[A comparative study of pulmonary elasticity and diffusion through the alveolocapillary membrane in major...

We studied 60 patients with collagen-vascular diseases with pulmonary manifestations (SLE-25; SSc-13; mixed connective tissue disease-12; RA-6; PD-DM-3; ankylosing spondylitis-1), 54 females and 6 males, mean age 42.4 +/- 9.9 years. We measured lung volumes (total lung capacity-TLC) by spirography (Flowscreen Jaeger) and body plethysmography (Bodyplethismograph Jaeger); compliance of the lungs (CL) and elastic recoil pressures at 100%, 80% and 70% TLC (PL,el 100%, 80%, 70% TLC) by the esophageal catheter method; diffusing capacity of the lungs by the single-breath method (DL,COSB) (Alveo-Diffusionstest Jaeger). DL,CO was diminished in 45 (75%) of cases. 11 patients (18.3%) had an increased elastic recoil, equally distributed between mild and severe decrease of DL,CO. Statistical significant correlations were found between TLC-DL,CO (r = 0.63; p < 0.001) and TL-CL (r = 0.49; p < 0.001). No correlations were found between DL,CO and PL,el 100, 80, 70% TLC. The results are expressed as percent of predicted value (% pred.). The mean values and standard deviation (X +/- sd) were calculated.

I) DL,CO is the most frequent altered pulmonary function test in collagen-vascular diseases with pulmonary manifestations; it seems to be a sensible parameter for diagnosing these diseases. 2) The alteration of DL,CO,CL and PL,el appears to be rather as a result of "shrinking lungs" due to respiratory muscle involvement than to an interstitial lung disease. 3) Elastic recoil pressures and compliance should be considered as routine pulmonary function test, important for the evaluation of treatment and prognosis.