Biomedical subjects

C Prefaut

Publications and source records attributed to C Prefaut.

At least 19 recordsLinked to original sources

PubMed1992

Caffeine increases maximal anaerobic power and blood lactate concentration.

The aim of this study was to specify the effects of caffeine on maximal anaerobic power (Wmax). A group of 14 subjects ingested caffeine (250 mg) or placebo in random double-blind order. The Wmax was determined using a force-velocity exercise test. In addition, we measured blood lactate concentration for each load at the end of pedalling and after 5 min of recovery. We observed that caffeine increased Wmax [964 (SEM 65.77) W with caffeine vs 903.7 (SEM 52.62) W with placebo; P less than 0.02] and blood lactate concentration both at the end of pedalling [8.36 (SEM 0.95) mmol.l-1 with caffeine vs 7.17 (SEM 0.53) mmol.l-1 with placebo; P less than 0.01] and after 5 min of recovery [10.23 (SEM 0.97) mmol.l-1 with caffeine vs 8.35 (SEM 0.66) mmol.l-1 with placebo; P less than 0.04]. The quotient lactate concentration/power (mmol.l-1.W-1) also increased with caffeine at the end of pedalling [7.6.10(-3) (SEM 3.82.10(-5)) vs 6.85.10(-3) (SEM 3.01.10(-5)); P less than 0.01] and after 5 min of recovery [9.82.10(-3) (SEM 4.28.10(-5)) vs 8.84.10(-3) (SEM 3.58.10(-5)); P less than 0.02]. We concluded that caffeine increased both Wmax and blood lactate concentration.

Adult↗

PubMed1991

Effects of moderate exercise on the pharmacokinetics of caffeine.

The effect of moderate exercise on the kinetics of caffeine in 12 healthy volunteers-6 heavy coffee drinkers (HD) and 6 light coffee drinkers (LD) has been studied. Kinetics at Rest was measured first (R): the subjects remained at rest for 8 h after a single 250 mg dose of caffeine. One week later, the Exercise Kinetics (E) was measured under the same conditions, but with the subjects performing moderate exercise (30% of VO2 max) during the first hour of the study. Exercise raised the maximal plasma caffeine concentrations (R: 7.28: E: 10.45) and reduced both the half-life (R 3.99 h: E 2.29 h) and the volume of distribution (R 37 l: E 20.9 l). Both during exercise and at rest. HD had a greater half-life elimination and volume of distribution than LD. The results suggest potentiation of the effects of caffeine during exercise and an increase in its distribution due to regular heavy coffee intake.

Administration, Oral↗

PubMed1991

Blood lactate increase during the force velocity exercise test.

Venous blood lactate concentration was measured during the force velocity exercise test in order to determine whether this test is strictly alactic or whether it draws upon lactic anaerobic metabolism. Nine trained male subjects, aged from 23 to 29 years, participated in this study. Two blood samples were drawn at rest, and then for each work load (1 kg to 10 kg): at the end of each sprint (S1) and at the 5th minute of recovery (S2). From the first braking force, venous blood lactate concentration increased very significantly during the force velocity test (p less than 0.001) and, once the peak of power has been obtained, the venous blood lactate concentration remained steady. The lactate increase for each load (delta[LA]) decreased significantly (p less than 0.01). From the beginning of the exercise to the peak of power, a significant positive correlation between the increase of power and the increase of blood lactate concentration measured at S2 existed (r = 0.71, p less than 0.001), whereas there was a negative correlation between the decrease of delta[LA] and the increase of power (r = -0.45, p less than 0.01). In conclusion, the repetition of sprints during the force velocity test induced a recruitment of lactic anaerobic metabolism. Maximal power must be considered as an alactic and lactic anaerobic power. The consequences of lactate accumulation in muscle may be a limitation of the maximal anaerobic power.

Acceleration↗

PubMed1991

[Influence of brief high intensity exercise on plasma adrenaline and noradrenaline levels].

This study was conducted to determine catecholamine response to maximal intensity exercise of a few seconds' duration. To do this, epinephrine (E) and norepinephrine (NE) levels were measured during Force-Velocity Test. Blood samples were taken at the end of each sprint. Compared to rest (E0 = 77.4 +/- 3.8 pg/ml), the E concentration significantly increased after the first sprint (E2 = 109.8 +/- 14.7 pg/ml) and after the last one (E8 = 126.9 +/- 19.4 pg/ml) which correspond to the exhaustion state of our subjects. NE concentration doubled after the first sprint (NE2 = 589.1 +/- 94.7 pg/ml) and remained at this level until the end of the test. E2 seems to have been a stress reaction to an unfamiliar test. E8 may represent the "exercise plus exhaustion" stimulus on the stimulation of the adrenal gland (AG). This would suggest that stimulus intensity plays a role even when duration is very brief, although the time factor seems to limit the response of AG. The evolution of NE suggest that the brief duration of the sprints may limit the adatation response of NE to energy demands.

Adult↗

PubMed1991

One year treatment with almitrine improves hypoxaemia but does not increase pulmonary artery pressure in COPD patients.

Almitrine bismesylate, a chemoreceptor agonist, improves hypoxaemia in a high percentage of chronic obstructive pulmonary disease (COPD) patients and its long-term use may thus be of interest in these patients. The course of pulmonary haemodynamics during a one year treatment was investigated in severe COPD patients (forced expiratory volume in one second FEV1 = 1,040 +/- 80 SEM ml) with persistent hypoxaemia (initial arterial oxygen tension (PaO2) in the range 6.6-8.6 kPa (50-65 mmHg]. Patients were given either almitrine (A, n = 27), 100 mg.day-1, during two consecutive months per quarter followed by a one month wash-out period (intermittent "schedule"), or placebo (P, n = 18) with the same schedule. Eleven patients in group A and 8 in group P could not complete the one year study because of lack of compliance, worsening of respiratory insufficiency, or for other reasons. In the remaining patients, PaO2 significantly increased in group A (n = 16) from 7.6 +/- 0.1 to 8.3 +/- 0.2 kPa (56.9 +/- 1.0 to 62.7 +/- 1.7 mmHg) (p less than 0.001) but not in group P (n = 10) from 7.5 +/- 0.3 to 7.9 +/- 0.3 kPa (56.1 +/- 2.3 to 59.1 +/- 2.1 mmHg). PaCO2 did not significantly change in either group. Pulmonary artery mean pressure (PAP) was stable in both groups: from 26.8 +/- 2.1 to 25.4 +/- 1.9 mmHg in group A, and from 20.6 +/- 1.1 to 20.9 +/- 1.5 mmHg in group P.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

[Respiratory risk of general surgery in adults].

Disorders of ventilation and postoperative bronchial and pulmonary infections still create serious problems in general surgery. Three factors determine these complications: (1) the transient and usually resolutive repercussions of anaesthesia on ventilation; (2) the sometimes deep and prolonged alteration of lung function directly due to the surgical procedure, and (3) the patient's underlying condition. In practice, this last group of surgical patients can be divided into fragile subjects (elderly people, pregnant women), subjects at risk (smokers, malnourished or obese patients) and disabled subjects suffering from chronic obstructive or restrictive lung disease, asthma or heart disease. Preoperative clinical, radiological and, chiefly, functional evaluation leads to preventive measures. Preparation for surgery relies, to a great extent, on respiratory physiotherapy which, if needed, may be integrated in a pneumological therapeutic program. Combined with an efficient postoperative analgesia and with an optional anaesthesia technique, respiratory physiotherapy is essential to the prevention of respiratory complications in surgery.

Adult↗

PubMed1990

A BASIC software program to estimate cardiac output and alveolar ventilation.

This software program adds two very interesting data to the usual results of exercise testing: an estimation of cardiac output according to the most recent validations and a reliable estimation of alveolar ventilation. The main advantage of this additional ventilatory and cardiovascular information using the same data: end-tidal PCO2.

Carbon Dioxide↗

PubMed1990

[Force-velocity test: effect of a heavy-load start on maximal anaerobic power and blood lactate levels].

The purpose of this study was to determine the effect of starting the force-velocity test with a heavy load on both maximal anaerobic power and blood lactate concentration. Nine male subjects aged 23.4 +/- 1.3 yr (mean +/- sem) participated in a first force-velocity test (FV1) which had an initial load of 1 kg (classical protocol). Then a week later in a second force-velocity test (FV2) which had an initial load corresponding to maximal power developed during FV1 (W1). The increase in load was of 1 kg for FV1 and FV2. Our results show that during FV2, compared to FV1: 1) maximal anaerobic power developed (W2) is superior to W1 (W1 = 1,165.2 +/- 70.4 W; W2 = 1,278.6 +/- 92.3 W; p less than 0.02); 2) blood lactate concentration after the first load is inferior (p less than 0.001); 3) blood lactate concentration is not significantly different at the peak of power. Thus, starting the force-velocity test with a heavy load allows an increase of maximal anaerobic power until a blood lactate concentration which may be compared to the one obtained during the classic force-velocity test. In conclusion, maximal anaerobic power measured during the force-velocity test seems to depend on protocol used.

Adult↗

PubMed1990

[Effect of acute or chronic administration of caffeine on performance and on catecholamines during maximal cycle ergometer exercise].

Seven men were studied during maximal cycle ergometer exercise, to assess the effects of a single or continuous caffeine ingestion on performance and catecholamine secretion. A single blind and randomised procedure was followed with three trials at 100 +/- 5% VO2 max until exhaustion. The first trial was performed after a single administration of 250 mg of caffeine (a). The second and third trials were performed after a treatment of 5 days with 250 mg caffeine per day (continuous = c) and after placebo (p). a and c caffeine administration, 60 min prior to exercise, did not significantly change the time to exhaustion, but increased the plasma levels of both epinephrine (E) and norepinephrine (NE) at exhaustion (p less than 0.05). Single ingestion of caffeine accelerated the elimination of E and NE and increased the maximal blood lactic acid. These data suggest that both single and continuous administration of caffeine do not enhance performance during maximal cycle ergometer exercise, but do increase the exercise response of catecholamine. Only a single administration modifies the blood lactate accumulation.

Adult↗

PubMed1989

Relationship between aerobic physical fitness and ventilatory control during exercise in young swimmers.

The aim of this study was to specify in young trained swimmers, during progressive exercise, whether different aerobic physical fitness goes along with differences in breathing pattern and in mouth occlusion pressure used as a non-invasive index of neuromuscular output. Ten children (aged 10.5-16 years) with high VO2 max (57.6 +/- 3.6 ml.min-1.kg-1) and ten children (aged 11-17 years) with moderate VO2 max (44 +/- 3.8 ml.min-1.kg-1) realized a maximal exercise test on a cycle ergometer. During the last minute of each power level we measured the following parameters: VO2, VCO2, VEBW, f, VTBW/TI,TI/TTOT, as well as mouth occlusion pressure (P0.1) and 'effective impedance' of the respiratory system (P0.1/VTBW/TI). Our results showed that at a same VCO2, children with high VO2 max had significantly lower P0.1, P0.1/VTBW/TI and f than children with moderate VO2 max and same VEBW/TI. At different levels of VO2, in the twenty children of the two groups, we have found significant correlations between VO2 max of each subject and P0.1 (P less than 0.01), P0.1/VTBW/TI (P less than 0.001). At a same VO2, children with a higher VO2 max showed significantly lower P0.1, P0.1/VTBW/TI at all levels of VO2 and lower VEBW and VTBW/TI at high level of VO2. At a same VE, the two groups of children showed the same values of VT/TI and f. In conclusion this study shows first, that different aerobic physical fitness does not go along with different breathing pattern, and second, that swimmers with high physical fitness have a lower ventilatory response to exercise but a higher ventilatory and neuromuscular efficiency during exercise than children with moderate physical fitness.

Adolescent↗

PubMed1989

[Participation of lactic anaerobic metabolism during short and intense repeated exercises].

The evolution of blood lactate concentrations has been studied during a force/velocity test on a cycloergometer in order to specify if the repetition of short (6 s) and intense exercises induced an important participation of lactic anaerobic metabolism. Seven moderately trained male subjects, aged from 23 to 29 years (mean = 24.92 +/- 0.79) participated in this study. Two blood samples (venous catheter) were performed, at rest, then for each work load (1 kg to 10 kg): at the end of the exercise (P1) and during the recovery at 5 min (P2). From the lowest work load, blood lactate concentration increased significantly, at the end of the exercise (F = 16.21; P less than 0.001) and during the recovery (F = 22.62; P less than 0.001). The mean values were respectively at the peak of power: 9.84 +/- 0.85 et 10.19 +/- 0.75 mmol.l-1. Once the peak of power was obtained, the blood lactate concentration remained steady. In conclusion, the repetition of short and intense exercises induced an important participation of lactic anaerobic metabolism. The lactate could be the limiting factor of the maximal power.

Adult↗

PubMed1988

Breathing pattern and load compensatory responses in young scoliotic patients.

The breathing pattern and mouth occlusion pressure developed in 0.1 seconds (P0.1) were measured at rest in sixteen young scoliotic patients in whom the blood gases were within the normal limits. The patients exhibited rapid and shallow breathing. P0.1 was increased above normal, indicating a compensatory increase of neuromuscular inspiratory drive in the face of a stiffer respiratory system. P0.1 (% predicted) correlated positively with the angle of scoliosis. Both duration of inspiration and inspiratory duty cycle correlated negatively with angle of scoliosis and P0.1 (% predicted). On theoretical grounds we show that these changes in breathing pattern are beneficial, both in terms of reducing the energy cost of breathing and preventing the development of inspiratory muscle fatigue.

Adolescent↗

PubMed1987

Effect of aerobic training quantity on the VO2 max of circumpubertal swimmers.

Maximal oxygen uptake (VO2 max) was measured in 38 swimmers aged 10-14 years. Thirty of 38 boys participated in this study for at least 2 consecutive years. Group 1 consisted of 23 subjects (48 measures) who trained for 7 h/week while group 2 consisted of 15 subjects (27 measures) who trained for 14 h/week. In group 2, VO2 max normalized to body weight was significantly higher at 14 years of age than at 10, whereas the increase was nonsignificant during this period in group 1. The subjects of group 2 showed a large increase of VO2 max/kg body weight from the age of 13, which corresponded in this study to the age of peak height growth velocity. The differences between the two groups were statistically significant at both 13 (P less than 0.02) and 14 years of age (P less than 0.05). At 13 and 14, the most trained subjects also showed significantly higher (P less than 0.05) values of maximal oxygen pulse/kg body weight (VO2 max/kg/HR max). Maximal heart rate (HR max) was similar in the two groups between 10 and 14 years of age. Therefore, we conclude that an increase in a training program of the aerobic type induces a large increase in VO2 max from the age of peak height growth velocity. This is likely due to an increase in the stroke volume.

Adolescent↗

PubMed1987

Is ventilatory anaerobic threshold a good index of endurance capacity?

This study was undertaken to assess whether ventilatory anaerobic threshold (T vent) reflected endurance capacity (EC) in sports medical control. Fifteen subjects performed two cycle ergometer tests. The first was a maximal exercise test, which consisted of increasing the load 20 W/min until exhaustion. During this test, the gas exchange anaerobic threshold was determined and VO2 max was measured. The second was an endurance exercise test, which consisted of asking the subject to work, as long as possible, a load representing 80% of his maximal aerobic power. During this test, we measured endurance time (ET). The statistical analysis showed the lack of relationship between VO2 max and ET and the linear correlations between VO2 T vent ml/min/kg and ET min (r = 0.521, P less than 0.05), VO2 T vent l/min and ET min (r = 0.524, P less than 0.05), and T vent % VO2 max and ET (r = 0.738, P less than 0.01). These results establish that ventilatory anaerobic threshold actually reflects endurance capacity. This relation can be explained referring to the muscle energetic metabolism during exercise. Therefore, T vent should be determined systematically in addition to VO2 max during maximal exercise tests to better evaluate physical fitness.

Adolescent↗

PubMed1986

[Underestimation of bronchial obstruction in sarcoidosis].

We compared the frequency of airway obstruction in 27 patients with pulmonary sarcoidosis using both spirography (FEV1, FEF25-75) and plethysmography (Gus50). FEF25-75 was abnormal in 5 patients and Gus in 8 patients; however, only 3 of them showed abnormal values of both parameters. In the 2 patients with only a spirographic obstruction we observed an increase in static lung compliance. In 5 patients without spirographic obstruction we observed an increase of the elastic recoil of the lung, which probably balanced the decrease of Gus, leading to normal flow. In conclusion, airway obstruction is not frequent in sarcoidosis and can be masked in fibrosing forms, if spirographic measurements only are used.

Adult↗

PubMed1986

Effects of adenosine triphosphate on pulmonary circulation in chronic obstructive pulmonary disease. ATP: a pulmonary vasoregulator?

Extracellular adenosine triphosphate (ATP) has potent systemic vasodilator and endothelial-dependent relaxant effects on precontracted vessels. Pulmonary uptake and metabolism of ATP have been described, but experimental effects on pulmonary vessels remain controversial in animals. The effects of an intravenously administered infusion of ATP on pulmonary hemodynamic and gasometric data were assessed in 18 patients with stable chronic obstructive pulmonary disease (COPD). Low doses of ATP (successive rates, 1 and 2 mumol/kg body weight, each for 20 min) were infused in pulmonary hypertensive (H; n = 6) and nonhypertensive (N; n = 6) patients. They were compared with a control group (C; n = 6) that received only solvent, using ANOVA. During ATP infusion, a significant pulmonary vasodilation was demonstrated as simultaneous decreases reached, respectively, -14.2% (Group H; p less than 0.005) and -13.8% (Group N; p less than 0.001) for mean pulmonary artery pressure (Ppa), and -31.7% (H; p less than 0.05) and -20.7% (N; p less than 0.01) for pulmonary vascular resistances (PVR), associated with some worsening of hypoxemia: -6.9% (H; p less than 0.01) and -11.8% (n; p less than 0.005). After ATP withdrawal, significant rebound of these data (above baseline values) reached +10.9% (H; p less than 0.05) and +4.4% (N; p less than 0.05) for Ppa and +24.9% (H; p less than 0.05) and +10.2% (N; p = NS) for PVR. At the low infusion rate used, ATP appeared to be a well-tolerated, short-acting, selective pulmonary vasolidating compound in patients with COPD, but therapeutic use remains premature.

Adenosine Triphosphate↗

PubMed1986

Long term studies on almitrine bismesylate in COPD patients.

Almitrine bismesylate is a chemoreceptor agonist which has been shown to improve arterial blood gas values in chronic obstructive pulmonary disease (COPD) patients, possibly through better ventilation/perfusion matching. On these basis, long term studies were undertaken to evaluate the therapeutic activity of almitrine bismesylate in COPD. We report here the overall results of 4 studies: a 6 months double blind placebo controlled study on clinical and biochemical data in 200 patients. a 12 months double blind placebo controlled study on clinical and hemodynamic data in 15 patients. a 12 months open study on clinical and biochemical data in 108 patients. a 52 months follow-up including therapeutic gap in 8 patients. Almitrine bismesylate group showed significant improvement of PaO2 and PaCO2 levels as compared with placebo group; this was found after 6 months of treatment and persisted after 12 months of treatment. 75% of almitrine treated patients were considered as responders, i.e. improved PaO2 and PaCO2 levels by at least 5 mmHg (0.665 KPa). Almitrine bismesylate groups showed significantly decreased dyspnea scores, received significantly less hospital care for acute decompensation or pulmonary infection and showed no significant change in hemodynamic parameters. After 20 months treatment interruption, patients showed progressively impairmed blood gas levels. Almitrine bismesylate ws well tolerated; nausea was occasionally observed and usually disappeared. Paresthesia was observed in some patients with identified predisposition. Altogether, these studies showed long term efficacy and acceptability of almitrine bismesylate in COPD patients with chronic respiratory failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Almitrine↗

PubMed1986

Compared effects of ATP vs adenosine on pulmonary circulation of COPD.

Pulmonary human vasomotor effects of purine nucleotides are unknown. We compared hemodynamic and gasometric effects of ATP vs ADO, using equimolar infusion rate, on 18 chronically hypoxemic COPD patients. ATP infusion (1 and 2 micro Mole per kilo over 20 min) induced pulmonary vasodilation, with a significant decrease of Ppa (-14% -p = 0.025), PVR (-26.6% p = 0.05) and PaO2 (-10.9% p = 0.025). No change was observed when ADO and control solvent were infused. The pulmonary vasodilator effect of infused ATP on COPD patients, seems to be independent of circulating ADO.

Adenosine↗