Some aspects of hyperventilation.

This thesis is concerned mainly with hyperventilation as it affects aircrew. A literature survey has been carried out on the causes and effects of hyperventilation and on its investigation and incidence in flight. Measurements of end tidal carbon dioxide tensions (PETCO2) were made during an anxiety-provoking experimental procedure. These measurements confirmed that anxiety can cause hyperventilation to such a level that the imposition of other stresses found in the flight environment could be expected to cause a performance decrement. Present methods for studying the incidence of hyperventilation in flight are unsatisfactory for various reasons. An attempt was made to develop a simple test for hyperventilation based on a rebreathing estimate of mixed venous carbon dioxide tension. However, examination of the results and a further examination of the basic physiology revealed that the procedure was unlikely to be fruitful. Further experiments were carried out to study the effects of hyperventilation on various respiratory variables and on the time course of the subsequent recovery. It was found that the carbon dioxide cost of hyperventilation was more than that found by other investigators, although estimates of other respiratory variables agreed with those found by further authors in similar circumstances; the possible reasons for this are discussed. Studies of psychomotor performance carried out at the same time failed to demonstrate a consistent decrement in performance with hypocapnia. Further experiments were carried out which suggest that the previously reported decrements in psychomotor performance during hypocapnia are related more to decrements in motor performance than to decrements in intellectual performance. Finally, suggestions are made for further work to be carried out in the same field