Bronchiolitis obliterans. A new form of rheumatoid lung?

I appreciate the comments of van Veenen et al. Data concerning comparison of pulmonary compliance and effective compliance in the patient receiving mechanical ventilation are needed. Good correlation between these measurements in patients with low compliance documents the simpler estimate of effective compliance as a useful monitoring tool in the patient who is receiving mechanical ventilation and has low compliance. Effective pulmonary compliance is altered by the state of relaxation of the patient and by characteristics of the chest wall and should be used only as an approximation of pulmonary compliance. Serial determination of either measurement does reflect alteration in mechanics of the respfratory system. Thus, changes in compliance in the patient with high compliance should be useful even though absolute values correlate poorly. It is sometimes difficult to keep an esophageal catheter in the patient with respiratory failure for long periods of time because of the need for nasogastric feeding and the concern about mechanical initation of the esophagus. We have recently used central venous fluctuations with respiration as an estimate of pleural pressure in patients with a thermodilution Swan-Canz catheter in place. The approximations of pleural pressure from the esophageal balloon and central venous line have correlated closely. We have made preliminary observations of the correlation between pulmonary compliance and effective compliance before and after production of noncardiogenic and cardiogemc pulmonary edema,1 pneumothorax,2 and mucous plugging and atelectasis3 in cxperimental animals. In our studies, changes in effective compliance correlated well with changes in pulmonary compliance. Roger C. Bone, M.D., F.C.C.P. Associate Professor of Medicine University of Arkansas Medical Center, Little Rock