Does Heart Rate Variability Predict Impairment of Operational Performance in Divers?

• Published in: Sensors (Basel, Switzerland) Vol. 24; no. 23; p. 7726
• Main Authors: Freiberger, John, Derrick, Bruce, Chon, Ki H., Hossain, Md Billal, Posada-Quintero, Hugo F., Cooter, Mary, Moon, Richard
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.12.2024; MDPI
• Subjects: Adult; Batteries; Carbon dioxide; Carbon Dioxide - analysis; Comparative analysis; diving; Diving - physiology; Electrocardiography; Evaluation; Female; Gases; Heart beat; Heart rate; Heart Rate - physiology; heart rate variability; Humans; Male; narcosis; Nervous system; nitrogen; Oxygen; oxygen toxicity; Physical fitness; Toxicity; United States; United States > US; carbon dioxide; MATB-II; k-nearest neighbor classifier; anesthesiology; hyperoxia; navy; nitrogen; hypercapnia; oxygen toxicity; random forest; underwater breathing; rapture of the deep; cognitive testing; diving; mission; SMOTE; support vector machine; flight simulator; heart rate variability; undersea; inert gas; cognitive impairment; narcosis
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s24237726

We examined data from Naval Sea Systems Command grant project N0463A-12-C-001, “Hypercapnia: cognitive effects and monitoring”, with the objective of validating or repudiating heart rate variability (HRV) as a warning sign of cognitive impairment from diving gas narcosis or oxygen toxicity. We compared HRV feature scores to their temporally corresponding cognitive outcomes under normal and narcotizing conditions to identify specific HRV features associated with cognitive changes. N0463A-12-C-001 was conducted between 17 September 2013 and 29 January 2016 and employed NASA’s multi-attribute task battery (MATB-II) flight simulator to examine the independent effects of CO2, N2, and O2 partial pressure on diver performance at simulated depths up to 61 msw (200 fsw). We assessed the association of 23 distinct HRV features scores from 432 of the study’s analyzable exposure stages in relation to MATB-II’s four performance subclasses (motor, memory, attention, strategy) while controlling for exercise and CO2, N2, and O2 gas partial pressure. Performance decrements were associated with normalized high-frequency HRVfeatures (HFnu, p = 0.0016) and the number of pairs of successive R-R intervals that differed by more than 50 ms (NN50count1, p = 0.04). Secondary analysis with stratification restricted to non-exercise stages showed that several HRV parameters, including root mean square of the successive difference (RMSSD, p = 0.0015), width of Poincaré plot (p = 0.0017), NN50count1 (p = 0.0019), and standard deviation of normal-to-normal R peaks (p = 0.0082), were associated with performance impairment. The RMSSD association retained statistical significance after Bonferroni correction for multiple tests. HRV features collected from divers tested under narcotizing conditions of breathing gas partial pressure and exercise were associated with performance impairment.