Worcester Polytechnic Institute Electronic Theses and Dissertations Collection

Title page for ETD etd-081111-141631

Document Typedissertation
Author NameBai, Yan
TitleEvaluation of the Effects of Hyperbaric Dive Environments on the Autonomic Nervous System Using Principal Dynamic Mode Analysis
DepartmentBiomedical Engineering
  • Ki H. Chon, Advisor
  • Yitzhak Mendelson, Committee Member
  • Domhnull Granquist-Fraser, Committee Member
  • Soussan Djamasbi, Committee Member
  • Joseph White, Committee Member
  • Keywords
  • principal dynamic mode
  • heart rate variability
  • autonomic nervous system
  • decompression sickness
  • SCUBA dive
  • hyperbaria
  • Date of Presentation/Defense2011-08-22
    Availability unrestricted


    As water covers over 75% surface area of the earth, humans have an innate desire to explore the underwater environment for various aims. Physiological responses are induced in humans and animals to adapt to different stresses imposed by the hyperbaric environment. When these stresses become overwhelming, certain hazards can occur to individuals in underwater or in similar hyperbaric environments, and they may include nitrogen narcosis, oxygen toxicity and decompression sickness (DCS). There are evidences showing that the autonomic nervous system (ANS) plays an important role in diving reflex and physiological responses to diving hazards. However, the assessment of the autonomic nervous activity during SCUBA dives and diving-related hazards are mostly absent from the literature. Thus, in order to evaluate the autonomic nervous alterations that may occur during diving, especially during DCS, the following three experiments were performed in this study: the simulated dives of human subjects in a hyperbaric chamber, the SCUBA diving performed in seawater and induced decompression sickness in a swine model. A novel algorithm developed in our lab, principal dynamic mode (PDM) analysis, is applied to the above data. It has been shown that the PDM is able to accurately separate the sympathetic and parasympathetic dynamics of the ANS, and subsequently it is able to obtain a better quantification of the autonomic nervous activity than a current golden-standard approach. Through the study, dominance of the parasympathetic modulation was found in both hyperbaric chamber and SCUBA diving conditions. And more stresses were present in real dives, compared to simulated dives in chamber. In the swine DCS model, we found neurological DCS and cardiopulmonary DCS resulted in different alterations in the ANS. Furthermore, tracking dynamics of the parasympathetic modulations via the PDM method may allow discrimination between cardiopulmonary DCS and neurological DCS, and has potential use as a marker for early diagnosis of cardiopulmonary DCS.

  • ybai.pdf

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