Young Healthy Humans Demonstrate Reduced Executive Function in Moderate Hypoxia

Abstract

BackgroundCognitive deficits resulting from mild hypoxia are difficult to quantify and reproduce consistently. The changes in executive function during acute hypoxia are still controversial. The purpose of present study was to assess changes in executive function during acute moderate hypoxia using a continuous performance test (Connors’ Continuous Performance test, CCPT‐II).MethodsNine young, healthy adults (7 women; 28 ± 1 years; BMI: 24.5 ± 3.0 kg·m−2) performed two sets of CCPT‐II during two different conditions: 1) 7 minutes of baseline (fraction of inspired oxygen (FiO2) = 0.21) and 2) 10 minutes of hypoxia (FiO2=0.118). The CCPT‐II is a test of executive cognitive function which requires subjects to strike a key when any letter except the letter X appeared on a computer monitor as quickly and accurately as possible. Reaction time, commission errors (response to X), and omission errors (failure to respond to a letter other than X) were recorded for each 140s of the CCPT‐II block. Arterial oxygen concentration (PaO2) was measured during the last 30sec of baseline and hypoxia from brachial artery catheter samples.ResultsPaO2 was reduced in hypoxia (baseline: 103.1 ± 1.5 mmHg vs. hypoxia: 43.2 ± 1.0 mmHg, P<0.01). During the trials of the CCPT‐II performed during hypoxia, reaction time was lower (i.e. faster) than during baseline (baseline: 451 ± 18 ms. vs. hypoxia: 437 ± 13 ms., P<0.01). Additionally, the number of commission errors was greater in hypoxia (baseline: 1.3 ± 0.6 errors·block−1 vs. hypoxia: 2.1 ± 0.8 errors·block−1, P<0.01). However, the number of omission errors was not different between the two conditions (baseline: 0.4 ± 0.2 errors·block−1 vs. hypoxia: 0.2 ± 0.1 errors·block−1, P=0.92).ConclusionsThe number of commission errors increased and the reaction time decreased during the CCPT‐II test performed in moderate hypoxia compared to baseline, demonstrating a decline in cognitive function during hypoxia. The faster and less accurate responses during hypoxia suggest a suppression of inhibitory pathways in the prefrontal or motor cortex that may contribute to the observed acute reduction in executive cognitive function.Support or Funding InformationThis project was funded by the Office of Naval Research (ONR), grant number N00014‐18‐D‐7001‐TO1.