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Biomedical subjects

G Simonneau

Publications and source records attributed to G Simonneau.

At least 163 records · Page 9Linked to original sources
PubMed1988

[Lung transplantation].

Three different ways of pulmonary transplants are feasible: heart and lungs together, one single lung or both lungs. While concerning the primitive or secondary pulmonary arterial hypertension, only the cardio-pulmonary transplant is possible, concerning the respiratory deficiency; the respective indications of each of these transplants are not yet clearly defined. During the postoperative period, rejection and bacteriological, viral, fungal or parasitical infections are responsible for a mortality of about 30%. In the long term, the transplant patients are in danger of respiratory insufficiency by obliterating bronchiolitis due to untreated chronic rejection. The development of these transplants is considerably limited by the rarity of donors whose lungs are usable and by the frequency of isolated heart removals to the prejudice of the cardiopulmonary bloc transplants.

Forecasting↗
PubMed1987

[Calculation of the ventilation-perfusion ratio in the scintigraphic diagnosis of pulmonary embolism].

Ventilation perfusion scanning fails to diagnose pulmonary embolism in matched defects. In 61 patients (19 with pulmonary embolism proved by angiography, 32 with chronic obstructive lung disease and 10 with acute bacterial pneumonia) we computed the ventilation perfusion ratio (V/Q) in these matched defects, using Krypton 81 m. This analysis demonstrated that the diagnosis of pulmonary embolism could be made with a specificity of 100% when the V/Q ratio was greater than 1.2 in the matched defects. Pulmonary embolism was characterized by a perfusion defect with a high V/Q ratio, even in Laennec infarction. In contrast, the analysis excluded the diagnosis of pulmonary embolism and suggested another disease when the V/Q was less than 0.95 with a specificity of 95%. Perfusion defects in acute pneumonia always had a V/Q less than 1. The diagnosis remained difficult in chronic obstructive lung disease when pulmonary embolism was suspected on subsegmental defects. Nevertheless this could be solved in about 50% of the cases by quantitative analysis. We feel, therefore, that ventilation perfusion scanning should be quantified by V/Q analysis to improve the diagnosis of pulmonary embolism.

Adult↗
PubMed1987

Recurrence of pulmonary embolism during anticoagulant treatment: a prospective study.

The risk of early recurrence of pulmonary embolism in patients with venous thromboembolic disease treated by anticoagulants is not well established. To determine the risk linked to contemporary proximal deep venous thrombosis, a prospective study was organised to give clinical and scintigraphic surveillance to 50 patients with angiographically proved pulmonary embolism plus phlebographically proved proximal deep vein thrombosis during the first 15 days of anticoagulant treatment. Perfusion lung scans were performed initially and on days 3, 7, and 15. Only two patients had a recurrence of pulmonary embolism during this period; both episodes were revealed by new symptoms, and one recurrence was fatal. The systematic performance of angiography in four patients found to have new scintigraphic defects led to the diagnosis of "spurious scintigraphic recurrence" in three of them. It is concluded that (a) adjusted anticoagulant treatment showed an effectiveness of 96% for preventing early recurrence of pulmonary embolism in this group of supposed high risk patients, and (b) in patients with recent pulmonary embolism new defects on systematic perfusion lung scans are not specific indicators of recurrent pulmonary embolism.

Adult↗
PubMed1987

[Heart-lung transplantation].

The combined transplantation of heart and lungs, first done successfully by the Stanford Team (USA) in 1982, at present seems to be superseding lung transplantation alone, and has broadened the indications of heart transplantation to include terminal heart failure with fixed pulmonary arterial hypertension. After reviewing the causes for failure in lung transplants, the authors stress the superiority of heart-lung transplants compared to isolated lung transplantations: healing of the tracheal anastomosis, ease of detection of rejects by endomyocardial biopsy and the lack of inhomogeneity of the ventilation/perfusion ratios. This operation still poses problems of surgical technique as the mediastinal nerves need to be preserved and the risk of haemorrhage linked to the mediastinal dissection or to the eventual pulmonary separation under cardiopulmonary bypass is important. Donor subjects for cardiopulmonary transplantation are rare as they ought to have a thoracic cage of matching size to the recipient and to be free of pulmonary infection and trauma. The post-operative complications are essentially those of immediate haemorrhage, graft rejection, pulmonary oedema and infection. The late complications are coronary atherosclerosis and bronchiolitis obliterans. The indications of such a transplant are currently reserved for primary or secondary pulmonary hypertension and to respiratory failure with a normal thoracic cage and ventilatory mechanics.

Heart Transplantation↗
PubMed1986

A single orally administered dose of almitrine improves pulmonary gas exchange during exercise in patients with chronic air-flow obstruction.

To verify if the improvement in gas exchange observed at rest with almitrine in patients with chronic air-flow obstruction is maintained at exercise, we studied 10 patients on a randomized, crossover, double-blind exercise protocol. After assessment of steady state of their disease, patients with FEV 1 less than 1.5 L.s-1 and PaCO2 less than 70 mmHg cycled 8 to 11 min at 80% of their previously determined maximal O2 uptake. Blood gases, arterial lactate (La), expired ventilation, (VE), O2 uptake (Vo2), Co2 production (VCO2), heart rate (HR), and arterial blood pressure (BP) were measured at rest, at mid-exercise, at end-exercise, and at 2, 14, 15, and 35 min of recovery. We found that at all stages of the study PaO2 was significantly higher in those who had received almitrine than in those who had received placebo; the mean increment was 11.9 torr at rest, 8.9 at end-exercise, and 13.7 at 15 min of recovery. Changes in PaCO2 and arterial (H+) were the opposite of those in PaO2; at end-exercise PaCO2 was 5.9 torr lower in those who had received almitrine, and pH was 7.36 versus 7.32 in those who had received placebo. No significant difference was found at all stages of the study between drug and placebo with respect to VE, VO2, VCO2, HR, and BP. But the ventilatory equivalent for oxygen, VE/VO2, was slightly higher in those who had received almitrine than in those who had received placebo during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1986

Intraesophageal perfusion of acid increases the bronchomotor response to methacholine and to isocapnic hyperventilation in asthmatic subjects.

Gastroesophageal reflux (GER) has been shown to be more frequent in people with asthma, but the mechanism by which it might aggravate asthmatic symptoms remains unclear. We compared the effects on maximal expiratory flow at 50% of VC (MEF50) of esophageal perfusion of hydrochloric acid (HCl) and of normal saline (NaCl) in 12 asthmatic subjects chosen at random. In all subjects, HCl perfusion did not change MEF50 but potentiated the bronchoconstriction induced by isocapnic hyperventilation of dry air (maximal decrease in MEF50 = 44 +/- 7% with HCl versus 22 +/- 5% with NaCl; p less than 0.001) or methacholine (provocative dose producing a 20% decrease in FEV1 = 349 +/- 99 micrograms with HCl versus 496 +/- 119 micrograms with NaCl; p less than 0.01). Seven of the asthmatic subjects were found to have GER on esophageal pH monitoring. In these subjects, HCl alone decreased MEF50 slightly but significantly (-17.5 +/- 5.5%; p less than 0.05), possibly reflecting the higher degree of basal bronchial hyperreactivity observed in this group. Thus, perfusion of acid into the distal esophagus caused slight but significant bronchoconstriction in asthmatic subjects with GER and increased the bronchoconstriction produced by isocapnic hyperventilation and by methacholine in asthmatic subjects without regard for the presence of GER.

Adolescent↗
PubMed1986

Cardiopulmonary effects of a single oral dose of almitrine at rest and on exercise in patients with hypoxic chronic airflow obstruction.

Almitrine, a new triazine derivative, was studied in a double-blind, randomized, parallel study in 16 patients with hypoxic chronic airflow obstruction (eight almitrine and eight placebo). At rest, compared to placebo, a 3 mg/kg single dose of almitrine given orally significantly increased the partial pressure of oxygen (mean increase: +12.0 +/- SEM 2.1 mm Hg, p less than 0.001) and decreased the partial pressure of carbon dioxide (mean decrease: -6.0 +/- 0.7 mm Hg, p less than 0.001); this improvement in arterial blood gases persisted on exercise. The lack of significant change in ventilation and the decrease in the alveolar-arterial oxygen gradient (mean decrease -10.0 +/- 1.9 mm Hg; p less than 0.001) at rest suggests a change in the distribution of the ventilation-perfusion ratio in the lung; such a change was confirmed by a krypton 81m isotopic study. Pulmonary hemodynamic responses were studied at rest and on exercise; a significant but slight increase in mean pulmonary artery pressure at rest (+4.0 +/- 1.5 mm Hg, p less than 0.05) was found.

Administration, Oral↗
PubMed1986

[Continuous treatment of asthma. Modalities, indications, monitoring].

Long-term treatment must be considered in cases of chronic asthma. Its main purpose is to suppress or decrease the frequency of acute dyspneic episodes; however, it may be more difficult to improve the bronchial obstruction of the patients. In allergic broncho-pulmonary aspergillosis, the treatment aims to prevent irreversible bronchiectasis. The methods and surveillance of long-term treatment are discussed.

Asthma↗
PubMed1985

Factors influencing pulmonary volumes and CO2 elimination during high-frequency jet ventilation.

An external spirometric method using a differential linear transformer was used to measure tidal volume (VT) and to determine factors influencing CO2 elimination and HFJV-induced "PEEP effect" in 15 critically ill patients under HFJV. VT increased with increasing driving pressure (DP) and decreasing frequency (f) and was influenced little by changes in I/E ratio. CO2 elimination, as reflected by the measurement of PaCO2, was mainly influenced by the absolute level of VT rather than by the product VT X frequency (PaCO2 = 5715/VT, r = 0.75, P less than 0.05). The primary phenomenon explaining HFJV-induced "PEEP effect" was intrapulmonary gas trapping due to incomplete exhalation of the first VT administered: the spontaneous relaxation times of these first VT were longer than expiratory time allotted to the ventilatory settings. HFJV-induced "PEEP effect" increased with I/E ratio, DP, and f and was markedly influenced by the mechanical properties of the total respiratory system. At given ventilatory settings, HFJV-induced "PEEP effect" was greater in patients with a normal or elevated time constant of the total respiratory system (tau RS) than in patients with a low tau RS. These results suggest that HFJV should not be used in patients with chronic obstructive pulmonary disease and asthma, and should be preferentially administered to patients having stiff lungs or decreased chest wall compliance.

Adult↗
PubMed1985

Hypercapnic acidosis induced by nutrition in mechanically ventilated patients: glucose versus fat.

Total parenteral nutrition (TPN) increases CO2 production (VCO2) in patients on intermittent positive-pressure ventilation who cannot match their CO2 excretion to the CO2 load, leading to an increase in PaCO2. We studied gas exchange and blood gas values in six patients with chronic respiratory failure, who were ventilated at low (6 +/- .7 L/min) and high (10 +/- 2 L/min) minute ventilation during three randomized nutritional regimens: control (255 kcal/day), glucose TPN (2550 kcal/day), and lipid TPN (3000 kcal/day). At the two levels of ventilation, TPN compared to control increased VCO2 and PaCO2 (p less than .01) and decreased pH (p less than .001). At low minute ventilation, the increase in VCO2 and the hypercapnic acidosis were less with lipid than with glucose TPN (p less than .05 and p less than .01, respectively). These results indicate that the risk of TPN-induced CO2 retention is lower if minute ventilation is increased before beginning TPN. Conversely, in patients with compromised ventilatory function, this risk could be higher during intermittent mandatory ventilation or weaning from the ventilator.

Acidosis↗
PubMed1985

[Rejection reaction and use of rifampicin in the treatment of tuberculosis in kidney transplantation].

Rifampicin is considered as one of the most potent antituberculous agents and is often used in renal transplant recipients. However, acute cellular rejection episodes were observed when rifampicin was prescribed in 4 tolerant renal transplant recipients. Acute rejection occurred in 3 out of the 5 patients, despite doubled daily dose of steroids. First, rifampicin is an enzymatic inducer and accelerates steroid metabolism. Secondly, rifampicin per se is an immunosuppressive drug, as already proved in animals. Rifampicin interferes with the active mechanisms involved in specific transplantation tolerance. In conclusion, we recommend a very cautious use of rifampicin in kidney transplant recipients.

Adult↗
PubMed1984

[Physiopathology of chronic bronchitis].

The physiopathology of chronic bronchitis consists of sequential reactions which progressively result in respiratory failure, blood gas abnormalities and finally, post-hypoxia cor pulmonale. Airway obstruction produces maldistribution of inspired gas and starts off a series of compensatory mechanisms with increased resting lung volume and prolonged expiration time resulting in diminution of tidal volume. Abnormal ventilation/perfusion ratios result in shunt and dead space effects, determine blood gas disorders and hypoxia due to reflex vasoconstriction and ultimately lead to pulmonary arterial hypertension with elevated cardiac output and increased vascular resistances. These physiopathological chain-mechanisms account for the clinical symptoms observed, including dyspnoea, episodes of acute bronchitis and in the end, signs of chronic cor pulmonale. They also indicate that the primary objective of treatment is to correct hypoxaemia. This can be achieved by continuous low flow rate oxygen therapy, by drugs capable of redistributing more evenly the ventilation/perfusion ratios and, accessorily, by respiratory analeptic agents. As regards the treatment of pulmonary arterial hypertension, one must admit that many uncertainties are still surrounding the use of vasodilators.

Bronchitis↗