The perfused human bronchiolar tube characteristics of a new model

Strips or rings of airway tissue are often used to study contractile responses of human airways in vitro. These preparations have the disadvantage that it is impossible to deliver stimuli selectively to the mucosal or serosal surface. Hence, they allow only for a limited evaluation of the modulatory role of the airway epithelium. We developed an in vitro model that allows independent stimulation from either the serosal or the mucosal side of human peripheral airways. Segments of human peripheral airways were perfused with a Krebs solution at a constant pressure, and responsiveness was measured as a change in flow rate. Pressure/flow relationships indicated laminar flow over a wide pressure range, and a working pressure of 6 cm H2O was chosen because this is a physiological transpulmonary pressure. When stepwise stretching the airway to 180% of its length, we noted an increase in baseline flow and a decrease in flow reduction after methacholine 10(-5) M. At 140% of the length, accurate and reproducible measurements of the sensitivity (EC50) to methacholine were obtained, and airway closure did not occur. A one-way analysis of variance (ANOVA) revealed that the between-patients differences accounted for 91% of the total variability for -log EC50. We conclude that this in vitro model offers interesting possibilities for evaluating the modulatory effects of the human airway epithelium. In addition, the model provides the opportunity to study human small-airway mechanical properties and secretory functions.