How is maximal expiratory flow reduced in canine postpneumonectomy lung growth?
Six dogs underwent left pneumonectomy (P) at 10 wk of age, while four littermates had a sham operation (C). All dogs were studied at 26 wk of age. Pressure capsules were placed on the right lung to measure lobar alveolar pressures and flows, and a Pitot-static tube was used to measure dynamic intrabronchial pressures. Vital capacity and lung elastic recoil did not differ between P and C. At all lung volumes studied, maximum expiratory flows (Vmax) in P were substantially lower than in C. Choke points in P were located more peripherally than in C. In central airways subjected to the same distending pressure, calculated cross-sectional area was significantly lower in P than in C, indicating different bronchial area-pressure behavior. In P, frictional resistances of the right lower, middle, and cardiac lobes were significantly higher than those in C. These results indicate that the reduction in Vmax in P was greater than would have been expected on the basis of reductions in central airway diameter alone. We calculated that, in the middle vital capacity range, approximately 60% of the decrease in Vmax was due to changes in dynamic central airways properties, and approximately 40% was due to increased lobar frictional resistance related to compensatory growth.
Georgopoulos
D
D
Department of Medicine, University of Manitoba, Winnipeg, Canada.
Mink
S N
SN
Oppenheimer
L
L
Anthonisen
N R
NR
D000403:Airway Resistance / Q000502:physiology; D000818:Animals; D001980:Bronchi / Q000502:physiology; D004285:Dogs; D008168:Lung / Q000254:growth & development / Q000502:physiology*; D008170:Lung Compliance / Q000502:physiology; D008176:Lung Volume Measurements; D008448:Maximal Expiratory Flow Rate; D010991:Plethysmography; D011013:Pneumonectomy; D011650:Pulmonary Alveoli / Q000502:physiology