Search PubMed⌕ Search

Biomedical subjects

M Meignan

Publications and source records attributed to M Meignan.

At least 55 records · Page 3Linked to original sources
PubMed1989

Chronic thromboembolic occlusion of main pulmonary artery does not reduce the lung clearance of 99mTc-DTPA.

In two patients with chronic unilateral massive pulmonary embolism, we studied the pulmonary epithelial permeability by measuring the clearance of inhaled and deposited 99mTc-DTPA aerosol. The clearances from the embolized lungs with complete or almost complete occlusion of a main pulmonary artery were more rapid than the clearances from the normal lung, which had an increased blood flow. This suggests that in chronic, embolized lung (1) the bronchial flow clears the inhaled solutes, and (2) there is an increase of epithelial permeability.

Adult↗
PubMed1988

Inhaled soluble aerosols insolubilised by lysosomes of alveolar cells. Application to some toxic compounds; electron microprobe and ion microprobe studies.

Our previous investigations have shown that, after systemic injection, certain toxic aluminium, chromium, uranium, and cerium salts are reabsorbed and eliminated by the renal cells by an identical process in which lysosomes play a special role. The elements are precipitated in these organelles in the form of insoluble phosphate due to the activity of acid phosphatase. In this work we have studied the disposition of the same elements after aerosol inhalation of water-soluble particles. The microanalytic methods used, electronic probe and ionic microanalysis, enable the chemical composition of mineral intracellular inclusions and the distribution of elements in the tissues to be determined. The elements studied are precipitated in the lysosomes of alveolar cells (macrophages and type 1 pneumocytes) in the form of insoluble phosphate due to the action of acid phosphatase. These toxic elements do not cross the alveolar-capillary barrier and do not cause any lesion in the organism. Thus a new mechanism for the elimination of hydrosoluble particles has been demonstrated that is of great interest in the overall process of defensive reactions of the organism.

Aerosols↗
PubMed1988

[Aerosol pulmonary scintigraphy. A new test in the diagnostic strategy of pneumocystis carinii pneumonia in patients with acquired immunodeficiency syndrome].

In eleven patients with AIDS and suspected Pneumocystis carinii pneumonia we measured the pulmonary clearance and half-life of aerosolized 99m Tc-DTPA (diethylenetriamine pentaacetate). We correlated the half-life with gallium scans and bronchoalveolar lavages. In all nine patients with Pneumocystis, this half-life was shorter than normal value, documenting a significant increase of lung epithelial permeability (p less than 0.001). Six of these 9 patients had abnormal gallium scans. However, in two patients with normal chest X-rays, PaO2 and gallium scans, only the reduced half-life of 99mTc-DTPA evidenced acute lung disease. After treatment, the results of the DTPA half-life correlated with the presence or absence of Pneumocystis. This method is, therefore, a sensitive initial diagnostic test in patients with suspected Pneumocystis pneumonia. A short half-life should prompt bronchoalveolar lavage even when PaO2 and/or chest X-rays and gallium scans are normal.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Interpretation of the krypton-81m dynamic series: the distribution of a tidal breath.

Lung scans during cyclic breathing of krypton-81m, an isotope with a 13-s half-life, were acquired in "list mode," where both temporal and spatial information are preserved. Subjects in the left lateral decubitus position breathed with two tidal volumes at each of two frequencies. Profiles of total activity over the acquisition period were examined. They showed little effect of frequency or tidal volume on the distribution of air between dependent and non-dependent regions. Dynamic series for ensemble-averaged breaths were constructed. The regional flow per unit volume was shown to correspond to the time derivative of the regional activity of the dynamic series divided by the corresponding activity. Both the relative timing of the gas flow to different lung regions and the flow per unit volume as a function of time were obtained from the dynamic series. The dependent lung was seen to be better ventilated throughout the respiratory cycle except for brief periods at the start of inspiration and the end of expiration. Most of the dead-space gas can be construed to enter and leave the dependent lung.

Female↗
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

Technetium-99m DTPA aerosol and gallium scanning in acquired immune deficiency syndrome.

In 11 non-smoking AIDS patients suspected of pneumocystis carinii pneumonia (PCP), the results of Tc-99m DTPA aerosol clearances, gallium scans, and arterial blood gases were compared with those of bronchoalveolar lavage (BAL). Nine patients had PCP. All had increased clearances five times higher than the normal (5.6 +/- 2.3% X min-1 vs 1.1 +/- 0.34% X min-1, N = 10, P less than 0.001), suggesting an increased alveolar permeability. Gallium scans were abnormal in six patients but normal or slightly abnormal in the three others. Four of these nine patients had normal chest x-rays. In two of these the gallium scan was abnormal, but in the two others, only the increased Tc-99m DTPA clearances showed evidence of lung disease. Two patients had normal BAL, with normal clearances and gallium scans. Four out of the nine patients with PCP were studied after treatment. Three recovered and had normal clearance and gallium scans. One still had PCP with increased clearance but normal gallium scan. Gallium scanning and Tc-99m DTPA clearance are useful for detecting lung disease in AIDS patients with suspected PCP and for prompting BAL when chest x-rays and PaO2 levels are normal. Due to its high sensitivity, a normal Tc-99m DTPA clearance could avoid BAL.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Measurement of lung volume with 81Krm in a dynamic scintigram.

The meaning of 81Krm counts obtained in a dynamic series of gated lung ventilation scans was evaluated in terms of flow rate, lung volume, or the flow/volume ratio. Flow and volume signals were recorded together with scintigraphic events in 29 subjects breathing 81Krm and after its decay, 127Xe as a tracer of lung volume. Gated ventilation scans and respiratory signals were reconstructed. Statistical analyses were carried out for linear regressions between total normalized counts detected by the gamma camera and (1) flow rate, (2) lung volume and (3) flow/volume ratio. Inspiration and expiration were analysed separately. For both isotopes, the best correlation was obtained between counts and lung volume (r greater than 0.93). No correlation was obtained between counts and flow rate or flow/volume ratio. Thus, we conclude that 81Krm count variations in gated scans correlate well with tidal volume.

Humans↗
PubMed1987

Lung epithelial permeability to aerosolized solutes: relation to position.

The lung epithelial permeability to inhaled solutes is primarily attributed to the degree of distension of the interepithelial junctions and thus of the alveolar volume. To assess this hypothesis, a submicronic aerosol of technetium-99m-labeled diethylenetriamine pentaacetate (99mTc-DTPA) was inhaled by eight normal subjects in left lateral decubitus (LLD). The regional lung clearance of 99mTc-DTPA was measured in LLD, then in right lateral decubitus (RLD) to reverse the relative distension of the alveoli. Although in LLD the deposition of the aerosol is the greatest in the gravity-dependent regions of the left lung, their 99mTc-DTPA clearances are significantly lower than those of the nondependent regions of the right lung (0.7 +/- 0.3 vs. 2 +/- 0.8%/min, P less than 0.001). In RLD, these regions placed in opposite positions significantly reversed their clearances (1.6 +/- 0.8 vs. 0.6 +/- 0.2%/min, P less than 0.001). Results indicate in lateral decubitus a gravity gradient of 99mTc-DTPA clearances independent of the aerosol deposition. This gradient of epithelial permeability to solutes appears to be influenced by the gradient of alveolar volume.

Adult↗
PubMed1986

Imaging and assessment of regional clearances of indium-111 labelled circulating immune complexes in humans.

The in vivo function of the reticulo-endothelial system in humans is currently studied by the blood clearance of 51Cr labeled RBC sensitized with IgG anti-Rh. By replacing 51Cr by 111In we developed a method which allows imaging and assessment of clearances of circulating immune complexes (CIC) by individual organs. Nine normal subjects were studied successively with 51Cr labelled CIC and 111In-labelled CIC by blood sampling and sequential imaging. Time activity curves were obtained over spleen, liver, heart lungs and kidneys. The blood clearance values were similar with 111In (T1/2 +/- SD = 23.4 min +/- 6.4 min) and 51 Cr (T1/2 = 22.9 min +/- 5.8 min). The blood clearance derived from the time activity curve obtained over the cardiac area (T1/2 = 26.6 min +/- 8.4 min) was not significantly different from that obtained by blood sampling. Most of the CIC were taken up by the spleen with a T1/2 of 20.3 min +/- 4.1 min. Although hepatic uptake was observed in all subjects, it was lower than that of the spleen and CIC were subsequently released from the liver in five of the nine patients. The spleen/liver ratio increased with time, reaching a plateau averaging 24.0 +/- 5.8 within 80 min in all subjects. CIC imaging allows, by a non-invasive procedure, the computation of CIC blood clearance and the estimation of the respective role of spleen and liver in phagocytic function.

Adult↗
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

Exercise increases the lung clearance of inhaled technetium-99m DTPA.

The regional lung clearance of a deposited aerosol of [99mTc] diethylenetriaminepentaacetic acid was successively computed at rest and at exercise in seven nonsmoking volunteers in upright posture. The subjects were seated on a bicycle with their backs against a gamma camera. At rest there was a gradient of clearance from the apex to the base of the lung, the apical clearance being significantly higher. At exercise this regional gradient was enhanced by a large and significant increase of the apical clearances (3.40 +/- 0.63% min-1 s.d. compared with 1.82 +/- 0.75% min-1 s.d. at rest, n = 7, p less than 0.01). By contrast the changes of the basal clearances were slight and unsignificant (1.46 +/- 0.71% min-1 s.d. compared with 1.40 +/- 0.82% min-1 s.d.). This increase of the apical lung clearance could be attributed primarily to the increase of apical blood flow induced by exercise and to the subsequent increase of the permeability surface area product.

Adult↗
PubMed1985

Factor analysis of 81mKr lung ventilation studies.

Factor analysis of dynamic structures (FADS) summarizes data depending on time and space in a few elementary components. Each of them associates a time-activity curve (factor) and the spatial distribution of the corresponding events. The aim was to evaluate the patterns, the number of components, and their possible link to physiology when FADS was applied to scintigraphic images representing a composite of a 81mKr ventilation cycle. In a study of 26 patients (10 normal, 16 pathologic), components were found that represent: (1) a rapid and steeply changing ventilation factor, corresponding mainly to bases in normal subjects and whole lung fields in patients, (2) a slower expiration and shorter inspiration ventilation factor distributed throughout both lung fields in all patients, (3) a constant activity curve, with an inspiratory activity peak distributed over both lung fields and the large airways, and (4) a factor including a phase shift with respect to the first; this was found significantly more often in patients with pathology.

Factor Analysis, Statistical↗
PubMed1985

An interactive software for 81mKr pulmonary ventilation gating.

An interactive software to gate scintigraphic list-mode data collected from ventilation studies using a radioisotope of an inert gas (81mKr) has been developed. It allows the detection of end expiration and end inspiration phases in a time activity curve. It involves six phases: filtering of the curve; preselection of local extrema; validation of the preselection; choice of the parameters for the reconstruction; control of the selected cycles and display of parameters such as frequency, expiration time, breath amplitude; reconstruction of images representing the distribution of ventilation during a mean respiratory cycle. This software was tested on 116 data sets without a failure. The interactive definition and control of the selected times made the algorithm useful regardless of the count rate and the frequency. It could be adapted to gate other periodic or semiperiodic physiological phenomena.

Computers↗
PubMed1984

Regional distribution of ventilation-perfusion ratios in acute pulmonary embolism.

Regional ventilation perfusion ratios have been computed in 44 patients with acute pulmonary embolism with a gamma-camera using Krypton 81m, a short-life radionuclide delivered by inhalation and infusion. This noninvasive technique is performed during tidal breathing and can be easily repeated. High V/Q's are detected in the embolic regions and low V/Q's in the nonembolic regions with a shift of the perfusion distribution towards these low values. This pattern disappears with recovery. This technique can be used in clinical practice for diagnostic purposes.

Acute Disease↗
PubMed1984

Microautoradiography of gamma-emitters: interest of latensification process.

Two techniques of microautoradiography were compared in order to assess their respective values to detect gamma-emitters usually used in nuclear medicine. Grain density microautoradiography (GD MARG) and track microautoradiography (T MARG) were performed on lymphocytes labeled with 99mTc, whose conversion electrons are able to provide a signal in nuclear emulsion. Microautoradiographs are presented, that clearly demonstrate the higher sensitivity, specificity and resolution obtained by T MARG. This technique seems particularly adapted to assess the distribution of gamma-emitters in cells and tissues.

Autoradiography↗
PubMed1984

Ion microscopy, a method for imaging the distribution of trace elements in the lung.

Analytical ion microscopy, a method of surface microanalysis, is applied to the detection of trace elements in the lung. With this method it is possible to obtain images of the distribution of any element in lung tissue sections with a resolution of 0.5 micron and with very high sensitivity (of an order of magnitude 3 or 4 times greater than with X-ray microanalysis). Under these conditions it is possible to study at the microscopic level the penetration into the lung cells of mineral materials administered in physiological amounts. The images are formed by ion microscopy of atoms sputtered as charged particles from the specimen, and these atoms are selected by mass spectrometry. This technique has been applied to the detection of aerosols (diam. less than 1 micron) of rare earths (thulium or cerium chloride), inhaled in very small amounts (20-50 micrograms), in cells from the lung of a rat. Images of the distribution of these elements were obtained in a few seconds or minutes, when X-ray microanalysis gave either a weak signal or none at all. Their behaviour in the lung could be easily studied several weeks after the end of the inhalation.

Aerosols↗