Hypoxia and SIDS

February 2, 1997

In the hypoxia theory of SIDS, is it thought to be one episode of hypoxia that is the cause of death or is it a constant reoccurrence of the situation that is doing accumulative damage? If someone is hypoxic and you provide oxygen, doesn't everything go back to normal or does it have a cumulative effect?

The presumption is that it is multiple (?chronic) low-grade hypoxia (breathing low oxygen levels). If it were more severe degrees of oxygen deprivation, or more acute, then there would be visible evidence of the problem and we know from all the parent reports that there is no visible evidence of low oxygen levels at any time between discharge from the newborn nursery and the day of death.

Although oxygen levels below the normal range appear to be much more important than increased carbon dioxide levels as related to breathing and to arousal from sleep, situations in the home causing lower oxygen levels in the air being breathed also typically would cause higher carbon dioxide levels. This is the basis of the "rebreathing" theory in regard to the hazard of prone sleeping and the apparent hazard of soft bedding even if sleeping on the back (such as a quilt).

I hope this is helpful.

Carl E. Hunt, M.D.
Toledo/Washington D.C.