Efficiency at Sorting Cards in Air and a 20 Per Cent Oxygen-Helium Mixture at Depths Down to 100 Feet and in Enriched Air

Abstract

Eighty men sorted packs of cards twice, once at the surface, and once at a depth of 33 or 100 ft (2 ats or 4 ats abs) or at the surface, breathing the equivalent partial pressure of oxygen at these depths. The gases breathed were air and 20 per cent oxygen in helium. Significantly more errors were made at a depth of 100 ft in air than at the surface in air (p <0·02). No such effect was found when breathing air at 33 ft or 20 per cent oxygen in helium at either depth. The oxygen-enriched mixtures breathed at the surface also showed nothing. On the first trial all groups working at depth sorted faster and less accurately on average than all groups working at the surface (p < 0·05). There was also a carry over of the rate of work from the first trial to the second (p < 0·05). A similar carry-over was found in a previous experiment, but in this the men normally worked more slowly in proportion to the depth. The increased rate of work reported here may be attributed to an increase in the level of arousal at depth.