The physiology and pathophysiology of human breath-hold diving

Abstract

This is a brief overview of physiological reactions, limitations, and pathophysiological mechanisms associated with human breath-hold diving. Breath-hold duration and ability to withstand compression at depth are the two main challenges that have been overcome to an amazing degree as evidenced by the current world records in breath-hold duration at 10:12 min and depth of 214 m. The quest for even further performance enhancements continues among competitive breath-hold divers, even if absolute physiological limits are being approached as indicated by findings of pulmonary edema and alveolar hemorrhage postdive. However, a remarkable, and so far poorly understood, variation in individual disposition for such problems exists. Mortality connected with breath-hold diving is primarily concentrated to less well-trained recreational divers and competitive spearfishermen who fall victim to hypoxia. Particularly vulnerable are probably also individuals with preexisting cardiac problems and possibly, essentially healthy divers who may have suffered severe alternobaric vertigo as a complication to inadequate pressure equilibration of the middle ears. The specific topics discussed include the diving response and its expression by the cardiovascular system, which exhibits hypertension, bradycardia, oxygen conservation, arrhythmias, and contraction of the spleen. The respiratory system is challenged by compression of the lungs with barotrauma of descent, intrapulmonary hemorrhage, edema, and the effects of glossopharyngeal insufflation and exsufflation. Various mechanisms associated with hypoxia and loss of consciousness are discussed, including hyperventilation, ascent blackout, fasting, and excessive postexercise O(2) consumption. The potential for high nitrogen pressure in the lungs to cause decompression sickness and N(2) narcosis is also illuminated.

Chronic adaptations of lung function in breath-hold diving fishermen

“…Moreover, the individual is subjected to respiratory deprivation of respiration and the effects of the increased hydrostatic pressure [13]. The magnitude of the physiological adaptations resulting from diving depends mainly on the individual's age and diving experience [7]. Therefore, the effect of physiological adaptations resulting from free diving stand out because there were no statistically significant differences in terms of age or the anthropometric variables (Table 1), which are important factors that could influence lung function [17].…”

“…The diving depth is limited by the understanding of Boyle's law, which states that for a given temperature, the product of pressure by volume is always constant. There are, therefore, physical limitations to the accumulation in or diversion of blood to the central region, accompanied by the deformation supported by the chest under hyperbaric conditions [2,7]. Accordingly, three possible outcomes may occur due to the environment in which there is an excessive pressure on the lung and chest during apnea: alveolar collapse with formation of atelectasis, infiltration of liquid from the capillaries into the airways and alveolar space, as well as disruption of the alveolar-capillary membrane with bleeding into the empty spaces.…”

“…Accordingly, three possible outcomes may occur due to the environment in which there is an excessive pressure on the lung and chest during apnea: alveolar collapse with formation of atelectasis, infiltration of liquid from the capillaries into the airways and alveolar space, as well as disruption of the alveolar-capillary membrane with bleeding into the empty spaces. These descriptions of changes in lung function, commonly found in apnea divers, are indicative of pulmonary edema [7]. Although there is no consensus among the experts on this matter [5], there is evidence of the occurrence of chronic Body height, body mass, and the chest and abdominal circumferences were measured and spirometric and respiratory muscle strength tests were conducted according to the ATS/ERS specifications [15].…”

Hemoptysis Due to Breath-Hold Diving Following Chemotherapy and Lung Irradiation

“…When the total lung capacity (TLC) is reduced to residual volume (RV), intrathoracic pressure is equal to hydrostatic pressure, and lung volume cannot decrease further because of the rigidity of the thorax. 2 As the chest wall approaches its elastic limit, a high negative transthoracic pressure develops, resulting in increased blood return to the thorax and an increase in pulmonary transcapillary wall pressure. Eventually, redistribution of blood to the chest may cause "stress failure" of the pulmonary capillaries, resulting in leakage of fluid and blood into the airspaces.…”

Training Rats to Voluntarily Dive Underwater: Investigations of the Mammalian Diving Response

“…In response to submersion under water, this reflexly-induced response consists of apnea, bradycardia and an alteration of blood flow that maintains flow to the heart, brain and exercising muscles while limiting flow to viscera and non-exercising muscles 2 . Many of the metabolic and cardiorespiratory aspects of the mammalian diving response have been well investigated 2,3 , including those in humans 4,5 . However, what has been relatively lacking, until recently, is investigation of the central integrative aspects of the diving response.…”