Human Respiratory Responses during High Performance Flight

Abstract : The respiratory responses of experienced military pilots have been studied during flight in a high performance jet aircraft. The importance and relevance of information about these responses have been reviewed, with particular emphasis in the difficulties of in-flight recording and the history of such experimentation in four specific areas of respiratory physiology: respiratory frequency and flow, added external resistance, hyperventilation and the metabolic cost of flying. In the present study, respiratory variables were measured continuously using an airborne system which recorded the output from physiological and aircraft instrumentation. In order to approach normal respiratory behaviour more closely, a specially designed low resistance breathing system was developed and used in conjunction with a modified infra-red carbon dioxide analyser. A unique feature of the latter, also specially developed, was the ability to calibrate the device during flight. Inspiratory flows (and hence volumes) and expired carbon dioxide tensions were recorded on several occasions in place of carbon dioxide analysis. Three set flight profiles (two general handling and one simulated combat) were precisely defined to allow comparability between subjects. A fourth, less structured but high workload sortie, involving air combat maneuvering (ACM), was flown on two occasions.