Physiology and enabling technologies for quantitative assessment of survivability during cold water immersion and rewarming: a review

Immersion in cold water alters physiological (including cardiovascular) state via complex interplay between external stressors (namely, hydrostatic pressure of ambient water and heat loss due to cold) and compensatory mechanisms in the body (namely, humoral and autonomic nervous system control). Prolonged immersion in cold water leads to life-threatening physiological states including death. In addition, rewarming can benefit or harm a casualty depending on the casualty's physiological state and compensatory reserve. However, technology for assessing the survivability of a casualty impacted by cold water immersion does not exist. Toward the overarching goal of fostering the development of next-generation triage and treatment guidance technology for resuscitation after cold water immersion, the goal of this paper is to help establish a comprehensive understanding of cardiovascular responses to cold water immersion and rewarming as well as relevant physiological measurement technologies which may enable status assessment in future implementations. We review literature on the influence of water immersion, exposure to cold, and rewarming on cardiovascular physiology. We summarize the existing findings into a comprehensive mechanistic understanding of typical cardiovascular responses to cold water immersion and rewarming through time. Then, we review literature on the physiological measurement and physiological signal analytics technologies applicable to cold water immersion settings. We conclude the paper with a perspective on outstanding challenges and opportunities pertaining to physiological sensing and analytics to enable autonomous assessment and treatment guidance for resuscitation after cold water immersion.