Report No: DOT/FAA/AM-97/7

Title and Subtitle: Effects of Simulated General Aviation Altitudes Hypoxia on Smokers and Nonsmokers

Report Date: March 1997

Authors: Nesthus, Thomas E., Garner, Robert P., Mills, Scott H., and Wise, Robert A.

Abstract: General aviation pilots are permitted to fly without the use of supplemental oxygen up to an altitude of 12,500 ft. However, hypoxia occurs at altitudes under 12,500 ft. Personal lifestyle, physical conditioning, and illness can interact with hypoxia to affect performance. This study evaluated physiological and cognitive performance of smokers and nonsmokers during sessions of mild hypoxia.

Methods: Nine male smokers and 9 nonsmokers, after passing a Class III flight physical, performed the Multi-Attribute Task Battery (MATB) during separate 2-hr. sessions while breathing oxygen mixtures that simulated sea level, 5,000 ft., 8,000 ft., and 12,500 ft. altitude conditions.

Results: Four physiological measures: transcutaneous partial pressures of oxygen and carbon dioxide (PtcO2 and PtcCO2), heart rate (HR), and oxyhemoglobin saturation (SaO2), demonstrated significant trends across the simulated altitude conditions and for some measures, between groups. Significant effects were found for MATB monitoring task measures. Smoking group and group by altitude interaction effects were also found for the monitoring task measures. Significant smoking group differences were found in tracking performance.

Discussion: Results of the physiological measures obtained, confirmed the study's targeted levels of hypoxia. Smokers exhibited elevated HR and lower PtcCO2 values, compared with nonsmokers. Elevated HR is consistent with nicotine effects. Reduced PtcCO2 values may indicate greater hyperventilation among the smokers. Group differences in MATB performance involved tasks that were adjacent to the attention demanding fuel management task for which performance results were the same. Consistent with smoking research and studies of combined lowered oxygen tension and carbon monoxide, smokers may have experienced a reduction of peripheral vision and their ability to visually monitor several tasks simultaneously. The smoker group exhibited higher error rates and false alarms for the peripherally-located monitoring tasks, and showed significantly poorer tracking task performance, compared to the nonsmoker group.

Key Words: Smoking, Hypoxia, Simulated Altitude, Supplemental Oxygen, Requirement for Aviation, Multiple Complex Task Performance

No. of Pages: 63