Journal of Applied Physiology, Vol 49, Issue 1 52-58, Copyright © 1980 by American Physiological Society
Ventilatory response to transient hyperoxia in head injury hyperventilation
A. G. Leitch, J. E. McLennan, S. Balkenhol, R. L. McLaurin and R. G. Loudon
We have measured breath-by-breath instantaneous minute ventilation (VIinst)
before, during, and after the administration of 10 breaths of 100% oxygen
to seven male patients with head injury hyperventilation. The patients were
hypoxemic (PaO2 61.2 +/- 6.3) and hypocapnic (PaCO2 26.6 +/- 5.9) with a
respiratory alkalosis (pH 7.53 +/- 0.06) while breathing air. Following the
oxygen VIinst fell on the average by 40 +/- 12.7% from 16.06 +/- 3.75
1.min-1 to a minimum of 9.73 +/- 3.20 1.min-1 at 20.4 +/- 2.9 s after the
first breath of oxygen. In the majority of our hyperventilating patients,
almost all of the resting hyperventilation could be abolished transiently
by 100% oxygen. This fall in ventilation represents the peripheral
chemoreceptor contribution to resting ventilation and is increased in the
head injury patients in comparison with normal subjects breathing air or
hypoxic gas mixtures, altitude-acclimatized subjects and patients who are
hypoxic because of chronic bronchitis or interstitial lung disease. We
suggest that the increased reflex hypoxic drive to ventilation found in our
patients is secondary to their cerebral injury, resulting in a reduction of
descending cortical inhibitory influences on the medullary respiratory
control centers.
