CAN PERIODIC BREATHING HAVE ADVANTAGES FOR OXYGENATION

A model of the chemoreceptor mediated control of breathing is analysed . Hypoxia is simulated as low equilibrium arterial oxygen both at alti tude and at sea level. Conditions for stable and unstable equilibria a re examined. Transition to instability leads to periodic breathing and the model predicts that this can cause arterial oxygen to oscillate a symmetrically about the equilibrium in some cases, causing the average to rise. Periodic forcing functions have been applied to cerebral blo od flow with the same effect on arterial oxygen. Such asymmetric oscil lations leading to enhanced oxygenation have been observed in pulse ox ymeter recordings from elderly postoperative patients. This may be imp ortant in interpreting studies of unstable breathing patterns and thei r possible relation to morbidity or mortality in infants (e.g. SIDS) a nd in the elderly (e.g. sleep apnoea, postoperative hypoxia). Periodic breathing could act as a protective adaptation to counteract pre-exis ting hypoxia.