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Biomedical subjects

P Vanuxem

Publications and source records attributed to P Vanuxem.

At least 19 recordsLinked to original sources
PubMed2002

Ascent rate, age, maximal oxygen uptake, adiposity, and circulating venous bubbles after diving.

Decompression sickness in diving is recognized as a multifactorial phenomenon, depending on several factors, such as decompression rate and individual susceptibility. The Doppler ultrasonic detection of circulating venous bubbles after diving is considered a useful index for the safety of decompression because of the relationship between bubbles and decompression sickness risk. The aim of this study was to assess the effects of ascent rate, age, maximal oxygen uptake (VO(2 max)), and percent body fat on the production of bubbles after diving. Fifty male recreational divers performed two dives at 35 m during 25 min and then ascended in one case at 9 m/min and in the other case at 17 m/min. They performed the same decompression stops in the two cases. Twenty-eight divers were Doppler monitored at 10-min intervals, until 60 min after surfacing, and the data were analyzed by Wilcoxon signed-rank test to compare the effect of ascent rate on the kinetics of bubbles. Twenty-two divers were monitored 60 min after surfacing. The effect on bubble production 60 min after surfacing of the four variables was studied in 47 divers. The data were analyzed by multinomial log-linear model. The analysis showed that the 17 m/min ascent produced more elevated grades of bubbles than the 9 m/min ascent (P < 0.05), except at the 40-min interval, and showed relationships between grades of bubbles and ascent rate and age and interaction terms between VO(2 max) and age, as well as VO(2 max) and percent body fat. Younger, slimmer, or aerobically fitter divers produced fewer bubbles compared with older, fatter, or poorly physically fit divers. These findings and the conclusions of previous studies performed on animals and humans led us to support that ascent rate, age, aerobic fitness, and adiposity are factors of susceptibility for bubble formation after diving.

Adipose Tissue↗
PubMed2001

Maximal exercise and muscle energy metabolism after recovery from exercise hyperthermia syndrome.

Muscle energy metabolism was studied in 30 subjects after recovery from exercise hyperthermia syndrome (EHTS subjects) and 15 healthy men with identical physical activities. Blood lactate, free fatty acid (FFA), serum creatine kinase activity (CK), and glycerol and the temperature in the auditory duct (T(c)) and on the thumb pad (T(sk)) were measured at rest and during and after maximal exercise on a cycloergometer. The EHTS subjects had a limitation of physical performance, with lowered values for maximal oxygen uptake (VO(2max), P < 0.0005), maximal workload (P < 0.05), and ventilatory threshold (V(t), P < 0.0005). The discrepancy between high plasma concentrations of FFA and the lack of decrease in respiratory ratio (RR) suggests that, in EHTS subjects, a very active release of FFA was not balanced by a proportional increase in catabolism. The increased skin temperature was smaller in EHTS subjects (P < 0.05 at 180 and 200 W). At the end of exercise, auditory duct temperature increase was higher in EHTS subjects than in control subjects (P < 0.05). This study thus showed an impairment of muscle metabolism and an abnormality of thermoregulatory mechanisms. These results may provide insight into the underlying physiopathological disturbance.

Adult↗
PubMed1999

Circulating venous bubbles in recreational diving: relationships with age, weight, maximal oxygen uptake and body fat percentage.

Decompression sickness (DCS) is recognized as a multifactorial phenomenon depending on several individual factors, such as age, adiposity, and level of fitness. The detection of circulating venous bubbles is considered as a useful index for the safety of a decompression, because of the relationship between bubbles and DCS probability. The aim of this work was to study the effects of individual variables which can be assessed non invasively, on the grades of bubbles detected 60 min, after diving by means of Doppler monitoring, in a sample of 40 male recreational scuba divers. The variables investigated were: age, weight, maximal oxygen uptake (VO2max) and percentage of body fat (%BF). Bubble signals were graded according to the code of Spencer. The relationships between the bubble grades (BG) and the variables investigated were studied using two methods: the differences between the average values of each variable at each BG were analyzed by the Scheffe test. Then we performed the non-parametric Spearman correlation analysis. Significant differences (P < 0.05) were found (Scheffe test) between average values of the variables at grade 0 and 3 (age: P = 0.0323; weight: P = 0.0420; VO2max: P = 0.0484), except for %BF (P = 0.1697). Relationships with P < 0.01 were found (Spearman correlation) between BG and the variables: age: p = 0.486, P = 0.0024; weight: p = 0.463, P = 0.0039; VO2max: p = -0.481, P = 0.0027; except for %BF: p = 0.362, P = 0.0237. This work showed that bubble production after hyperbaric exposures depends on several individual factors. The effects of age, weight and VO2max are more significant than the effect of %BF. We concluded that to take into account such variables in decompression tables and diving computer programs should allow to adapt the decompression procedures to individual risk factors and reduce the DCS probability.

Adult↗
PubMed1998

Blood ammonia and ventilation at maximal exercise.

This study, intended to evaluate the role of ammonia (NH3) as a ventilatory stimulus, was conducted in three groups of subjects: 14 sedentary individuals, 12 triathletes, 5 patients with a glycolytic deficiency (Mc Ardle disease). All subjects performed maximal exercise tests on a cycle ergometer. Ventilation measured at maximal oxygen consumption (VE 100%) was correlated with lactatemia (lactate 100%) and ammonemia (NH3 100%) in the sedentary group, but only with ammonemia in triathletes, although NH3 100% and lactate 100% were correlated in both groups, which suggests that correlation between VE 100% and NH3 100% is not a false correlation. In patients with Mc Ardle disease, unable to produce lactate during exercise, VE 100% was correlated with NH3 100%. NH3 may act indirectly by increasing the production of lactate in cereberal tissue. Another hypothesis rests on the fact that the catabolism of ammonia leads to an increase in intracerebral glutamate which may act as a ventilatory stimulus.

Adult↗
PubMed1997

Impairment of muscle energy metabolism in patients with sleep apnoea syndrome.

Impairment of muscle energy metabolism has been demonstrated in normal subjects with chronic hypoxaemia (altitude chronic respiratory failure). The purpose of this study was to verify the hypothesis that a comparable condition could develop in patients with sleep apnoea syndrome (SAS), considering that they are exposed to prolonged and repeated hypoxaemia periods. Muscle metabolism was assessed in 11 patients with SAS performing a maximal effort on cycloergometer. In comparison with normal subjects, SAS patients reached lower maximal loads [144 +/- 7 vs. 182 +/- 10 W (P < 0.005)] and lower peak oxygen uptakes [26.4 +/- 1.2 vs 33.2 +/- 1.4 ml kg-1 min-1 (P < 0.005)]. Abnormal metabolic features were found: maximal blood lactate concentration was significantly lower than in normal subjects [0.034 +/- 0.004 vs. 0.044 +/- 0.002 mmol l-1 W-1 (P < 0.05)]; and lactate elimination rate, calculated during a 30-min recovery period, was reduced [0.127 +/- 0.017 vs, 0.175 +/- 0.014 mmol l-1 min-1 (P < 0.025)]. The extent of these anomalies correlated with the severity of SAS. The patients also showed higher maximal diastolic blood pressures than normal subjects [104 +/- 5 vs. 92 +/- 4 mmHg (P < 0.05)]. These results can be interpreted as indications of an impairment of muscle energy metabolism in patients with SAS. Decrease in maximum blood lactate concentration suggests an impairment of glycolytic metabolism, while decrease in the rate of lactate elimination indicates a defect in oxidative metabolism. Since no respiratory pathology apart from SAS was found in this group of patients, it seems legitimate to link the genesis of these impairments to repeated bouts of nocturnal hypoxaemia.

Ammonia↗
PubMed1993

[Bronchial provocation tests. Comparison of 2 inhalation methods].

This study was performed to compare two methods of aerosols delivery and inhalation in a bronchial provocation test with carbachol : the stocked method (S) where the aerosol is previously stocked in a spirometer bell before inhalation and the dosimeter method (D) where the aerosol is directly inhaled after nebulization. Fourteen subjects (seven normal and seven asthmatic) underwent bronchial challenges with the two techniques. Bronchial sensitivity was calculated on SRaw-dose response curves to carbachol. SGaw-dose response curves were also constructed and the slopes of these curves were used to measure bronchial reactivity. Within subjects sensitivity values were lower with the D method than with the S method (40 +/- 5 micrograms (S E) versus 450 +/- 50 micrograms respectively in asthmatics, 340 +/- 30 micrograms versus 2350 +/- 130 micrograms respectively in healthy subjects). Reactivity values were higher with the dosimeter method (2,7 +/- 0,7 x 10(-5) versus 27 +/- 4 x 10(-5) in healthy and 10 +/- 1 x 10(-5) versus 106 +/- 16 x 10(-5) in asthmatics). The dosimeter method had greater efficacy, was less time consuming and appeared to be a useful method for carrying out standardised non-specific bronchoprovocation test.

Adult↗
PubMed1993

Pulmonary function changes 100 days and one year after bone marrow transplantation.

The pulmonary function of patients receiving autologous or allogeneic bone marrow transplantation (BMT) was studied before, 100 days after and 1 year after BMT. The 117 patients studied before transplantation showed a slight reduction in average total lung capacity (TLC) and transfer coefficient (KCO). These reductions were related to haematological disease, previous pulmonary disease or irradiation, or use of toxic lung chemotherapy. Studies 100 days after BMT showed TLC and KCO decreases of 5% and 8%, respectively. These decreases were related to different factors in autologous and allogeneic BMT. The results were influenced by previous pulmonary status in autologous BMT patients and the occurrence of GVHD in allogeneic BMT patients. Seventy patients underwent pulmonary function testing 1 year after BMT. The decrease in TLC values was greater in autologous BMT than in allogeneic BMT patients (107 +/- 3% to 100 +/- 3% versus 113 +/- 3% to 112 +/- 2%, respectively) although TLC remained normal in both groups. KCO values dropped significantly in both populations. Relapse of the initial disease was an important factor impairing lung function in the autologous group. TLC and KCO changes were strongly related to mortality in both groups. These results emphasise the need for frequent pulmonary function tests after BMT to detect and quantify lung function changes.

Adult↗
PubMed1975

[The role of afferent barosensory neurons in respiratory and bronchomotor control].

Ventilatory and bronchomotor responses to baroreceptor afferent stimulation were studied in anaesthetized rabbits breathing spontaneously. The stimuli used were either the increase in carotid sinus pressure or the electrical stimulation of the cut central end of the aortic nerve. Respiratory effects of aortic barodenervation were also studied. Normoxic, normocapnic steady state was verified by repeated measurement of PO2, PCO2 and pH in arterial blood. Stimulation of both aortic and carotid baroreceptors provoked an early decrease of tidal volume and total pulmonary resistances without change in respiratory frequency. Aortic nerve stimulation induced an important and slowly adapting ventilatory and bronchomotor effect, whereas changes in carotid sinus pressure produced slight variation in respiratory parameters. Aortic nerve section resulted in an early and prolonged increase of total pulmonary resistances. Surgical or chemical (atropine) vagotomy did not change the bronchodilation observed under stimulation of the carotid sinus; however this effect was suppressed by intravenous injection of propranolol. This observation shows the importance of the sympathetic outflow in the genesis of bronchomotor responses following baroreceptor stimulation. In conclusion the baroreceptor stimulation provokes simultaneous decrease of both ventilation and total pulmonary resistances; aortic nerves seemed to exert permanent control on bronchomotor tone.

Animals↗