Intraparenchymal canine airway segments with branches tied off were mounted between two fluid-filled cannulas in an organ chamber. Airways were inflated to successive volumes ranging from 4 to 100% of the segment volume at 25 cmH2O. At each volume, pressure was monitored during isovolumetric contractions elicited by 10-3 M acetylcholine. Small bronchi developed pressures > 30 cmH2O in response to acetylcholine at all volumes and were able to constrict to closure. Large bronchi developed pressures > 30 cmH2O only near maximal volumes and were able to constrict to only 30% of maximal volume. Maximal active pressures occurred at low volumes in small bronchi and at high volumes in large bronchi. However, maximal active circumferential tension and stress occurred at near-maximal volumes in both large and small bronchi. Circumferential length active-stress curves and maximal active-stress development for bronchi and trachealis muscle strips were similar. Similar length active-stress properties in different bronchi may produce significant differences in volume-pressure characteristics.
ASJC Scopus subject areas
- Physiology (medical)