Surrounding structures affect pressure-diameter behavior of excised dog bronchi

Abstract

The effects of adjacent large blood vessels, fibroelastic membrane, and parenchyma on pressure-diameter (P-D) behavior of intrapulmonary bronchi were studied in five dog lung lobes. Central lobar airways were inflated separately by blocking all branches with beads and inflating the distal lobar air spaces via pleural capsules. After bronchial P-D curves were obtained at fixed pleural pressures (Ppl) of -30, -10, and -5 cmH2O, the P-D properties of the isolated bronchi were measured in each of four stages of dissection: 1) lobar artery and vein were left attached to the bronchus, but parenchyma was removed to within 1-2 mm of the limiting membranes; 2) all remaining parenchyma was carefully removed; 3) the large vessels were removed, leaving the bronchial fibroelastic membrane intact; and 4) the fibroelastic membrane was peeled from the bronchus. From stage 1 it was deduced that in the intact lobes, peak peribronchial parenchymal stress (Px) averaged -29.2 cmH2O at Ppl = -30 cmH2O). In stage 2 bronchial recoil was reduced only approximately 5%. The major decrease (approximately 35%) occurred in stage 3, indicating that interaction between vessels and bronchi contributed significantly to bronchial stiffness. A final decrease of approximately 10% was seen in stage 4. We conclude that Px in the intact state is similar to Ppl at a transpulmonary pressure of 30 cmH2O and that stages 1 or 2 may provide a better basis for estimating Px than the commonly employed bronchus free of vessels and tissue.

Dynamics of Respiration during Rapid Rate Mechanical Ventilation in Anesthetized and Paralyzed Rabbits

“…Dynamic distention of the airways is limited by bronchomotor tone and by the passive properties of the airway wall and the surrounding parenchymal structures (28,29). During early development bronchomotor tone is decreased and the lung parenchyma is relatively underdeveloped.…”

Interdependence of flow between lobes reduces maximal emptying postresection in dogs

“…The magnitude of peribronchial pressure has been investigated in various studies and has been found to approximate lung recoil pressure. Nakamura et al (16,17) deduced that in intact lobes, peak peribronchial parenchymal stress averaged Ϫ29 cmH 2 O at total lung capacity. Because bronchial transmural pressure of intraparenchymal airways is determined by peribronchial interstitial pressure, the loss of parenchymal attachments would have a significant effect on bronchial cross section during forced deflation.…”

“…In the lung, the visceral pleura is reflected from the parenchyma onto the lobar bronchi, and this reflection extends upward onto the central airways. It has been shown that a negative interstitial or peribronchial pressure develops between the parenchyma and the lobar bronchus, and this negative interstitial pressure is determined by the degree of parenchymal inflation (16,17,20,21,23). When lobes are removed, it is possible that peribronchial pressure (i.e., pressure between reflected pleura and central airways) may also become less negative during the forced expiratory maneuver compared with the intact lung.…”