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Biomedical subjects

G Atlan

Publications and source records attributed to G Atlan.

At least 37 records · Page 2Linked to original sources
PubMed1992

Influence of posture on mechanical parameters derived from respiratory impedance.

The influence of posture on respiratory mechanics was investigated in 10 healthy volunteers, using the forced pseudorandom noise technique. Subjects were studied in four randomly selected positions: sitting; sitting with the head turned sideways; supine; and prone with the head turned sideways. Respiratory compliance (Crs), inertance (Irs) and resistance estimated at 4 Hz (R4), were calculated by fitting respiratory impedance by a 4 parameter model with a frequency dependent resistance. When subjects changed from sitting to lying, whilst maintaining the head in the same position in relation to the body, Irs increased and Crs decreased, probably due to gravitational effects. R4 was significantly higher in the supine position than in either of the sitting or the prone positions. These results demonstrate that changes in lung volume cannot completely explain the influence of posture on respiratory resistance, and indicate upper airway geometry as a determinant factor of respiratory resistance.

Adolescent↗
PubMed1992

[Partial anterior chondrotomy in the correction of prominent ears. Apropos of 140 re-examined cases].

336 patients have been operated for protruding ears. 140 of them have a long term postoperative follow-up. The anterior partial chondrotomies are opposed to the other surgical procedures and give the opportunity for a comparative and retrospective study. Surgical indications and procedures, use of antibiotics, postoperative follow-up, and complications are studied. 95% of results are good or very good whatever the surgical procedure. The authors remain the posterior and anterior access for partial chondrotomy.

Adolescent↗
PubMed1992

[A comparative study of 2 series of mandibular osteosynthesis using screwed plates].

In a retrospective study, we compared monocortical internal fixation versus bicortical screwing in the treatment of the mandibular fractures. Between 1983 and 1985, 40 patients underwent bicortical screw plate osteosynthesis and 46 were treated with the monocortical screw plate technique. The results are favorable to bicortical screwing, as regards both infection and pseudarthrosis. Monocortical screwing caused fewer occlusal disorders than bicortical screwing. Best on the increased amount of complications we decided to abandon the using of monocortical in favour with bicortical plates.

Bone Plates↗
PubMed1991

EMG spectral shift- and 31P-NMR-determined intracellular pH in fatigued human biceps brachii muscle.

We have simultaneously recorded human biceps brachii intracellular pH, estimated by 31P-NMR, and EMG spectral shift, during isometric contraction and recovery in six subjects. This method allows us to concurrently study several components of muscle fatigue. The results show a clear dissociation between the recovery of intracellular pH, force-generating capacity, and the shift to low frequency of the EMG power spectrum induced by fatiguing exercise.

Electromyography↗
PubMed1991

[Current indications for coral in craniofacial surgery. A 10-year experience].

After a ten year clinical experience of coral implants in Cranio-Facial Surgery, the authors can precise the up to date indications. 55 patients received coral inlays. Two varieties of coral have been used, Goniopora and Polyphylla, demonstrating complementary properties. Filling of bony defects and volumetric increase specially held our attention. Coral may be discussed versus autologous bony grafts in very circumscribed indications.

Animals↗
PubMed1991

[Teleradiographic analysis of the face in facial asymmetry].

The authors emphasize the interest of the frontal cephalometric analysis in facial asymmetries; principles of a simple cephalometric study are given. They analyse the mandibular abnormalities and his maxillary participation. Possibility of surgical treatment and postoperative control can be done. Three cases are presented. This method concerns post traumatic as well as congenital facial asymmetries.

Adolescent↗
PubMed1990

Hormonal and metabolic changes during exercise in cirrhotic patients.

The metabolic response to exercise was compared in 10 cirrhotic patients (P) in a stable clinical condition and in 6 sedentary, age-matched, normal subjects (C) performing 32 minutes of treadmill exercise with the same constant workload corresponding to three to four times their resting oxygen uptake. Taking indirect calorimetry as reference, respiratory exchanges indicated that cirrhotic patients consumed carbohydrates almost exclusively, unlike the normal controls, who consumed lipids and glucids in about the same proportions (RQ: 0.98 +/- 0.04 v 0.87 +/- 0.04, P less than .0001). In the patients, this carbohydrate path of exercise metabolism lowered glycemia from the resting value of 5.23 +/- 0.16 mmol/L to 4.03 +/- 0.37 mmol/L (P less than .0001) and raised the plasma lactate concentration from 2.08 +/- 0.24 mmol/L at rest to 3.48 +/- 0.32 mmol/L at the eighth minute of exercise (P less than .001), thus suggesting defective liver glyconeogenesis. Fatty free acids and glycerol remained almost constant during exercise, whereas catecholamines increased. Insulin levels were high in patients at rest (67.1 +/- 14.5 U/mL v 15.1 +/- 3.5 U/mL); they declined sharply at the onset of exercise but nevertheless remained high compared to those observed in the controls (P less than .0001). Glucagon increased in exercising patients from 88.3 +/- 21.3 pg/mL to 127.4 +/- 30.6 pg/mL (NS). Esterified plasma carnitine declined in the patients from 13.0 +/- 2.2 mumol/L to 8.6 +/- 1.5 mumol/L (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1990

Submaximal oxygen consumption in liver cirrhosis. Evidence of severe functional aerobic impairment.

We studied maximal aerobic work capacity in 24 cirrhotic patients whose clinical condition was well compensated. Nineteen of our patients had no heart or lung disease, and five had mild mechanical ventilatory impairment. The patients performed incremental exercise on a treadmill until subjective exhaustion. The maximal exercise levels reached by all were relatively low and led to a lower observed maximal oxygen uptake (VO2 max), than predicted uptake (19.6 +/- 0.5 vs. 37.9 +/- 0.6 ml/kg; p less than 0.001). Observed VO2 max values correlated strongly with the Pugh score, which reflects the degree of liver failure (r = -0.571; p less than 0.01). Since there were no clear cardiac or pulmonary causes to explain the decrease in work capacity, these observations suggest that liver cirrhosis might induce or be accompanied by muscular impairment. VO2 max, which seems to decline with the functional severity of the disease, may be a useful index for evaluating the capacity of patients for physical rehabilitation.

Exercise Test↗
PubMed1990

Plasma levels of atrial natriuretic factor, renin activity, and aldosterone in patients with chronic obstructive pulmonary disease. Response to O2 removal and to hyperoxia.

To examine the interrelations between humoral systems involved in the circulatory and body fluid volume homeostasis of patients with chronic obstructive pulmonary disease (COPD), we measured plasma levels of renin activity (PRA), aldosterone (Aldo), and atrial natriuretic factor (ANF) in 14 patients with stable COPD who used continuous O2 therapy. Hemodynamics, blood gases, and plasma hormone levels were measured (1) while patients received supplemental O2; (2) after 30 min O2 discontinuation; and (3) after a 30-min period of 96% O2 breathing. Plasma immunoreactive ANF concentrations were 196 +/- 50 pg/ml during O2 breathing and were positively related to transmural pulmonary arterial wedge pressure (tPpaw, r = 0.90, p less than 0.001) and to PaCO2 (r = 0.57, p less than 0.02). Compared to normal subjects matched for age and sex, patients had higher plasma ANF levels (196 +/- 52 versus 72 +/- 6 pg/ml, p less than 0.01), similar PRA (2.1 +/- 0.5 versus 1.3 +/- 0.3 ng/ml/h, NS), and slightly lower plasma Aldo (98 +/- 17 versus 156 +/- 19 pg/ml, p less than 0.05). Discontinuation of O2 while decreasing PaO2 from 70 +/- 3 to 50 +/- 3 mm Hg resulted in a significant increase in pulmonary arterial pressure (Ppa) from 29 +/- 2 to 32.5 +/- 3 mm Hg (p less than 0.01) and cardiac index (Cl) from 3.6 +/- 0.1 to 3.9 +/- 0.1 L/min/m2 (p less than 0.01) and a decrease in systemic arterial pressure (Psa) from 96 +/- 3 to 91 +/- 2 mm Hg (p less than 0.05); transmural cardiac filling pressures and pulmonary vascular resistance (PVR) were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Effects of propranolol and pindolol on plasma ANP levels in humans at rest and during exercise.

In attempt to elucidate whether the beta-adrenoceptor is involved in the control of atrial natriuretic peptide (ANP) secretion, plasma immunoreactive ANP level was measured at rest, in recumbent and upright positions, and during graded maximal ergocycle exercise in nine healthy male subjects (23 +/- 0.5 years of age) treated for 3 days with nonselective beta-blockers propranolol (150 mg/day) or pindolol (15 mg/day) or with placebo. The effects of beta-blockers, which differ by their hemodynamic actions at rest because of the intrinsic sympathomimetic activity of pindolol, were compared. Maximal O2 consumption (VO2max) during beta-blockade was not significantly different from the placebo value. Resting heart rate was not affected by pindolol treatment but was decreased with propranolol (-10 beats/min). Both beta-blockers caused a reduction in heart rate at all the exercise intensities. Mean blood pressure was not affected by beta-blockade at rest but was significantly reduced during exercise. During placebo treatment, plasma ANP increased in response to exercise intensities greater than 65% of VO2max. At 100% VO2max plasma ANP was nearly doubled (101.5 +/- 14 pg/ml) compared with the basal value in upright position (56.6 +/- 15 pg/ml). beta-Blockade caused a marked elevation in plasma ANP at all the levels of activity. Despite different hemodynamic responses to pindolol and propranolol, both beta-blockers produced similar increases in the basal level of plasma ANP. These rises were maintained in the course of exercise tests, and no significant difference was found between propranolol and pindolol. We conclude that beta-adrenoceptor mechanisms are not directly responsible for tonic and exercise-induced ANP secretion in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Effects of sustained exercise on pulmonary clearance of aerosolized 99mTc-DTPA.

The effects of intensive prolonged exercise on the pulmonary clearance rate of aerosolized 99mTc-labeled diethylenetriaminepentaacetate (99mTc-DTPA) and pulmonary mechanics were studied in seven healthy nonsmoking volunteers. 99mTc-DTPA clearance and pulmonary mechanics (lung volumes and compliance) were assessed before and after 75 min of constant-load exercise performed on a treadmill, corresponding to 75% of maximal O2 uptake. Because both clearance measurements were made in similar conditions of pulmonary blood flow, respiratory rate, and tidal volume, changes in clearance rate can be assumed to represent changes of alveolar epithelial permeability. After exercise, total, apical, and basal clearance were significantly increased (P less than 0.01, 0.05, and 0.05, respectively) and the increases in total clearance and tidal volume observed during exercise were significantly correlated (P less than 0.05). In contrast, no significant change was found in pulmonary mechanics. These results show that prolonged intensive exercise induces an increase in epithelial permeability, which appears to be related to the mechanical effects of sustained increased ventilation. Because no change was evidenced in pulmonary volumes or in lung elasticity, our results suggest that this increase may result from alteration of the intercellular tight junctions rather than from a surfactant deficiency.

Adolescent↗
PubMed1985

On line determination of airway resistance by plethysmography and microcomputer.

On line determination of airway resistance is carried out by an Apple II connected to a flow body plethysmograph. Recognition of the panting maneuver is performed in real time. Linear drift of plethysmographic volume V is eliminated by taking the derivatives V and Vm of V and mouth flow Vm. Linear regression of V on Vm yields an estimate R of airway resistance, at a volume close to functional residual capacity FRC. The values of FRC is given by linear regression of V on Pm, the derivative of mouth pressure. No significant difference has been found between the estimates of the specific conductance sG calculated by linear regression and by spectral analysis of V and Vm. As variability of sG can be kept below 10%, the regression technique appears to be reliable for routine patient testing and pharmacological studies.

Airway Resistance↗
PubMed1984

Lung mechanics in growing guinea pigs.

Lung mechanics were studied in four groups of guinea pigs: neonatal (1), prepubertal (II), postpubertal (III) and adult (IV). The animals were anesthetized and tracheotomized, and an esophageal catheter was inserted. Functional residual capacity (FRC) was measured by body plethysmography. After curarization, the lungs were inflated to a transpulmonary pressure of 30 cm H2O. The resulting change in volume was added to FRC to obtain the total lung capacity (TLC). Lung compliance (CL) normalized for dry lung weight (CL/LW) was calculated. An exponential function was fitted to the experimental P-V curve and the shape constant k was considered as an index of lung distensibility. During growth TCL (ml) increased with BW (g): TLC = 0.3 BW0.69 (r = 0.96). Two significantly different equations (P less than 0.001) were found between TLC (ml) and LW (g): between I and II, TLC = 32.4 LW1.24 (r = 0.88) and between III and IV, TLC = 22.9 LW0.53 (r = 0.73). An increase in lung distensibility as reflected by a significant increase in both CL/LW and the shape constant k was observed. In neonates and in prepubertal animals CL/LW was equal to 1.53 +/- 0.64 and to 2.38 +/- 0.51 ml/cm H2O/g (mean +/- 1 SD), respectively (P less than 0.01) and k to 0.146 +/- 0.026 and 0.219 +/- 0.035 cm H2O-1 (P less than 0.001). From prepuberty to adulthood no further significant changes were observed. These results showed that even in a species with an advanced maturation at birth, lung mechanics changed with growth.

Aging↗
PubMed1984

Total respiratory pressure-volume curves in the adult respiratory distress syndrome.

To assess the value of measuring compliance in the adult respiratory distress syndrome, sequential pressure-volume curves were obtained in 19 patients with this syndrome. Analysis of the pressure-volume curves allowed separation of the patients into the following four groups: (1) group 1 (n = 6), normal compliance measured during deflation, little hysteresis, and no inflection in the ascending limb of the pressure-volume tracing; (2) group 2 (n = 8), normal compliance during deflation, increased hysteresis, and presence of an inflection; (3) group 3 (n = 10), decreased compliance during deflation, marked hysteresis, and presence of an inflection; and (4) group 4 (n = 10), reduced compliance during deflation, no increased hysteresis, and no inflection. These patterns were correlated with the stage of the adult respiratory distress syndrome and to the pattern of the chest x-ray film. Group 2 corresponds to the initial stage of the syndrome and to pure alveolar opacities on the chest x-ray film. Group 3 is seen later in the course of the syndrome and corresponds to mixed alveolar and interstitial opacities. Group 4 corresponds to patients with end-stage adult respiratory distress syndrome (two weeks) and a predominant interstitial pattern on the chest x-ray film. Group 1 corresponds to a nearly normal chest x-ray film and to recovery.

Adolescent↗
PubMed1982

Role of surface tension and tissue in rat lung stress relaxation.

When the volume of the lung is maintained constant after an initial change of volume, stress relaxation (SR) occurs as a slow decay of transpulmonary pressure (PTP). In order to define which structure in the lung is responsible for SR a multiple exponential fitting of the PTP variation has been made. Excised rat lungs were placed in a fluid-filled box with trachea connected to atmosphere and submitted to stepwise changes of volume. Single volume steps (0.2 ml) were performed for lungs filled with either air or saline and the variations of PTP were monitored until steady state was reached. An exponential model (time constant = 6.5 +/- 0.4 (SD) and 92 +/- 6 s) described adequately the SR for air-filled lungs (n = 6) whereas only one exponential (time constant = 6.7 +/- 1.3 s) was required for saline-filled lungs. Multiple volume step experiments were also performed in air-filled lungs to obtain pressure volume loops. These hysteresis loops have been adequately simulated by use of the exponential model. It can be concluded that (1) lung tissue and air-liquid interface are both responsible for the SR with, respectively, short and long time constants and (2) the same relaxation function is able to describe both stress relaxation and static hysteresis in such experimental conditions.

Animals↗