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Cardiac and humoral changes induced by recreational scuba diving

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Abstract

The aim of this study was to evaluate the prevalence and the possible clinical relevance of circulating bubbles after a recreational scuba dive. Twenty healthy subjects (18 male, 2 female; age range 25-36 yr) underwent a Doppler-echocardiographic study in basal conditions and 1.9+/-0.2 h after a recreational scuba dive. Venous blood samples were taken just before the two ultrasonic studies to obtain leukocyte and platelet counts and plasma activity of angiotensin-converting enzyme (ACE; assumed as pulmonary endothelial damage marker). Circulating bubbles were observed in the right heart chambers of 12 subjects after the dive. The echocardiographic and humoral data were evaluated before and after diving in subjects with and without circulating bubbles. At the postdive evaluation, a significant increase in right ventricular dimensions (37.4+/-3.9 vs. 40.7+/-4.0 mm; P < 0.01) and a significant reduction of early diastolic filling velocities of both right (59.1+/-16.4 vs. 48.9+/-6.9 cm x s-(-1); P < 0.05) and left (76.2+/-9.9 vs. 67.5+/-10.2 cm x s(-1); P < 0.02) ventricle were observed in the group with circulating bubbles. In the same group, significant increases in ACE activity (92.9+/-41.1 vs. 105.9+/-41.7 U x liter(-1); P < 0.05), platelets (217+/-34 vs. 232+/-35 10(3) x microl(-1); P < 0.01), and granulocytes (3,704+/-715 x microl(-1) vs. 5,212+/-1,995 x microl(-1); P < 0.001) were observed. The bubble-free group showed only a postdive significant decrease of left ventricular early diastolic filling velocity (74+/-6.8 vs. 62.6+/-4.5 cm x s(-1); P < 0.005). These data may indicate that circulating gas bubbles are associated with cardiac changes, suggesting a right ventricular overload and an impairment of ventricular diastolic performance. Postdive humoral and hematologic changes are consistent with the hypothesis that "silent" gas bubbles may damage pulmonary endothelium and activate the reactive systems of the human body.
Scanned for the Undersea and Hyperbaric Medical Society by The Rubicon Foundation
in cooperation with Global Underwater Explorers. (http://rubicon-foundation.org)
Scanned for the Undersea and Hyperbaric Medical Society by The Rubicon Foundation
in cooperation with Global Underwater Explorers. (http://rubicon-foundation.org)
Scanned for the Undersea and Hyperbaric Medical Society by The Rubicon Foundation
in cooperation with Global Underwater Explorers. (http://rubicon-foundation.org)
Scanned for the Undersea and Hyperbaric Medical Society by The Rubicon Foundation
in cooperation with Global Underwater Explorers. (http://rubicon-foundation.org)
Scanned for the Undersea and Hyperbaric Medical Society by The Rubicon Foundation
in cooperation with Global Underwater Explorers. (http://rubicon-foundation.org)
Scanned for the Undersea and Hyperbaric Medical Society by The Rubicon Foundation
in cooperation with Global Underwater Explorers. (http://rubicon-foundation.org)
Scanned for the Undersea and Hyperbaric Medical Society by The Rubicon Foundation
in cooperation with Global Underwater Explorers. (http://rubicon-foundation.org)
Scanned for the Undersea and Hyperbaric Medical Society by The Rubicon Foundation
in cooperation with Global Underwater Explorers. (http://rubicon-foundation.org)
... Venous gas emboli (VGE) can cause increased pulmonary resistance and subsequently increases the right-side volume load of the heart. There are also indications of bubbles impairing ventricular relaxation (Marabotti 1999). ...
... Compared to previous studies involving trimix or CCR divers, our data were concordantly pointing toward impaired cardiac performance. There are previous studies reporting somewhat similar results, also after recreational dives (Marabotti et al. 1999, Marabotti 2013a, 2013b, Boussuges et al. 2006. Other previous studies show varying results and therefore we designed our research in a way that two major diving-related stressors to the cardiovascular system, extreme cold and pressure, would play a great role in our research. ...
... Scuba diving, performed within no-decompression limit or with decompression demand, induces bubble formation in the majority of divers, also without any symptoms of decompression illness. The presence of VGE has been associated with cardiac changes, especially right ventricular overload and a possible impairment of ventricular relaxation (Marabotti et al. 1999(Marabotti et al. , 2013a. The bubbles have been speculated to interact with the vascular bed via both direct mechanical effects (wedging into pulmonary capillaries) and via mediators (e.g., vasoactive substances), increasing pulmonary vascular resistance, hence affecting function of the heart's right side (Marabotti et al. 1999(Marabotti et al. , 2013aDujic et al. 2006). ...
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Purpose Dive-induced cardiac and hemodynamic changes are caused by various mechanisms, and they are aggravated by cold water. Therefore, aging divers with pre-existing cardiovascular conditions may be at risk of acute myocardial infarction, heart failure, or arrhythmias while diving. The aim of this study was to assess the effect of a single decompression CCR dive in arctic cold water on cardiac function in Finnish technical divers. Methods Thirty-nine divers performed one identical 45 mfw CCR dive in 2–4 °C water. Hydration and cardiac functions were assessed before and after the dive. Detection of venous gas embolization was performed within 120 min after the dive. Results The divers were affected by both cold-water-induced hemodynamic changes and immersion-related fluid loss. Both systolic and diastolic functions were impaired after the dive although the changes in cardiac functions were subtle. Venous inert gas bubbles were detected in all divers except for one. Venous gas embolism did not affect systolic or diastolic function. Conclusion A single trimix CCR dive in arctic cold water seemed to debilitate both systolic and diastolic function. Although the changes were subtle, they appeared parallel over several parameters. This indicates a real post-dive deterioration in cardiac function instead of only volume-dependent changes. These changes are without a clinical significance in healthy divers. However, in a population with pre-existing or underlying heart problems, such changes may provoke symptomatic problems during or after the dive.
... Inert gases, when breathed under elevated pressure, dissolve in increased amounts in body tissues and fluids. If divers surface at an inappropriate rate (e.g., too fast or without obligatory decompression stops), such gases do not remain in a dissolved state and form numerous tissue and vascular bubbles that may cause well-documented damage to different organ systems, known as decompression incidents, including arterial endothelial dysfunction [2] and changes in cardiovascular function [3][4][5]. Other effects, such as alterations in cognitive functions, motor control, and mood have also been reported in scuba diving [6][7][8]. ...
... The bubble grade at rest (before a cough) for the air prebreathing protocol was 2 (1-3), and for the O2 prebreathing protocol this value was 1.5 (0-2.25), as measured 30 min after the dive (p < 0.005, Figure 3). The bubble grade after a cough for the air prebreathing protocol was 3 (2)(3)(4), and for the O2 prebreathing protocol this value was 2 (1.5-3), as measured 30 min after the cough (p = 0.035; Figure 3). ...
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Introduction: This research was performed to examine the effects of air and oxygen prebreathing on bubble formation, flow-mediated dilatation, and psychomotor performance after scuba dives. Methods: Twelve scuba divers performed two dives using a gas mixture of oxygen, nitrogen, and helium (trimix). In a randomized protocol, they breathed air or oxygen 30 min before the trimix dives. Venous bubble formation, flow-mediated dilatation, and psychomotor performance were evaluated. The participants solved three psychomotor tests: determining the position of a light signal, coordination of complex psychomotor activity, and simple arithmetic operations. The total test solving time, minimum single-task solving time, and median solving time were analyzed. Results: The bubble grade was decreased in the oxygen prebreathing protocol in comparison to the air prebreathing protocol (1.5 vs. 2, p < 0.001). The total test solving times after the dives, in tests of complex psychomotor coordination and simple arithmetic operations, were shorter in the oxygen prebreathing protocol (25 (21–28) vs. 31 (26–35) and 87 (82–108) vs. 106 (90–122) s, p = 0.028). Conclusions: In the oxygen prebreathing protocol, the bubble grade was significantly reduced with no change in flow-mediated dilatation after the dives, indicating a beneficial role for endothelial function. The post-dive psychomotor speed was faster in the oxygen prebreathing protocol.
... While the vast majority of divers have no history of heart disease and active divers score better than the general population on known risk factors , cardiovascular problems were reported as being prominentsecond only to drowning -as cause of diver fatalities in the Divers Alert Network's annual diving report . Prior human experimental studies of diveinduced cardiovascular changes have largely been limited to recording of baseline and post-dive data (Marabotti et al., 1999;Boussuges et al., 2006;Dujic et al., 2006). Thus, limited knowledge of functional parameters exist to describe the progression of cardiovascular changes taking place during the dive, which may be important for the tolerance of diving stress and outcome. ...
... Our experiments were performed in a dry pressure chamber, which limits the general interpretation of the result. Dry dives are not directly comparable to SCUBA diving where water immersion induces prolonged cardiovascular changes (Marabotti et al., 1999(Marabotti et al., , 2013Boussuges et al., 2009), and influences bubble production and DCS risk (Obad et al., 2007;Gaustad et al., 2010). To improve the understanding of cardiovascular responses to wet diving, future studies should include LV pressure-volume recording in immersed animals. ...
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Cardiovascular risk is elevated in divers, but detailed information of cardiac function during diving is missing. The aim of this study was to apply an intact rat model with continuous monitoring of cardiac left ventricular (LV) function in a simulated diving experiment. Thirteen rats were inserted with a LV pressure–volume catheter and a pressure transducer in the femoral artery to measure hemodynamic variables, and randomly assigned to diving (n = 9) and control (n = 4) groups. The diving group was compressed to 600 kPa in air, maintained at pressure for 45 min (bottom phase), and decompressed to surface at 50 kPa/min. Data was collected before, during, and up to 60 min after exposure in the diving group, and at similar times in non-diving controls. During the bottom phase, stroke volume (SV) (−29%) and cardiac output (−30%) decreased, whereas LV end-systolic volume (+13%), mean arterial pressure (MAP) (+29%), and total peripheral resistance (TPR) (+72%) increased. There were no changes in LV contractility, stroke work, or diastolic function. All hemodynamic variables returned to baseline values within 60 min after diving. In conclusion, our simulated dive experiment to 600 kPa increased MAP and TPR to levels which caused a substantial reduction in SV and LV volume output. The increase in cardiac afterload demonstrated to take place during a dive is well tolerated by the healthy heart in our model, whereas in a failing heart this abrupt change in afterload may lead to acute cardiac decompensation.
... This blood shift phenomenon induces an increase in right cardiac preload, evidenced by dilation of the inferior vena cava and the RV. 13,[27][28][29] Negative pressure ventilation, generated by negative SLL, further amplifies this phenomenon. 13 According to the Frank-Starling law, the increase in right cardiac preload and thus the filling of the right ventricle induced by immersion naturally should result in enhanced contraction of the right ventricle. ...
... Although not measured in the current study, it is possible that venous gas emboli (VGE) could have been generated in some subjects during and following decompression because of nitrogen off-gassing. VGE can induce a variety of biological effects [31] through their interaction with blood [32,33], incitement of epithelium damage, and microcirculatory impairment [34] that can result in an inflammatory response [35,36]. As VGE are filtered by the lungs it is possible that some of the biochemical products and metabolites resulting from the effects of the VGE are carried in the circulation and are subsequently reflected in the EBC. ...
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Prolonged exposure to hyperbaric hyperoxia can lead to pulmonary oxygen toxicity (PO2tox). PO2tox is a mission limiting factor for special operations forces divers using closed-circuit rebreathing apparatus and a potential side effect for patients undergoing hyperbaric oxygen (HBO) treatment. In this study, we aim to determine if there is a specific breath profile of compounds in exhaled breath condensate (EBC) that is indicative of the early stages of pulmonary hyperoxic stress/PO2tox. Using a double-blind, randomized ‘sham’ controlled, cross-over design 14 U.S. Navy trained diver volunteers breathed two different gas mixtures at an ambient pressure of 2 ATA (33 fsw, 10 msw) for 6.5 h. One test gas consisted of 100% O2 (HBO) and the other was a gas mixture containing 30.6% O2 with the balance N2 (Nitrox). The high O2 stress dive (HBO) and low O2 stress dive (Nitrox) were separated by at least seven days and were conducted dry and at rest inside a hyperbaric chamber. EBC samples were taken immediately before and after each dive and subsequently underwent a targeted and untargeted metabolomics analysis using liquid chromatography coupled to mass spectrometry (LC-MS). Following the HBO dive, 10 out of 14 subjects reported symptoms of the early stages of PO2tox and one subject terminated the dive early due to severe symptoms of PO2tox. No symptoms of PO2tox were reported following the nitrox dive. A partial least-squares discriminant analysis of the normalized (relative to pre-dive) untargeted data gave good classification abilities between the HBO and nitrox EBC with an AUC of 0.99 (±2%) and sensitivity and specificity of 0.93 (±10%) and 0.94 (±10%), respectively. The resulting classifications identified specific biomarkers that included human metabolites and lipids and their derivatives from different metabolic pathways that may explain metabolomic changes resulting from prolonged HBO exposure.
... Self-contained underwater breathing apparatus (SCUBA) diving with compressed air, the most common type of gas used in diving, is associated with venous gas bubbles formation, arterial endothelial dysfunction (1), and other cardiovascular changes (2)(3)(4). The excess gas taken up into the tissues during the compression phase of the dive (descent) has to be eliminated when returning to the surface during pressure reduction (decompression). ...
Article
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Aim To assess the effect of air, gas mixture composed of 50% nitrogen and 50% oxygen (nitrox 50), or gas mixture composed of 1% nitrogen and 99% oxygen (nitrox 99) on bubble formation and vascular/endothelial function during decompression after self-contained underwater breathing apparatus diving. Methods This randomized controlled study, conducted in 2014, involved ten divers. Each diver performed three dives in a randomized protocol using three gases: air, nitrox 50, or nitrox 99 during ascent. The dives were performed on three different days limited to 45 m sea water (msw) depth with 20 min bottom time. Nitrogen bubbles formation was assessed by ultrasound detection after dive. Arterial/ endothelial function was evaluated by brachial artery flow mediated dilatation (FMD) before and after dive. Results Nitrox 99 significantly reduced bubble formation after cough compared with air and nitrox 50 (grade 1 vs 3 and vs 3, respectively, P = 0.026). Nitrox 50 significantly decreased post-dive FMD compared with pre-dive FMD (3.62 ± 5.57% vs 12.11 ± 6.82% P = 0.010), while nitrox 99 did not cause any significant change. Conclusion Nitrox 99 reduced bubble formation, did not change post-dive FMD, and decreased total dive duration, indicating that it might better preserve endothelial function compared with air and nitrox 50 dive protocols.
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