Pulmonary Edema and Upper Airway Obstruction

Abstract

To the Editor:We thank Masa-Jimenez et al for their interest in our article. We did not wish to imply that changes in lung volume were the only possible mechanism at work here. Since we did not measure lung volume at FRC, we can only speculate that this might have been increased. The fact that the diaphragms were not visibly flattened does not rule out the possibility that lung volume at FRC was increased, since this increase could have occurred by increasing rib cage volume rather than shortening and descent of the diaphragm.Regarding changes in pleural pressure swings, although it is true that maximum pleural pressure generated by performing a maximal inspiratory maneuver descreases as one approaches TLC, this does not imply that the negative swings in pleural pressure do not increase even with increasing FRC. During attacks of asthma in humans, maximum pleural pressure during inspiration decreases considerably, even though FRC increases.1Freedman S. Tattersfield A.E. Pride N.B. Changes in lung mechanics during asthma induced by exercise.J Appl Physiol. 1975; 38: 974-982Crossref PubMed Scopus (47) Google Scholar, 2Holmes D.W. Campbell A.H. Barter C.B. Acute changes of lung volumes and lung mechanics in asthma and in normal subjects.Thorax. 1978; 33: 394-400Crossref PubMed Scopus (26) Google Scholar We are unaware of any data that refute or confirm the hypothesis that there is a tendency for edema formation during asthma, and suggest that this issue be a subject for future investigation. To the Editor: We thank Masa-Jimenez et al for their interest in our article. We did not wish to imply that changes in lung volume were the only possible mechanism at work here. Since we did not measure lung volume at FRC, we can only speculate that this might have been increased. The fact that the diaphragms were not visibly flattened does not rule out the possibility that lung volume at FRC was increased, since this increase could have occurred by increasing rib cage volume rather than shortening and descent of the diaphragm. Regarding changes in pleural pressure swings, although it is true that maximum pleural pressure generated by performing a maximal inspiratory maneuver descreases as one approaches TLC, this does not imply that the negative swings in pleural pressure do not increase even with increasing FRC. During attacks of asthma in humans, maximum pleural pressure during inspiration decreases considerably, even though FRC increases.1Freedman S. Tattersfield A.E. Pride N.B. Changes in lung mechanics during asthma induced by exercise.J Appl Physiol. 1975; 38: 974-982Crossref PubMed Scopus (47) Google Scholar, 2Holmes D.W. Campbell A.H. Barter C.B. Acute changes of lung volumes and lung mechanics in asthma and in normal subjects.Thorax. 1978; 33: 394-400Crossref PubMed Scopus (26) Google Scholar We are unaware of any data that refute or confirm the hypothesis that there is a tendency for edema formation during asthma, and suggest that this issue be a subject for future investigation.