Inhaled drug consumption and asthma mortality in Greece.
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Administration, Inhalation↗
Biomedical subjects
C G Melissinos
Publications and source records attributed to C G Melissinos.
Chest wall shape during forced expiratory maneuvers.
Abdominothoracic shape during the forced vital capacity was studied in 10 normal subjects using magnetometers to monitor anteroposterior diameters at the level of the manubrium, xiphoid, and epigastrium, lateral rib cage diameter at the xiphoid level, and vertical motion of the rib cage. Thoracic cross-sectional area change at the xiphoid level was found to lag lung volume change, due to an early paradoxical increase (or lack of change), of lower anteroposterior rib cage diameter. To the extent that the resulting rib cage deformation can influence the pleural pressure gradient, the observed shape changes provide a potential mechanism for early preferential emptying of the upper lobes and later more homogeneous emptying in forced, compared to slow, vital capacity maneuvers. Comparisons of shape changes during Valsalva and abdominal expiratory ("expulsive") maneuvers suggest that lower rib cage deformation may not simply be due to the action of rib cage muscles affecting predominantly the lateral rib cage but rather the results of diaphragmatic activity and the influence of abdominal shape on the lower rib cage.
Adult↗
Pattern of diaphragmatic activity during forced expiratory vital capacity.
We measured transdiaphragmatic pressure (Pdi) during forced expiratory vital capacity (FVC) maneuvers in 13 normal subjects and electromyographic activity of the diaphragm (edi) in 8 of these subjects. In all subjects, Pdi increased at the initiation of the FVC. In most, this increase lasted 30--50 ms and reached levels well above the Pdi observed at total lung capacity (TLC). After the initial transient increase, approximately half of the subjects demonstrated a substantial fall in Pdi to values near the relaxation level in the mid-vital capacity (VC) volume range, while half showed a second large increase in Pdi in this volume range. Seven of eight subjects tested showed a rapid decrease in Edi at the onset of the FVC, reaching a minimum in 30--50 ms. After this initial transient decrease, Edi increased in six subjects in the mid-VC volume range, in association with secondary rises in Pdi. In two subjects, Edi remained low throughout the remainder of the FVC, and Pdi in the mid VC range was generally lower. These results are consistent with the conclusion that the diaphragm is neither electromyographically silent nor mechanically unimportant during the FVC. Changes in abdominothoracic configuration, superimposed upon "antagonistic" activity of the diaphragm, result in substantial reductions in pleural (esophageal) pressure that may influence regional lung emptying during the FVC.
Abdominal Muscles↗
Time dependence of maximum flow as an index of nonuniform emptying.
Nonhomogeneous lungs are predicted to exhibit time dependence of maximal expiratory flow (Vmax): faster regions would contribute more flow early in the expiration, whatever the initial volume, resulting in different Vmax at a given total lung volume, depending on how long flow limitation has been operating. To test this concept a new technique was developed that permits accurate superimposition of Vmax data over small volume intervals. When quick-release interrupted partial curves with similar volume history but different volume of initiation were compared over their late common-volume segments, the volume-history effects could be differentiated from time dependence of the Vmax. Such time dependence was found in 7 of 7 bronchitics, 3 of 5 smokers, and 0 of 14 nonsmokers tested. We conclude that the emptying during the forced expirations is not uniform even in mild disease states and the time dependence of Vmax is a sensitive test of lung inhomogeneity.
Adult↗
Maximum expiratory flow changes induced by longitudinal tension on trachea in normal subjects.
Maximal expiratory flow (Vmax) was noticed to increase in some subjects during neck hypertension. Maximal expiratory flow volume (MEFV) curves were obtained in 15 normal young subjects at regular and hyperextended neck posture. Eleven of the subjects had consistently higher Vmax during neck hyperextension at high lung volumes, accompanied by MEFV configuration changes in the form of the obliteration of a concavity towards the volume axis that existed in the curve at regular neck posture. Effort independency was documented at lung volumes where the changes occurred. Radiographic studies indicate tracheal elongation with a relatively fixed carina during neck hyperextension. We propose that at high lung volumes in normal young subjects, the flow-limiting mechanism resides in the trachea and that the increased Vmax with neck hyperextension. We propose that at high lung volumes in normal young subjects, the flow-limiting mechanism resides in the trachea and that the increased Vmax with neck hyperextension reflects the effect of tracheal elongation which stiffens the trachea under dynamic conditions and increases its tube-wave speed. This concept was confirmed by MEFV curves obtained from anesthetized tracheostomized dogs when increased tracheal longitudinal tension resulted in an increase of Vmax.
Adult↗