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INTRODUCTION: Exposure to low oxygen environments (hypoxia) can impair cognitive function; however, the time-course of the transient changes in cognitive function is unknown. In this study, we assessed cognitive function with a cognitive test before, during, and after exposure to hypoxia.METHODS: Nine participants (28 4 yr, 7 women) completed Conners Continuous Performance Test (CCPT-II) during three sequential conditions: 1) baseline breathing room air (fraction of inspired oxygen, FIo2 0.21); 2) acute hypoxia (FIo2 0.118); and 3) recovery after exposure to hypoxia. End-tidal gas concentrations (waveform capnography), heart rate (electrocardiography), frontal lobe tissue oxygenation (near infrared spectroscopy), and mean arterial pressure (finger photoplethysmography) were continuously assessed.RESULTS: Relative to baseline, during the hypoxia trial end-tidal (-30%) and cerebral (-9%) oxygen saturations were reduced. Additionally, the number of commission errors during the CCPT-II was greater during hypoxia trials than baseline trials (2.6 0.4 vs. 1.9 0.4 errors per block of CCPT-II). However, the reaction time and omission errors did not differ during the hypoxia CCPT-II trials compared to baseline CCPT-II trials. During the recovery CCPT-II trials, physiological indices of tissue hypoxia all returned to baseline values and number of commission errors during the recovery CCPT-II trials was not different from baseline CCPT-II trials.DISCUSSION: Oxygen concentrations were reduced (systemically and within the frontal lobe) and commission errors were increased during hypoxia compared to baseline. These data suggest that frontal lobe hypoxia may contribute to transient impairments in cognitive function during short exposures to hypoxia.Uchida K, Baker SE, Wiggins CC, Senefeld JW, Shepherd JRA, Trenerry MR, Buchholtz ZA, Clifton HR, Holmes DR, Joyner MJ, Curry TB. A novel method to measure transient impairments in cognitive function during acute bouts of hypoxia. Aerosp Med Hum Perform. 2020; 91(11):839844.

INTRODUCTION: The reasons for wide variability in the incidence of decompression sickness (DCS) are not well known, but diet may play a role. The hypothesis of the present study was that raising plasma triglycerides via a high-fat meal would increase the rate of nitrogen washout and, therefore, might be a useful adjunct when denitrogenation is used to reduce the likelihood of DCS in diving and exposure to altitude. METHODS: Nitrogen elimination was measured for 125 min in 10 subjects by gas chromatography while they breathed a normoxic argon-oxygen mixture at sea level. Measurements were performed on separate days after high-fat and control, low-fat meals. RESULTS: The high-fat meal increased blood triglycerides by 236 +/- 86% while there was no significant change after the control meal. Despite causing a significant increase in cardiac output (21.6 +/- 13.8%), there was no difference in nitrogen elimination after high-fat (817.4 +/- 233.1 ml) vs. control (828.3 +/- 180.5 ml). DISCUSSION: These data suggest that raising blood triglycerides via a high-fat meal does not affect the rate of whole-body nitrogen elimination. The lack of effect of the increase in cardiac output may be due to an increased blood flow to the gastrointestinal tract being negated by decreased blood flow in other vascular beds.