Positive expiratory pressure as a method for preventing the impairment of attentional processes by hypoxia

This study investigated the effects of hypoxia on parallel/preattentional a nd serial/attentional processes in early vision, and the use of a positive- end-expiratory-pressure (PEEP) to prevent the impairment in performance. Tw enty-one subjects were submitted to an X-h hypoxia exposure in a hypobaric chamber (4500 m, 589 hPa, 22 degrees C), both with and without a 5-cm H2O P EEP. Subjects carried out a visual search task consisting of detecting a ta rget among distracters in normoxia, in acute and in prolonged hypoxia. Conj ointly their sensitivity to acute mountain sickness (AMS) was scored throug h the Lake Louise AMS scoring system. Results showed that prolonged hypoxia slowed serial/attentional processing whereas parallel/preattentional proce sses were not impaired either by acute or by prolonged hypoxia. PEEP preven ted serial/attentional processes from slowing and those effects were more c learly observed in rite AMS sensitive subjects with respect to the AMS inse nsitive subjects. These results suggest that: the slowing induced by prolon ged hypoxia is specific to an early visual process that pilots the scanning of an attentional spotlight throughout the visual field.