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Biomedical subjects

M Demedts

Publications and source records attributed to M Demedts.

At least 217 records · Page 12Linked to original sources
PubMed1983

Respiratory muscle dysfunction in systemic lupus erythematosus.

An assessment of pulmonary mechanics revealed weakness of inspiratory and expiratory muscles as cause of the restrictive ventilatory defect (vital capacity: 47 +/- 10 percent predicted) in seven (ages 33 to 62 years) out of 26 consecutive patients with systemic lupus erythematosus (SLE). Maximal inspiratory transdiaphragmatic pressures were reduced mainly due to the markedly increased (more positive) esophageal pressures. During maximal expiratory efforts, esophageal and gastric pressures were grossly decreased. These abnormalities probably may be considered part of a more generalized, yet subclinical muscle disorder due to the SLE with, however, predominant involvement of the respiratory muscles. The abnormalities were not related to the use of corticosteroids or generalized inanition. The static expiratory lung compliance was reduced in all patients (55 +/- 18 percent predicted), but normalized immediately following passive inflation of the lungs to transpulmonary pressures of more than 30 cm H2O in two of the three subjects tested. The volume restriction was not progressive over a period of 38.5 patient-years.

Adult↗
PubMed1983

Eosinophilic pneumonia without radiographic pulmonary infiltrates.

In a 52-year-old man, chronic eosinophilic pneumonia (CEP), suggested by clinical history and marked eosinophilia in the peripheral blood and in the bronchoalveolar lavage fluid, has been diagnosed on open lung biopsy. Nevertheless, chest roentgenograms never showed any infiltration during the course of the disease. Extensive etiologic examination remained negative. Steroid therapy induced a dramatic clinical response, disappearance of the eosinophilia in the peripheral blood and in the bronchoalveolar lavage fluid, and quick normalization of pulmonary function. We suggest that a typical history and markedly eosinophilic alveolitis allows one to make the diagnosis of CEP even in the presence of normal chest film findings.

Biopsy↗
PubMed1983

Plasma angiotensin converting enzyme in the diagnosis and monitoring of disease activity in sarcoidosis.

The value of plasma angiotensin converting enzyme (plasma-ACE) as an indicator of activity in sarcoidosis was evaluated using strictly defined clinical, radiological, functional and pathologic criteria. The cross-sectional study involved 75 untreated patients. Fifty-four with active sarcoidosis had a significantly higher plasma-ACE (68.5 +/- 22.6 U/ml) than 8 with possibly active disease (44.6 +/- 9.5 U/ml; p less than 0.001), 13 with inactive disease (41.8 +/- 13.3 U/ml; p less than 0.001) and 69 healthy controls (35.9 +/- 9.4 U/ml; p less than 0.001). Within the active disease group, no significant differences in plasma-ACE were found, when subdivided by chest X-ray stage or by possible, subsequent, corticosteroid therapy. The longitudinal study was made on 36 patients with active sarcoidosis. In 70% of the additional examinations, the clinical evolution was correlated with the changes in plasma-ACE. This relationship showed no significant difference (p greater than 0.1) between the 17 patients who remained untreated and the 19 patients who received steroids. This study emphasizes that plasma-ACE is a very useful indicator of the activity of sarcoidosis and is valuable in monitoring the evolution of the disease whether spontaneous or corticosteroid-induced.

Adult↗
PubMed1983

Radiographic evaluation of regional pulmonary dimensions and volumes: effect of age.

On chest radiographs performed at spirometrically controlled residual volume (RV), functional residual capacity (FRC) and total lung capacity (TLC), several distances were measured in 8 young and 7 elderly male subjects. Regional volumes above and below the minor fissure were calculated using Barnhard's method for thoracic gas volume determination. When the volumes above and below the fissure were expressed as a percentage of their volume at TLC, and related to overall lung volumes (in percent of TLC), graphs similar to the ones obtained in scintigraphic studies were obtained. This illustrates that the present radiographic method may provide information on regional pulmonary volumes. Regional TLC of the upper zone was larger in elderly subjects than in young ones, while the opposite was true for regional TLC of the lower zone, indicating that maximal regional expansion changes with age. For the upper zone, the changes in diameters between RV and TLC were largest in antero-posterior direction and smallest in cranio-caudal direction. For the lower zone, changes were largest in cranio-caudal direction. This suggests an anisotropic expansion of the upper and lower zone. This anisotropy was more pronounced in the young than in the elderly subjects.

Adult↗
PubMed1983

Mechanism of phase V in the single breath washout curve.

The underlying mechanism of the occurrence of a downward phase V at the end of a bolus washout curve was investigated in three healthy subjects. Phase V appeared not to originate from apical zones with low concentration of tracer gas but from dependent lung zones, which were not pathological. Indeed: 1) a reversed, upward, terminal slope was obtained when the bolus had been directed to the lung base by imposing a transition of the body through 180 degrees between inspiration and expiration or by inhaling a bolus close to TLC; 2) phase V was also present on N2 washout curves and, thus, originated from zones with smaller RV/TLC than the apical ones. Phase V increased with flow rate.

Adult↗
PubMed1982

Diaphragm dysfunction in mixed connective tissue disease. A case report.

A patient with mixed connective tissue disease (MCTD) presented the typical signs of respiratory muscle weakness and marked diaphragm dysfunction: reduced maximal ex- and inspiratory transrespiratory pressures (measured at FRC), maximal transdiaphragmatic pressures and transpulmonary pressures at TLC, FRC and RV. this insufficiency of the diaphragm was also responsible for the restrictive ventilatory defect and the decreased static lung compliance with high diffusing capacity per unit lung volume.

Adult↗
PubMed1982

Pulmonary function in moderate neuromuscular disease without respiratory complaints.

Pulmonary function studies were carried out in 29 patients with moderate neuromuscular disease who had virtually no respiratory complaints. The earliest and most pronounced abnormalities were decreased transrespiratory pressures. Next a restrictive pulmonary defect with increased residual volume and a proportional decrease of maximal expiratory flows occurred, together with a decrease in static lung compliance. Because of a decrease in transpulmonary pressure at total lung capacity and often an increase in diffusing capacity per unit lung volume the above mentioned restrictive defects were attributed to muscular weakness and interstitial lung disease was excluded. Finally, some ventilation inequality could be found, probably originating in the poorly ventilated supradiaphragmatic regions.

Adult↗
PubMed1981

Model of elasticity of the human lung.

A model of the elasticity of the human lung has been developed to evaluate the relative importance of the characteristics of the lung parenchyma, of thorax configuration, and of gravity on the vertical gradients of pleural pressure and regional volumes, and on the linear displacements of lung tissue, of various lung volumes. The predictions of the model are compared with available experimental data. It is suggested that the bulk elasticity modulus of the human lung is high with respect to that of canine lungs, that the shearing forces are low ("effective" Poison's ratio of about 0.4-0.45), and that the variations of regional pleural pressures and volumes during deflation are determined primarily by the interaction between lung weight and changes in thorax configuration.

Adult↗
PubMed1978

Regional esophageal pressures with lobar obstruction in dogs.

The right lower lobes (RLL) of intact horizontal dogs were obstructed at FRC during spontaneous breathing and artificial ventilation (IPPB). At end inspiration, pressure within the RLL became less than tracheal pressure, and pressure in the lower esophagus declined to a greater extent than in the upper esophagus. Tidal pressure swings in the obstructed RLL were larger than in the esophagus during spontaneous breathing but smaller during IPPB implying that the elastic recoil of the RLL decreased during inspiration at the mediastinal side. All these changes were intensified during RLL atelectasis and counteracted by strapping of the lower chest wall. These results indicate that: (a) around a lobe moving out of phase with the rest of the lung, a force is created tending to minimize the lobar volume differences; (b) the obstructed lobe is deformed during inflation of the rest of the lung; (c) esophageal (and hence pleural) pressure gradient is modified by this localized intrapulmonary pathology apparently due to shape interactions between chest wall and lung.

Airway Obstruction↗
PubMed1978

Comparison of 133Xe washout curves after bolus inhalation, perfusion, and equilibration.

In 6 healthy subjects and 13 patients with chronic obstructive lung disease, 133Xe washout curves after bolus inhalation, perfusion and equilibration were compared, using a gamma camera and computerized data handling. In healthy subjects the washout after equilibration was significantly slower than after the two other procedures. As this phenomenon occurred at the basal zones, it was attributed to the presence of airway closure in some units. In patients, the three washouts were significantly different from each other. This indicated the existence of intraregional inhomogeneity in ventilation, perfusion and ventilation-perfusion ratio. Our conclusion is that comparison of these different washout methods yields valuable information not only on absolute values of pulmonary function but also on the intraregional distribution, which cannot be obtained by other examinations.

Adult↗
PubMed1978

Emphysema with minor airway obstruction and abnormal tests of small airway disease.

In 9 patients complaining primarily of exertional dyspnea, the diagnosis of early emphysema was made on the basis of a decrease of the elastic recoil of the lung and of the single breath diffusing capacity, in the presence of only minor airway obstruction as estimated from the routine pulmonary function tests. Closing volume, the alveolar plateau, dynamic compliance and maximal flow at 50% of the vital capacity were markedly abnormal; the maximal flow-static recoil pressure relationships suggest, however, that none of the patients suffered from small airway disease. We conclude that one should systematically consider early emphysema in the differential diagnosis of small airway disease.

Adult↗
PubMed1976

A new method to determine frequency characteristics of the respiratory system.

A technique is described allowing one to determine simultaneously the resistance and reactance of the total respiratory system for various frequencies. During spontaneous breathing, regularly recurring impulses are produced at the mouth by means of a loud speaker. A Fourier analysis of the mouth pressure and flow signals yields mean resistance and reactance values, over 16 s, for all harmonics of 2 Hz up to 30 Hz. The values are in good agreement with those obtained in the absence of breathing and those determined by means of the forced oscillation technique and by body plethysmography. The reproducibility of the measurements is satisfactory (coefficient of variation: 11.6%).

Electronics↗
PubMed1976

Xenon and nitrogen single-breath washout curves in patients with airway obstruction.

In patients with chronic obstructive lung disease, we determined single-breath N2 and 133 Xe washout curves, and regional distributions of volumes (Vr) and of 133Xe boluses inhaled at residual volume (VIRV). Patients suffering from emphysema with minimal airway obstruction demonstrated large closing volumes and apicobasal distribution gradients, apparently because of a steep pulmonary recoil pressure-volume curve. In one subject with basal small airway disease there was no vertical gradient in regional residual volume; closing volume was increased with the 133Xe technique but almost absent with the N2 technique. Patients with moderate-to-severe airway obstruction had upward-sloping alveolar plateaus without distinct phase IV, and small apicobasal differences in Vr and VIRV. The latter resulted probably from increased regional differences in time constants counteracting the influence of gravity. Finally, patients with severe airway obstruction and basal emphysema demonstrated a rising N2 but a descending 133Xe plateau; the gradient for VIRV was normal, and reversed for Vr. This pattern was attributed to nongravitational differences in time constants causing a first in-first out distribution.

Adolescent↗
PubMed1976

Respiratory failure: correlation between encephalopathy, blood gases and blood ammonia.

In 59 patients with respiratory insufficiency due to chronic obstructive pulmonary disease (COPD) the relationship between the state of consciousness, the blood gases and blood ammonia were studied. Interindividually, a significant correlation was found between the encephalopathy and SaO2, PaCO2 or ammonia, and also between the blood gases and ammonia. On the other hand, an intraindividual study, performed on patients with minor cerebral dysfunction, showed that only PaCO2 was significantly correlated with the stage of consciousness. Ammonia did not appear to have a neurotoxic influence. The ammonia level seemed to be influenced primarily by other factors than the blood gases, although there was a borderline influence of SaO2 on aterial ammonia and a significant influence of PaCO2-HCO3 and pH on venous ammonia.

Adult↗