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Biomedical subjects

K A Kirsch

Publications and source records attributed to K A Kirsch.

28 records · Page 2Linked to original sources
PubMed1984

Venous pressure in man during weightlessness.

To determine whether the body fluid shift from the lower limbs toward the head that occurs during spaceflight leads to lasting increases of venous pressure in the upper body, venous pressure and hematocrit measurements were made on four astronauts before flight and 1 and 12 hours after recovery and compared with measurements in space. During the mission the hematocrit was elevated and the venous pressure lowered by 1 to 8 centimeters of water as compared with the preflight data. One hour after landing the hematocrit decreased, indicating a hemodilution, venous pressures were unexpectedly high, and a body weight loss of 4 to 5 percent was observed. Twelve hours later the venous pressures were the lowest recorded during the study. The fluid shift apparently takes place during the first several hours of spaceflight. Thereafter, the pressure in the peripheral veins and the central circulation is lower than that measured before flight.

Body Fluids↗
PubMed1981

Fluid control mechanisms after exercise dehydration.

Since the osmocontrol- (osmolality), the renin-angiotensin-(PRA), and the volume control-(central venous pressure, CVP) systems are involved in the maintainance of the salt-water balance, we investigated the pattern of these parameters in the recovery period after exercise dehydration in 13 well trained long-distance runners. On average, after exercise the athletes had lost 3.1% of their body weight (BW). After eating and drinking the BW was still 1.3% below control value, indicative of continuing deficits. Plasma osmolality increased, however, from an average value of 286-290 mosmol/kg after exercise as well as postprandially, but the change was not significant. PRA-Levels rose significantly from 0.167-0.599 ng/ml . h after exercise and decreased to 0.333 ng/ml . h postprandially. CVP was significantly altered after exercise (-3.5 cm H20) as well as postprandially (-2.4 cm H20). The results suggest that the salt-water balance is maintained by the interplay of all the three systems. In conflicting situations, however, as when intercompartmental water- and solute-shifts take place during the recovery period, the volume control system triggered off by the CVP is the dominant corrective response to the prevailing deficits.U

Blood Physiological Phenomena↗
PubMed1981

Feeding patterns of endurance athletes.

Feeding pattern was studied in 13 long distance runners, eight cyclists and eight sedentary men. The timing of the food and fluid intakes, the kind and the amount of food and fluids taken, the body weight (BW), and the exercise schedules were recorded on 3 or 4 successive days under ad libitum conditions of feeding and drinking. The subjects remained in energy and water balance, since the BW measured in the morning during the observation periods did not change significantly. The total caloric intake was 13 876 kJ per day in the runners and 26 282 kJ per day in the cyclists, exceeding the estimated basic metabolic rate by 103% and 250% respectively. The total water intakes were 33 and 36 ml . kg-1 . 24 h-1. The athletes consistently showed a nibbling pattern, characterized by frequent eating and drinking (average 8-10 per day). In the runners 63% of eating and drinking were synchronized, in the cyclists only 49% (p less than 0.01). In both groups drinking occurred most frequently in the morning, at noontime and in the evening. After 8 p.m. 45% of the total daily fluid intake occurred. In all likelihood the fluid intake followed an underlying circadian rhythm. The total intake frequency was determined by the total caloric needs.

Adolescent↗
PubMed1980

Tissue compliance in superficial tissues along body axis in man.

A previously described miniature plethysmograph which allowed the measurement of tissue volumes in superficial tissues was enclosed in a small plexiglass chamber and attached to the frontal area, sternum, dorsum and the tibia. The tissues interposed between bone and skin underneath the chamber were exposed to pressures between +/- 3 and +/- 15 mmHg in order to test tissue deformability. The pressure application induced within the first 5 s a fast component of tissue deformation comprising between 75-90% of the total deformation followed by a slow component which lasted till the end of the pressure application. The highest deformability was found in the tissues of the sternum and dorsum whereas the stiffest tissues were in the pretibial area. Assuming the tissue deformation is due to a translocation of fluid into or out of the pressurized tissue, the tissue compliance was calculated. This calculated tissue compliance was 19.2 ml . 1,000 ml-1 . mmHg-1 in the sternum and 6.4 ml . 1,000 ml-1 . mmHg-1 (P < 0.01) in the pretibial area applying a pressure of +/- 3 mmHg. The differences observed are due to the morphological arrangement of the tissue fibres which in turn have to counteract the gravity forces to which the tissues are usually exposed during upright standing.

Animals↗
PubMed1980

A new miniature plethysmograph to measure volume changes in small circumscribed tissue areas.

With an ultrasonic method tissue layer thickness was measured in man in circumscribed superficial tissue areas where the underlaying bone provided good backwall echos. In a 5 mm tissue layer changes of +/- 0.2% could be reliably detected. Knowing the height of the tissue cylinder between the surface of the skin and the bone allowed to calculate the tissue volume. The ultrasonic probes could therefore serve as miniature plethysmograph. Several probes were attached in the frontal region, sternum, along the vertebral column and along the tibia simultaneously. Changes of the volume content of the superficial shell tissues were induced by orthostasis, water immersion and heat exposure. It was possible to assess quantitatively the volume shifts into or out of the superficial tissues. During orthostasis 166 ml of fluid left the superficial tissues of the cephalad parts of the body and 164 ml could be traced in the dependent parts. Heat exposure was followed by a pooling 140 ml in the tissues studied. The most pronounced tissue volume changes were observed in the forehead region during heat exposure.

Electronics↗
PubMed1978

Sex-dependent changes in plasma globulins in women and men exposed to heat stress.

Healthy, sedentary women and men, aged 20 to 30 years, were exposed to the same degree of intermittent heat stress in a sauna bath. Blood samples were taken immediately before and at various intervals after heat exposure. The concentrations and intravascular masses of IgG, IgA, IgM, alpha1-antitrypsin, transferrin and alpha2-macroglobulin were determined by the radial immunodiffusion technique and by the measurement of plasma volume. Losses in body weight and plasma volume were lower in women than in men. The globulin concentrations increased significantly in both sexes after heat exposure. The sum of the masses of individual globulins increased only in women, a change interpreted as globulin shifts from the interstitial into the vascular space. Whereas it is unlikely that sex-dependent differences in these shifts are due to changes in vascular permeability, it seems that the protein composition of the lymphatic fluid entering the vascular space plays an important role in these shifts.

Adult↗
PubMed1976

Plasma volume, albumin and globulin concentrations and their intravascular masses. A comparative study in endurance athletes and sedentary subjects.

Plasma volume, hematocrit, intravascular protein concentration, colloid osmotic pressure and the intravascular mass of proteins were measured in 49 sedentary subjects and 40 endurance athletes (long-, middle distance runners, cyclists). The plasma volume in sedentary subjects was 42.7(35.8-51.7) ml/kg body weight (BW) as compared to 54.6(46.7-65.9) ml/kg BW in athletes. The protein concentrations were 71.0 (66.5-77.1) g/l in sedentary subjects and 69.0 (64.8-75.2) g/l in athletes. The respective numbers for the hematocrit were 44.6 (40.1-49.25)% and 42.8 (38.2-49.6)%, for the colloid osmotic pressure 38.0 (36.0-40.5) cm H2O (n=35) and 30.0 (25.0-34.4) cm H2O (n=31), for the intravascular mass of proteins 3.09 (2.45-4.01) g/kg BW and 3.75 (3.31-4.67) g/kg BW. All differences were statistically significant at least on the 5% level. The physiological consequences for athletes of having a lower hematocrit and lower protein concentration but a higher intravascular mass of proteins (+22%) for their waterbalance as well as for their dietary protein intake are discussed. Endurance exercise stimulates mainly the synthesis of albumin and globulins produced by the liver resulting in an expansion of the PV. The protein synthesis of the RES does not seem to respond to exercise stimulus.

Humans↗
PubMedDate not supplied

Current views and future programs in cardiovascular physiology in space.

The volume shift of 2000 cm3 from the lower to the upper part of the human body during weightlessness gave rise to theoretical and practical questions which are addressed in this communication. The analysis revealed that the mobilized fluid reduced the interstitial fluid of the lower extremities by 40%. Applying the current ideas in the field of interstitial tissue physiology to these problems, one must conclude that the fluid displacement can only be brought about by a change of the interstitial tissue compliance. Based on the observations made by the astronauts and on our working hypothesis, a method was proposed to follow the fluid migration and to measure the tissue compliance in man. Results are reported from experiments under terrestrial conditions. They show that the tissue compliance indeed can be modulated. Applying the method in space can eventually help to clarify several concepts in terrestrial physiology.

Adaptation, Physiological↗
PubMedDate not supplied

The cardiac filling pressure following exercise and thermal stress.

Under heat stress, a decrease of the central venous pressure (CVP) was regularly observed, raising the question of whether this reaction is a limiting factor for the circulation. In animal experiments it could be shown, however, that despite a lowered CVP, which depended on the elevated body temperatures, a high cardiac output (CO), as well as an elevated stroke volume could be maintained. A low CVP went hand in hand with a low total peripheral resistance. It was argued that under these circumstances the low CVP was not limiting because the intrinsic factors of the heart (sympathetic stimulation) were capable of maintaining a high CO. In human experiments the lowered CVP had to be seen in relation to the degree of dehydration. Regardless of whether the plasma volume remained constant, as in exercise, or declined, as in thermal stress (sauna), the CVP followed the volume depletion of the vascular and extravascular space, and it might well be that under these circumstances CVP is limiting. In this case, however, the altered CVP must be seen first as a monitor for the fluid deficit and not as a factor controlling cardiac function.

Adaptation, Physiological↗