Prevalence of patent foramen ovale (PFO) and MRI-lesions in mild neurological decompression sickness (type B-DCS/AGE).

BACKGROUND: Neurological decompression sickness (DCS/AGE) may cover two variants with either severer and probably central nervous (Type A) or milder and sometimes doubtful neurological symptoms (Type B). The pathophysiology of the Type B-DCS/AGE might be different from the Type A-variant. In Type A-DCS/AGE a higher PFO-prevalence (patent foramen ovale) points towards an embolic origin of the Type A-symptomatology. This is not necessarily expected for the Type B-DCS/AGE if the pathophysiology here is micro-embolic or even non-embolic. METHODS: 18 patients with Type B-DCS/AGE were tested against matched controls for presence and size of a PFO with echocardiography and transcranial ultrasound with echo-contrast. Prevalence and number of Type A-brain lesions were visualized by cranial MRI as possible sequelae from gas-embolic events. RESULTS: PFO-prevalence in both groups, the patients with Type B-DCS/AGE (5/18) as well as the controls (7/18) was similar to published PFO-prevalences in normals without any difference between patients and controls (p = 0.725). Also the number of MRI-lesions (ACFs) was the same for Type B-DCS/AGE cases (15 ACFs in 5 patients) and controls (37 ACFs in 8 divers). CONCLUSION: Indirect findings suggesting embolic brain injuries are found with similar frequency in patients with Type B-DCS/AGE and normal controls, which is in contrast to data about Type A-DCS/AGE. This is compatible with different pathophysiological mechanisms involved in the Type A- and Type B-DCS/AGE.

Cerebral autoregulation is temporarily disturbed in the early recovery phase after dynamic resistance exercise.

AIM: To determine cerebral blood-flow velocity (CBFV) and parameters of dynamic cerebral autoregulation (CA) during and after exhausting resistance exercise. METHODS: Strength endurance (23 repetitions) and maximal strength training (8 repetitions) in 16 female and 16 male athletes on a leg curler (m. quadriceps training; approx. 2 s contraction) in the upright position. Registration of ECG, blood pressure by Finapres, CBFV by transcranial Doppler (TCD), and breathing by a Zak breathing-belt. Additional repetitive ergospirometry (O2-uptake, CO2-elimination, ventilation) and blood gas analyses were performed in a subgroup of seven athletes. From BP and CBFV cerebrovascular resistance (CVR), pulsatility index (PI) as well as LF-power, gain and phase-angle (frequency analysis) were derived. RESULTS: All athletes showed significant (p<0.01) 15 % to 30 % increases in CBFV during both training sets without signs of flow depression due to Valsalva maneuvers. In the early recovery, when blood pressure rapidly decreased, CBFV amplitude significantly (p<0.01) increased for 60-80 seconds with mean flow (Vm) at the exercise level, while CVR and PI showed conflicting results, similar to a presyncopal reaction. Ergospirometry and blood gas analyses revealed no evidence of major changes in pCO2, but phase angle was reduced (p<0.001) after exercise, together with an LF power increase (p<0.001). CONCLUSION: An unexpected increase in CBFV amplitude and in Vm occurs directly after dynamic resistance exercise without increased pCO2, which is comparable to a maximum leg press with hypercapnia. CVR and PI results as well as data from frequency analysis show similarities to presyncopal reactions, on the one hand, and point towards a temporarily disturbed cerebral autoregulation, on the other.

Incidence of abnormal cerebral findings in the MRI of clinically healthy divers: role of a patent foramen ovale.

BACKGROUND: To investigate incidence and number of abnormal cerebral hyperintensities (ACFs) in Magnet Resonance Imaging (MRI) and its relation to a patent foramen ovale (PFO) in divers with no history of decompression illness. METHODS: Cohort study on 50 divers (21-5500 dives). MAIN OUTCOME MEASURES: Incidence and number of ACFs visualized by cranial MRI and presence and size of a PFO as documented by echocardiography and transcranial Doppler ultrasound (TCD) with echocontrast. RESULTS: A total of 137 ACFs was found in the 50 subjects, with a significant correlation between the number of dives and number of ACFs (r = 0.28; p < 0.05); but after correction for age, the remaining correlation (r = 0.15) did not reach significance. In 18 divers, a PFO was present by either the application of echocardiography or TCD; in 12 divers, the PFO was of high hemodynamic relevance. Ten of 18 divers with a PFO had at least one ACF, while in the remaining 32 divers, only 14 had at least one ACF (56% versus 44%, p = NS). Seven of 14 divers (50%) with 4 ACFs had a PFO, compared to 11 of 36 (31%) with less than 4 ACFs (p = NS). CONCLUSION: In this cohort of healthy divers, in contrast to an earlier report, no significant association was found between PFO presence and incidence or number of ACFs.

Noninvasive myocardial contractility monitoring with seismocardiography during simulated dives.

OBJECTIVE: To determine if bradycardia during hyperbaric exposure is accompanied by a negative influence on myocardial contractility. METHODS: Accelerometer-based registration of myocardial compression waves with Seismocardiography (SCG) for noninvasive contractility monitoring. Comparative pulmonary artery (PA) catheter study (9 ICU-patients, mean = 67ys) with ejection-fraction (EF) equivalent versus sum of g-values of contraction phase in SCG, and Preload (leg-positioning). Test with monitoring of changes in Contractility Index (ContrI) derived from the SCG-power spectrum (contraction phases, area under curve). Hyperbaric chamber study (0.6MPa dive-simulation) in 14 healthy divers. Quantitative SCG-(ContrI, power spectra) and ECG-recording. RESULTS: Correlation between changes in EF (PA catheter) and in the g-values (SCG) was r(SP) = 0.87 (p < 0.0001). ContrI increased in the leg-positioning test parallel to preload increase, heart rate remained stable. During hyperbaric exposure (0.6MPa) heart rate decrease was highly significant (68 to 58 min(-1); p < 0.001), ContrI and power spectra remained nearly unchanged, SCG registration was noise free. CONCLUSIONS: Hyperoxic bradycardia during simulated dives is not accompanied by impaired contractility measured with SCG, which is concordant to findings with invasive methods in current literature. SCG is suitable for noninvasive and stress free contractility monitoring and patient surveillance in a hyperbaric chamber.

Determinants of fat mass in prepubertal children.

The aim of the present study was to compare variables of metabolism, physical activity and fitness to body composition in normal and overweight children in a cross-sectional study design. Body composition was assessed by anthropometric measurements and bioelectrical impedance analysis in forty-eight prepubertal children (age 5-11 years, thirteen normal-weight, thirty-five overweight). Total energy expenditure (EE) was measured by combination of indirect calorimetry (for measurement of resting EE) and individually calibrated 24 h heart-rate (HR) monitoring. Activity-related EE and physical activity level (PAL) were calculated. Time spent with min-by-min HR>FLEX HR was also used as a marker of moderate habitual and vigorous activities. Aerobic fitness (O2 pulse (O2 consumption:HR at submaximal steady-state heart rate), submaximal O2 consumption (VO2submaximal), RER at a HR of 170 beats per min) was determined by bicycle ergometry. Muscle strength of the legs (maximal isometric strength of musculus quadriceps and of musculus ischiocruralis (Fa max and Fb max respectively)) was measured by computer tensiometry. When compared with normal children, overweight children had higher skinfold thicknesses (sum of skinfold thicknesses at four sites +160 %), fat mass (+142 %), waist (+24 %) and hip circumferences (+14 %), resting EE (+13 %) and RER (+5 %). No significant group differences were found for fat-free mass, muscle mass, total EE, activity-related EE, PAL, HR>FLEX HR, VO2submaximal, O2 pulse, Fa max and Fb max as well as the fat-free mass- or muscle mass-adjusted values for resting EE, aerobic fitness and muscle strength. When compared with normal children, overweight children had a lower measured v. estimated resting EE (Delta resting EE) and spent more time watching television. There were positive relationships between fat-free mass(x) and resting EE(x), total EE(y), aerobic fitness(y) and muscle strength(y), but only Delta resting EE(x) and HR>FLEX HR(x) correlated with fat mass(y). In a stepwise multivariate regression analysis resting EE adjusted for fat-free mass and Delta resting EE were significant determinants of % fat mass and explained 29.7 % of its variance. Thus, in the present cross-sectional study, resting EE was the most important determinant of fat mass.

Association between different attributes of physical activity and fat mass in untrained, endurance- and resistance-trained men.

The objective of this cross-sectional study was to assess different attributes of physical activity and fitness and their relationship to nutritional state in endurance- and resistance-trained, compared to untrained men. The subjects were 42 men matched for age, of which 13 were untrained [UT, mean age 30.2 years, mean height 180.7 cm, mean body mass 83.6 kg, mean body mass index (BMI) 25.6 kg.m-2], 14 were endurance-trained athletes (ET, mean age 29.6 years, mean height 178.4 cm, mean body mass 74.0 kg, mean BMI 23.2 kg.m-2) and 15 were resistance-trained athletes (RT, mean age 28.4 years, mean height 183.4 cm, mean body mass 94.1 kg, mean BMI 27.4 kg.m-2). Fat mass (FM), fat free mass (FFM), muscle mass (MM) and total body water (TBW) were assessed using anthropometry and bioelectrical impedance analysis. Resting energy expenditure was measured by indirect calorimetry (IC) and total energy expenditure (TEE) by a combination of IC and individually calibrated 24-h heart-rate monitoring. The activity related energy expenditure (AEE) and the physical activity level were calculated. Movements were assessed using pedometry. Aerobic fitness was determined using ergometry, muscle strength [quadriceps muscle (Famax), ischiocruralis muscle (Fbmax), biceps muscle (Fcmax), triceps muscle (Fdmax)] by computer tensiometry. Different time domain indexes of heart rate variability (HRV) were examined during sleep, rest and the whole day as an index of sympathetic nervous system (SNS) activity. When compared with UT and RT, ET had reduced body masses and FM, but increased percentage TBW (P < 0.05 and P < 0.01, respectively). FFM and MM were increased in RT, when compared with UT and ET (P < 0.01). ET had higher TEE, AEE, pedometry derived activities, oxygen consumption and power during vigorous exercise than RT and UT (P < 0.05 and P < 0.01, respectively). Respiratory exchange ratio at moderate exercise intensities was increased in RT (P < 0.05). In the 12 time domain indexes of HRV 6 and 10 were higher in ET than in RT and UT respectively (P < 0.05 or P < 0.01, respectively) suggesting an increased SNS activity in ET. By contrast, Famax, Fcmax and Fdmax were elevated in RT (P < 0.01). FM was negatively associated with aerobic fitness, but not with muscle strength. We concluded that the physiological and metabolic adaptations to exercise and nutritional state differ between ET and RT subjects. Participation in RT results predominantly in changes in body composition and strength but not in energy expenditure, movements and SNS activity. The opposite was the case for ET. Aerobic fitness, physical activity, movements and activity of SNS were all increased but body mass and FM were decreased. The latter finding may support the idea that, with regard to possible health benefits, ET is more effective than RT.

Is TV viewing an index of physical activity and fitness in overweight and normal weight children?

OBJECTIVE: To assess relationships between TV viewing and body composition, energy expenditure, physical activity, fitness and nutrition habits in prepubertal children. DESIGN: Cross-sectional study. SUBJECTS: Sixty prepubertal children (mean body mass index: 20.8 kg m(-2), age: 5-11 years, overweight: n = 52, normal weight: n = 8). METHODS: TV consumption, socio-economic status (SES) and nutrition habits were estimated by questionnaires. Fat mass and fat-free mass were assessed by anthropometrics and bioelectrical impedance analysis, and resting energy expenditure by indirect calorimetry. Total energy expenditure was measured by a combination of indirect calorimetry and individually calibrated 24-hour heart rate (HR) monitoring. Activity-related energy expenditure and physical activity level were calculated. Aerobic fitness (VO2 submax) was determined by ergometry, muscle strength (musculus quadriceps, musculus ischiocruralis) was measured by computer tensiometry. Children were stratified according to their daily TV consumption: 1 h of TV per day (group II). RESULTS: When compared with children of group I, children of group II had increased body weight, body mass index, skinfolds, fat mass and prevalence of overweight (P < 0.05 and <0.01, respectively). By contrast, fat-free mass, energy expenditure, measures of physical activity and muscle strength were similar. Children of group II had normal absolute VO2 submax but reduced adjusted VO2 submax (P < 0.05). They also had parents with a lower educational level (P < 0.05). Similar nutritional habits were observed in both groups. There were no significant differences in the observed parameters between children with high (1-3 h day(-1)) and very high (>3 h day(-1)) TV viewing. CONCLUSIONS: There is a positive relationship between TV viewing and fatness. Increased TV viewing does not reflect reduced 24-hour energy expenditure as assessed by 24-hour HR monitoring, submaximal VO2, muscle strength or poor dietary intake. Increased TV consumption is associated with a low SES.

Relationships between physical activity, physical fitness, muscle strength and nutritional state in 5- to 11-year-old children.

The purpose of the present study was to assess different aspects of physical activity and fitness in order to develop a basis for sport programmes for overweight and obese children. Eighty-eight prepubertal children (49 boys, 39 girls, 4.8-11.4 years old, 61% obese, 14% overweight and 25% normal weight) were examined. Body composition was assessed by combined use of anthropometrics and bioelectrical impedance analysis. Resting energy expenditure (REE) and total energy expenditure (TEE) were measured by indirect calorimetry (IC) and individually calibrated 24-h heart rate (HR) monitoring, respectively. Activity-related energy expenditure (AEE) and physical activity level (PAL) were calculated from TEE and REE. Fitness [assessed by O2-pulse, respiratory exchange ratio (RER) at submaximal work intensities] was determined by ergometry. The maximal isometric muscle strength of the legs (m. quadriceps, Fa max, m. ischiocruralis, Fb max) was measured by computer tensiometry. Children were grouped according to their nutritional state, AEE, O2-pulse and muscle strength. When compared with normal weight children, obese and overweight children had increased fat mass (FM), fat-free mass (FFM), waist-to-hip ratio and REE, but no group differences were observed for TEE, AEE, and PAL. Obese and overweight children spent more hours per day watching TV. After correction for body weight and FFM, no group differences in REE were observed, but normal weight children had a higher O2-pulse than overweight and obese children. By contrast, RER was increased in the latter group. The fittest group had the lowest body weight, BMI, FM and FFM. Children with a low O2-pulse spent more hours per day watching TV. Grouping children according to their degree of muscle strength, younger children (4-7.5 years) did not show group differences in nutritional state, energy expenditure, physical activity and fitness. However, in the group of 7.6- to 11-year-old children, those with the greatest muscle strength and FFM had reduced BMI, skin folds, FM and FFM. FM correlated inversely with O2-pulse, but was not associated with TEE, AEE, PAL or muscle strength. By contrast TV consumption was positively associated with FM. To summarize, overweight and obese children were less fit and watched more TV than their normal weight counterparts. FM did not correspond to TEE, AEE or PAL. Muscle strength was not associated with FM in young children, but was inversely associated with FM in older children. Our cross-sectional data are consistent with the idea that increased fitness and reduced physical inactivity may prevent children from being overweight.

No effect of gender on different components of daily energy expenditure in free living prepubertal children.

BACKGROUND: There are limited and controversial data on the influence of gender on metabolic rate in prepubertal children. OBJECTIVE: To assess the effect of gender on resting energy expenditure (REE), activity-related energy expenditure (AEE), total energy expenditure (TEE) and physical activity level (PAL) in free-living prepubertal children. DESIGN: Cross-sectional study. SUBJECTS: 40 prepubertal children (24 boys, 16 girls, 4-11 y old (mean age: 7.0 +/- 1.2 y), BMI 13.1-32.0 kg/m2). MEASUREMENTS: Energy expenditure was measured by the combination of indirect calorimetry and individually calibrated 24 h heart rate monitoring. Body composition was assessed by anthropometrics and bioelectrical impedance analysis. Socio-cultural and socio-economic factors, as well as activities of daily living, were estimated by questionnaire for the parents. Boys and girls were matched for fat-free mass (FFM, boys: 25.9 +/- 8.5 kg; and girls: 24.4 +/- 4.5 kg, n.s.) and fat mass (FM, boys: 11.6-5.9 kg; and girls: 10.8 +/- 3.3 kg, n.s.). RESULTS: We found no sex difference in REE, AEE and TEE. PAL was 1.4 +/- 0.3 for boys and 1.2 +/- 0.4 for girls. REE and TEE were significantly related to FFM (r=0.62, r=0.81, r=0.60). FFM was found to be the most significant determinant of REE (r2=0.70). REE accounted for the largest part of the variance in TEE (r2=0.46). Gender had no significant effect. CONCLUSIONS: There is no effect of gender on energy expenditure in prepubertal children.

Blood lactate changes in men during graded workloads at normal atmospheric pressure (100 kPa) and under simulated caisson conditions (400 kPa).

OBJECTIVES: A hyperbaric environment may influence lactate metabolism due to hyperoxia affecting biochemical pathways. The purpose of our study was to determine the blood lactate levels occurring at high workloads in a sample of professional divers under simulated caisson conditions. The ambient air pressure was equivalent to a diving depth of 30 m of seawater (400 kPa). METHODS: A total of 23 healthy male subjects performed graded bicycle exercise in a dry hyperbaric chamber up to a maximum of 3.5 W kg(-1) body weight at normal (100 kPa) and elevated ambient air pressure (400 kPa). The blood lactate level and the heart rate were measured. RESULTS: In comparison with control conditions, the heart rate and the peripheral blood lactate level were significantly lower at depth for all workloads. CONCLUSIONS: The differences between the normobaric and hyperbaric lactate values may be explained by an overall improvement in lactate metabolism at elevated ambient pressure, especially in the working muscles and the organs responsible for the lactate reduction, i.e., the liver. The reduced heart rate may be an effect of the improved tissue oxygen supply at depth.

Orthostatic hypotension: how to avoid it during antihypertensive therapy.

This was a double-blind randomized study comparing the efficacy of two alpha 1-antagonists, bunazosin retard and prazosin retard, in 185 patients with mild to moderate essential hypertension. Additionally, specific orthostatic tolerance was evaluated by a standardized test (Schellong test). Both 1 to 4 mg prazosin daily and 6 or 12 mg bunazosin daily achieved satisfactory blood pressure reduction (diastolic pressure reduced by at least 10 mm Hg) in 48% and 41% of patients, respectively. The average diastolic blood pressure reduction measured 24 h after drug administration was 9.8 mm Hg in the bunazosin group and 7 mm Hg in the prazosin group. A comparison of blood pressure profiles during specific orthostatic tolerance tests did not show any significant difference between the two groups. However, the symptoms of orthostatic hypotension were significantly less frequent and less severe with bunazosin compared with prazosin. Nineteen patients with essential hypertention were randomized for treatment with either prazosin retard (4 mg) or bunazosin retard (12 mg). The blood flow and the venous capacity were recorded by means of a plethysmograph while the patient was in a supine position and after tilting into the upright position. The peripheral resistance of the calf while the patient was in a supine position during placebo is 38.8 +/- 25.9 U, during bunazosin 28.5 +/- 17 U, and during prazosin 29.7 +/- 27.1 U. The difference between the two alpha-blockers and placebo is statistically significant. There was no effect on venous tone and venous capacity when tilting into the upright position.

Ammonia and lactate: differential information on monitoring training load in sprint events.

Two hypotheses were tested concerning training relevance of ammonia in capillary blood compared with lactate after extensive and intensive high-paced runs. 1. There is a load threshold at which ammonia concentration deviates statistically significantly from the pre-load level, while lactate indicates already anaerobic metabolic processes at extensive training loads. Increased ammonia concentration is understood as the activation of type IIb fibers. 2. The increase in ammonia is primarily a consequence of increasing training load intensity. The hypotheses were tested in a field experiment with male sprinters n = 13. The experimental plan followed a design of repeated measures in a 4 x 4 Latin-square. The subjects completed four high-pace runs (300 m) at 82.5%, 85%, 87.5%, and 90% of the maximum running intensity (identified in a contest). The results confirmed our first hypothesis. Significant increase in ammonia concentration was not found until after four runs at an intensity of 87.5% or after one 300-m run at maximum running speed. In contrast to this, a glycolytic reaction became evident in one run at 82.5% of the maximum intensity. Lactate concentration exceeded the anaerobic threshold at this point. Definite instructions for training practice cannot be made at the present state of research.

Cardiovascular reactions during exhausting isometric exercise while windsurfing on a simulator or at sea.

Eleven amateurs and two internationally ranked windsurfers performed isometric exercise on a windsurfing simulator to the point of exhaustion. The two professional windsurfers maintained their position during exercise two times longer than those of the other group. The following mean values (n = 11) were measured during the exercise: the blood pressure increased from 114 +/- 6.6/70 +/- 11.5 to 177 +/- 8.6/93 +/- 10.3 mmHg, the heart rate from 63 +/- 13 to 103 +/- 16 bts/min, blood flow in the forearm from 6.4 to 7.4 ml/(100 ml tissue x min), and the lactate level in the capillary blood from 0.9 +/- 0.2 to 1.9 +/- 0.4 mmol/l. The post-exercise hyperemia reached values of 28.2 ml/ (100 ml tissue X min). There was neither a significant correlation between the time of exercise and the handgrip force (MVC = maximal voluntary) nor the calculated force of the forearm. Motivation was interpreted as an exercise-prolonging factor. At sea and with high wind (7 Beaufort), the heart rate reached a maximum of 200 bts/min, but the lactate level did not reach more than 3.0 mmol/l.

[Therapeutic aspects of orthostatic dysfunction]. / Aspekte zur Therapie orthostatischer Dysregulationen.

In two open intraindividual controlled clinical trials efficacy of placebo, Dihydergot and etilefrine as well as a combination of Dihydergot and etilefrine on the parameters "venous capacity", "circulatory response to orthostatic stress" and "blood pressure" was compared under acute and chronic therapy. Under acute conditions (15 healthy individuals; medication: placebo 0.25 Dihydergot i.v., 15 mg etilefrine p.o., 0.25 mg Dihydergot plus 15 mg etilefrine p.o.) superiority of the combination could be demonstrated concerning tonisation of the capacitance vessels and improvement of circulatory regulation during orthostasis, as indicated by less pronounced increase in heart rate. In a further study, in which 14 healthy individuals with relatively low blood pressure (RR syst./RR diast. 114/78 mm Hg) received each for one week 20 mg etilefrine, 2 mg Dihydergot or the combination (Dihydergot plus), blood pressure increased significantly (p less than or equal to 0.05) under the combination. The effect was due to the etilefrine component of the combination as could be inferred from the assessment of efficacy.