Abstract
Breath-hold diving involves highly integrative physiology and extreme responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure. With astonishing depth records exceeding 100 m, and up to 214 m on a single breath, the human capacity for deep breath-hold diving continues to refute expectations. The physiological challenges and responses occurring during a deep dive highlight the coordinated interplay of oxygen conservation, exercise economy, and hyperbaric management. In this review, the physiology of deep diving is portrayed as it occurs across the phases of a dive: the first 20 m; passive descent; maximal depth; ascent; last 10 m, and surfacing. The acute risks of diving (i.e., pulmonary barotrauma, nitrogen narcosis, and decompression sickness) and the potential long-term medical consequences to breath-hold diving are summarized, and an emphasis on future areas of research of this unique field of physiological adaptation are provided.
Highlights
Breath-hold diving is a ubiquitous activity for recreation, sustenance, military, and sport; it involves highly integrative physiology and extreme responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure (Ferretti, 2001; Bain et al, 2018b; FitzClarke, 2018)
Humans live in a pressurized air environment, with the pressure at sea level standardized to 760 mmHg or 1 absolute pressure in atmospheres (ATA)
There is a reduction in oxidative metabolism of the brain (Bain et al, 2017), which complement the gradual rise in cerebral blood flow that occurs across an apnea, serving to sustain cerebral oxygen demands (Willie et al, 2015) – and prolong consciousness
Summary
Breath-hold diving is a ubiquitous activity for recreation, sustenance, military, and sport; it involves highly integrative physiology and extreme responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure (Ferretti, 2001; Bain et al, 2018b; FitzClarke, 2018). Since the famous anecdote of Giorgios Statti diving to 70 m in 1913; the attainment of 100 m by Jacques Mayol in 1976; and, more recently, Herbert Nitsch reaching a staggering 214 m in 2007, the human capacity for deep breath-hold diving has continually extended the physiological limits and refuted expectations. Physiological limits do exist and adverse consequences readily occur when these limits are exceeded. The purpose of this review is to outline the basic physics that govern apnea diving, discuss the challenges, physiological responses, and associated clinical consequences of diving to depth
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