Thorax, 1977, 32, 749-751
Incidence of decompression-induced pulmonary haemorrhage in young and old rats H. S. FANG AND B. F. GUO From the Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan, China
Fang, H. S. and Guo, B. F. (1977). Thorax, 32, 749-751. Incidence of decompression-induced pulmonary haemorrhage in young and old rats. Seventeen young rats (40-52 days of age) and 17 old rats (545-702 days of age) were decompressed from one atmospheric pressure to an ambient pressure of 30 mmHg in 0-25 second. It was found that 11 of 34 young lungs (32%) and 23 of 34 old lungs (68%) showed decompression-induced pulmonary haemorrhage. The difference was statistically significant. The pulmonary haemorrhage of the old rats was markedly more severe than that of the young rats. It is generally accepted that the delicate structure decompression. The decompression rate was of the pulmonary tissue is potentially the most measured by means of a Statham model PM6+4 vulnerable part of the body during a rapid decom- 15-350 pressure transducer through a Grass polypression. In our previous studies evidence has been graph. The time needed for rapid decompression presented that the frequency of occurrence and from 760 mmHg to 30 mmHg, corresponding to a the severity of decompression-induced pulmonary simulated altitude from ground level to 72 000 feet, haemorrhage could be influenced by binding of was 025 second. In each experiment, a pair of the body (Fang, 1966), bilateral cervical vagotomy, rats, one young and one old, were decompressed occlusion of carotid arteries and intravenous ad- together. In order to avoid post-decompression ministration of epinephrine (Fang and Tang, 1972), hypoxia acting as a complicating factor, all rats prolonged starvation (Fang and Lin, 1972) or semi- were recompressed after decompression. The rats starvation (Lin and Fang, 1973), hypothalamic were killed and necropsy was carried out within a obesity (Liu and Fang, 1975), long-term inter- few minutes after recompression. The lungs were mittent exposure to hypoxia (Fang and Chen, then carefully examined for gross evidence of 1976a), and previous repeated decompressions haemorrhage. The severity of decompression(Fang and Chen, 1976b). So far as we are aware, induced pulmonary haemorrhage was graded acno study has ever been reported concerning the in- cording to the following scale: 0 no haemorrhage; fluence of age on the incidence of decompression- + slight haemorrhage (a few petechial haemorinduced pulmonary haemorrhage. The present rhages); + + moderate haemorrhage (haemorwork was done for this purpose. rhagic area was less than 25% of the lungs); and + + + severe haemorrhage (haemorrhagic Methods area was 25-50% of the lungs).
Seventeen young rats (40-52 days of age) and 17 Results old rats (545-702 days of age) were used for these experiments. All rats (Sprague Dawley strain) were The frequency of occurrence and the severity of unanaesthetised. Rapid decompression was accom- pulmonary haemorrhage in both young and old plished by the rupture of a sheet of exposed x-ray rats subjected to a single rapid decompression are film separating a small animal chamber at one indicated in the Table. It will be noted that only atmospheric pressure and a large vacuum chamber, 11 of 34 young lungs (32%) revealed lung damage using the method described previously (Fang, varying from slight to moderate haemorrhage. No 1966). The small animal chamber was kept open severe pulmonary haemorrhage was found in such to room air until immediately before the rapid young rats. In the old rats, however, lung damage 749
H. S.
750
Fang and B. F. Guo
Table Pulmonary haemorrhage in young and old rats after a single rapid decompression from one atmospheric pressure to an ambient pressure of 30 mmHg in 0 25 second Old rats
Young rats
Pulmonary
Pulmonary haemorrhage* Rat no.
Sex
M M M M F F F F F M M M F F M M M
Age (days)
51 51 40 40 51 51 51 51 52 52 52 23 50 25 51 27 51 29 50 31 50 33 50 Average 50 Total lungs showing haemorrhage I 3 5 7 9 11 13 15 17 19 21
Body weight (g)
76 79 70 66 67 46 67 75 72 118 115 72 79 44 79 93 71 77
Rt lung
Lt lung
0 0 + 0 0 0 0 0 + + 0 + 0 0 + 0 +
0 0 + + 0 0 0 0 ++ 0 0 + 0 0 + 0 0
lit
haemorrhage*
Rat no.
2 4
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34
Sex
M M M M F F F F F F M M F F M M M
Age (days) 605
605 605 605 545 545 545 605 557 557 702 702 702 702 702 702
646 625 Total lungs showing haemorrhage
Body weight (g) 433 431 434 399 282 264 298 236 300 286 452 435 240 229 455 415 415 353
Rt
Lt
lung
lung
+ + + +++ + + 0 +++ ++ ++
++ + +++ 0 0 0
+++ + 0 + 0 +++ 0 0
+++ ++ ++ ++ ++ 0 0 0 ++ + + +
23t
*0 No haemorrhage. + Slight haemorrhage. + + Moderate haemorrhage. + + + Severe haemorrhage.
tP