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Biomedical subjects

G Leftheriotis

Publications and source records attributed to G Leftheriotis.

At least 37 records · Page 2Linked to original sources
PubMed1995

Ankle systolic blood pressure following sub-maximal and maximal exercises in healthy young men.

Although recent studies have compared the effect of progressive exercise tests to constant moderate work load tests on ankle systolic blood pressure (ASBP) and ankle to arm index (AAI) in claudicants, little is known about the relation of ASBP and AAI to work load in healthy young men. Fifteen normal volunteers were asked to cycle 40, 60, 80, 100% of VO2max. Ankle and humeral pressures were recorded simultaneously, at rest and 1 minute after the end of each test. Thereafter, AAI was calculated as the ratio of ankle to humeral systolic pressure. Compared to resting values: 134.8 +/- 13.9 mmHg, ASBP increased significantly following sub maximal tests up to 157.8 +/- 28.1 mmHg (p < 0.005), but was not increased following maximal exercise: 141.5 +/- 28.2 mmHg (NS). On the other hand, AAI showed a progressive decrease from 1.14 +/- 0.06 at rest to 1.06 +/- 0.08 (p < 0.005), but 0.98 +/- 0.07 (p < 0.005), to 0.84 +/- 0.06 (p < 0.005) and to 0.75 +/- 0.09 (p < 0.005) following 40, 60, 80 and 100% of VO2max respectively. In summary, AAI following exercise is inversely related to workload whereas ASBP is not. We suggest that when studying ankle systolic blood pressure response to heavy load exercises, results should always be compared to humeral pressure, and expressed as ankle to arms indexes.

Adult↗
PubMed1994

Diameter and blood velocity changes in the saphenous vein during thermal stress.

Although volume, pressure or flow in superficial veins have been studied extensively, little is known about venous blood velocity during thermal stress. Most authors have suggested that the velocity is decreased in the dilated superficial veins during heat stress to facilitate heat loss, and is increased during cooling as the vein is constricted. Duplex ultrasound has been used to study saphenous cross sectional area (CSA) and mean maximal venous blood velocity (BV) in ten healthy volunteers (age 22-31 years). Compared with unstressed mean values, 4.8 (SD 2.6) mm2, CSA increased to 9.3 (SD 2.1) mm2 (P < 0.005) during heat stress and decreased to 2.1 (SD 1.9) mm2 (P < 0.005) during cold stress. These results are consistent with previous studies, but the absolute CSA of the saphenous vein has never been estimated during thermal stress. The BV increased from 0.07 (SD 0.02) m.s-1 to 0.29 (SD 0.11) m.s-1 (P < 0.005) during warming. During cooling, BV tended to decrease: 0.05 (SD 0.03) m.s-1 (N.S). We would suggest that heat loss during thermal stress can be facilitated by the rapid turnover of warm blood, and not (as usually suggested) by the prolonged cooling of each blood sample in the dilated superficial veins.

Adult↗
PubMed1994

Diameter and velocity changes in the femoral vein during thermal stress in humans.

Unlike most studies on deep veins performed with simultaneous suppression of cutaneous blood flow, a sonographic study of femoral diameter and blood flow velocity changes in response to thermal stress was performed while cutaneous flow was preserved. In 11 normal subjects, mean peak blood flow velocity and diameter of the femoral vein were measured at rest and during indirect whole body heating and cooling. Mean peak venous blood flow velocity was 0.12 +/- 0.06 m s-1 at rest, 0.35 +/- 0.23 m s-1 (P < 0.001) during heat stress, and 0.13 +/- 0.07 m s-1 during cold stress (NS). Femoral venous diameter was 5.3 +/- 0.9 mm at rest, 5.1 +/- 1.0 mm (P < 0.05) during warming, and 5.4 +/- 81.0 mm (NS) during cooling. This study showed a decrease in diameter during thermal stress. However, as mean femoral venous blood-flow velocity was doubled during heat stress, femoral venous blood flow was increased. Thus, it is suggested that during heat stress part of the increase in cutaneous flow is returned through deep veins.

Adult↗
PubMed1994

Venous return in lower limb during heat stress.

We used ultrasound to study venous return during heat stress. We measured venous cross-sectional area (CSA) and blood flow velocity (BFV) of nine femoral veins and nine saphenous veins. During heat stress, saphenous CSA increased from 4.7 +/- 2.6 mm2 (mean +/- SD) to 9.1 +/- 2.3 mm2 (P < 0.01), whereas femoral CSA was 22.7 +/- 9.5 mm2 at rest and 22.0 +/- 9.6 mm2 during heat stress (NS). Meanwhile, BFV increased from 0.06 +/- 0.02 to 0.30 +/- 0.10 m/s (P < 0.01) in the saphenous vein and from 0.14 +/- 0.08 to 0.38 +/- 0.23 m/s (P < 0.005) in the femoral vein. Maximal venous outflow (MVO) was the product of CSA and BFV. During heat stress, MVO showed an eightfold increase in the saphenous veins (from 22.7 +/- 18.2 to 180.7 +/- 86.7 ml/min) and a 2.5-fold increase in the femoral veins (from 143.4 +/- 52.9 to 354.0 +/- 126.9 ml/min). The results showed that one-half of the cutaneous blood flow increase during heat stress returned through the deep collecting veins in the lower limb. Thereafter, although there was no venodilation of deep veins compared with superficial veins, the deep veins remain the main pathway for the venous return during heat stress.

Adult↗
PubMed1993

Effects of thiopental on middle cerebral artery blood velocities: a transcranial Doppler study in children.

The effect of an intravenous injection of thiopental on middle cerebral artery blood velocities was assessed by transcranial pulsed Doppler monitoring in 20 children: ten head-injured patients and ten control subjects. Thiopental induced a moderate but immediate decrease of middle cerebral artery blood velocities in both groups; this variation was significant (P < 0.01) and more prolonged in the head-injured than in control patients. Transcranial Doppler ultrasonography thus appears to be suitable for monitoring children in intensive care units and could help to avoid the use of thiopental in patients with low cerebral artery blood flow velocity.

Adolescent↗
PubMed1992

[Circulatory changes of the middle cerebral artery during syncopes produced by the head-up tilt test].

Velocity of the middle cerebral artery was recorded with transcranial pulsed doppler in 10 neurally-mediated syncopes elicited by 60 degrees head-up tilt test. Mean arterial blood pressure decreased by -36 +/- 16 percent (P < 0.0001) and heart rate by -6 +/- 27 percent (P < 0.05). Mean middle cerebral artery velocity decreased by -48 +/- 16 percent (P < 0.0001); Pourcelot's resistance index increased by 74 +/- 47 percent (P < 0.0001) and Gosling's pulsatility index by 218 +/- 111 percent (P < 0.0001). However, resistance normalized with mean arterial pressure showed no significant increase (+ 14 +/- 28 percent; NS). The decrease in diastolic velocity as well as mean arterial blood pressure and heart rate was significantly lower when loss of consciousness occurred. Contrary to those of other authors, our results do not support the hypothesis that syncopes result from a paradoxical cerebral vasoconstriction since no significant changes were observed in resistance normalized with mean arterial pressure. Thus, decrease in cerebral perfusion is likely to be the result of a decrease in cerebral perfusion pressure.

Adult↗
PubMed1992

Blood flow and muscle bio-energetics by 31P-nuclear magnetic resonance after local cold acclimation.

To clarify the origin of local cold adaptation and to define precisely its influence on muscle bio-energetics during local exercise, five subjects were subjected to repeated 5 degrees C cold water immersion of the right hand and forearm. The first aim of our investigation was therefore carried out by measuring local skin temperatures and peripheral blood flow during a cold hand test (5 degrees C, 5 min) followed by a 10-min recovery period. The 31P by nuclear magnetic resonance (31PNMR) muscle bio-energetic changes, indicating possible heat production changes, were measured during the recovery period. The second aim of our investigation was carried out by measuring 31PNMR muscle bioenergetics during handgrip exercise (10% of the maximal voluntary contraction for 5 min followed by a 10-min recovery period) performed both at a comfortable ambient temperature (22 degrees C; E) and after a cold hand test (EC), before and after local cold adaptation. Local cold adaptation, confirmed by warmer skin temperatures of the extremities (+30%, P less than 0.05), was related more to an increased peripheral blood flow, as shown by the smaller decrease in systolic peak [-245 (SEM 30) Hz vs -382 (SEM 95) Hz, P less than 0.05] than to a change in local heat production, because muscle bioenergetics did not vary. Acute local cold immersion decreased the inorganic phosphate:phosphocreatine (PC) ratio during EC compared to E [+0.006 (SEM 0.010) vs +0.078 (SEM 0.002) before acclimation and +0.029 (SEM 0.002) vs +0.090 (SEM 0.002) after acclimation respectively, P less than 0.05] without significant change in the PC:beta-adenosine triphosphate ratio and pH. Local adaptation did not modify these results statistically. The recovery of PC during E increased after acclimation [9.0 (SEM 0.2) min vs 3.0 (SEM 0.4) min, P less than 0.05]. These results suggested that local cold adaptation is related more to peripheral blood flow changes than to increased metabolic heat production in the muscle.

Acclimatization↗
PubMed1991

Effects of hypotension on cutaneous and subcutaneous blood flow in anaesthetized humans.

The aim of this study was to determine the effect of controlled hypotension on subcutaneous and cutaneous haemodynamics in humans. Moderate hypotension was achieved with nitroglycerin (NTG) and sodium nitroprusside (SNP) infusion during narconeuroleptanalgesia in seven patients. Subcutaneous and cutaneous blood flow were measured by a superficial and deep heat clearance (HC) technique. The mean arterial pressure (BPa) decreased by 23%-30% and heart rate (fc) increased but only during NTG infusion (+22%; P less than 0.02). Subcutaneous and cutaneous blood flows remained unchanged despite a significant decrease in calculated cutaneous resistance (NTG: -26%, P less than 0.01; SNP: -34%, P less than 0.02] and subcutaneous vascular resistance changed only with SNP (-31%, P less than 0.02). After hypotension was discontinued the subcutaneous blood flow decreased (-13%, P = 0.05), whereas subcutaneous vascular resistance returned to its control values. An inverse relationship was found between fc and BPa (NTG: r = -0.525, P less than 0.01; SNP: r = -0.622, P less than 0.01) as well as with subcutaneous blood flow (NTG: r = -0.653, P less than 0.001; SNP: r = -0.573, P less than 0.01). In addition, we found oscillatory changes in deep HC values which differed in magnitudes (NTG 0.22 (SEM 0.09) W.m-1.degree C-1 vs SNP 0.42 (SEM 0.1) W.m-1.degrees C-1, P less than 0.01) and frequencies (NTG 0.02 (SEM 0.006) Hz vs SNP 0.01 (SEM 0.002) Hz, P less than 0.01). Despite unchanged blood flow, the effects of controlled hypotension on cutaneous and subcutaneous haemodynamics were different depending on the type of drug. These differences may have been related to counterregulatory responses and/or to direct vascular effects.

Adult↗
PubMed1990

Finger and forearm vasodilatatory changes after local cold acclimation.

To determine the vascular changes induced by local cold acclimation, post-ischaemia and exercise vasodilatation were studied in the finger and the forearm of five subjects cold-acclimated locally and five non-acclimated subjects. Peak blood flow was measured by venous occlusion plethysmography after 5 min of arterial occlusion (PBFisc), after 5 min of sustained handgrip at 10% maximal voluntary contraction (PBFexe), and after 5 min of both treatments simultaneously (PBFisc + exe). Each test was performed at room temperature (25 degrees C, SE 1 C) (non-cooled condition) and after 5 min of 5 degrees C cold water immersion (cooled condition). After the cold acclimation period, the decrease in skin temperature was more limited in the cold-acclimated compared to the non-acclimated (P less than 0.01). The PBFisc was significantly reduced in the cooled condition only in the cold-acclimated subjects (finger: 8.4 ml.100 ml-1.min-1, SE 1.1, P less than 0.01; forearm: 5.8 ml.100 ml-1.min-1, SE 1.5, P less than 0.01) compared to the non-cooled condition. Forearm PBFexe was significantly decreased in the cooled condition only in the cold-acclimated subjects (non-cooled: 7.4 ml.100 ml-1.min-1, SE 1.2; cooled: 3.9 ml.100 ml-1.min-1, SE 2.6, P less than 0.05) indicating that muscle blood flow was also reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1990

A computerized bioelectrical cardiac monitor.

The use of a micro-computer improves the performance of an impedance cardiograph. The impedance signals and the ECG are real-time processed and four analog signals are displayed on the screen. A beat-to-beat estimation of cardiac output and several indexes are computed and displayed. User's interface is by interactive screen menus. Some facilities permit data identification, storage and post-processing. The software has been designed in such a way as to be adaptable to each specific application and to enable the development of new routines for cardiac signal processing. The signals recorded in healthy patients are in agreement with the results of other similar studies.

Adult↗
PubMed1990

[Carotid dissection. Study of 28 cases. Contribution of Doppler exploration, ultrasonic diagnosis and Doppler color echography].

Carotid dissections often go undetected or are confused with an arteriosclerotic cause; in fact, they rarely require surgical treatment. Twenty-eight extracranial carotid dissections (in 25 patients) without direct cervical traumatism were explored successively by pulsed and duplex Doppler ultrasonography complemented in 10 cases by color Doppler flow imaging and secondarily in all cases by arteriography. Pulsed Doppler (DMS Angiodop 481 with 4 and 8 MHz probes) found severe hemodynamic signs in 93% of cases: 6 occlusions, 11 generally extensive or high tight stenoses and 9 significant slowdowns in carotid and ophthalmic artery circulation. For the same internal carotid artery, duplex Doppler (Ultramark 4 or Sonedap 40 with 5, 7.5 and 10 MHz probes) initially showed 5 occlusions and 2 stenoses (4 with fusiform features), 2 double canal images, 8 internal carotid arteries with tubular features (internal caliber less than or equal to 2 mm) and 2 segmental ectasias. There were only 3 other lesions with arteriosclerotic features, 2 of which were minor. Duplex imaging was thus suggestive in 57% of cases. Color Doppler flow imaging enabled precise visualization of these features, better analysis of occlusions and clear detection of 2 other false canal images. After 2 years of follow-up, Doppler ultrasound showed recanalization in 47% of cases with no anticoagulant complications. These combined ultrasonic explorations would thus appear to be useful for early diagnosis of carotid dissections, for guiding arteriography and for facilitating the monitoring of patients under anticoagulant.

Adult↗
PubMed1989

Antigravity suit inflation: kidney function and cardiovascular and hormonal responses in men.

To investigate the effects of lower body positive pressure (LBPP) on kidney function while controlling certain cardiovascular and endocrine responses, seven men [35 +/- 2 (SE) yr] underwent 30 min of sitting and then 4.5 h of 70 degrees head-up tilt. An antigravity suit was applied (60 Torr legs, 30 Torr abdomen) during the last 3 h of tilt. A similar noninflation experiment was conducted where the suited subjects were tilted for 3.5 h. To provide adequate urine flow, the subjects were hydrated during the course of both experiments. Immediately after inflation, mean arterial pressure increased by 8 +/- 3 Torr and pulse rate decreased by 16 +/- 3 beats/min. Plasma renin activity and aldosterone were maximally suppressed (P less than 0.05) after 2.5 h of inflation. Plasma vasopressin decreased by 40-50% (P less than 0.05) and plasma sodium and potassium remained unchanged during both experiments. Glomerular filtration rate was not increased significantly by inflation, whereas inflation induced marked increases (P less than 0.05) in effective renal plasma flow (ERPF), urine flow, osmolar and free water clearances, and total and fractional sodium excretion. No such changes occurred during control. Thus, LBPP induces 1) a significant increase in ERPF and 2) significant changes in kidney excretory patterns similar to those observed during water immersion or the early phase of bed rest, situations that also result in central vascular volume expansion.

Adult↗
PubMed1989

Orthostatic responses following 30-day bed rest deconditioning with isotonic and isokinetic exercise training.

To determine if intensive isotonic or isokinetic exercise training during 30 d of -6 degrees head-down bed rest (BR) would accentuate orthostatic intolerance, 19 men (32-42 years) were divided into a no-exercise control group (N = 5), and isotonic (Quinton ergometer, N = 7) and isokinetic (Lido ergometer, N = 7) exercise groups. Training was two 30-min periods per day for 5 days per week. Changes (* = p less than 0.05) in peak VO2 uptake (L/min) from control day 2 to BR day 29 were: isotonic +1.4%, isokinetic -10.2%*, no exercise -20.1%*. Changes in resting plasma volume (ml) from control day 1 to BR day 30 were: isotonic -3.7%, isokinetic -18.0%*, and no exercise -17.2%*. A 60 degrees head-up tilt test was administered on control day 1 and BR day 30; the test was terminated at 60 min or when presyncopal signs and/or symptoms occurred. Changes in means tilt tolerance were: isotonic, 42 to 34 min (delta = -8 min*); isokinetic, 53 to 30 min (delta = -23 min*); and no exercise, 46 to 30 min (delta = -16 min*). Mean day 30 group tolerances were all significantly lower than day 1 tolerances, but the reductions were not different between groups. Because there was no obvious relationship between type of exercise, exercise energy expenditure, change in peak VO2, or change in resting plasma volume and the consistent reduction in post-BR tilt tolerances, it appears that the orthostatic intolerance was due mainly to the reduction in body hydrostatic pressure from the -6 degrees head-down body position, and was not related to the level of physical fitness. Thus, factors other than training status are probably involved.

Adult↗
PubMed1988

Cutaneous and subcutaneous blood flow during general anaesthesia.

The vasodilator effect of anaesthetic agents on cutaneous vessels has often been investigated. In contrast, although subcutaneous tissue is concerned with metabolism and thermoregulation, the effects of anaesthesia on subcutaneous blood flow have not been well documented. The purpose of this study was to determine the magnitude of changes in cutaneous and subcutaneous blood flow during general anaesthesia in Man. Anaesthesia was induced with flunitrazepam in 15 patients before facial plastic surgery. Blood flow was estimated using heat thermal clearance (HC). Two HC sensors in different areas allowed the measurement of superficial and deep HC. Systolic (SABP), diastolic (DABP) and mean arterial blood pressure (MABP), heart rate (HR), and rectal and mean skin temperature were also recorded. After induction of anaesthesia, HR increased significantly (p less than 0.05) whereas SABP, DABP and MABP remained unchanged. The rectal-toe temperature gradient fell from 6.3 +/- 4.1 degrees C to 3.4 +/- 1.1 degrees C (p less than 0.01) suggesting a reduction in vasomotor tone. Superficial HC increased from 0.37 +/- 0.06 to 0.42 +/- 0.08 W.m-1.degrees C-1 (p less than 0.05) whereas deep HC decreased from 0.33 +/- 0.07 to 0.31 +/- 0.09 W.m-1.degrees C-1 (NS) and returned to the control value thereafter. Rectal temperature and mean skin temperature were unchanged. The changes in deep HC are similar to those previously observed in muscle during induction of anaesthesia. Our results show that anaesthesia mainly affects cutaneous blood flow, without any significant change in subcutaneous blood flow during the early phase of anaesthesia in human beings.

Adult↗
PubMed1986

Skin blood flow changes in anaesthetized humans: comparison between skin thermal clearance and finger pulse amplitude measurement.

The effect of general anaesthesia on skin blood flow in the left hand, measured by a new non-invasive probe using the thermal clearance method was examined. A mercury silastic gauge was placed around the third left finger and the plethysmographic wave amplitude was recorded to measure changes in finger pulse amplitude. Heart rate (HR), mean arterial blood pressure (MABP) and skin temperature were also recorded. General anaesthesia was induced by droperidol and phenoperidine injection and propanidid infusion in eight female patients. Skin thermal clearance, plethysmographic wave amplitude, HR, MABP and skin temperature were 0.40 +/- 0.02 w X m-1 degree C-1, 9 +/- 1 mm, 98 +/- 5 beats X min-1, 12.50 +/- 0.93 kPa and 33.3 +/- 3.4 degrees C respectively. The minimal value of MABP was 9.58 +/- 1.06 kPa, whereas skin thermal clearance, plethysmographic wave amplitude, HR and skin temperature increased to 0.45 +/- 0.02 w X m-1 degree C-1, 29 +/- 3 mm, 110 +/- 4 beats X min-1 and 34.4 +/- 0.4 degrees C. Changes in skin thermal clearance correlated well with plethysmographic wave amplitude. Statistically significant changes in these two parameters occurred before significant change in HR, MABP or skin temperature. The results show that the new non-invasive probe using the thermal clearance method appears to be a useful device for measuring cutaneous microcirculation in anaesthetized humans, and responds more quickly than change in skin temperature, which is a delayed effect of skin blood flow change. Our results also show that the intensity of cutaneous vasodilatation induced by general anaesthesia did not relate to the vascular tone before anaesthesia.

Adult↗
PubMed1986

Relationship between pulse amplitude and thermal exchange in the finger: the effect of smoking.

In 24 healthy volunteers finger pulse amplitude and heart rate (HR) were monitored by pulse plethysmography and thermal exchange from the finger and were compared before and after the smoking of a single cigarette. Thermal exchange was measured using a direct calorimeter consisting of a recording bath and a reference bath, both of which were filled with water at 18 degree C. The subject immersed the two distal phalanx of a finger into the recording bath. The water thermal gradient between both baths after 4 min of finger immersion and the maximal value of heat loss from the finger to the water were recorded. Decreases in the water thermal gradient (from 6.06 to 5.33 degrees C, P less than 0.05) in maximal value of heat loss (from 22.5 to 18.75 w.m-2, P less than 0.01) and in plethysmographic wave amplitude (from 25.8 to 14.6 mm, P less than 0.01) and increased HR (from 72 to 83 beats min-1) were observed in smokers. These changes were not statistically significant in non-smokers. Water thermal gradient and maximal value of heat loss correlated with plethysmographic wave amplitude before and after smoking but not with HR in the 24 subjects studied. The present study shows a good relationship between vascular phenomena and thermal exchange in the fingers. The variations of finger pulse amplitude provide an adequate and sensitive adjustment of thermal exchange since the effects of smoking a single cigarette can be detected by both PWA and calorimetric measurements in the finger.

Adult↗
PubMed1986

Non-invasive measurement of skin blood flow: comparison between plethysmography, laser-Doppler flowmeter and heat thermal clearance method.

A comparison was made between (a) a new probe measuring heat thermal (HTC), (b) plethysmography and (c) a Laser-Doppler (LDF) technique during changes in skin blood flow (SkBF) on six subjects, each participating in a single experiment. Increase of SkBF was induced by heating the body skin with an electric cover. Heat thermal clearance correlated well with the forearm blood flow (FBF) (r = 0.69-0.97) and with LDF measurements (r = 0.86-0.92) in each experiment, Laser-Doppler flowmeter also correlated well with FBF (r = 0.73-0.97). However, the relationship between HTC, LDF and FBF varied from one experiment to another. Values for HTC and for LDF at zero FBF, extrapolated from the regression relationships, ranged from 6.438 to 10.919 k, and from -0.37 to +0.17 volt respectively. The value for HTC at zero LDF extrapolated from the regression relationships ranged from 4.109 to 12.413 k. Values for HTC and LDF when blood flow to the arm was mechanically occluded ranged from 5.17 to 10.71 k and from 0.07 to 0.24 volt respectively. Thus HTC, LDF and FBF measurement of SkBF appear to produce the same response pattern during reflex cutaneous vasodilatation. Each of these three methods measured SkBF in different skin areas and at different depths in the skin, which might also explain the variability in their relationship.

Adult↗