FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM-79/10

Title and Subtitle: Effects of propranolol on time of useful function (TUF) in rats

Report Date: February 1979

Authors: Higgins EA, McKenzie JM, Funkhouser GE, Mullen SR

Abstract: To assess the effects of propranolol on tolerance to rapid decompression, a series of experiments was conducted measuring time of useful function (TUF) in rats exposed to a rapid decompression profile in an altitude chamber. In other experiments TUF was measured for rats exposed to an oxygen/nitrogen gas mixture which produced a hypoxic condition equivalent to that in the decompression experiments. The findings were:

1. Rats become less tolerant to hypoxia of an onset rate comparable to that of rapid decompression when given propranolol, and this intolerance is further exacerbated by an increase in physical exertion.
2. Younger animals are more susceptible to this type of hypoxia, but propranolol has no greater effect on hypoxia tolerance in younger animals.
3. None of the reduced tolerance can be attributed to a shift in the oxyhemoglobin dissociation curve.

In rats the curve is shifted slightly to the left, whereas in man there is a reported shift to the right. Because propranolol impairs tolerance to hypoxia in experimental animals, it is important to assess its effects on human tolerance.

Key Words: Propranolol, Altitude tolerance, Rapid decompression, Hypoxia

No. of Pages: 11