Skin microvascular reactivity in trained adolescents.

Whilst endothelial dysfunction is associated with a sedentary lifestyle, enhanced endothelial function has been documented in the skin of trained individuals. The purpose of this study was to investigate whether highly trained adolescent males possess enhanced skin microvascular endothelial function compared to their untrained peers. Seventeen highly and predominantly soccer trained boys (V(O)(2)(peak): 55 +/- 6 mL kg(-1) min(-1)) and nine age- and maturation-matched untrained controls (V(O)(2)(peak): 43 +/- 5 mL kg(-1) min(-1)) aged 13-15 years had skin microvascular endothelial function assessed using laser Doppler flowmetry. Baseline and maximal thermally stimulated skin blood flow (SkBF) responses were higher in forearms of trained subjects compared to untrained participants [baseline SkBF: 11 +/- 4 vs. 9 +/- 3 perfusion units (PU), p < 0.05; SkBF(max): 282 +/- 120 vs. 204 +/- 68 PU, p < 0.05]. Similarly, cutaneous vascular conductance (CVC) during local heating was superior in the forearm skin of trained versus untrained individuals (CVC(max): 3 +/- 1 vs. 2 +/- 1 PU mmHg(-1), p < 0.05). Peak hyperaemia following arterial occlusion and area under the reactive hyperaemia curve were also greater in forearm skin of the trained group (peak hyperaemia: 51 +/- 21 vs. 35 +/- 15 PU, p < 0.05; area under curve: 1596 +/- 739 vs. 962 +/- 796 PUs, p < 0.05). These results suggest that chronic exercise training in adolescents is associated with enhanced microvascular endothelial vasodilation in non-glabrous skin.

Bacteria and endotoxin removal from bicarbonate dialysis fluids for use in conventional, high-efficiency, and high-flux hemodialysis.

The use of bicarbonate-based dialysis fluids in hemodialysis centers in the United States has increased with the advent of high-efficiency and high-flux hemodialysis. However, bicarbonate dialysis fluids can support rapid bacterial growth and high endotoxin concentrations. This study determined the efficacy of an ultrafiltration device in reducing the bacterial and endotoxin concentrations in bicarbonate dialysis fluids. A polysulfone hollow fiber dialyzer was used to ultrafilter bicarbonate concentrate before entering the central proportioner and bicarbonate dialysate after exiting the proportioner in single patient dialysis machines. Pre- and post-ultrafilter samples were collected for bacterial and endotoxin assays over 10 months. Ultrafiltration of bicarbonate concentrate reduced bacterial and endotoxin concentrations from 288,330 colony forming units (CFU)/ml and 42,804 pg/ml to 0.47 CFU/ml and 109 pg/ml, respectively. Ultrafiltration of the dialysate in single patient systems decreased bacterial and endotoxin concentrations from 15,889 CFU/ml and 1,746 pg/ml to 0.003 CFU/ml and 0.109 pg/ml, respectively. These results demonstrate that ultrafiltration of bicarbonate dialysis fluids is effective in reducing bacterial and endotoxin contamination inherently associated with the use of bicarbonate-based dialysates.

Vaginal birth after cesarean or repeat cesarean section: medical risks or social realities?

Despite the known medical safety and success of vaginal birth after cesarean section, rates of planned repeat cesarean sections remain high. The process involved in women's decisions to choose vaginal birth after cesarean section or repeat cesarean section was investigated by a questionnaire study at a private and a public hospital. Women were questioned regarding timing, influence of others, reasons for their choice, satisfaction with the decision, etc. Results from 160 respondents showed that over half the women identified themselves as the primary decision maker. Physicians exerted more influence on the decisions of patients at the public hospital than on the patients at the private hospital. Overall, social exigencies appeared to play a more important role than an assessment of the medical risks in making these decisions.

Hyperbaric liver dysfunction in saturation divers.

Earlier demonstration of elevated blood thyroid hormones and transaminase activities during controlled chamber dives to 540 and 660 msw [at AMTE(PL), Gosport, England; 1980 and 1981] led to the suspicion that high compression may interfere with liver function. Further studies, here described, of blood thyroid hormone level changes during the course of subsequent dives indicate that thyroxine and reverse triiodothyronine elevations are to be expected during any period of sustained compression, to depths as shallow as 61 msw. Moreover, blood levels of thyroxine-binding globulin (TBG), measured in the 540 and 660 msw dives, were also shown to rise, probably accounting for the hormone changes. This elevation is not confined to TBG, being demonstrable in at least six other glycoproteins (sex hormone-binding globulin, transferrin, ceruloplasmin, haptoglobin, alpha 1 acid glycoprotein, and alpha 2 macroglobulin). Since all these proteins share identical or very similar metabolic fates within the liver, these findings lend further weight to our hyperbaric liver dysfunction theory. How such disturbances may come about is discussed, together with its possible implications apropos high pressure nervous syndrome and divers' well-being and capabilities while at depth.

U.K. deep diving trials.

Using a breathing medium of 40 kPa oxygen, remainder helium, 18 volunteer subjects participated in a series of 15 exposures to pressures equivalent to depths of 180-540 m s.w. The time of exposure at these pressures was mostly 2 days, except for the 540 m s.w. exposure, when 6 days were spent at full pressure. Compression procedures, based upon placing 'stages' at 60 m s.w. intervals, evolved with experience and proved to be a highly successful way of achieving acceptable pressure-time courses. Decompression combined slow linear release of pressure with overnight halts for sleep. On one occasion a depth of 660 m s.w. was reached by breathing 40 kPa oxygen, 10% nitrogen, remainder helium. Throughout all exposures, teams of investigators followed the changes in cardiovascular, respiratory, haematological, neurophysiological and metabolic status, and mental performance of the volunteers. Some major findings were that the neurophysiological and behavioural changes could be assigned to the motor, or vestibular, or cerebral, or autonomic systems, and were mainly first observed during compression. The subjects suffered, apparently from severe nitrogen narcosis, when breathing 10% (by volume) nitrogen in oxygen-helium at 420 m s.w. Lung ventilation was remarkably adaptable to the oxygen requirements of exercise at all depths, but cardiac output was adversely affected at 540 m s.w., particularly for heavier workloads. Ventilatory responses to carbon dioxide were significantly elevated after diving. Thermal balance was seen to be precarious, but nevertheless it was achieved by the normal subjective assessments of comfort. Water loss was affected by diminished evaporation from the skin. Skin temperature sensitivity was changed and took many days after the dives to return to normal. Energy requirements increased for work purposes, but basal metabolic rate was undisturbed. Body chemistry altered at pressures in excess of 300 m s.w., for example thyroid hormone and nitrogen balances were affected. No decompression sickness was encountered until the pressures were low, but marked haematological changes could occur during decompression. Every change that occurred during these dives reverted to normal, mostly before the end of the decompression. It is concluded that diving with oxygen-helium breathing mixtures to depths as great as 540 m s.w. can be effective and safe. An attempt is made to assess the physiological significance of the principal findings.