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Biomedical subjects

M Decramer

Publications and source records attributed to M Decramer.

At least 145 records · Page 8Linked to original sources
PubMed1985

Mechanical coupling between the ribs and sternum in the dog.

We measured the axial (cranio-caudal) displacements of the sternum and the second and seventh bony ribs using linear displacement transducers in five supine anesthetized dogs during passive inflation and deflation, during quiet breathing and static inspiratory efforts before and after bilateral phrenicotomy, and during tetanic stimulation of either the sternocleidomastoids or the sternal fibers of the rectus abdominis. Quiet inspiration before and after phrenicotomy was always associated with a caudal displacement of the sternum and a cranial displacement of the seventh rib; the second rib, however, was either motionless or also showed an inspiratory caudal displacement. During static inspiratory efforts, the second rib was always moving in concert with the sternum in the caudal direction, while the seventh rib, in particular after phrenicotomy, usually moved in the cranial direction. Finally, for any given axial (cranial or caudal) displacement of the sternum, stimulation of the sternocleidomastoid or rectus abdominis muscles invariably caused the second rib to move disproportionately more than the seventh. These results indicate that the upper ribs are more tightly linked to the sternum than the lower ribs. This presumably results from the fact that the costal cartilages increase in length from above downwards, and it implies that the upper portion of the rib cage behaves more as a unit with the sternum than the lower portion.

Animals↗
PubMed1985

Relationship between parasternal intercostal length and rib cage displacement in dogs.

The relationship between parasternal intercostal length and rib cage cross-sectional area was examined in nine supine dogs during passive inflation and during quiet breathing before and after phrenicotomy. Parasternal intercostal length (PSL) was measured with a sonomicrometry technique, and rib cage cross-sectional area (Arc) was measured with a Respitrace coil placed around the middle rib cage. During active inspiration as well as during passive inflation, PSL decreased as Arc increased. However, the relationship between PSL and Arc during active inspiration, whether in the intact or phrenicotomized animal, was almost invariably different from that during passive inflation, so that the same increase in Arc was associated with a greater decrease in PSL in the former than in the latter instance. This difference between passive inflation and active inspiration is probably due to the active contraction of the parasternals during inspiration and the consequent caudal displacement of the sternum. In upright humans, the sternum moves cephalad and not caudad during inspiration, so the relationship between PSL and Arc during active breathing might be similar to that during passive inflation.

Animals↗
PubMed1985

Respiratory resistance in dogs by the single-breath and the forced oscillation methods.

Total respiratory resistance (Rrs) was measured in six anesthetized dogs with two different methods: the single-breath (SB) method, which provides the time constant of the system during a relaxed expiration and the forced oscillation (FO) method, which uses a pseudorandom noise signal applied at the airway opening. The comparison was made in three conditions: before muscle paralysis (A), after muscle paralysis (B), and after tracheal banding (C). In conditions A and B the two computed resistances correlated very well with each other (r = 0.98). No systematic difference between Rrs values obtained with the two methods was found. In condition C the respiratory resistance was clearly nonlinear from the flow-volume curves during SB and could be described with Rohrer's equation: Rrs = K1 X V + K2 X V2, where K1 and K2 are Kohrer's constant and V is flow. Rrs measured with FO was not frequency dependent during tracheal banding (C) and was virtually equivalent to K1. Since the FO method uses low flows as the input of the respiratory system and K1 could be ascribed to laminar flow, the numerical matching appears reasonable and tends to reinforce the validity of both methods of measurement. We conclude that, for the normal respiratory system, FO and SB methods are approximately equivalent. In the presence of a markedly alinear central airway resistance with normal lungs, the SB method appears to provide a more adequate description of the flow-resistive properties of the system.

Airway Resistance↗
PubMed1985

Contractile properties of intercostal muscles and their functional significance.

To have some insight into the functional coupling between the parasternal intercostals (PS) and the diaphragm (DPM), we have examined the isometric contractile properties of bundles from canine PS and DPM muscles. Bundles of external (EXT) and internal (INT) interosseous intercostals were studied for comparison. In addition we have related sonometrically measured length of the intercostals in vivo at supine functional residual capacity (FRC) to in vitro optimal force-producing length (Lo). We found that 1) intercostal twitch speed is significantly faster than DPM, thus displacing their relative force-frequency curve to the right of that of the DPM; 2) the ascending limb of the active length-tension curve of all intercostals lies below the DPM curve; i.e., at 85% Lo, PS force is 46% of maximal force (Po), whereas DPM force is still 87% Po; 3) for any given length change beyond Lo, all intercostals generate greater passive tension than the DPM; 4) Po is greater for the intercostals than the DPM; and 5) at supine FRC, both EXT and INT in dogs are nearly operating at Lo, whereas the PS are operating at a length greater than Lo. We conclude that 1) PS produce less force than DPM during breathing efforts involving low- (10-20 Hz) stimulation frequencies, but they generate more force than DPM when high- (greater than 50 Hz) stimulation frequencies are required; and 2) the pressure-generating ability of the PS is better preserved than that of the DPM with increases in lung volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Volume-time profile during relaxed expiration in the normal dog.

Airway opening pressure, esophageal pressure, and flow were obtained during relaxed expirations in two normal anesthetized paralyzed dogs. The signal-to-noise ratio in the flow signals was greatly increased by averaging 10 different signals obtained with the same lung inflation volume. Numerical integration of an averaged flow signal then yielded the time course of the volume of the respiratory system above functional residual capacity (the elastic equilibrium volume). Comparison of volume signals obtained with different inflation volumes suggests that the resistance of the respiratory system increases with flow. The flow-volume and semilog volume curves show that expiration is induced by two apparently separate mechanisms: one causes emptying of most of the expired volume over a time interval of much less than 1 s, whereas the other contributes a relatively small amount to the expired volume over a significantly longer time (greater than or equal to 1 s). We postulate the first mechanism to be due to that of the respiratory system behaving like a single unit, with an elastance that is slightly volume dependent, emptying through a single airway which has a resistance that increases with flow. From the nature of airway opening pressure and esophageal pressure measured after occlusion in midexpiration, we conclude that the second mechanism is due to the viscoelastic properties (i.e., creep) of the respiratory system. The properties are manifest mainly in the chest wall.

Animals↗
PubMed1984

Salutary effect of fall in abdominal pressure during diaphragm paralysis.

To examine the mechanical effects of the fall in abdominal pressure (Pab) that occurs during inspiration in diaphragmatic paralysis, we studied lung inflation and rib cage expansion before and after the abdomen was opened in nine spontaneously breathing dogs with bilateral phrenicotomy . We measured Pab, tidal volume, and parasternal electromyographic (EMG) activity during quiet breathing and CO2-induced hyperpnea. In six dogs, we also measured changes in anteroposterior and transverse rib cage diameters, the resting length of the parasternal intercostal muscles, and the amount of shortening of these muscles during inspiration. Opening the abdomen caused a marked reduction in the fall in Pab during inspiration and invariably resulted in a decrease in tidal volume (mean decrease, 13%), which contrasted with marked increases in inspiratory rib cage expansion and in the amount of parasternal intercostal shortening. The procedure, however, did not affect the resting length or inspiratory EMG activity of the parasternals . These findings indicate that although the fall in Pab, which occurs during inspiration in diaphragmatic paralysis, causes paradoxical inward displacement of the ventral abdominal wall, it has a salutary effect on tidal volume. This phenomenon is probably due to the fact that the diaphragm is part of the abdominal wall.

Abdominal Muscles↗
PubMed1984

Mechanical arrangement of costal and crural diaphragms in dogs.

To assess the mechanical arrangement of the costal and crural parts of the diaphragm, we studied changes in diaphragmatic length with piezoelectric crystals in 17 supine anesthetized dogs. During control resting inspiration, the crural part usually shortened more and earlier than the costal part. After phrenicotomy, the crural part always lengthened during inspiration, whereas the costal part shortened or lengthened. These interanimal differences disappeared after opening of the abdomen; the costal part then always lengthened during inspiration. During stimulation of one part, the relaxed nonstimulated part always lengthened. However, when compared with the relationship between length and transdiaphragmatic pressure (Pdi) obtained during passive deflation, the lengthening of the relaxed part during stimulation of either part was small. This difference between predicted and measured Pdi-length relationship decreased in magnitude as lung volume increased above functional residual capacity (FRC) and increased as residual volume was approached. These results indicate that 1) even during quiet breathing the diaphragm in the dog is not a single functional entity; 2) at FRC the costal and crural portions of the diaphragm behave as if they were mechanically arranged partly in parallel and partly in series; and 3) they gradually move into a pure mechanical series arrangement as lung volume increases.

Animals↗
PubMed1984

Respiratory changes in parasternal intercostal length.

In an attempt to understand the role of the parasternal intercostals in respiration, we measured the changes in length of these muscles during a variety of static and dynamic respiratory maneuvers. Studies were performed on 39 intercostal spaces from 10 anesthetized dogs, and changes in parasternal intercostal length were assessed with pairs of piezoelectric crystals (sonomicrometry). During static maneuvers (passive inflation-deflation, isovolume maneuvers, changes in body position), the parasternal intercostals shortened whenever the rib cage inflated, and they lengthened whenever the rib cage contracted. The changes in parasternal intercostal length, however, were much smaller than the changes in diaphragmatic length, averaging 9.2% of the resting length during inflation from residual volume to total lung capacity and 1.3% during tilting from supine to upright. During quiet breathing the parasternal intercostals always shortened during inspiration and lengthened during expiration. In the intact animals the inspiratory parasternal shortening was close to that seen for the same increase in lung volume during passive inflation and averaged 3.5%. After bilateral phrenicotomy, however, the parasternal intercostal shortening during inspiration markedly increased, whereas tidal volume diminished. These results indicate that 1) the parasternal intercostals in the dog are real agonists (as opposed to fixators) and actively contribute to expand the rib cage and the lung during quiet inspiration, 2) the relationship between lung volume and parasternal length is not unique but depends on the relative contribution of the various inspiratory muscles to tidal volume, and 3) the physiological range of operating length of the parasternal intercostals is considerably smaller than that of the diaphragm.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Regional differences in abdominal pressure swings in dogs.

The pressure swings under the costal (Pcos) and crural diaphragms (Pcru) and between the intestinal loops (Pint) were compared with the swings in gastric pressure (Pga) in 13 supine anesthetized dogs. Pcos, Pcru, and Pint were measured with air-filled latex balloons in eight dogs and saline-filled catheters in five. Pga was measured with an air-filled balloon in all dogs. During quiet breathing differences were often present, the directions of which were variable from animal to animal. During mechanical ventilation, all pressures increased, but both Pcos and Pcru increased more than Pga, whereas only a small change was observed in Pint. During bilateral stimulation of the costal diaphragm, Pcos invariably increased more than Pga and Pint, whereas almost no change was observed in Pcru. During bilateral stimulation of the crural diaphragm, Pcru invariably increased more than Pga, Pint, and Pcos. During abdominal muscle stimulation as during external abdominal compression, Pint always increased more than Pcos and Pcru. During lower rib cage compression, Pga, Pcos, and Pcru increased more than Pint. During sternocleidomastoid stimulation, all pressure swings were negative, but the change in Pint was always smaller than in Pcos, Pcru, or Pga. Inhomogeneities observed with balloons and saline-filled catheters were similar. After the abdomen was filled with 2 liters of saline all pressure swings became much more homogeneous.

Abdomen↗
PubMed1983

Effects of unilateral hypoxia on neuroepithelial bodies in rabbit lungs.

The present study was undertaken to investigate the influence of regional (unilateral) alveolar hypoxia on the intrapulmonary neuroepithelial bodies (NEB), which contain bioactive substances and are distinctly innervated. Eight (4-wk-old) rabbits were subjected to unilateral hypoxia. The animals were anesthetized by an intramuscular injection of Hypnorm and breathed spontaneously during the experiment. The right lung received a hypoxic gas mixture (10% O2-90% N2) and the left lung a hyperoxic mixture. Blood gas measurements indicated that no systemic hypoxemia or acidosis occurred under these conditions. Lung samples were examined by electron microscopy to determine morphometrically the extent of a secretory exocytosis at the basal cell pole of the NEB and by a microspectrographical analysis of the formaldehyde-induced fluorescence to quantify the NEB serotonin content. After 20 min of unilateral hypoxia the NEB in the right hypoxic lung exhibited an increased exocytosis and a lower serotonin content in comparison with the left hyperoxic lung NEB. These results indicate that NEB react to regional alveolar hypoxia by secreting serotonin and/or peptides to the surrounding lung tissue (blood vessels, smooth muscle, nerve endings, etc.).

Animals↗
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↗
PubMed1982

Evaluation of bedside myocardial scintigraphy with 201Tl in acute myocardial infarction.

Bedside myocardial scintigraphy was performed on 149 patients admitted to the Coronary Care Unit (CCU), after IV injection of 74 MBq 201Tl, using a mobile gamma camera (Dynamo). The study was displayed on Polaroïd pictures, without any image treatment, and read by two independent readers. Clinical history, findings, and final diagnosis were assessed by an independent clinician. The following conclusions were reached: 1) The sensitivity of the study for the detection of a recent myocardial infarction (MI) was 0.84 with a specificity of 0.87. 2) There was a good correlation between scintigraphic and ECG localization. 3) No firm correlation was found between scintigraphic and enzymatic estimates of infarct size. 4) Abnormal visualization of the right ventricle was probably associated with more extensive infarction.

Aged↗
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↗
PubMedDate not supplied

Diagnostic value of transesophageal echocardiography in platypnea.

Platypnea is a rare syndrome of orthostatic dyspnea frequently caused by an interatrial right-to-left shunt. The diagnosis is difficult. Assessment of arterial blood gases reveals orthostatic desaturation. In the past, definite diagnosis necessitated catheterization in the supine and upright position. Now transesophageal echocardiography on a tilt table combined with a peripheral venous contrast study provides correct diagnosis in a safe and easy way.

Aged↗
PubMedDate not supplied

Lung volume reduction surgery (LVRS) for emphysema: initial experience at the University Hospital Gasthuisberg. Leuven LVRS Group.

Emphysema is a disabling disease, for which there is no curative therapy available today. Lung transplantation offers a valuable option for a very selected number of patients, however, due to the enormous organ shortage, only few patients can be offered such a therapy. Recently there has been important resurgence of interest in lung volume reduction surgery and as a consequence, we have embarked in such a program since may 1997. We have now performed unilateral lung volume reduction surgery in 29 emphysema patients (25 on the right and 4 on the left side). Twenty-four patients were already discharged home. There has been no perioperative mortality. The mean hospital stay was 19.8 +/- 11.4 days (range, 8-47 d). Twenty patients of whom we already have follow-up data during 6 months (m) form the further basis of this report. Six weeks after the procedure the FEV1 increased from 0.82 +/- 0.28 L (28 +/- 8%) to 1.05 +/- 0.39 L, a mean increase of 28%. There was a further increase of the FEV1 to a maximum of 1.06 +/- 0.42 L at 6 m, a mean maximum increase of 29% (p = 0.0046, ANOVA). Similarly, the FVC increased from 2.80 +/- 1.10 L to 3.15 +/- 1.00 L, a mean increase of 12.5%. A further increase was also obtained at 6 m and was 19.6% (3.35 +/- 1.05 L, p = 0.014, ANOVA). The maximum decrease in RV was obtained at 3 m (from 5.91 +/- 1.37 L to 4.37 +/- 0.85 L (p = 0.0001, ANOVA), a mean decrease of 26%. The maximum TLC decrease was demonstrated at 3 m (from 8.71 +/- 1.71 L to 7.60 +/- 1.56 L (p = 0.002, ANOVA), a mean decrease of 12.8%. Afterwards there was again a gradual raise of the TLC. The six minute walking distance increased from 231 +/- 31 m to 272 +/- 34 m (p = NS) after pulmonary rehabilitation and to 416 +/- 77 m at 3 m and 415 +/- 18 m at 6 m (p = 0.0002, ANOVA) after the operation. The quality of life (measured with a standardized questionnaire, the Nottingham Health Profile) improved significantly in several domains (e.g. mobility, pain, energy, emotions and social) at 3 m postoperatively. There was one late death (at 6 m) due to an unknown cause. The actuarial survival rate was therefore 100% at 3 m and 95% at 12 m. In conclusion, unilateral thoracoscopic lung volume reduction surgery is a new and safe treatment modality for patients suffering from severe end-stage emphysema. The objective and subjective improvement is marked and the mortality is very low. Rigid selection criteria are, however, necessary to be able to guarantee an optimal result.

Actuarial Analysis↗
PubMedDate not supplied

Distribution of muscle weakness in patients with stable chronic obstructive pulmonary disease.

PURPOSE: The authors determined the degree of respiratory and peripheral muscle weakness in patients with moderate to severe chronic obstructive pulmonary disease (COPD). Differences in severity of muscle weakness among muscle groups may provide treatment options, such as selective muscle training, to adapt the exercise prescription in pulmonary rehabilitation programs. In addition, this information may add to the knowledge on the mechanisms of muscle weakness. METHODS: Respiratory and peripheral muscle force were quantified in 22 healthy elderly subjects and 40 consecutive COPD patients (forced expiratory volume in 1 second, percent of predicted value [% pred] 41 +/- 19; transfer factor for carbon monoxide, % pred 47 +/- 26) admitted to a pulmonary rehabilitation program. Lung function, diffusing capacity, isometric force of four peripheral muscle groups (handgrip, elbow flexion, shoulder abduction, and knee extension), neck flexion force, and maximal inspiratory and expiratory pressures were measured. RESULTS: Patients had reduced respiratory muscle strength (mean 64% of control subjects' value [% control]) and peripheral muscle strength (mean 75% control) compared to normal subjects. Inspiratory muscle strength (59 +/- 18% control) was significantly lower than expiratory muscle strength (69 +/- 25% control) and peripheral muscle strength (P < 0.01). Neck flexion force (80 +/- 19% control) was better preserved than maximal inspiratory pressure and shoulder abduction force (70 +/- 15% control, P < 0.01). Handgrip force (78 +/- 16% control) and elbow flexion force (78 +/- 14% control) were significantly less affected than shoulder abduction force (70 +/- 15% control, P < 0.01). Finally, shoulder abduction force and knee-extension force (72 +/- 24% control) were not significantly different. CONCLUSIONS: Muscle weakness in stable COPD patients does not affect all muscles to a similar extent. Inspiratory muscle force is affected more than peripheral muscle force, whereas proximal upper limb muscle strength was impaired more than distal upper limb muscle strength.

Aged↗
PubMedDate not supplied

Exercise training in COPD: how to distinguish responders from nonresponders.

PURPOSE: Pulmonary rehabilitation programs consistently have improved exercise capacity, quality of life, and symptoms over the past decade. Although training has been shown to be an essential component of the rehabilitation program, individual patients do not always benefit to the same extent. The present study was designed to investigate which patients were achieving significant benefit of exercise training. METHODS: Forty-nine stable outpatients with moderate to severe COPD (FEV1 37 (15)%pred) were evaluated before and after 12 weeks of exercise training (3 times per week). Responders in exercise capacity were defined as having 15% increase in maximal workload and/or 25% increase in walking distance, while responders in quality of life showed an improvement of at least 10 points on the chronic respiratory disease questionnaire. With multivariate discriminant analysis, responders were distinguished from nonresponders based upon their initial characteristics. RESULTS: Thirty-two patients were responders in terms of improved exercise capacity. Ventilatory reserve (VE/MVV), inspiratory muscle strength (Plmax), and peripheral muscle strength (handgrip force and quadriceps force) were significant predictors of the training response (P < 0.05) (accuracy 80% P < 0.001). Although the explained variance was modest, patients that were clearly ventilatory limited and had normal skeletal muscle strength were not likely to benefit from exercise training in terms of exercise capacity. No physiologic variables predicted whether a patient would increase quality of life after exercise training. CONCLUSION: Patients with reduced exercise capacity who experience less ventilatory limitation to exercise and more reduced respiratory and peripheral muscle strength are more likely to improve with exercise training. Improvements in quality of life after exercise training were significant but remained unpredictable with variables included in the present trial.

Aged↗