Influence of Lung Inflation on the Cross-Sectional Area of Central Airways in Normals and in Patients with Lung Disease

Abstract

The influence of lung inflation on the cross-sectional area of the trachea and main bronchi was investigated in 2 normal subjects, 2 patients with emphysema, and 1 patient with pulmonary fibrosis. Fiberoptic cinebronchoscopy was used to measure the cross-sectional area of the airways using calibrated small Teflon discs placed on the airway wall as reference. As an estimate of airway compliance at intermediate lung volumes, radial distensibility was defined as the change in cross-sectional area per change in airway pressure minus esophageal pressure divided by the cross-sectional area at functional residual capacity. Both in normal subjects and in patients with emphysema, the radial distensibility was larger in the trachea than in the main bronchi without differences between the right and left main bronchus. The area-pressure curves revealed alinearity and hysteresis in both groups with an increased distensibility in pulmonary emphysema. In a patient with pulmonary fibrosis, the distensibility was decreased by a factor of ten and the area-pressure curve was linear. These observations suggest altered static mechanics of extraparenchymal, intrathoracic airways in patients with pulmonary emphysema and fibrosis.

Tracheal distensibility in cystic fibrosis

“…An increase in tracheal CSA was found only in patients with CF. This is unexpected and in contrast to previous studies with the acoustic reflection technique [19], CT scan [20], or fibreoptic cinebronchoscopy [21]. Using the CT scan, DOLYNIUK and FAHEY [20] observed on average a 16% increase in extrathoracic (as well as in intrathoracic) tracheal area between FRC and TLC.…”

Physiology of the lung in idiopathic pulmonary fibrosis

“…Interestingly, airway volume was higher in IPF than in controls and non-IPF ILDs, suggesting that increased airway volume may be somewhat IPF-specific [69]. Anecdotal evidence indicates reduced distensibility of the proximal airways in IPF, although it is not clear whether this is related to either reduced compliance of the airway wall or to changes in airway transmural pressure due to increased lung recoil [85].…”

Nonlinear mechanical property of tracheal cartilage: A theoretical and experimental study

“…Changes in the mechanical properties of the trachea may contribute to altered lung function in obstructive lung diseases. For example, weakening of the wall structures of large airways has been found in chronic obstructive pulmonary disease (Baier et al, 1981), and altered cartilage geometry and elasticity appear to play a role in tracheomalacia (Lomasney et al, 1989;Newth et al, 1990;Baroni et al, 2005;Murgu and Colt, 2006). In these diseases, tracheal collapse is often observed with the flexible tracheal cartilage changing its curvature and the mucosal membrane dropping into the cavity causing obstruction.…”