Surrounding Structures Affect Pressure-diameter Behavior of Excised Dog Bronchi

The effects of adjacent large blood vessels, fibroelastic membrane, and parenchyma on pressure-diameter （P-D） behavior of intrapulmonary bronchi, and the peribronchial pressure （Px） were studied in five dog lung lobes. All branches from the main lobar bronchus were blocked with beads and the lobe was inflated. After bronchial P-D curves were obtained at fixed pleural pressures （Ppl） of -30, -10 and -5 cmH2O, the bronchi were dissected and P-D properties measured under four conditions: （1） Lobar artery and vein remained attached to the bronchus and parenchyma remained with 1-2 mm thick; （2） all remaining parenchyma was carefully removed, leaving the large vessels attached to the bronchus; （3） the large vessels were removed, leaving only the bronchial fibroelastic membrane intact; （4） the fibroelastic membrane was peeled from the bronchus. In condition （1）, it was estimated that the peak Px averaged -29.2 cmH2O at Ppl=-30 cmH2O. In condition （2）, the peak Px declined by 5%. The major decrease in the peak Px （about 35%） occurred in condition （3）, indicating that interdependence between vessels and bronchi contributed significantly to bronchial stiffness, a final decrease of 10% in the peak Px was seen in condition （4）. Px in （1） was therefore estimated to be similar to Ppl at a transpulmonary pressure of 30 cmH2O, and may provide a better basis for estimating bronchial mechanics than the commonly employed bronchus free method.departmental bulletin pape