Episodes of hypoxia, hyperoxia, asphyxia or a combination of them are assumed to play a pathogenetic role in necrotizing enterocolitis. We attempted to isolate a variable by observing the histological changes in the intestine after exposure to repetitive hypoxia or asphyxia in the developing chick embryo incubated under normoxia or hyperoxia conditions. We incubated 31 fertile eggs in 21% O2 and divided in control group 1 (n=8), test group 1A (n=10) exposed to acute hypoxia (100% N2), and test group 1B (n=13) exposed to asphyxia by occluding the chorioallantoic vein. Another group(n=39) was incubated in 60% O2 and divided to control group 2 (n=7), test group 2A (n=22) exposed to hypoxia and test group 2B exposed to asphyxia(n=10). Duration of hypoxia and asphyxia was 5 minutes and repeated six times with a recovery period of 15 minutes in chick embryos from day 11 until day 20. Chick embryos were removed from there eggs 24 hours post-intervention, immediatly after decapitation the intestine was dissected and fixed in 10% formaline for histological examination. At light-microscopy histological changes in the mucosa, muscle and vessel were described.

Percentages of necrosis or vasodilatation in chick embryos incubated at 21% O2 or 60% O2 exposed to hypoxia or asphyxia (see table).

Table 1
Full size table

Conclusion: At both incubation conditions asphyxia caused more severe necrosis than hypoxia. However, hypoxia produced necrosis when combined with hyperoxia.