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Biomedical subjects

Y Castaing

Publications and source records attributed to Y Castaing.

At least 19 recordsLinked to original sources
PubMed1998

Anticholinergic versus beta 2-agonist on gas exchange in COPD: a comparative study in 15 patients.

beta-agonist bronchodilators are known to influence gas exchange and ventilation-perfusion relationships in asthmatic patients, where they induce hypoxaemia via hypoxic vasoconstriction. As this effect could have serious consequences in chronic obstructive pulmonary disease (COPD) patients with chronic hypoxaemia, alternative agents have been sought. It has been shown that inhaled anticholinergic drugs may be of value in this condition. In the present study, we compared the effects of salbutamol (Sb) and ipratropium bromide (IB) inhalation on gas exchange in 15 patients with stable COPD. All patients had a history of COPD (mean arterial oxygen tension (Pa,O2) = 8.2 +/- 1.0 kPa (61.8 +/- 7.3 mmHg) forced expiratory volume in one second (FEV1) = 39 +/- 12%; FEV1/vital capacity (VC) = 42 +/- 6%) and no evidence of acute respiratory failure. Haemodynamic and gas exchange data were recorded after right catheterization by the multiple inert gas elimination technique. Measurements were made under basal conditions, after two puffs of freon propellant (placebo) and after two puffs of either 200 micrograms Sb or 200 micrograms IB in a randomized design. Sb and IB reduced airway resistances to the same extent, but had no significant influence on the haemodynamic and ventilation parameters. There was a slight but significant decrease in arterial carbon dioxide tension (Pa,CO2) = 6.0 +/- 0.8 versus 6.4 +/- 0.8 kPa (45.4 +/- 5.9 versus 47.9 +/- 6.3 mmHg) p < 0.05 with an enhanced perfusion distribution heterogeneity and a slight improvement in ventilation homogeneity shown by a decrease of the decimal logarithm of SD of the ventilation distribution (LogSDV) after inhalation of IB relative to control. Since these alterations did not affect arterial oxygen tension we concluded that inhalation of these doses of salbutamol or ipratropium bromide do not affect gas exchange in patients with stable chronic obstructive pulmonary disease. The normal home treatment: inhalation of two puffs of these bronchodilating drugs thus appears to be safe. The choice of agent will depend on the extent of the bronchodilator effect in a given individual.

Administration, Inhalation↗
PubMed1994

Effect of inhaled nitric oxide on hemodynamics and VA/Q inequalities in patients with chronic obstructive pulmonary disease.

Nitric oxide (NO) has been reported to be an endothelium-derived relaxing factor, and hypoxic pulmonary vasoconstriction seems to be enhanced by inhibitors of endothelially dependent vascular relaxation. We examined the circulatory effects of inhalation of 15 ppm NO in air in 14 hypoxic patients suffering from chronic obstructive pulmonary disease (COPD). Of these patients 4 breathed 100% O2 before NO. The effects of NO inhalation on pulmonary gas exchange were also studied in 12 of these patients using the multiple inert gas elimination technique, 3 of whom breathed air, 100% O2, and 15 ppm NO in air in succession. Under baseline conditions, both mean +/- SD pulmonary artery pressure and pulmonary vascular resistance were increased (Ppa = 24.3 +/- 10.4 mm Hg and PVR = 3.3 +/- 1.1 mm Hg/L/min, respectively). Although the pulmonary circulatory effects were not immediate, with no detectable changes after 1 min NO inhalation, Ppa and PVR fell significantly (-19.1 +/- 10.5%, p < 0.02 and -29.3 +/- 15.1%, p < 0.02, respectively) after 10 min NO inhalation. Moreover, the extent of the NO-induced reduction in Ppa was found to depend on the level of baseline pulmonary arterial hypertension. No systemic circulatory effects were observed. The mean VA/Q ratio and the dispersion of ventilation and blood flow distributions were not altered by NO inhalation, although there was a significantly higher percentage of ventilation (7.3 +/- 7.3%, p < 0.05) in poorly and unperfused areas (VA/Q > 10).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1993

Effects of inspiratory flow rate alterations on gas exchange during mechanical ventilation in normal lungs. Efficiency of end-inspiratory pause.

The influence of inspiratory flow rate (TI), without changing respiratory frequency, tidal volume, and FIO2, was investigated in 11 normal lungs in patients undergoing mechanical ventilation because of central respiratory failure due to stable coma. The patients were anesthetized and paralyzed. They first received a conventional ventilation (TI = 25 percent, pause = 10 percent) and then, were submitted to four different TI values, randomly administered without any end-inspiratory pause (EIP) (TI = 20 percent; TI = 33 percent; TI = 50 percent; TI = 67 percent). In the middle and at the end of the procedure, a return to basal conditions was introduced. At each ventilator setting, the following were obtained: respiratory flow (Pneumotachograph Fleish No. 2), airway pressure, FRC changes (inductive plethysmography), arterial and mixed venous blood gases, hemodynamic data, and VA/Q ratios distribution using multiple inert gases technique. EIP suppression provides a significant increase in VA/Q mismatch (until TI = 50 percent) and in shunt effect (between 3 and 9 percent of cardiac output [QT]). The absence of simultaneous PaO2 change is due to increasing PVO2 linked to a higher QT. The shorter the TI, the higher the PaCO2 connected with a relative alveolar hypoventilation. However, increasing TI without EIP significantly decreases ventilation distribution inequalities. This improvement is concomitant with a rise in FRC (FRC67-FRC20 = 0.340 +/- 0.450, p < 0.05) without any change in other variables or auto-PEEP production. In summary, in subjects with very slight mechanical lung impairment (peak inspiratory pressure = 20.5 +/- 5.3 cm H2O at TI = 20 percent and 15.2 +/- 3.3 cm H2O at TI = 67 percent), this study confirms the deleterious effect of EIP suppression and TI decrease. One can compensate for this effect of EIP absence by increasing TI as soon as it reaches TI = 67 percent, ie, inverse ratio ventilation.

Aged↗
PubMed1992

Influence of cardiac output on oxygen exchange in acute pulmonary embolism.

We investigated interactions between cardiac output, VA/Q distribution pattern, pulmonary gas exchange, O2 transport, and tissue oxygenation in 16 patients during the acute phase of pulmonary embolism (PE). The effects of breathing room air, O2 therapy (FIO2 = 0.40) (11 patients), and dobutamine (four patients) were studied after right catheterization using the multiple inert gas elimination technique. The pattern of VA/Q ratio distributions was found to depend essentially on cardiac output level. The individual blood flow perfusing ventilated areas was found to be inversely related to the mean VA/Q ratio of blood flow distribution. PVO2 was directly related to cardiac index (p less than 0.02), and negatively related to the mean VA/Q of blood flow distribution. In view of the influence of low VA/Q ratios and PVO2 on arterial hypoxemia, our results showed that the heart's response to PE conditioned the strategy of pulmonary gas exchange and O2 transport. Oxygen breathing led to a slight but consistent fall in cardiac output (-0.6 +/- 0.5 L/min, p less than 0.01). However, although PaO2 remained normal and PVO2 was slightly improved, we found no evidence for a role of hypoxic pulmonary vasoconstriction in the pulmonary hypertension observed during the acute phase of PE. Administration of dobutamine improved O2 transport and tissue oxygenation, although PaO2 remained constant or even fell in some cases because of increased VA/Q mismatch.

Acute Disease↗
PubMed1992

[Sequential administration of a reduced dose of almitrine to patients with chronic obstructive bronchopneumopathies. A controlled multicenter study].

Recent multi-centre studies have shown that high doses of Almitrine (100-200 mg per day), lead to a significant improvement in the hypoxaemia of patients presenting with chronic airflow obstruction, but that a high blood level (greater than 500 ng/ml) is often seen after 1 year, sometimes associated with signs of peripheral neuropathy. In order to maintain Almitrine blood levels in the range 200-300 ng/ml we have used an intermittent regime (with a "window" of 1 month every 3 months) and a dose limited to 100 mg per day. 102 hypoxic patients with chronic airflow obstruction, who were in a stable state were included. 65 patients were in the Almitrine group (A) and 37 patients in the placebo group (P). The treatment lasted for 1 year. In addition there was a 3 monthly follow up with arterial blood gases and spirometry, a clinical neurological examination and also electrophysiology, initially and after 6 and 12 months. 43% of patients in group A and 32% of patients in group P, left the study, most often due to poor cooperation, but sometimes as a result of side effects. After 12 months the PaO2 rose significantly in group A from 59.1 +/- 0.7 to 65.8 +/- 1.6 mmHg (p less than 0.001) whilst it was not changed in group P. The PaCO2 did not change in either group. On the other hand there was a significant fall in the subgroup of patients with hypercapnia in group A (p less than 0.001). The outcome of the neurological and electrophysiological assessments did not show any significant difference between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Chronic inflammatory demyelinating polyneuropathy in childhood: ultrastructural features of peripheral nerve biopsies in four cases.

Peripheral nerve biopsies (PNB) from four children suffering from subacute or chronic inflammatory demyelinating polyneuropathy were studied by electron microscopy. Remyelinating features with onion bulb formations, inflammatory cell infiltrates and active demyelinating lesions were strongly suggestive of the disease. In the first case, a second PNB, performed after 7 months of severe subacute course, showed a striking evolution of the lesions. In the second case and in spite of severe neurological symptoms, the PNB was almost normal, suggesting that inflammatory lesions were mainly located in the proximal parts of the nerve. No signs of active demyelination could be seen in the third case but onion bulb formations and inflammatory cell infiltrates were present. In the fourth case, characteristic lesions of active demyelination were associated with a history of familial polyneuropathy; this association suggests an auto-immune process in certain kindreds with hereditary motor and sensory neuropathy.

Adolescent↗
PubMed1989

Hemodynamic disturbances and VA/Q matching in hypoxemic cirrhotic patients.

Arterial oxygen desaturation is commonly found in patients with cirrhosis of the liver, but severe hypoxemia is unusual. To investigate the mechanism of the impairment in gas exchange, six severely hypoxemic (mean PaO2, 55.9 +/- 5.9 mm Hg) cirrhotic patients (five confirmed by biopsy), without pulmonary or cardiovascular disease and in the absence of acute hepatic disease, were submitted to right heart catheterization. Inequalities of VA/Q were estimated in the respiratory steady state using the multiple inert gas technique. The mean pulmonary arterial pressure was low (7.2 +/- 2.3 mm Hg) and the cardiac output high (Q = 11.0 +/- 2.06 L/min), indicating a low PVR. The VA/Q mismatching of the ventilated and perfused units ranged from mild to moderate, but a large percentage of Q flowed through unventilated areas. Furthermore, there was a significant difference between predicted and measured PaO2 (9.27 +/- 5.9 mm Hg; p less than 0.01), which was attributed to either an unmeasured postpulmonary shunt (between portal and pulmonary vein) or a diffusion defect. The impairment in gas exchange in these patients is thus due primarily to an intrapulmonary, and possibly extrapulmonary, shunt. This was thought to be due mainly to an impaired regulatory mechanism of the microcirculation by the hepatic dysfunction.

Adult↗
PubMed1988

Pulmonary gas exchange in Andean natives with excessive polycythemia--effect of hemodilution.

Pulmonary gas exchange in Andean natives (n = 8) with excessive high-altitude (3,600-4,200 m) polycythemia (hematocrit 65.1 +/- 6.6%) and hypoxemia (arterial PO2 45.6 +/- 5.6 Torr) in the absence of pulmonary or cardiovascular disease was investigated both before and after isovolemic hemodilution by use of the inert gas elimination technique. The investigations were carried out in La Paz, Bolivia (3,650 m, 500 mmHg barometric pressure). Before hemodilution, a low ventilation-perfusion (VA/Q) mode (VA/Q less than 0.1) without true shunt accounted for 11.6 +/- 5.5% of the total blood flow and was mainly responsible for the hypoxemia. The hypoventilation with a low mixed venous PO2 value may have contributed to the observed hypoxemia in the absence of an impairment in alveolar capillary diffusion. After hemodilution, cardiac output and ventilation increased from 5.5 +/- 1.2 to 6.9 +/- 1.2 l/min and from 8.5 +/- 1.4 to 9.6 +/- 1.3 l/min, respectively, although arterial and venous PO2 remained constant. VA/Q mismatching fell slightly but significantly. The hypoxemia observed in subjects suffering from high-altitude excessive polycythemia was attributed to an increased in blood flow perfusing poorly ventilated areas, but without true intra- or extrapulmonary shunt. Hypoventilation as well as a low mixed venous PO2 value may also have contributed to the observed hypoxemia.

Adult↗
PubMed1987

[Hemodialysis with a high permeability membrane in the treatment of encephalopathy of fulminant hepatitis].

Twenty-nine patients with fulminant hepatic failure and at least grade III encephalopathy were treated by haemodialysis with a polyacrylonitrile membrane. Aetiology was toxic in five patients, viral in eleven (2 due to hepatitis A virus and 9 presumed due to hepatitis B virus), not found in thirteen. Each patient was dialysed for 4 h every day, until he regained consciousness or died. Conscious level was improved after dialysis in 59% of patients. Thirteen patients survived (44.8%) :4 toxic hepatitis, 4 viral hepatitis B, 1 viral hepatitis A, 4 hepatitis of unknown aetiology. A comparison of plasma concentrations of amino acids measured by chromatography before and after 113 periods of haemodialysis in 23 patients showed significant decrease in aromatic amino acids (p less than 0.001), a significant increase in two branched-chain amino acids :leucine (p less than 0.001) and isoleucine (p less than 0.001), and a significant increase in Fischer's ratio (p less than 0.001). In survivors, factor V concentration on admission and Fischer's ratio on admission were significantly higher than in those who died (p less than 0.02 for both), but there was no significant difference in the difference between Fischer's ratio before and after haemodialysis. Haemodialysis was well tolerated, except for short periods of hypotension and a small but significant fall in platelet counts. Improvement in cerebral function during haemodialysis was previously demonstrated by various authors, but the effect on survival rate remained controversial. The survival rate obtained in this controlled study is clearly higher than those obtained by conservative management alone.

Acrylic Resins↗
PubMed1986

Improvement in ventilation-perfusion relationships by almitrine in patients with chronic obstructive pulmonary disease during mechanical ventilation.

Although the respiratory stimulant effects of almitrine bismesylate (AB) via an action on the peripheral chemoreceptors have been demonstrated, the mechanism of its intrapulmonary action has not yet been elucidated. In order to abolish the stimulation of ventilation, observed in studies on spontaneously breathing patients, an investigation of patients suffering from severe COPD under constant mechanical ventilation, with FIO2 = 0.21, during the weaning period was carried out. Eighteen patients were randomly divided into 2 groups (9 receiving 1.5 mg/kg AB and 9 receiving placebo). The ventilatory and hemodynamic variables, blood and alveolar gases, and the VA/Q ratio distributions using the multiple inert gas technique were collected before treatment with drug or placebo, as well as 90 and 180 min afterwards. The PaO2 was found to be raised 90 min after AB administration (+57 +/- 3.9 mm Hg, p less than 0.01) and remained above the baseline value at 180 min (+5.4 +/- 4.6 mm Hg, p less than 0.01). Compared with those in the placebo group, these increases were significant (p less than 0.01). A slight decrease in PaCO2 but similar in the 2 groups was observed despite constant ventilation. The hemodynamic data were the same for the 2 groups. The changes in overall criteria of the distributions (mean VA/Q and SD) were small. The main finding was a decrease in the percentage of the perfusion flowing through the true shunt and the underventilated areas after AB treatment. In the control group, the blood flow percentage in the true shunt and low VA/Q units was either stable or increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Almitrine↗
PubMed1985

Series dead space for inert gases in healthy subjects.

In ten normal subjects, series dead space was determined for six intravenously infused inert gases (SF6, ethane, cyclopropane, fluothane, ether, acetone) from their expired and alveolar concentrations. The method for sampling alveolar gas was based on the criterion of identity of mean alveolar and expired gas exchange ratios. Inert gases were analysed chromatographically. Acetone, the most soluble gas, yielded the lowest dead space, the difference to the other gases being about 4.5%. This is probably due to the non-infinite value of the series dead space ventilation-perfusion ratio (VA/Q) which was estimated at about 2,000. The diffusivity, inversely related to the molecular weight, also played a role, the heaviest gas (fluothane) having a greater dead space than the lightest (ethane). The underestimation of the dead space from acetone is expected to be greater in subjects with low tidal volume and high bronchial blood flow, i. e. in some patients with respiratory disease.

Humans↗
PubMed1985

Determinants of hypoxemia during the acute phase of pulmonary embolism in humans.

The determinants of hypoxemia were studied in 10 patients with acute pulmonary embolism demonstrated by pulmonary angiography. Two patients were mechanically ventilated, and in the 8 who breathed room air spontaneously, the mean arterial PO2 was 61.5 mmHg. Measurements of the distributions of ventilation (VA) and perfusion (Q) against VA/Q ratios by the multiple inert gas infusion technique demonstrated an increase in VA/Q inequality. The major part of pulmonary blood flow was distributed in a mode near to, or slightly above, a VA/Q ratio of 1. The cumulative fraction of blood in true shunt and low VA/Q mode (VA/Q less than 0.01) was 9.1%. For a small part of the AaDO2 (13%), an oxygen diffusional component was found. The remaining hypoxemia was due to the fall in the mixed venous PO2 (PVO2), irrespective of its cause: low cardiac output, low hemoglobin concentration, high oxygen consumption, low P50. The fall in PVO2 led to a fall in end-capillary blood PO2 in both shunt or ventilated and perfused units. We conclude that the major determinant of hypoxemia in these patients suffering from acute pulmonary embolism is the fall in PVO2. This is enhanced by a moderate increase in the fraction of blood flowing through low VA/Q units. Diffusion impairment plays only a minor role.

Acute Disease↗
PubMed1985

Gas exchange alterations in patients with chronic obstructive lung disease.

In a series of 23 patients with COPD, Wagner et al showed three distinct patterns of VA/Q distributions and a correlation between Burrows' clinical classification and the observed distribution patterns. Using the inert gas method, we studied 51 patients suffering from severe but stable COPD (FEV1 = 0.84 +/- 0.38 L; PaO2 = 58.5 +/- 10.5 mm Hg; PaCo2 = 48 +/- 6 mmHg; Ppa = 22 +/- 8 mmHg) breathing room air in a steady state. The H pattern (high mode of VA in high VA/Q) was found in 24 cases. There was an L pattern (Q mode in low VA/Q units) in nine cases and an HL (high-low) pattern in 16 cases (two patients were assigned another group). The analysis of the distribution data confirmed that VA/Q heterogeneity was the main factor underlying gas exchange disturbances in COPD. The PaO2 of the H subjects was higher than that of both HL (p less than 0.02) and L subjects. The true shunt value in the L group was significantly lower than in the H and HL groups. However, the relationship between clinical or functional aspects and distribution was not direct. The fraction of patients of H, HL, or (H + HL) types was nearly identical in the three clinical groups. The H pattern was found to be predominant in cases of COPD.

Aged↗
PubMed1985

[The inert gas method in respiratory physiopathology].

The main results obtained, in healthy or unhealthy man, with the inert gas method are gathered together. The major factor at the source of hypoxemia is the uneven distribution of VA/Q ratios. The fall in the partial pressure of oxygen in mixed venous blood amplifies this effect. Only hypoxemia, during muscular exercise, in patients with interstitial lung diseases could be explained, in part, by a decrease in membrane diffusion and a reduction in the transit time of blood in pulmonary capillaries. The differences between the methods used to analyse pulmonary gas exchange are discussed.

Adult↗
PubMed1984

[Influence of almitrine dimesylate on gas exchange. Preliminary results in patients with chronic obstructive bronchopneumopathies under artificial ventilation].

From a study conducted in 1981 in patients with chronic obstructive pulmonary disease breathing spontaneously, it was concluded that almitrine ensured a more even distribution of ventilation-perfusion ratios in the lung. Another study has recently been undertaken to suppress the effects of stimulated ventilation observed and to measure more accurately the pulmonary vascular effect of this new drug. This was a randomized double-blind drug versus placebo trial using the same doses of almitrine (1.5 mg/kg orally) in patients of the same type under stable artificial respiration controlled by repeated measurements of ventilation during the weaning period at the end of an episode of acute respiratory failure. The preliminary results obtained in one-half of the patients (4 under almitrine, 4 under placebo) are reported. There was little difference in haemodynamic values between the two groups. Improvement in PaO2 was maximum 90 min after almitrine was administered and varied from 0.7 to 1.4 kPa; there was no modification in the control group. In the absence of any change in ventilation and respiratory rate, perfusion was reduced in lung areas with low ventilation-perfusion ratio. These partial results seem to confirm that almitrine exerts a moderate, though real, effect on pulmonary vessels.

Almitrine↗
PubMed1983

[Treatment of 3 cases of status asthmaticus with halothane].

Three serious cases of status asthmaticus with severe hypercapnic acidosis unresponsive to adequate conventional therapy were treated by halothane. The efficiency of this treatment was assessed by the clinical state of the patient, the blood gases and the changes in peak airway pressure. Two patients improved dramatically in less than 24 h. No signs of cardiac toxicity of this drug were noted in spite of acid-base disturbances. These three cases showed the beneficial effect of halothane's-beta 2 stimulation in the treatment of status asthmaticus.

Acute Disease↗