Shape and regional volume in immersed lung lobes.
We froze 10 isolated canine lower lobes by immersing them in chlorothene (sp gr 1.4) at -20 degrees C. In six instances the contralateral lower lobe was frozen over dry ice. The lobes were then sliced horizontally, and the volume and weight of each slice were measured so that expansion (specific volume) and the amount of tissue (weight) could be assessed as a function of distance down the lung. Lobes frozen under chlorothene at low [35% total lung capacity (TLC)] and medium [60% TLC] volumes demonstrated a gradient of regional expansion that was about half that predicted on the basis of pleural surface pressure. Lobes frozen under chlorothene at high volumes [80% TLC] did not demonstrate a significant gradient of regional expansion. These results demonstrated tissue interdependence. When lobes frozen under chlorothene were compared with contralateral lobes frozen over dry ice, substantial differences in shape were evident. Chlorothene-frozen lobes had greater vertical height, and a smaller fraction of their weight was present in dependent regions: lobes frozen in chlorothene had half as much tissue over the lower 40% of their vertical height as did lobes frozen over dry ice. We demonstrated two mechanisms by which relative homogeneity of regional expansion was maintained in response to differences in pleural pressure, tissue interdependence and tissue movement from more compressed to less compressed regions.
D000399:Air Pressure; D000818:Animals; D004285:Dogs; D007101:Immersion; D008168:Lung / Q000033:anatomy & histology / Q000502:physiology*; D008176:Lung Volume Measurements; D009929:Organ Size; D014109:Total Lung Capacity