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Biomedical subjects

F Schrijen

Publications and source records attributed to F Schrijen.

At least 19 recordsLinked to original sources
PubMed1992

Pressure/flow relation in the peripheral pulmonary vascular bed in dogs: a preliminary study.

In order to test a technique for the determination of the pressure/flow relationship in the peripheral pulmonary vascular bed, the perfusion pressure changes with increasing and then decreasing flow in a small part of the lung (around 1 ml) were studied in anaesthetized supine dogs, after insertion of a specially designed double distal lumen Swan-Ganz catheter. One lumen was used for the pressure measurement, one for infusion of saline by a pump with variable flow, from 0.1 to 1.0 ml s-1. A conventional thermodilution Swan-Ganz catheter was also advanced in the pulmonary artery, to measure pressures in the pulmonary circulation as well as cardiac output. During infusion in the wedged catheter, right atrial, pulmonary arterial and balloon occlusion wedge pressures did not change. The pressure/flow curve of the occluded vascular bed showed a shape similar to that of collapsible tubes, with a pressure plateau at high flow, but this could also be due to vascular recruitment. The curve exhibited hysteresis, with a lower pressure when flow decreased. The slope of the initial part of the curve increased, on average, from 54 +/- 9 during normoxia to 91 +/- 27 mmHg s ml-1 during hypoxia (FIO2 = 0.10); this difference was not significant, but the perfusion pressure at high flow was significantly higher during hypoxia (P less than 0.05). Using blood instead of saline would allow the determination of the peripheral pulmonary vascular resistance under physiological conditions, and further work is needed to estimate the sensitivity and the reproducibility of this technique.

Animals↗
PubMed1992

[Relationship between right ventricular ejection fraction and pulmonary pressure in man].

This clinical study analysed the changes in right ventricular ejection fraction induced by changes in right ventricular afterload using a new thermodilution catheter linked to a rapid response computer which allowed instantaneous measurements of the right ventricular ejection fraction. The first group comprised 16 patients referred for coronary angioplasty with single vessel disease (isolated proximal stenosis of one of the two main branches of the left coronary artery) and a normal left ventricular ejection fraction (> or = 55%) and mean pulmonary artery pressure of < 25 mmHg: right ventricular ejection fraction and mean pulmonary artery pressure were measured under basal conditions and after 60 seconds' coronary occlusion with the balloon catheter in order to assess the effects of the reactional increase in afterload on the right ventricular ejection fraction. The second group comprised 11 patients with dilated primary cardiomyopathy with decreased left ventricular ejection fraction (< 50%) and mean pulmonary artery pressure > or = 25 mmHg: the right ventricular ejection fraction and mean pulmonary artery pressure were measured under basal conditions and after intravenous trinitrin (performed to evaluate the pulmonary reaction to vasodilators) in order to analyse the effects of the reduction of afterload on right ventricular ejection fraction. Negative linear correlations were observed between the right ventricular ejection fraction and mean pulmonary artery pressure under basal conditions (r = -0.72; p < 0.005) and between the right ventricular ejection fraction and mean pulmonary artery pressure after changing the conditions of afterload (r = -0.82; p < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Differential effects on right ventricular function of transient right, left anterior descending and left circumflex coronary occlusions during percutaneous transluminal coronary angioplasty.

Right ventricular function was studied by means of a thermodilution catheter before, during and after percutaneous transluminal angioplasty of the proximal right (group 1, n = 8), left anterior descending (group 2, n = 8) or left circumflex (group 3, n = 8) coronary artery. All patients had evidence of myocardial ischemia, with single-vessel disease affecting the proximal segment of one of the three major coronary arteries; no patient had had a previous myocardial infarction and all had normal cardiac function at baseline study. Cardiac index decreased during balloon inflation. Mean pulmonary artery pressure was unaffected in group 1 but increased in group 2 (from 19 +/- 5 to 31 +/- 11 mm Hg, p less than 0.01) and in group 3 (from 19 +/- 2 to 22 +/- 5 mm Hg, p less than 0.05). Right ventricular ejection fraction decreased from 62 +/- 9% to 52 +/- 10% (p less than 0.01) in group 1 and from 64 +/- 7% to 44 +/- 10% (p less than 0.005) in group 2, and returned to normal within 2 min after balloon deflation in both groups. In group 3, right ventricular ejection fraction was unchanged during balloon inflation (58 +/- 5% at baseline, 58 +/- 9% at 60 s, p = NS). Therefore, brief occlusion of the proximal segments of the left anterior descending or right coronary artery results in marked alteration of right ventricular performance that is probably caused by right ventricular free wall ischemia in the right coronary group and by the concomitant effects of septal ischemia and increased right ventricular afterload in the left anterior descending artery group.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1991

Circulatory response to repeated exercise in patients with chronic lung disease.

The pulmonary and systemic circulatory response to repeated exercise has been studied in 24 patients with chronic lung disease, mainly chronic bronchitis. The exercise consisted of supine bicycling at a constant low load (from loadless pedalling to 30 W) for 10 min with a 20 min rest period between exercises. Cardiac output was similar during the first (E1) and the second (E2) exercise periods, as well as pulmonary vascular resistance. Systemic arterial pressure, however, was lower during E2 than during E1, and this difference was significantly correlated with lung function (VC% predicted, FEV1 and FEV1% predicted) and blood gases at rest and during exercise. The patients with PaO2 below 65 mm Hg showed a larger increase in systemic arterial pressure during E1 and a smaller increase during E2 than the others. The larger increase might be due to a vasoconstrictor effect of hypoxemia and/or of the functional residual capacity increase observed in such patients with exercise. Whatever the mechanism involved, these results show that the systemic circulation is modified in patients with chronic lung disease. Results after some intervention have to be interpreted with caution if the protocol includes two exercise periods.

Adult↗
PubMed1991

One year treatment with almitrine improves hypoxaemia but does not increase pulmonary artery pressure in COPD patients.

Almitrine bismesylate, a chemoreceptor agonist, improves hypoxaemia in a high percentage of chronic obstructive pulmonary disease (COPD) patients and its long-term use may thus be of interest in these patients. The course of pulmonary haemodynamics during a one year treatment was investigated in severe COPD patients (forced expiratory volume in one second FEV1 = 1,040 +/- 80 SEM ml) with persistent hypoxaemia (initial arterial oxygen tension (PaO2) in the range 6.6-8.6 kPa (50-65 mmHg]. Patients were given either almitrine (A, n = 27), 100 mg.day-1, during two consecutive months per quarter followed by a one month wash-out period (intermittent "schedule"), or placebo (P, n = 18) with the same schedule. Eleven patients in group A and 8 in group P could not complete the one year study because of lack of compliance, worsening of respiratory insufficiency, or for other reasons. In the remaining patients, PaO2 significantly increased in group A (n = 16) from 7.6 +/- 0.1 to 8.3 +/- 0.2 kPa (56.9 +/- 1.0 to 62.7 +/- 1.7 mmHg) (p less than 0.001) but not in group P (n = 10) from 7.5 +/- 0.3 to 7.9 +/- 0.3 kPa (56.1 +/- 2.3 to 59.1 +/- 2.1 mmHg). PaCO2 did not significantly change in either group. Pulmonary artery mean pressure (PAP) was stable in both groups: from 26.8 +/- 2.1 to 25.4 +/- 1.9 mmHg in group A, and from 20.6 +/- 1.1 to 20.9 +/- 1.5 mmHg in group P.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

AaDO2 as a predictor of pulmonary hypertension resulting from pulmonary emboli.

The authors examined the records of all patients referred for right heart catheterization between 1963-84 because of persistent dyspnoea after one or more episodes of pulmonary emboli. Patients with a history of congestive heart failure, angina, restrictive or obstructive pulmonary disease that could explain their symptoms were excluded. Catheterization was performed 15.8 +/- 24 months after the first suspected episode of pulmonary embolism. Seven of the 29 patients included had resting pulmonary hypertension (PH). All of these had an alveolo-arterial oxygen difference (AaDO2) greater than 25 mmHg. Twenty patients of the group, taken as a whole, had an AaDO2 greater than 25 mmHg. Information was available from 1 month to 5 years later in 6/9 patients with an AaDO2 less than 25 mmHg. In all of them dyspnoea improved or resolved. Information was available in 15/20 patients with AaDO2 greater than 25 mmHg. Three of 8 patients without PH but with an increased AaDO2 on the initial catheterization developed PH within 2 years. Dyspnoea increased in 1 of the remaining five. Four patients who initially had PH developed right heart failure 6 months-3 years later. In the remaining 3, dyspnoea was stable in 1, increased in 1 and one patient died with autopsy evidence of multiple pulmonary emboli. Abnormal oxygenation predicts the presence or subsequent development of PH in patients who are chronically dyspnoeic after pulmonary embolism.

Blood Pressure↗
PubMed1990

Inter- and intrasubject variability of the thermodilution measurement of right ventricular ejection fraction and volume in patients with chronic obstructive pulmonary disease.

STUDY OBJECTIVE: To determine the spontaneous changes in volumetric indices of right ventricular function assessed by thermodilution. DESIGN: The study involved measurements of inter- and intraindividual variation of right ventricular function in human subjects at rest and at two different levels of low load supine bicycle exercise. SUBJECTS: The subjects were 23 patients with chronic obstructive pulmonary disease, referred for evaluation by right heart catheterisation. Mean (SEM) age was 55.4 (2.2) years and all were in sinus rhythm. MEASUREMENTS AND RESULTS: Successive measurements of ejection fraction and right ventricular end diastolic and end systolic volumes were made by thermodilution with a fast response thermistor mounted in a Swan-Ganz catheter. Five measurements were made at rest (R), and three measurements during each of two levels of exercise (E1, E2). Group average values for each period showed no significant changes with time; interindividual variability was expressed as the coefficient of variation (VC1 = SD/means), intraindividual variability (VC2) as square root of mean value of individual variances. Interindividual variability increased from rest to exercise, while intraindividual variability was lower during exercise, presumably because the variables were more steady. For ejection fraction, VC1, was 23% at rest, 29% for E1 and 32% for E2, while VC2 was 21%, 12% and 15% respectively; for right ventricular end diastolic volume, VC1 was 23% at rest, 29% and 28% during exercise, and VC2 was 17%, 12% and 11% respectively. In some patients cold injection induced bradycardia and spuriously high values of ejection fraction. CONCLUSIONS - It is important to monitor heart rate before and during thermodilution measurements and to take into account only those made with stable heart rate. Injectate temperature should be above 10 degrees C.

Cold Temperature↗
PubMed1990

[Changes in right ventricular ejection fraction in right coronary angioplasty].

In order to analyse the response of the right ventricule (RV) to transient myocardial ischaemia, the RV ejection fraction was measured using a new rapid response thermodilution catheter in 15 patients (14 men and 1 woman: average age 58 +/- 7 years) referred for percutaneous transluminal coronary angioplasty of a dominant right coronary artery. Only patients with single vessel disease with a proximal stenosis of the right coronary without a visible collateral circulation who had no previous history of myocardial infarction were included. Right heart catheterisation was performed with a rapid-response thermodilution catheter which enabled measurement of heart rate, cardiac index, RV end-diastolic and end-systolic volumes and RV ejection fraction. Angioplasty was carried out with the usual steerable balloon catheters. During balloon inflation, there was a slight increase in RV end-diastolic volume (from 78 +/- 11 ml/m2 to 85 +/- 13 ml/m2 at 60 seconds; p less than 0.01) and a large increase in RV end-systolic volume (from 29 +/- 8 ml/m2 to 35 +/- 8 ml/m2 at 30 seconds and 43 +/- 11 ml/m2 at 60 seconds, p less than 0.001) leading to a significant decrease in RV ejection fraction (from 62 +/- 8% to 56 +/- 6% at 30 seconds and 51 +/- 7% at 60 seconds; p less than 0.001). All parameters returned to basal values two minutes after the dilatation. Acute occlusion of the proximal segment of the right coronary artery is therefore associated with a marked change in right ventricular function which rapidly returns to normal after the coronary circulation is restored.

Aged↗
PubMed1989

Metabolic CO2 removal by dialysis: THAM vs NaOH infusion.

New methods of respiratory support are needed to reduce the high mortality rate of acute respiratory failure. To simplify the procedures of extracorporeal CO2 elimination under apneic oxygenation, one approach is to replace the membrane lung by a hemodialyzer and to administer an alkali, since hemodialysis requires a lower blood flow rate than blood-gas exchange. This study compared the effectiveness of trishydroxymethyl aminomethane (THAM) and NaOH in this procedure. Twelve male Anglo-Poitevin dogs (25 to 33 kg) were anesthetized, curarized and mechanically hypoventilated (VE = 41% of the control value). After not less than 15 min, a venovenous shunt was used for dialysis with blood flow of 7-10 ml. min.-1kg-1 for at least 8 hours. The dialysate contained no acetate, bicarbonate or lactate, but was alkalinized to a pH of 8-9 by the addition of NaOH. A solution of THAM (0.5 N) was infused into the right heart at the rate of 0.30 ml.min.-1kg-1 in six animals, and NaOH (0.15 N) was infused in the other six at the rate of 0.80 ml.min-1kg-1. The injected volumes were compensated for by an equivalent amount of ultrafiltration. Elimination of CO2 (mean TCO2 = 2.3 ml.min.-1kg-1) was the same with both methods and the difference for the electrolytes and acid-base equilibrium was only very small. However, hemolysis was six times greater with NaOH than with THAM. Despite ultrafiltration, a similar marked weight gain was observed from the second hour of the experiment in the NaOH series, but only after 7 hours with THAM. It thus appears that hemodialysis combined with alkalinisation is still too complex a procedure to be safely applied in acute or chronic pulmonary failure.

Acidosis↗
PubMed1988

Natural variability of pulmonary haemodynamics.

In the interpretation of the effect of a drug or intervention in a single patient, it is desirable to know the spontaneous fluctuations of the variable under study. A few studies have determined pulmonary haemodynamic variability in acute and short-term intervals. It seems reasonable to adopt a confidence limit of 6 mmHg or 22% for PPA changes to be significant. The long-term evolution is difficult to determine because of the unavoidable patient selection for repeat examinations several years apart, and because of the necessary treatment. In slight or moderate pulmonary hypertension the changes in PPA with time seem to be of small magnitude: less than 1 mmHg per year.

Exercise↗
PubMed1988

Cardiorespiratory function and pathological findings in heart-lung block reimplanted after hypothermic preservation.

A good result from the heart-lung transplantation depends on the quality of the preservation of cardiopulmonary transplants. To determine the functional and pathological status of the heart-lung block after preservation for several hours, we performed 10 heterologous heart-lung transplantations in Beagle dogs (weight 13.5 kg) under extracorporeal circulation. Weight and length compatibility between donor and receiver was ensured. Measurements of hemodynamics, lung mechanics and blood gases were performed in the donor and in the receiver before the transplantation, and in the receiver after heart-lung reimplantation. Histological studies were carried out by biopsy on the heart and on the lung of the donor before removal, at the beginning of the preservation at low temperature, after 3 h of ischemia in cold, and every hour after recirculation in the heart-lung block. Myocardial preservation was conducted with cold cardioplegia at 4 degrees C (Ringer lactate solution with high potassium). Lung preservation was achieved by injecting a Euro-Collins solution at 4 degrees C, with addition of dog plasma, into the pulmonary artery; during the whole ischemic phase, the lung parenchyma was maintained at 0 degrees C, and inflated at a 10 cm H2O pressure. After transplantation, we observed that cardiac output was low in all cases, with normal or subnormal pulmonary arterial pressure. Dynamic lung compliance was very low immediately after transplantation, and increased when restarting the circulation, but deteriorated again after several hours. At the same time alveolo-arterial O2 pressure difference and arterio-alveolar CO2 pressure difference progressively increased, due to the extensive gas exchange impairment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Cause of the raised wedge pressure on exercise in chronic obstructive pulmonary disease.

Patients with chronic obstructive pulmonary disease (COPD) markedly increase their pulmonary artery wedge pressure on mild exercise even though they have no overt left heart disease and no increase in the esophageal pressure (as a reflection of mean intrathoracic pressure). We wondered if lung distension due to gas trapping during the hyperpnea of exercise might cause the wedge pressure to rise by increasing juxtacardiac pressures above esophageal pressures. If this were so, then (1) tachypnea alone, without exercise, should cause the FRC and intracardiac pressures to increase in patients with COPD, (2) there should be an increase in FRC associated with the rise in wedge pressure on exercise, and (3) these changes should not occur in patients without COPD. We studied 39 patients with COPD (Ppa = 21 +/- 6 mm Hg [mean +/- SD], FEV1 [% predicted] = 39 +/- 16) and 13 control patients with similar pulmonary artery pressures but no airflow obstruction (Ppa = 22 +/- 20 mm Hg, FEV1 [% predicted] = 110 +/- 24). In those with COPD, light exercise raised the FRC by 0.5 +/- 0.5 L. Tachypnea alone, at the rate present during exercise, raised the FRC by 0.6 +/- 0.4 L and there was a 10% increase in left lower lobe area on lateral chest X-ray. Wedge, right atrial, and pulmonary artery pressures rose together during tachypnea with and without exercise. By contrast, in the control patients without COPD, the right atrial pressure change on exercise did not reflect that of the left atrium in extent or direction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Variability of the pulmonary vascular response to acute hypoxia in chronic bronchitis.

Hypoxic pulmonary vasoconstriction is considered as one of the factors leading to pulmonary hypertension in patients with chronic bronchitis, but the magnitude and the variability of the pulmonary vascular response to hypoxia in these patients have not been well established. We investigated the pulmonary hemodynamic changes induced by breathing two hypoxic mixtures (FIO2 = 0.15 and 0.13) in 26 patients with chronic bronchitis with airway obstruction (FEV1/VC = 49 +/- 14 percent). Results show that there is a wide variability of the pulmonary vascular response to acute hypoxia in chronic bronchitis patients, but it is not possible to say whether such differences play a role in the natural history of the disease.

Blood Pressure↗
PubMed1987

[Is the theoretical blood volume the optimum for chronic respiratory insufficiency? Hemodynamic study of chronic bronchitis patients as a function of the hematocrit].

We have studied oxygen transport and haemodynamics in 19 clinically stable chronic bronchitis split into two groups with comparable blood gases but different haematocrits (Group I = 33%, Group II = 51.5%). The aim of the study was to assess the suitability of bringing the blood volume down to the predicted normal value by repeated venesection. The respiratory function was moderately altered in these patients. The pulmonary and systemic vascular resistance were significantly more elevated in Group II. The arterial oxygen transport was comparable in the two groups. On the other hand for Group I the systolic work of the right ventricle was greater on account of the increased cardiac output. We have not observed any difference in blood volume between the two groups of patients. These results suggest that a return to the predicted blood volume is not recommended without some doubts in chronic bronchitis with polycythaemia.

Blood Pressure↗
PubMed1987

Cardiovascular changes during isometric and dynamic exercise in chronic lung disease.

To compare circulatory changes during dynamic and isometric exercise in patients with chronic lung disease, vascular pressures and cardiac output were measured in pulmonary and systemic circulation. The patients, mainly chronic bronchitics, were divided according to pulmonary vascular resistance (PVR): six patients with PVR below 120 dyn.s.cm-5, and 17 with PVR above this value. Exercise was performed using the legs, in a supine position, at low load. Oxygen consumption increased, on average, from 270 ml/min at rest, to 340 ml/min during isometric exercise, and 585 ml/min during dynamic exercise. Isometric exercise produced an increase in systemic artery pressure similar to that of dynamic exercise, but other vascular changes were of much smaller magnitude: pulmonary artery pressure increased by 4 mmHg with isometric exercise, and by 14 mmHg during dynamic exercise, on average; for cardiac output, these changes were 0.8 and 3.3 l/min, respectively. The pressure/flow relationship in the pulmonary circulation was comparable for both types of exercise. Changes in filling pressures in relation to stroke volume were more marked in the group of patients with elevated pulmonary vascular resistance. Changes in wedge pressure and in right atrial pressure were remarkably parallel for patients with normal as well as with high pulmonary vascular resistance.

Blood Pressure↗