Effects of Breath-Hold Deep Diving on the Pulmonary System

Breath-hold diving strategies to avoid loss of consciousness: speed is the key factor

The aim of this study was to investigate the impact of breath-hold diving strategies regarding loss of consciousness (LOC). Three international competitions were examined through video in constant weight diving with (CWT) or without (CNF) fins. We analysed three breath-hold parameters (time, speed, and movements count) for the following phases: active descent, passive descent, turning, and ascent. Divers who had LOC during CNF were slower in the active descent phase, faster in the passive descent phase with a longer turn, and slower in the ascent phase than divers who did not have LOC. They also had lower amplitude and higher frequency. Men were deeper (72.9 m vs. 56.3 m) for a longer dive time (181.1 s vs. 154.6 s), faster, with a greater amplitude than women. In CWT, divers with an LOC had longer dive times (197 s vs. 167 s) with a faster active descent phase. Men had lower amplitude and greater frequency than women. This is the first study showing that breath-hold divers undergoing an LOC event shown differences in efficiency during CWT and CNF regarding velocities, amplitudes, and frequencies. In conclusion, our results suggest that the speed parameter during active descent phase influence the LOC.

Unlocking the depths: multiple factors contribute to risk for hypoxic blackout during deep freediving

PURPOSE

To examine the effect of freediving depth on risk for hypoxic blackout by recording arterial oxygen saturation (SpO2) and heart rate (HR) during deep and shallow dives in the sea.

METHODS

Fourteen competitive freedivers conducted open-water training dives wearing a water-/pressure proof pulse oximeter continuously recording HR and SpO2. Dives were divided into deep (> 35 m) and shallow (10-25 m) post-hoc and data from one deep and one shallow dive from 10 divers were compared.

RESULTS

Mean ± SD depth was 53 ± 14 m for deep and 17 ± 4 m for shallow dives. Respective dive durations (120 ± 18 s and 116 ± 43 s) did not differ. Deep dives resulted in lower minimum SpO2 (58 ± 17%) compared with shallow dives (74 ± 17%; P = 0.029). Overall diving HR was 7 bpm higher in deep dives (P = 0.002) although minimum HR was similar in both types of dives (39 bpm). Three divers desaturated early at depth, of which two exhibited severe hypoxia (SpO2 ≤ 65%) upon resurfacing. Additionally, four divers developed severe hypoxia after dives.

CONCLUSIONS

Despite similar dive durations, oxygen desaturation was greater during deep dives, confirming increased risk of hypoxic blackout with increased depth. In addition to the rapid drop in alveolar pressure and oxygen uptake during ascent, several other risk factors associated with deep freediving were identified, including higher swimming effort and oxygen consumption, a compromised diving response, an autonomic conflict possibly causing arrhythmias, and compromised oxygen uptake at depth by lung compression possibly leading to atelectasis or pulmonary edema in some individuals. Individuals with elevated risk could likely be identified using wearable technology.

Arterial blood gases' analysis in elite breath-hold divers at extreme depths

PURPOSE

To showcase results of arterial blood gases' analysis in elite breath-hold divers sampled at depths where their total lung capacities are below their residual lung volume on surface.

METHODS

Three male elite breath-hold divers performed body plethysmographies to determine their lung volumes. Two dives were performed, one on normal inhalation to 60 m of depth and the second on complete exhalation to 10 m of depth. Blood samples were taken on five occasions; before the first dive, at 60 and 10 m of depth and immediately after resurfacing after both dives.

RESULTS

Arterial blood gases' analysis at 60 m of depth showed an increase in partial pressures of oxygen and carbon dioxide, a consequent decrease in pH and an increase in concentration of HCO₃^-. After resurfacing, in two divers, values mostly returned to normal; hypoxemia was observed in one diver. At 10 m of depth, all values showed similar variation, and hypoxemia was observed in the same diver but at depth. Upon resurfacing, all values returned to normal.

CONCLUSION

This is the first study performed at depths where the total lung capacities of participants are below their residual lung volumes at the surface. Partial pressure of carbon dioxide increases at depth to higher than normal values causing pH to decrease thus exceeding the buffering potential of the blood. In addition, previous assumptions that maximum depth in breath-hold divers is where total lung capacity is reduced to their residual volume proved wrong as our group of divers had no symptoms after resurfacing.

Effects of lung volume and trigeminal nerve stimulation on diving response in breath-hold divers and non-divers

PURPOSE

This study investigated the effects of lung volume and trigeminal nerve stimulation (TS) on diving responses in breath-hold divers (BHDs) and non-divers (NDs).

METHODS

Eight BHDs and nine NDs performed four breath-hold trials at different lung volumes, with or without TS, and one trial of TS. Haemodynamic parameters and electrocardiograms were measured for each trial.

RESULTS

During the TS trial, the total peripheral resistance increased more in BHDs. Breath-hold performed at total lung capacity showed a more pronounced decrease in stroke volume and cardiac output in BHDs. The decrease in heart rate and increase in total peripheral resistance were more pronounced in BHDs when breath-holding was performed with TS.

CONCLUSION

The more pronounced diving response in BHDs was attributed to the greater increase in total peripheral resistance caused by TS. Furthermore, the lower stroke volume and cardiac output in BH performed at total lung capacity could also cause a more pronounced diving response in BHDs.

Decompression Illness in Repetitive Breath-Hold Diving: Why Ischemic Lesions Involve the Brain?

Nitrogen (N₂) accumulation in the blood and tissues can occur due to breath-hold (BH) diving. Post-dive venous gas emboli have been documented in commercial BH divers (Ama) after repetitive dives with short surface intervals. Hence, BH diving can theoretically cause decompression illness (DCI). “Taravana,” the diving syndrome described in Polynesian pearl divers by Cross in the 1960s, is likely DCI. It manifests mainly with cerebral involvements, especially stroke-like brain attacks with the spinal cord spared. Neuroradiological studies on Ama divers showed symptomatic and asymptomatic ischemic lesions in the cerebral cortex, subcortex, basal ganglia, brainstem, and cerebellum. These lesions localized in the external watershed areas and deep perforating arteries are compatible with cerebral arterial gas embolism. The underlying mechanisms remain to be elucidated. We consider that the most plausible mechanisms are arterialized venous gas bubbles passing through the lungs, bubbles mixed with thrombi occlude cerebral arteries and then expand from N₂ influx from the occluded arteries and the brain. The first aid normobaric oxygen appears beneficial. DCI prevention strategy includes avoiding long-lasting repetitive dives for more than several hours, prolonging the surface intervals. This article provides an overview of clinical manifestations of DCI following repetitive BH dives and discusses possible mechanisms based on clinical and neuroimaging studies.

RESEARCH ON SCIENTIFIC SPORTS TRAINING OF STUDENTS MAJORING IN PHYSICAL EDUCATION

ABSTRACT Introduction: The organization of high-level sports teams in colleges and universities is an important measure for my country's competitive sports to break the traditional monopoly and monopoly pattern and go to the market and society in an all-around way. It helps to improve the cultural quality of Chinese athletes and cultivate new sports talents for comprehensive development. It can make full use of universities’ multidisciplinary and high-tech advantages, increase the technological content of competitive training, and accelerate the improvement of sports level. Objective: This article intends to take the diving team as an example to explain the role and significance of scientific training in developing competitive sports in my country's ordinary colleges and universities and put forward suggestions for the establishment, organization, and implementation of scientific training. Methods: The scientific research support system used in the thesis includes: physiological and biochemical monitoring, health and sports injury monitoring, nutrition and weight monitoring, psychological consultation and monitoring, technical training support system, training quality management system, physical training support system, and athlete training database. Results: The in-depth research on diving training focuses on: (1) the detection and evaluation of diving technique training; (2) the training of divers’ specific strength qualities; (3) the monitoring of nutrition and weight of female athletes; (4) Pre-match psychological training for outstanding diving athletes. Conclusions: The diving team's training shows that scientific and systematic training is an important guarantee for high-level student-athletes training in ordinary universities in my country. Level of evidence II; Therapeutic studies - investigation of treatment results.

Association Between Arterial Oxygen Saturation and Lung Ultrasound B-Lines After Competitive Deep Breath-Hold Diving

Breath-hold diving (freediving) is an underwater sport that is associated with elevated hydrostatic pressure, which has a compressive effect on the lungs that can lead to the development of pulmonary edema. Pulmonary edema reduces oxygen uptake and thereby the recovery from the hypoxia developed during freediving, and increases the risk of hypoxic syncope. We aimed to examine the efficacy of SpO₂, via pulse-oximetry, as a tool to detect pulmonary edema by comparing it to lung ultrasound B-line measurements after deep diving. SpO₂ and B-lines were collected in 40 freedivers participating in an international deep freediving competition. SpO₂ was measured within 17 ± 6 min and lung B-lines using ultrasound within 44 ± 15 min after surfacing. A specific symptoms questionnaire was used during SpO₂ measurements. We found a negative correlation between B-line score and minimum SpO₂ (r_s = −0.491; p = 0.002) and mean SpO₂ (r_s = −0.335; p = 0.046). B-line scores were positively correlated with depth (r_s = 0.408; p = 0.013), confirming that extra-vascular lung water is increased with deeper dives. Compared to dives that were asymptomatic, symptomatic dives had a 27% greater B-line score, and both a lower mean and minimum SpO₂ (all p < 0.05). Indeed, a minimum SpO₂ ≤ 95% after a deep dive has a positive predictive value of 29% and a negative predictive value of 100% regarding symptoms. We concluded that elevated B-line scores are associated with reduced SpO₂ after dives, suggesting that SpO₂ via pulse oximetry could be a useful screening tool to detect increased extra-vascular lung water. The practical application is not to diagnose pulmonary edema based on SpO₂ – as pulse oximetry is inexact – rather, to utilize it as a tool to determine which divers require further evaluation before returning to deep freediving.

Heart Rate and Muscle Oxygenation Kinetics During Dynamic Constant Load Intermittent Breath-Holds

Introduction: Acute apnea evokes bradycardia and peripheral vasoconstriction in order to conserve oxygen, which is more pronounced with face immersion. This response is contrary to the tachycardia and increased blood flow to muscle tissue related to the higher oxygen consumption during exercise. The aim of this study was to investigate cardiovascular and metabolic responses of dynamic dry apnea (DRA) and face immersed apnea (FIA).

Methods: Ten female volunteers (17.1 ± 0.6 years old) naive to breath-hold-related sports, performed a series of seven dynamic 30 s breath-holds while cycling at 25% of their peak power output. This was performed in two separate conditions in a randomized order: FIA (15°C) and DRA. Heart rate and muscle tissue oxygenation through near-infrared spectroscopy were continuously measured to determine oxygenated (m[O₂Hb]) and deoxygenated hemoglobin concentration (m[HHb]) and tissue oxygenation index (mTOI). Capillary blood lactate was measured 1 min after the first, third, fifth, and seventh breath-hold.

Results: Average duration of the seven breath-holds did not differ between conditions (25.3 s ± 1.4 s, p = 0.231). The apnea-induced bradycardia was stronger with FIA (from 134 ± 4 to 85 ± 3 bpm) than DRA (from 134 ± 4 to 100 ± 5 bpm, p < 0.001). mTOI decreased significantly from 69.9 ± 0.9% to 63.0 ± 1.3% (p < 0.001) which is reflected in a steady decrease in m[O₂Hb] (p < 0.001) and concomitant increase in m[HHb] (p = 0.001). However, this was similar in both conditions (0.121 < p < 0.542). Lactate was lower after the first apnea with FIA compared to DRA (p = 0.038), while no differences were observed in the other breath-holds.

Conclusion: Our data show strong decreases in heart rate and muscle tissue oxygenation during dynamic apneas. A stronger bradycardia was observed in FIA, while muscle oxygenation was not different, suggesting that FIA did not influence muscle oxygenation. An order of mechanisms was observed in which, after an initial tachycardia, heart rate starts to decrease after muscle tissue deoxygenation occurs, suggesting a role of peripheral vasoconstriction in the apnea-induced bradycardia. The apnea-induced increase in lactate was lower in FIA during the first apnea, probably caused by the stronger bradycardia.

Going to Extremes of Lung Physiology-Deep Breath-Hold Diving

Breath-hold diving involves environmental challenges, such as water immersion, hydrostatic pressure, and asphyxia, that put the respiratory system under stress. While training and inherent individual factors may increase tolerance to these challenges, the limits of human respiratory physiology will be reached quickly during deep breath-hold dives. Nonetheless, world records in deep breath-hold diving of more than 214 m of seawater have considerably exceeded predictions from human physiology. Investigations of elite breath-hold divers and their achievements revised our understanding of possible physiological adaptations in humans and revealed techniques such as glossopharyngeal breathing as being essential to achieve extremes in breath-hold diving performance. These techniques allow elite athletes to increase total lung capacity and minimize residual volume, thereby reducing thoracic squeeze. However, the inability of human lungs to collapse early during descent enables respiratory gas exchange to continue at greater depths, forcing nitrogen (N₂) out of the alveolar space to dissolve in body tissues. This will increase risk of N₂ narcosis and decompression stress. Clinical cases of stroke-like syndromes after single deep breath-hold dives point to possible mechanisms of decompression stress, caused by N₂ entering the vasculature upon ascent from these deep dives. Mechanisms of neurological injury and inert gas narcosis during deep breath-hold dives are still incompletely understood. This review addresses possible hypotheses and elucidates factors that may contribute to pathophysiology of deep freediving accidents. Awareness of the unique challenges to pulmonary physiology at depth is paramount to assess medical risks of deep breath-hold diving.

Breath-Hold Diving - The Physiology of Diving Deep and Returning

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.

Temporal changes in pulmonary gas exchange efficiency when breath-hold diving below residual volume

NEW FINDINGS

What is the central question of this study? How does deep breath-hold diving impact cardiopulmonary function, both acutely and over the subsequent 2.5 hours post-dive? What is the main finding and its importance? Breath-hold diving, to depths below residual volume, is associated with acute impairments in pulmonary gas exchange, which typically resolve within 2.5 hours. These data provide new insight into the behaviour of the lungs and pulmonary vasculature following deep diving.

ABSTRACT

Breath-hold diving involves highly integrative and extreme physiological responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure. Over two diving training camps (Study 1 and 2), 25 breath-hold divers (recreational to world-champion) performed 66 dives to 57 ± 20 m (range: 18-117 m). Using the deepest dive from each diver, temporal changes in cardiopulmonary function were assessed using non-invasive pulmonary gas exchange (indexed via the O₂ deficit), ultrasound B-line scores, lung compliance and pulmonary haemodynamics at baseline and following the dive. Hydrostatically induced lung compression was quantified in Study 2, using spirometry and lung volume measurement, enabling each dive to be categorized by its residual volume (RV)-equivalent depth. From both studies, pulmonary gas exchange inefficiency - defined as an increase in O₂ deficit - was related to the depth of the dive (r²  = 0.345; P < 0.001), with dives associated with lung squeeze symptoms exhibiting the greatest deficits. In Study 1, although B-lines doubled from baseline (P = 0.027), cardiac output and pulmonary artery systolic pressure were unchanged post-dive. In Study 2, dives with lung compression to ≤RV had higher O₂ deficits at 9 min, compared to dives that did not exceed RV (24 ± 25 vs. 5 ± 8 mmHg; P = 0.021). The physiological significance of a small increase in estimated lung compliance post-dive (via decreased and increased/unaltered airway resistance and reactance, respectively) remains equivocal. Following deep dives, the current study highlights an integrated link between hydrostatically induced lung compression and transient impairments in pulmonary gas exchange efficiency.