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Biomedical subjects

R Pariente

Publications and source records attributed to R Pariente.

At least 91 records · Page 5Linked to original sources
PubMed1985

Effect of hypophosphatemia on diaphragmatic contractility in patients with acute respiratory failure.

We studied the effects of hypophosphatemia on diaphragmatic function in eight patients with acute respiratory failure who were artificially ventilated. Their mean serum phosphorus level was 0.55 +/- 0.18 mmol per liter (normal value, 1.20 +/- 0.10). The contractile properties of the diaphragm were assessed by measuring the transdiaphragmatic pressure generated at functional residual capacity during bilateral supramaximal electrical stimulation of the phrenic nerves. Diaphragmatic function was evaluated in each patient before and after correction of hypophosphatemia, which was achieved by administration of 10 mmol of phosphorus (as KH2PO4) as a continuous infusion for four hours. After phosphate infusion, the mean serum phosphorus level increased significantly (1.33 +/- 0.21 mmol per liter, P less than 0.0001). The increase in serum phosphorus was accompanied by a marked increase in the transdiaphragmatic pressure after phrenic stimulation (17.25 +/- 6.5 cm H2O as compared with 9.75 +/- 3.8 before phosphate infusion, P less than 0.001). Changes in the serum phosphorus level and transdiaphragmatic pressure were well correlated (r = 0.73). These results strongly suggest that hypophosphatemia impairs the contractile properties of the diaphragm during acute respiratory failure, and they emphasize the importance of maintaining normal serum inorganic phosphate levels in such patients.

Acute Disease↗
PubMed1985

[Function of the respiratory muscles in acute cardiac decompensation].

In anesthetized dogs the performance of the respiratory muscles during cardiogenic shock and their influence on its outcome was studied. Shock was induced by cardiac tamponade. Cardiac output during shock amounted to 25-35% of control and was kept constant. Minute ventilation (VE) initially increased and then progressively decreased until respiratory arrest. The latter was due to impairment of respiratory muscle contractility, the pressure generated by the diaphragm (Pdi) decreasing despite a marked increase in the diaphragmatic electromyogram and of the phrenogram. Mechanical ventilation during shock prolonged survival for the same decrease in cardiac output, and also decreased substantially the severity of lactic acidosis. Furthermore, blood flow to the respiratory muscles during shock was different in the animals breathing spontaneously (SB) from that in mechanically ventilated animals (MV). The fraction of cardiac output distributed to the respiratory muscles during control amounted to 1.85% in MV and 2.79% in SB. With shock this decreased to 1.55% in MV while in SB it decreased by 21%, which suggests that mechanical ventilation during shock preserves a large portion of cardiac output used by the respiratory muscles during spontaneous breathing, thus making it available to other organs.

Animals↗
PubMed1985

Bilateral phrenic stimulation: a simple technique to assess diaphragmatic fatigue in humans.

Transdiaphragmatic pressure (Pdi) and the rate of relaxation of the diaphragm (tau) were measured at functional residual capacity (FRC) in six normal seated subjects during single-twitch stimulation of both phrenic nerves. The latter were stimulated supramaximally with needle electrodes with square-wave impulses of 0.1-ms duration at 1 Hz before and after diaphragmatic fatigue produced by resistive loaded breathing. Constancy of chest wall configuration was achieved by monitoring the diameter of the abdomen and the rib cage with a respiratory inductive plethysmograph system. During control the peak Pdi generated during the phrenic stimulation amounted to 34.4 +/- 4.2 (SE) cmH2O and represented in each subject a fixed fraction (17%) of its maximal transdiaphragmatic pressure. After diaphragmatic fatigue the peak Pdi decreased by an average of 45%, amounting to 18.1 +/- 2.7 cmH2O 5 min after the fatigue run, and tau increased from 55.2 +/- 9 ms during control to 77 +/- 8 ms 5 min after the fatigue run. The decrease in peak Pdi and the increase in tau observed after the fatigue run persisted throughout the 30 min of the recovery period studied, the peak Pdi amounting to 18.4 +/- 2.8 and 18.9 +/- 3.3 cmH2O and tau to 81.3 +/- 5.7 and 88.7 +/- 10 ms at 15 and 30 min after the end of the fatigue run, respectively. It is concluded that diaphragmatic fatigue can be detected in man by bilateral phrenic stimulation with needle electrodes without any discomfort for the subject and that the decrease in diaphragmatic strength after fatigue is long lasting.

Action Potentials↗
PubMed1985

Effects of hypocalcemia on diaphragmatic strength generation.

We studied the effects of hypocalcemia on diaphragmatic force and diaphragm blood flow (Qdi) in 12 anesthetized dogs. The diaphragm was electrically stimulated with intramuscular electrodes surgically implanted in the ventral surface of each hemidiaphragm. The transdiaphragmatic pressure (Pdi) during supramaximal (50 V) 2-s stimulations applied over a frequency range of 10-100 Hz was measured with balloon catheters during tracheal occlusion at functional residual capacity. A catheter was placed via the femoral vein into the left inferior phrenic vein, and Qdi was measured by timed volume collections of left inferior venous effluent. A catheter was introduced in a femoral artery to monitor blood pressure (BP). In five additional dogs, the force generated by the sartorius muscle during electrical stimulation was also studied concomitantly to diaphragmatic force. The animals were mechanically ventilated throughout the experiment, and the arterial blood gases and pH were maintained constant. Hypocalcemia was induced by a continuous infusion of EGTA (70 mg X kg-1 X h-1), which led to a progressive decrease (P less than 0.0001) of ionized calcium plasmatic level from 2.21 +/- 0.4 meq/1 during control to 1.69 +/- 0.06, 1.25 +/- 0.5, and 1.07 +/- 0.5 meq/1 after 30, 60, and 120 min, respectively. Hypocalcemia decreased progressively Pdi, which amounted to 84 +/- 3 (P less than 0.001) and 98 +/- 2% of control values for the low frequencies (10 and 20 Hz) and the high frequencies (50 and 100 Hz), respectively, after 30 min of EGTA infusion and to 74 +/- 5 and 79 +/- 6% for the low and high frequencies, respectively, after 120 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Work of breathing in patients with chronic obstructive pulmonary disease in acute respiratory failure.

In 11 spontaneously breathing patients with chronic obstructive pulmonary disease (COPD) in acute ventilatory failure, we measured the total inspiratory (WItot) and total resistive (WI + Eres) work rate of breathing, together with lung mechanics (dynamic pulmonary elastance and inspiratory and expiratory pulmonary flow resistance). All variables were markedly increased compared with those in normal subjects. No significant correlation was found between WItot and WI + Eres with lung mechanics data. However, when WItot and WI + Eres were expressed per liter of ventilation, a significant positive correlation was found with all lung mechanics data. These results indicate that although in patients acutely ill with COPD, work rate and work per liter of ventilation are increased, only the latter is related to the severity of pulmonary mechanical impairment, and it could be used as one of the criteria for extubation. In addition, our results indicate that at end-expiration the alveolar pressure was positive (range, 6 to 13 cm H2O) in all patients (intrinsic PEEP), a fact that must necessarily affect hemodynamics; furthermore, it imposes an extra burden on the inspiratory muscles.

Acute Disease↗
PubMed1985

[Effect of glucocorticoids in chronic dyspneic asthma: histological and immunohistochemical study of the bronchial mucosa].

This prospective study was done in 8 patients with chronic asthma, hospitalised for an exacerbation of their illness without any evidence of airway infection. The intention was to measure both qualitatively and quantitatively the impact of high dosage glucocorticoids on the inflammatory changes of the bronchial mucus in such patients. Biopsies of the proximal bronchi by fibreoscopy were taken before and after 6 to 9 days of Prednisolone (0.5-0.75 mg/kg per day), this treatment led to a relative rise in the FEV1 (VEMS) of at least 15%. These biopsies were fixed in Bouin and Paraffin, and the sections simultaneously processed for qualitative identification (histochemical and immuno-peroxidasic) of cells infiltrating the bronchial mucosa and for a count of these cells in a pre-determined sub-epithelial zone. It was noted: In all patients at the entry to the study: an essentially lympho-monocytic cellular infiltrate of the bronchial mucosa, a virtual absence of neutrophils, and various abnormalities of the surface epithelium. After 6 to 9 days of steroids there was a persistence of epithelial lesions and in 6 out of 8 patients a statistically significant fall in the density of the inflammatory infiltrate. In 75% patients suffering from exacerbations of chronic asthma, the improvement in the ventilatory function with dosage corticotherapy was accompanied by a fall in the level of inflammatory infiltrate in the proximal bronchi.

Adult↗
PubMed1984

Effects of theophylline on diaphragmatic strength and fatigue in patients with chronic obstructive pulmonary disease.

We studied the effects of theophylline on diaphragmatic strength and fatigue in 15 patients with severe chronic obstructive pulmonary disease. Diaphragmatic strength was assessed by measurement of the transdiaphragmatic pressure generated at functional residual capacity during a maximal inspiratory effort against closed airways. Diaphragmatic fatigue was induced by resistive loaded breathing. The electrical activity of the diaphragm was recorded with an esophageal electrode during the fatigue runs, and the high-low ratio of the electrical signal was analyzed to assess diaphragmatic fatigue. Studies were performed before and after 7 and 30 days of theophylline administration (mean plasma level, 13 +/- 2 mg per liter). A control group received a placebo instead of theophylline. Theophylline increased maximal transdiaphragmatic pressure by 16 per cent after 7 days of administration (P less than 0.01), and this increase persisted after 30 days. No significant change in maximal transdiaphragmatic pressure was observed in the group given the placebo. Theophylline also suppressed diaphragmatic fatigue in all patients who received it. We conclude that theophylline has a potent and long-lasting effect on diaphragmatic strength and fatigue in patients with fixed airway obstruction.

Diaphragm↗
PubMed1984

Effects and mechanism of action of terbutaline on diaphragmatic contractility and fatigue.

We studied the effects of intravenously administered terbutaline on diaphragmatic force and fatigue during electrical stimulation of the diaphragm in 17 anesthetized dogs. The diaphragm was stimulated indirectly through the phrenic nerves with electrodes placed around the fifth roots and directly with electrodes surgically implanted in the abdominal side of each hemidiaphragm. Transdiaphragmatic pressure (Pdi) during direct or indirect supramaximal 2-s stimulation applied over a frequency range of 10-100 Hz was measured with balloon catheters during tracheal occlusion at functional residual capacity. In seven dogs the administration of terbutaline (0.5 mg) had no effect on Pdi at any stimulation frequency applied directly or indirectly. The effect of terbutaline (0.5 mg) on diaphragmatic fatigue was then tested in 10 other dogs. Diaphragmatic fatigue was produced by continuous 20-Hz electrical supramaxial stimulation of the phrenic nerves during 30 min. At the end of the fatigue procedure Pdi decreased by 50 +/- 5 and 30 +/- 8% of control values at 10 and 100 Hz, respectively, for either direct or indirect stimulation. The decrease in Pdi for low frequencies of stimulation (10 and 20 Hz) lasted 100 +/- 18 min, whereas it lasted only 40 +/- 10 min for the high frequencies (50 and 100 Hz). When terbutaline (0.5 mg) was administered after the fatiguing procedure, Pdi increased within 15 min by 20 +/- 4% at 10 Hz and by 12 +/- 3% at 100 Hz for either direct or indirect stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Effects of aminophylline on diaphragmatic fatigue during acute respiratory failure.

The effects of aminophylline on diaphragmatic fatigue and recovery in the face of hypoxemia and hypercapnic acidosis were studied in anesthetized, spontaneously breathing, dogs. The phrenic nerves were stimulated supramaximally at 10, 20, 50, and 100 Hz during 2 s with electrodes placed around the fifth roots, and the resulting transdiaphragmatic pressure (Pdi) was measured with balloon catheters. The dogs were occluded before the stimulations at functional residual capacity. The latter was monitored by measuring the end-expiratory transpulmonary pressure, which remained constant throughout the experiment. Diaphragmatic fatigue was produced by resistive loaded breathing. At the end of the runs, which lasted 15 +/- 2 min, all the dogs were severely hypoxemic (30 +/- 5 mmHg), hypercapnic (65 +/- 4 mmHg), and acidotic (7.1 +/- 0.05). During the fatigue runs, phrenic stimulation resulted in a marked decrease in Pdi, which amounted at 20 Hz to 70 +/- 8% and 45 +/- 12% of the control values 5 min after the onset of the fatigue runs and at the end, respectively. After recovery (3 h), Pdi and arterial blood gas determinations returned to control values. Identical fatigue runs were repeated with aminophylline infusion (loading dose, 6 mg/kg in 10 min and maintenance dose, 1 mg/kg/h), leading to a plasmatic concentration of 16.4 +/- 2 mg/l. Aminophylline protected the diaphragm against fatigue, and despite the presence of hypoxemia and hypercapnic acidosis, the Pdi generated for a 20 Hz stimulation of the phrenic nerves at identical times of the preceding run amounting to 100 +/- 15% and 85 +/- 10% of control values, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis, Respiratory↗
PubMed1984

[Validity of mortality data in respiratory diseases in France and 7 other countries of the E.E.C].

A recent study of mortality due to respiratory disease, carried out in the eight member countries of the European Economic Community (E.E.C.) has shown different levels of mortality between the countries. To establish whether these variations in mortality were real or due to methods of filing and coding, a study of death certification was carried out in each country based on 10 common clinical diagnostic categories to assess overall accuracy. In France, 75 doctors picked a random, were asked to fill in a form for each observation as though it were a real death. The cause of death was coded by the usual national centre and re-coded by a reference centre in London. The protocol was similar for each country taking part. Important differences were found between and within each country. Some arise from the way in which doctors write out the death certificates (an excess of deaths from "other disease of the respiratory tract" in France and from cardio-vascular diseases in Italy), in others the way of coding was due to (an "excess of deaths by other disease of the respiratory tract" in Belgium). The degree of concordance depends on the complexity of the case (possible interaction of several pathologies), particular national characteristics, and whether account of these is made by the medical profession. These divergences can in part explain the different mortality statistics from respiratory disease between countries of the E.E.C. Later on it will be necessary to make the wording and the coding of the death certificate more standardised within the E.E.C.

Death Certificates↗
PubMed1983

Laser oncology in Italy: experimental research and clinical applications at the National Cancer Institute, Milan.

CO2, Nd:YAG, and argon lasers have been used for 5 years for experimental and clinical procedures at the National Cancer Institute of Milan under the auspices of the National Research Council. Experimental data regarding tumor cell spread through lymphatic and hematic channels and cell viability in the fumes after CO2 laser irradiation are reported. New advantages in the combined treatment modalities have been demonstrated, since the synergism between the low power argon laser beam and chemotherapeutic agents (anthracyclines) was assessed on cell cultures and the least toxic and the most effective doses of the drugs were identified. Due to the optical properties of the laser beam, physical measurements of the delivered energy and mathematical calculation of the energy per tissue volume unit to be ablated increase the precision in microsurgery especially when conservative managements are indicated. Main applications in surgical oncology, and comparison versus conventional methods, both with vaporization and excisional techniques, according to specific therapeutic protocols, in general surgery, otolaryngology, gynecology, and endoscopy, even on an outpatient basis, are finally illustrated in a series of 600 cases.

Animals↗
PubMed1983

Diaphragmatic contractility enhanced by aminophylline: role of extracellular calcium.

We have studied the effects of aminophylline on diaphragmatic contractility in 12 anesthetized dogs. The phrenic nerves were stimulated supramaximally (20 Hz, 0.1 ms) with electrodes placed around the fifth roots, and the transdiaphragmatic pressure (Pdi) generated at functional residual capacity (FRC) was measured with balloon catheters. Constancy of FRC was monitored by measuring the end-expiratory transpulmonary pressure, the dogs being occluded at FRC before the stimulations. The electrical activity of the diaphragm (Edi) during the stimulations was recorded with electrodes inserted in both hemidiaphragms. Phrenic stimulations during an infusion of aminophylline (10 mg/kg in 5 min) increased Pdi by 25 +/- 8% of control values, whereas the Edi remained unchanged. This potentiating effect of aminophylline was abolished when an identical dose was injected during a continuous infusion of a calcium blocker (verapamil, 0.1 mg X kg-1 X min-1). Infusion of another methylxanthine compound, caffeine (10 mg/kg), also increased Pdi for an identical electrical phrenic nerve stimulation by 21 +/- 6% compared with control values. However, the potentiating effect of caffeine was not abolished by verapamil. We conclude that aminophylline in vivo increases diaphragmatic contractility and that extracellular calcium is necessary for this action, a mechanism not shared by another methylxanthine compound, caffeine.

Aminophylline↗
PubMed1983

Increased ventilation caused by improved diaphragmatic efficiency during aminophylline infusion.

The mechanism underlying the increase in ventilation (VE) observed during aminophylline infusion was investigated in 12 anesthetized spontaneously breathing dogs. Progressive doses of aminophylline were infused every 30 min, leading to plasmatic levels of 10 to 20, 20 to 30, 30 to 50 mg/L. The increase in VE observed while increasing aminophylline plasmatic concentration ranged from 4.2 +/- 6 to 9.5 +/- 1.2 L/min. Concomitantly to VE, we measured an index of the inspiratory neuromuscular output of the diaphragm, the transdiaphragmatic pressure generated at FRC 0.1 s after the onset of a spontaneous inspiration developed against closed airways (Pdi0.1). For each plasmatic level of aminophylline, Pdi0.1 increased as VE (117 +/- 4, 126 +/- 2, 140 +/- 6% of control values for 10 to 20, 20 to 30, 30 to 50 mg/L, respectively). To establish the role played by an improvement in diaphragmatic contractility in the increase in Pdi0.1 with aminophylline, we measured for each plasmatic level of aminophylline the transdiaphragmatic pressure generated at FRC against closed airways during supramaximal stimulation at 10, 20, 50, and 100 Hz of the 2 phrenic nerves (Pdi). Pdi increased while increasing aminophylline plasmatic level for all the frequencies of stimulation. A relationship was found between Pdi and Pdi0.1 at any aminophylline plasmatic level as well as with VE. No change in the mechanical properties of the respiratory system occurred with aminophylline. We conclude that the increase in VE observed after aminophylline administration in our animal model is essentially due to an improvement in diaphragmatic contractility rather than an increase in the central nervous system output.

Aminophylline↗
PubMed1983

[Physiopathology of acute decompensation in chronic obstructive respiratory insufficiency].

The acute decompensation of chronic obstructive respiratory failure is characterised by a deterioration of the respiratory mechanics which leads to a reduction of maximum ventilatory output, the respiratory muscles are placed at a mechanical disadvantage and in attempting to compensate are vulnerable to muscle fatigue. A large part of ventilation is wasted in ventilatory dead space. Total ventilation is normal but tidal volume is shallow and respiratory rate rapid. This type of breathing is partially responsible for the large dead space effect. Respiratory centre activity is greatly increased. The prescription of bronchodilators is debatable because there is a risk of increasing the dead space effect. The hypoxic and hypercapnic stimuli have a weak and roughly similar effect on ventilatory control, but the effect of pure oxygen on PaCO2 is due to factors other than those relating to respiratory centre activity.

Acute Disease↗
PubMed1983

[Respiratory pathology of isocyanates].

Isocyanates are chemical compounds used in making polyurethane (for flexible or rigid foam, paint, varnish, glue and textiles). In strong concentrations isocyanates are powerful irritants producing chemical bronchopulmonary lesions. In weak doses they are responsible for occupational asthma and more rarely allergic alveolitis. Long term exposure to isocyanates may produce a deterioration in pulmonary function in asymptomatic patients. The pathophysiology of isocyanate asthma remains uncertain: immunological data remains contradictory while isocyanates have been shown to have a Betablocking effect. The maximum allowable concentration in the working environment, at present proposed in the U.S.A. is 0.005 ppm.

Alveolitis, Extrinsic Allergic↗
PubMed1983

[Mortality from respiratory diseases among agricultural and non-agricultural workers in France from 1970 to 1974].

The mortality due to respiratory disease was studied in France between 1970 and 1974 as well as in seven other countries in the European Economic Community. The French results were presented as an index of mortality by cause of death, enabling a comparison of the mortality in different groups of the population. Data was supplied for 7 diagnostic groups defined according to List A of the International Classification of Diseases. The population studied consisted of men and women between 15 to 64 years, classified according to residence (urban or rural) and profession (agricultural worker or not). In addition the indices of mortality for farmers or agricultural employees were compared to men of the same social class, for the same period. The comparisons between the urban and the rural background revealed an excess mortality for respiratory tuberculosis, lung cancer, bronchitis, emphysema and asthma for those in urban areas. In the rural environment an excess mortality was noted for acute respiratory diseases in both men and women; this was also found comparing agricultural to non-agricultural workers. Lastly, if one compared agricultural and non-agricultural workers of the same social class, deaths due to acute and chronic respiratory infections were higher in the agricultural workers. These results show the relative importance already stressed in other studies, of acute respiratory diseases in agricultural workers.

Adult↗