The Effects of a Combination of Hypoxia and Positive Pressure Breathing on an Indicator of Aircrew Operational Effectiveness

In the event of rapid decompression to altitudes in excess of 40,000 feet, 100% oxygen must be supplied to aircrew at a positive pressure in order to prevent hypoxia. However, positive pressure breathing (PPB) with an oronasal mask represents a considerable physical stress in itself.
The aim of the present study was to examine the effects of a combination of a given level of normobaric hypoxia (PIO2=67 mmHg) and/or PPB (45 mmHg) on the performance of eight male subjects (22 to 34 years old) using an indicator of
operational effectiveness (NASA Multi-Attribute Task Battery).
Two types of lower body counter-pressure protection were applied (standard and full coverage anti-G trousers) in conjunction with a range of pressure ratios established between anti-G trousers and chest counter-pressure garment (1:1 for standard coverage, and 1:1, 1.5:1 and 3:1 for full coverage).
PPB at 45 mmHg was found to represent a considerable distraction, in particular to subjects’ hand-eye co-ordination (p<0.05). Hypoxia was also found to impair performance (p<0.05), and the effects of hypoxia and PPB appeared to be additive on one aspect of the task.