed when alcohol treatment was added to cold immersion provides information for speculation on mechanisms of volume diuresis.

Adult↗
PubMed1981

Expired air volumes of males and females during cold water immersion.

Expired air volumes were measured from a random population of adult male and female human volunteers before and during short-term immersion in either cold (13.53 +/- 0.13 degrees C) or warm (33.18 +/- 0.11 degrees C) water. A statistically significant difference was found in the pulmonary ventilation over the first 4 min of immersion between males and females when immersed in cold water. The swim suits worn could not account for the differences observed. No statistically significant difference in pulmonary ventilation was found between males and females during warm water immersion. A numerically smaller group of volunteers was preheated in a sauna before immersion in cold or warm water and this resulted in an attenuated ventilatory response. In this instance there is no statistically significant difference in ventilation between males and females. Also, in another small group of volunteers, surface and deep skin temperatures were continuously measured before and during immersion in cold water. The rates of change of deep skin temperature between males and females were found to be similar.

Adult↗
PubMed1976

Closing volumes in man immersed to the neck in water.

Closing volumes (CV), along with residual volume (RV), vital capacity (VC), along with residual volume (RV), vital capacity (VC), and expiratory reserve volume (ERV) were determined in 10 subjects in the dry and while immersed to the neck in water. Closing volumes during immersion increased 41.3% (P less than 0.001) over dry values while RV decreased 9.35% (P less than 0.001) and VC decreased 9.94% (P less than 0.001). The large decrease of 71.3% (P less than 0.001) in ERV resulted in the impingement of closing capacity (CV + RV) on the tidal volume in 9 out of 10 subjects. We interpret this to mean that airway closure occurs during tidal ventilation in immersed subjects and may result in impaired gas exchange. When tourniquets were applied to all four limbs during immersion closing volumes increased only 32.1%, but increased to 64.3% when they were removed. If engorgement of peribronchial vessels predisposes airways to collapse, a reduction of plasma volume during an extended period of immersion might lessen this possibility. In a series of long term (2.5-h) immersion experiments where moderate reductions (-10 to -7%y in plasma volume were observed, we found, however, no correlative changes in closing volume.

Adult↗
PubMed1977

Diaphragmatic function during immersion.

Diaphragmatic function during immersion to midneck level was studied in upright mongrel dogs, using constant electrophrenic stimulation. Effectiveness of diaphragmatic contraction was analyzed in terms of inspired volume (VT) (with airways open), and change in intrathoracic pressure (Pmus) (with the respiratory system occluded). Hydrostatic compression of the immersed body decreased functional residual capacity (FRC) to 55% base-line value (FRCO), resulting in a 2.8-fold increase in Pmus. In spite of this Pmus increase, VT often decreased during immersion, averaging only 83% VTO (base-line value in air). Hence, immersion was associated with a marked stiffening of the respiratory system. The Pmus increase during immersion persisted after restoration of FRC to FRCO, and was related to diaphragmatic length being greater in water than in air under condition of iso-lung volume. In all, there were three factors affecting diaphragmatic function during immersion: FRC reduction, change in thoracic configuration, and stiffening of the respiratory system.

Animals↗
PubMed1978

Alcohol and respiratory and body temperature changes during tepid water immersion.

Resting subjects were immersed for 30 min in water at 22 and 30 degrees C after drinking alcohol. Total ventilation, end-tidal PCO2, rectal temperature, aural temperature, mean skin temperature, heart rate, and oxygen consumption were recorded during the experiments. Blood samples taken before the immersion period were analyzed by gas-liquid chromatography. The mean blood alcohol levels were 82.50 +/- 9.93 mg.(100 ml)-1 and 100.6 +/- 12.64 mg (100 ml)-1 for the immersions at 22 and 30 degrees C, respectively. There was no significant change in body temperature measured aurally or rectally, mean surface skin temperature, or heart rate at either water temperature tested. Total expired ventilation was significantly attenuated for the last 15 min of the immersion at 22 degrees C, after alcohol consumption as compared to the ventilation change in water at 22 degrees C without ethanol. This response was not consistently significantly altered during immersion in water at 30 degrees C. It is evident that during a 30-min immersion in tepid water with a high blood alcohol level, body heat loss is not affected but some changes in ventilation do occur.

Body Temperature↗
PubMed1978

Contribution of peripheral pooling to the renal response to immersion in the dog.

The present investigation evaluated the renal and hemodynamic responses to head-out water immersion in dogs. Dogs were immersed in the vertical (seated) position in a 34 degrees C bath. Urine flow (V), osmolar clearance (Cosm), free water clearance (CH2O), sodium excretion (UNa+V), potassium excretion (UK+V), GFR, effective renal plasma flow (ERPF), central venous pressure (CVP), and cardiac output (CO) all increased significantly during immersion. This response was unchanged by bilateral cervical vagotomy or by deoxycorticosterone acetate and antidiuretic hormone administration. The control values of these dogs were low and indicated a state of peripheral vascular pooling which was readjusted to normal by the immersion maneuver. The renal and hemodynamic values during the period of immersion were similar to values of a group of dogs which were recumbent in air. Furthermore, when the latter group of dogs were tilted head down 19 degrees, there was no further increase in any of the measured parameters. These data are consistent with the view that water immersion in the upright dog simply redistributes blood volume back to that level seen in the recumbent dog, a position which is more natural for this species.

Animals↗
PubMed1980

Fluid shifts and endocrine responses during chair rest and water immersion in man.

To determine the effect of external water pressure per se on intercompartmental fluid volume shifts, plasma and urine electrolytes, osmotic and endocrine responses were compared in four men (21-22 yr) during 8 h of water immersion (TH2O = 34.4 degrees C) and during 8 h of chair rest (Ta = 22.5 degrees C), followed by16 h of bed rest in both regimens. Water intake was 1,800 ml during 8-h exposures. Urine volume during immersion was 2,954 ml/8 h and 1,538 ml/8 h (P less than 0.01) during chair rest; the respective decreases in extracellular volume (ECV) were 2,230 ml/8 h and 1,892 ml/8 h. Losses from the intersititial volume (1.81 vs. 1.67 liters) and plasma volume (0.43 vs. 0.23 liters) during immersion and chair rest, respectively, were approximately proportional to theri normal ratios. With a negative H2O balance (corrected for blood withdrawal) during immersion of 1,234 ml and a positive balance (190 ml) during chair rest, there appeared to be a shift of ECV to the intracellular compartment in both regimens. There was suppression of both plasma arginine vasopressin (AVP) and renin activity (PRA) during chair rest and immersion. It appears that the increased central blood volume, as opposed to increased plasma osmolality, is the primary stimulus for AVP suppression. In hyperhydrated subjects, about half (6.7%) of the immersion plasma volume loss of 12.6% could be attributed to orthostatic responses associated with the upright body position during chair rest and the remaining half to the external water pressure.

Adult↗
PubMed1980

Initial renal responses of nonhuman primate to immersion and intravascular volume expansion.

Experiments were performed in anesthetized Macaca fascicularis monkeys to determine if the initial renal responses of these animals to head-out vertical water immersion and isoncotic, isotonic volume expansion are similar, especially with regard to the onset of any changes in solute or water excretion. Significant increases in urine flow, sodium excretion, and osmolar clearance occurred after 10 min of immersion but not until 30 min after volume expansion. Potassium excretion increased during immersion but decreased after volume expansion. Mean arterial blood pressure increased after 30 min of immersion but was unchanged after volume expansion. Indices of vascular filling, central venous pressure in the immersed animals and left ventricular end-diastolic pressure in the volume-expanded animals, increased immediately after the intervention. Effective renal plasma flow increased in both groups but glomerular filtration rate was not consistently elevated. These results suggest that, in the nonhuman primate, immersion and volume expansion exert their renal effects through different afferent and/or efferent mechanisms and should not be considered as similar volume stimuli.

Animals↗
PubMed1980

Characterization of renal response to prolonged immersion in normal man.

During the initial phase of spaceflight, there is a translocation of fluid from the lower parts of the body to the central vascular compartment with a resultant natriuresis, diuresis, and weight loss. Whether this natriuresis and diuresis result in the attainment of a new steady state or whether the circulatory adjustment is incomplete is the subject of continuing controversy. Because water immersion is regarded as an appropriate model for studying the redistribution of fluid that occurs in weightlessness, we carried out an immersion study of relatively prolonged duration in order to characterize the temporal profile of the renal adaptation to central hypervolemia. Twelve normal male subjects underwent an immersion study of 8-h duration in the sodium-replete state. Immersion resulted in marked natriuresis and diuresis which were sustained throughout the immersion period. The failure of that natriuresis and diuresis of immersion to abate or cease despite marked extrcellular fluid volume contraction as evidenced by a mean weight loss of -2.2 +/- 0.3 kg suggests that central blood volume was not restored to normal and that some degree of central hypervolemia probably persisted.

Adolescent↗
PubMed1983

Effect of central vascular engorgement and immersion on various lung volumes.

The purpose of this study was to determine the relative contribution of central vascular engorgement (CVE) and increased hydrostatic pressure on various lung volumes during head-out immersion in water. Residual volume (RV) and vital capacity (VC) were determined on 12 male volunteers under three randomly assigned conditions: control, CVE, and immersion. CVE was produced via G-suit inflation. There were significant (P less than 0.01) mean decreases, compared with the control value, of 4.9% (280 ml) and 5.9% (340 ml) in VC during CVE and immersion, respectively. RV was not significantly changed across the three conditions. It was concluded that more than 80% of the decrease in VC during immersion can be attributed to CVE. However, the mechanism by which CVE decreased VC is still unclear. In addition, these data suggest that RV is relatively insensitive to the increase in CVE normally associated with immersion. Therefore, during immersion, RV is not simply the result of the balance of these opposing forces (i.e., CVE and hydrostatic pressure), as previously suggested.

Adult↗
PubMed1984

Immersion diuresis without expected suppression of vasopressin.

To investigate fluid, electrolyte, and plasma vasopressin (PVP) and renin activity (PRA) responses, six men (20-35 yr) were immersed to the neck (NI) in water at 34.5 degrees C for six h after overnight food and fluid restriction. Diuresis was 1,061 +/- 160 (SE) ml/6 h during immersion and water balance was -1,285 +/- 104 ml/6 h. Preimmersion PVP was 0.7 +/- 0.2 pg/ml and increased to 3.0 +/- 0.6 pg/ml (P less than 0.05) at 6 h. PVP was unchanged at 1.2 +/- 0.1 pg/ml in the 6-h seated nonimmersion experiment at 25 degrees C. Plasma volume increased by 7.8 +/- 1.6% (P less than 0.05) at 60 min of NI and decreased thereafter. Serum osmolality was constant (292 +/- 1 mosmol/kg) throughout NI, whereas PRA decreased progressively from 1.9 to 0.5 ng angiotensin I X ml-1 X h-1 (P less than 0.05) at the end of immersion. In spite of moderate thirst just before NI, thirst sensations were attenuated and no water was consumed ad libitum during immersion. These data indicate that PVP is not suppressed when there is no fluid intake during immersion and suggest that the action of factors other than PVP suppression are necessary to explain the mechanism of immersion diuresis.

Adult↗