Pulmonary capillaries are more resistant to stress failure in dog than rabbit. Mathieu-Costello, Odile, David. C. Willford, Zhenxing Fu, Richard M. Garden, and John B. West. Department of Medicine, University of California San Diego, La Jolla CA 92093-0623
APStracts 2:0204A, 1995.
We have previously shown that stress failure of pulmonary capillaries occurs at transmural pressures (Ptm) of about 50 cmH2O (40 mmHg) and above in rabbit lung. In the present study, we examined whether pulmonary capillaries are more resistant to failure in dog than rabbit. This might be expected because of the greater athletic ability of dogs and therefore their presumably greater tolerance to large cardiac outputs and higher pulmonary vascular pressures. We used a similar experiment procedure as in our previous study in rabbit. Twelve anesthetized mongrel dogs (22.1 +/- 5.2 (SD) kg) were divided in 4 groups of 3 animals each for in situ lung perfusion at Ptm of 32.5, 72.5, 92.5 and 112.5 cmH2O. The perfusion sequence was 1 min of autologous blood, followed by 5 min saline-dextran washout and then 10 min perfusion fixation with glutaraldehyde solution, all perfusions at the same preset Ptm. A few disruptions (< 1 to 5/mm) were seen at Ptms of 32.5 and 72.5 cmH2O. This contrasted with the group mean values of 27.8 +/- 8.6 (SE) endothelial breaks and 13.6 +/- 1.4 epithelial breaks/mm at Ptm of 72.5 cmH2O in rabbit. At Ptms of 92.5 and 112.5 cmH2O, the frequency of endothelial and epithelial disruptions increased in dog lung but it remained relatively small (group mean values < 10/mm) compared to rabbit, and there was a large variability between animals. We measured the thickness of the blood-gas barrier because this is pressumably an important factor in its strength. The thickness was significantly greater in dog than rabbit at 32.5 cmH2O. Unlike in rabbit, neither total nor interstitial thickness increased significantly with increasing pressure. The stress failure curves relating the number of breaks/mm epithelium and endothelium were right-shifted by about 40 cmH2O compared to rabbit. These results indicate that pulmonary capillaries are more resistant to stress failure in dog than rabbit. 

Received 11 November 1994; accepted in final form 4 May 1995.
APS Manuscript Number A1158-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.