Carbon dioxide protects simulated driving performance during severe hypoxia

Abstract

Purpose We sought to determine the effect of acute severe hypoxia, with and without concurrent manipulation of carbon dioxide (CO2), on complex real-world psychomotor task performance. Methods Twenty-one participants completed a 10-min simulated driving task while breathing room air (normoxia) or hypoxic air (PETO2 = 45 mmHg) under poikilocapnic, isocapnic, and hypercapnic conditions (PETCO2 = not manipulated, clamped at baseline, and clamped at baseline + 10 mmHg, respectively). Driving performance was assessed using a fixed-base motor vehicle simulator. Oxygenation in the frontal cortex was measured using functional near-infrared spectroscopy. Results Speed limit exceedances were greater during the poikilocapnic than normoxic, hypercapnic, and isocapnic conditions (mean exceedances: 8, 4, 5, and 7, respectively; all p ≤ 0.05 vs poikilocapnic hypoxia). Vehicle speed was greater in the poikilocapnic than normoxic and hypercapnic conditions (mean difference: 0.35 km h−1 and 0.67 km h−1, respectively). All hypoxic conditions similarly decreased cerebral oxyhaemoglobin and increased deoxyhaemoglobin, compared to normoxic baseline, while total hemoglobin remained unchanged. Conclusions These findings demonstrate that supplemental CO2 can confer a neuroprotective effect by offsetting impairments in complex psychomotor task performance evoked by severe poikilocapnic hypoxia; however, differences in performance are unlikely to be linked to measurable differences in cerebral oxygenation.

The effect of breathing hypoxic gas (15% FIO2) on physiological and behavioral outcomes during simulated driving in healthy subjects

“…Although these few previous studies in healthy subjects and patients have successfully measured driving performance, we do believe our scoring method is a practical and more robust method of assessing DB/driving performance, which others could use in future. This form of assessment is evident in a recent publication (Bloomfield et al., 2023 ).…”

“…Only one of these studies gave the FIO 2 concentration. Recently, a study has shown worse driving performance with severe hypoxia; however, this was not surprising as the subjects' mean SpO 2 was approximately 71% (Bloomfield et al., 2023 ). We felt their methods of assessing DB and ours had a similar approach.…”

“…Previous investigations in healthy subjects have shown an equal balance of studies for and against the effects of hypoxia on driving behavior (DB) (Bloomfield et al., 2023 ; Colombo et al., 2005 ; Sung et al., 2005 ; Zhang et al., 2022 ). Due to the small number of studies in healthy subjects, COPD patient studies were also used for comparison (Karakontaki et al., 2013 ; Orth et al., 2008 ; Skovhus Prior et al., 2015 ).…”