Dysanaptic growth of conducting airways after pneumonectomy assessed by CT scan.
In immature dogs after pneumonectomy (PNX), pulmonary viscous resistance is persistently elevated predominantly as a result of a high airway resistance (Raw). We examined the anatomical basis for this observation by using computerized tomography scans obtained from foxhounds 4-10 mo after right PNX. Airways of the left lower lobe were followed from generations z = 0 (trachea) to z = 12. By 4 mo post-PNX, airway length increased significantly relative to sham-operated dogs, but airway cross-sectional area (CSA) did not. By 10 mo post-PNX, average airway CSA was 24% above that in controls. Theoretically, the increased airway length and CSA should reduce lobar Raw by 50%. However, post-PNX airway dilatation did not normalize total CSA, and estimated resistance due to turbulence and convective acceleration increased threefold; i.e., the 50% reduction in lobar Raw would be offset by the loss of four of seven lobes. Thus the expected reduction in work of breathing in the whole animal is only ~30%, consistent with previously measured work of breathing in pneumonectomized dogs. We conclude that airway structure adapts slowly and incompletely, resulting in limited functional compensation.
Dane
D Merrill
DM
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9034, USA.
Johnson
Robert L
RL
Hsia
Connie C W
CC
D000403:Airway Resistance; D000818:Animals; D004285:Dogs; D008168:Lung / Q000000981:diagnostic imaging* / Q000254:growth & development*; D011013:Pneumonectomy; D011184:Postoperative Period; D011312:Pressure; D013902:Radiography, Thoracic; D014057:Tomography, X-Ray Computed; D014939:Work of Breathing