Effect of the chest wall and blood volume on pulmonary distensibility.

To determine the reason for increased pulmonary distensibility in excised lungs, we performed deflation pressure-volume (PV) studies in 24 dogs. Exponential analysis of PV data gave K, an index of distensibility. Lung volume was measured by dilution of neon. Compared with measurements obtained in the supine position, with the chest closed, and with esophageal pressure (Pes) to obtain transpulmonary pressure, K was not changed significantly with the chest strapped, with pleural pressure to obtain transpulmonary pressure, or with the chest open. From displacement of PV curves obtained in the supine position and with the chest closed or open, we estimated that Pes was 0.18 kPa greater than average lung surface pressure. An increase in K in the prone and head-up positions was attributed to a traction artifact decreasing Pes. Exsanguination increased K and produced a relative increase in gas volume. These results show that overall pulmonary distensibility is unaffected by an intact chest wall. An increase in K and gas volume after exsanguination probably reflects a decreased pulmonary blood volume, with collapse of capillaries increasing the alveolar volume-to-surface ratio.

Characterisation of human lung elastin-derived peptides.

The enzymatic breakdown of human lung elastin by leukocyte elastase precedes the development of pulmonary emphysema, and releases elastin-derived peptides (EDPs) into the circulation. While raised levels of EDPs measured by enzyme-linked immunosorbent assay (ELISA) have been proposed as a possible marker for early detection of emphysema, average normal values of EDPs measured by different investigators have differed by up to a factor of 1000. Standardisation of the methodology for elastin purification and EDP production in vitro is required to ensure the accuracy of EDP measurements in vivo, because antiserum used in the ELISA is raised against the EDPs produced in vitro. In the present study elastin was purified from human lung by sequential biochemical extraction, and solubilised by leukocyte elastase. Molecular weight distribution of EDPs produced by partial and complete elastin digestion were compared by gel exclusion chromatography. A method for successful separation of EDPs by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) is reported. The implications of these results for further immunological characterisation of these peptides are discussed with a view to standardisation of the techniques employed for the measurement of EDPs in vivo.

Lung volume and distensibility in insulin-dependent diabetes mellitus.

The effect of insulin-dependent diabetes mellitus on pulmonary function was studied in 22 diabetic nonsmokers (11 men) with a mean age of 40 yr (SE, 4 yr) and no history of cardiorespiratory disease. Exponential analysis of static pressure-volume data obtained during deflation of the lungs gave the exponent K, an index of pulmonary distensibility. In the diabetic subjects, mean values for total lung capacity, functional residual capacity, VC, and FEV1 were similar to predicted values. Diffusing capacity, K, and in K did not differ significantly from corresponding values in healthy subjects. The regression of in K on age was significant (R = 0.52; p less than 0.01) and similar to that obtained for 124 healthy subjects. The findings show that insulin-dependent diabetes mellitus does not affect pulmonary function. This study does not support the routine testing of lung function in otherwise well diabetic nonsmokers.

Management of fibrosing alveolitis with polymyositis dermatomyositis.

A 38-year-old man with polymyositis-dermatomyositis developed acute life-threatening fibrosing alveolitis. We report a two year follow-up of this patient, during which control of alveolitis was obtained using prednisolone, and was maintained with the addition of cyclophosphamide. Relapse of myositis responded to increased prednisolone. Serial measurements of vital capacity and transfer factor assisted management of alveolitis, but changes in vital capacity preceded changes in transfer factor, and were more convenient to perform during frequent outpatient review.

Inspiratory gas flow induced by cardiac systole.

This study was made to quantify the inspiratory gas flow pulse produced by cardiac systole. Ten adults (9 men, 1 woman; age 24-65 yr) were studied, of whom two had respiratory muscle weakness. The inspiratory flow pulse commenced 50-60 msec after the R wave of the ECG and lasted 106 (SD22) msec. In eight subjects seated and breathing through a mouthpiece, the flow pulse reached a peak of 120 (SD 58) ml sec-1 and displaced a volume of 6.6 (SD 2.3) ml (range 3.6-9.9 ml). Similar results were obtained using a nasal mask. By adding an external airway resistance, the effective intrathoracic pressure responsible for inspiratory flow was estimated to be -0.21 (SD 0.03) cm H2O. Duplicate studies showed little variation in pulse volume. The mechanism of the inspiratory gas flow pulse and its contribution to gas exchange is discussed.