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Biomedical subjects

F Schrijen

Publications and source records attributed to F Schrijen.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1986

Maximal oxygen consumption and pulmonary circulation in patients with chronic bronchitis.

In order to study the relations between maximal oxygen consumption during exercise (VO2max) and the pulmonary circulation when pulmonary artery pressure (PPA) and pulmonary vascular resistance (PVR) are normal or close to normal, we evaluated twenty-three patients with chronic bronchitis, in stable clinical condition. All these patients performed a progressive exercise test on a bicycle ergometer until exhaustion (VO2max); they were also subjected to right heart catheterization at rest and during light exercise at constant load. In these patients with moderate functional impairment, we observed on average a significant, although weak, correlation (r = -0.52, P less than 0.01) between pulmonary vascular resistance at rest and VO2max. When VO2max exceeded 2 1 min-1, PVR was below 210 dyn s cm-5. From the heart rate during maximal exercise we computed the oxygen pulse (O2Pmax). In eight patients O2Pmax was reduced (less than or equal to 11 ml) with maximal heart rate close to its predicted value; in seven of these subjects PVR was abnormal and Ppa at rest was at least 20 mmHg. Thus it seems that in chronic obstructive bronchitis mild disturbances in pulmonary circulation may be a contributory factor in the limitation of exercise performance, and a maximal exercise test may help to detect pulmonary hypertension in these patients.

Adult↗
PubMed1986

Oxygen consumption and transport in stable patients with chronic obstructive pulmonary disease.

We studied the relationship between oxygen consumption and systemic oxygen transport in 30 clinically stable patients with chronic obstructive pulmonary disease (COPD) before and after increasing oxygen transport by passive leg elevation to raise the cardiac output. Results were compared with those observed in 10 patients with silicosis. The effect of leg elevation on oxygen consumption was also studied in 12 normal subjects. Oxygen consumption was measured by a closed circuit system, cardiac output by the direct Fick method, and arterial oxygen content by a cooximeter. Supine oxygen consumption was correlated with oxygen transport in patients with COPD (r = 0.50, p less than 0.01), and with leg elevation transport increased from a mean of 516 +/- 23 (SEM) to 567 +/- 26 ml X min-1 X m-2 and consumption increased from a mean of 136 +/- 3 to 148 +/- 4 ml X min-1 X m-2 (both p less than 0.01). In patients with silicosis, leg elevation raised mean oxygen transport from 620 +/- 40.0 to 745 +/- 54.0 ml X min-1 X m-2 and mean consumption from 161 +/- 6 to 192 +/- 6 ml X min-1 X m-2 (both p less than 0.01). In normal subjects, no change in oxygen consumption was observed with leg elevation (154 +/- 8 to 152 +/- 6 ml X min-1 X m-2).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗
PubMed1986

Pulmonary haemodynamic response to two-stage exercise in patients with chronic bronchitis.

The pressure/flow relationship in the pulmonary circulation has been studied in 43 patients with chronic bronchitis, at rest (R) and during exercise at two levels: 30 or 40 W (E1), and 60 or 80 W (E2), without interruption. For the entire group, pulmonary vascular resistance was 142 +/- 70 dyn X s X cm-5 at rest, 131 +/- 55 at the first exercise level and 118 +/- 60 at the second level. Individual changes were variable, however; a "linearity index" was computed as delta(PPA-PW)/delta Q from the first to the second exercise level divided by the same value from rest to the first exercise level. This index was below 0.75 in 27 patients (i.e. the pressure/flow slope was lower for the second exercise level and the pressure/flow curve was concave to the flow axis), it was above 1.25 in nine patients (i.e. the slope increased with exercise and the pressure/flow curve was convex to the flow axis), and the pressure/flow relationship was close to rectilinear in seven patients. Functional disturbances were mild in these subjects, and in the majority of them pulmonary vascular resistance did not increase with exercise.

Adult↗
PubMed1985

The influence of hypoxemia on tritiated digoxin plasma kinetics and tissue distribution in the conscious dog.

The goals of this study were to document the effect of hypoxemia on the distribution of digoxin in conscious dogs. For this purpose, 6 beagles were exposed to air and 6 others to an atmosphere containing 10% O2, to generate a PaO2 equal to 46.3 +/- 0.3 mmHg (mean +/- SEM). The animals received 25 micrograms/kg of digoxin containing 2.17 micrograms/kg of 3H-digoxin, and then blood and urine samples were collected over the next 48 h, at which time they were killed to determine digoxin concentrations in several tissues. Five additional beagles were used to assess the influence of hypoxemia on the blood perfusion to these tissues using radioactive microspheres. The results, expressed as digoxin equivalents, indicated that hypoxemia increased the digoxin apparent volume of distribution (2.85 +/- 0.10 versus 2.01 +/- 0.11 L/kg; p less than 0.001) and the time required to achieve this distribution (9.7 +/- 1.4 versus 2.6 +/- 0.3 h; p less than 0.01). As digoxin clearance was not influenced by hypoxemia, the half-life was increased from 25.2 +/- 1.5 to 33.4 +/- 1.3 h (p less than 0.01). With hypoxemia, digoxin concentrations increased significantly in the brain and diaphragmatic muscle, but only marginally in other organs, including the heart, the latter despite a significant increase in blood flow. It is concluded that hypoxia does change digoxin disposition but does not increase digoxin heart concentrations. Therefore, factors other than changes in digoxin plasma kinetics and heart distribution may be responsible for the decrease in digitalis tolerance during hypoxemia.

Animals↗
PubMed1984

Respiratory and circulatory adaptation to isometric and dynamic exercise in chronic lung disease.

Changes at the beginning of isometric and dynamic low level exercise were studied in 23 patients with chronic lung disease. Ventilation, oxygen consumption and vascular pressures in systemic and pulmonary circulation were continuously monitored, and cardiac output was measured by thermodilution every minute. Circulatory changes took place suddenly at the beginning of isometric exercise and gradually during dynamic exercise. Ventilatory changes followed almost the same progressive pattern in both types of exercise. Ventilation increase in relation to oxygen uptake was slightly smaller during isometric exercise. Pulmonary artery pressure showed no further increase after the initial change, although ventilation was still rising.

Adaptation, Physiological↗
PubMed1984

Is it possible to predict pulmonary arterial hypertension from an exercise test?

In patients with chronic lung disease, the response to exercise can be impaired by ventilatory and/or circulatory disturbances. The response to a standard exercise varies according to the load in relation to the maximum load the subject can tolerate. Thus it seems more suitable to study the maximum tolerated, i.e. maximum workload expressed as VO2 max. We compared the results of VO2 max and pulmonary haemodynamic variables in 43 patients with chronic bronchitis. VO2 max ranged from 0.720 to 3.010 l/min. The relation between VO2 max and pulmonary artery pressure at rest or its increase with low level exercise was very poor, but there was a trend towards an increase in pulmonary vascular resistance in patients with low VO2 max, although a number of patients with low VO2 max had normal pulmonary vascular resistance. The ratio between heart rate at maximum workload and maximum heart rate according to age (heart rate obs/pred) was above 95% in the patients with pulmonary vascular resistance above 250 dyn.s. cm-5; it varied widely in the patients with normal or slightly elevated pulmonary vascular resistance. When VO2 max was below normal, and heart rate obs/pred low, it is probable that the decrease in VO2 max was due to ventilation impairment, or to a lack of cooperation. Oxygen pulse at VO2 max was also reduced in patients with high pulmonary vascular resistance, but a large range of values was observed in the rest of the patients. A high oxygen pulse at VO2 max however allows to rule out severe pulmonary artery hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1982

Pulmonary blood volume in chronic lung disease: changes with legs raised and during exercise.

Pulmonary blood volume (PBV) was measured by double injection (pulmonary artery trunk and wedged pulmonary artery) in 43 patients with chronic lung disease, at rest supine, with the legs raised, and during light exercise. At rest, PBV was reduced slightly in group 1 (eight with silicosis), but notably in groups 2 (16 bronchitis patients) and 3 (19 patients! with pulmonary vascular restriction). With the legs raised, PBV increased by 14 percent in group 1, 7 per cent in group 2, and 5 percent in group 3. From rest to exercise, the pressure increase was much greater in groups 2 and 3 than in group 1. The slope of the pressure-volume curve, delta V/delta P, was lower in groups 2 and 3, which could mean that lung vessel distensibility was reduced in these groups, or that, despite its low value, PBV was near its maximum capacity already at rest.

Blood Volume↗
PubMed1980

Pentose pathway in pulmonary fibrosis due to chronic paraquat poisoning.

In 14 beagle dogs, paraquat was infused in fractional doses to produce pulmonary fibrosis while avoiding fatal liver and kidney lesions. Activity of the three enzymes of the pentose pathway: glucose-6-phosphate dehydrogenase (G-6-PDH), glutathione reductase (GR) and glutathione peroxidase (GSH Px), which supply reduced equivalents against oxidant agents, were measured in the mediastinal lobe of the lung. After a single low dose (2-3 mg/kg body weight), GR and GSH Px activities were reduced. After repeated paraquat doses, pentose pathway enzyme activities were higher than after a single low dose; however, they did not significantly exceed the normal values as determined in control dogs. The activities of G-6-PDH, GR and GSH Px correlated with the total paraquat dose and with the extent of pulmonary fibrosis measured with an electronic image analyzer. The activity of pulmonary lactate dehydrogenase, which was also reduced after a single low dose of paraquat, did not show the same correlations.

Animals↗
PubMed1980

Haemodynamic changes during multistage exercise in patients with chronic lung disease.

A group of 20 patients with chronic lung disease (mainly chronic bronchitis) was studied at rest and during continuous exercise with increasing load, i.e. O Watts (loadless pedalling), 30 and 60 Watts. Ventilatory and haemodynamic measurements, as well as blood gas analysis, was performed at the end of a 5-minute steady state at rest and for each level of exercise. There was no progressive deterioration of blood gases with exercise. Haemodynamic values increased with exercise, already during loadless pedalling. Pulmonary vascular resistance, however, did not change, and the relation between cardiac output and pulmonary driving pressure was a straight line passing through the origin, although its slope was three times higher than in normal persons.

Blood Pressure↗
PubMed1980

Haemodynamic reaction to exercise and increased afterload in the detection of right heart failure in pulmonary diseases.

The effect of steady-state exercise and of increased afterload by angiotensin infusion on the right ventricular function was examined in 21 patients with chronic obstructive lung disease (COLD). 15 of them were always free from cardiac failure and 6 of them have had clinical signs of failure at the time of examination. Despite significant differences in various parameters between compensated (C) and decompensated (D) subjects, only the right ventricular filling pressure during both experimental procedures was able to differentiate the majority of individual C and D patients. The authors discuss the mechanisms of haemodynamic response to both stress tests and their significance for clinical evaluation of patients with COLD and for research into right ventricular contractility.

Adult↗
PubMed1978

Haemodynamic variables during repeated exercise in chronic lung disease.

1. Pulmonary and systemic haemodynamics during repeated exercise were studied in 28 patients with chronic lung disease of various etiology, 16 of whom suffered from chronic bronchitis. They performed a moderate exercise repeated after a 20 min rest period. Ventilatory variables, blood gas tensions, cardiac output and vascular pressures (right ventricular end-diastolic, pulmonary arterial, wedge and systemic arterial) were measured at rest, during exercise and again at rest and during the same exercise. 2. Ventilation and blood gas tensions were similar during the two rest and exercise periods; there was, however, a slightly significant difference in oxygen consumption and hydrogen ion concentration between the first and the second exercise period. Pulmonary arterial and wedge pressures were lower during the second rest and exercise, right ventricular filling pressure was lower at rest, and systemic arterial pressure during the second exercise. Cardiac output and pulmonary vascular resistance were unchanged. 3. Changes in systemic arterial pressure were significantly different in a group of patients with arterial oxygen desaturation or perfusion defects, compared with those patients without such impairment.

Adult↗