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Front. Physiol. | doi: 10.3389/fphys.2018.00110

Effect of shallow and deep SCUBA dives on heart rate variability

  • 1University of Massachusetts Amherst, United States
  • 2Stony Brook Medicine, United States
  • 3Navy Experimental Diving Unit, United States
  • 4Biomedical Engineering, University of Connecticut, United States

Prolonged and high pressure diving may lead to various physiological changes including significant alterations of autonomic nervous system (ANS) activity that may be associated with altered physical performance, decompression sickness, or central nervous system oxygen toxicity. Ideally, researchers could elucidate ANS function before, during, and after dives that are most associated with altered function and adverse outcomes. However, we have a limited understanding of the activities of the ANS especially during deeper prolonged SCUBA diving because there has never been a convenient way to collect physiological data during deep dives. This work is one of the first studies which was able to collect electrocardiogram (ECG) data from SCUBA divers at various depths (33, 66, 99, 150 and 200 ftsw; equivalent to 10.05, 20.10, 30.17, 45.72, and 60.96 meters of salt water, respectively) breathing different gas mixtures (air, nitrox and trimix). The aim of this study was to shed light on cardiac ANS behavior during dives, including deep dives. With the aid of dry suits, a Holter monitor that could handle the pressure of a 200-ft. dive, and a novel algorithm that can provide a useful assessment of the ANS from the ECG signal, we investigated the effects of SCUBA dives with different time durations, depths and gas mixtures on the ANS. Principal dynamic mode analysis of the electrocardiogram, which has been shown to provide accurate separation of the sympathetic and parasympathetic dynamics, was employed to assess the difference of ANS behavior between baseline and diving conditions of varying depths and gas mixtures consisting of air, nitrox and trimix. For all depths and gas mixtures, we found consistent dominance in the parasympathetic activity and a concomitant increase of the parasympathetic dynamics with increasing diving duration and depth. For 33 ft. and 66 ft. dives, we consistently found significant decreases in heart rates and concomitant increases in parasympathetic activities as estimated via the PDM and root mean square of successive differences (RMSSD) for all time intervals (from the first 5 min to the last 30 min) at the bottom depth when compared to the baseline depth at sea level. The sympathetic dynamics

Keywords: SCUBA, autonomic nervous system (ANS), heart rate variability (HRV), principal dynamic modes, Trimix, Nitrox, Decompression Sickness

Received: 14 Sep 2017; Accepted: 05 Feb 2018.

Edited by:

Luca Mesin, Politecnico di Torino, Italy

Reviewed by:

Paolo Melillo, Università degli Studi della Campania "Luigi Vanvitelli" Caserta, Italy
Silvestro Roatta, Dipartimento di Neuroscienze Rita Levi Montalcini, Università degli Studi di Torino, Italy  

Copyright: © 2018 Noh, Bai, White, Florian, Brink and Chon. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Ki Chon, University of Connecticut, Biomedical Engineering, Storrs, United States,