CHEST WALL STIFFNESS IN PATIENTS WITH CHRONIC RESPIRATORY MUSCLE WEAKNESS

Publisher Website
Google Scholar
Abstract
Using the weighted spirometer technique, chest wall compliance (Cw) was studied in 16 nonobese patients with chronic weakness of the respiratory muscles and 20 healthy control subjects. To evaluate the validity of the technique, while Cw was being measured, thoracoabdominal configuration was monitored with 2 pairs of linearized magnetometers and electrical activity of the external oblique with a concentric needle electrode in 3 healthy subjects and 4 patients. In 3 subjects electrical activity from the intercostal muscles and diaphragm was also recorded throughout the procedure. The method was reproducible within 5.8% and provided Cw values that compared well with those yielded by the relaxation technique. In each subject, the weight-induced shifts in end-expiratory lung volume showed a very good linear correlation with the changes in transrespiratory pressure at end-expiration (r .gtoreq. 0.91). In none of the subjects tested did the electromyograms reveal any intercostal, diaphragmatic, or abdominal muscle activity at end-expiration, nor did the end-expiratory level ever show a significant departure from the relaxed thoracoabdominal configuration, thus suggesting adequate respiratory muscle relaxation. Reduction in inspiratory muscle force in the patients ranged from 17-94% of predicted (mean .+-. SE, 43 .+-. 6). Decrease in vital capacity, total lung capacity and functional residual capacity averaged 59, 34 and 15% of predicted, respectively. Patient and control groups showed a large interindividual variability regarding Cw. It varied from 0.117-0.258 l/cm H2O (mean .+-. SE, 0.162 .+-. 0.012) in patients and from 0.163-0.366 l/cm H2O (mean .+-. SE, 0.248 .+-. 0.013) in healthy subjects. Cw was below the control range in 12 of the 16 patients and the difference between the patient and control groups was significant (P < 0.001). The weighted spirometer technique allows accurate measurement of chest wall compliance. Chest wall stiffness develops in patients with long-standing respiratory muscle weakness.

This publication has 3 references indexed in Scilit: