Variability in circulating gas emboli after a same scuba diving exposure (original) (raw)
Related papers
Determinants of arterial gas embolism after scuba diving
Journal of Applied Physiology, 2012
Scuba diving is associated with breathing gas at increased pressure, which often leads to tissue gas supersaturation during ascent and the formation of venous gas emboli (VGE). VGE crossover to systemic arteries (arterialization), mostly through the patent foramen ovale, has been implicated in various diving-related pathologies. Since recent research has shown that arterializations frequently occur in the absence of cardiac septal defects, our aim was to investigate the mechanisms responsible for these events. Divers who tested negative for patent foramen ovale were subjected to laboratory testing where agitated saline contrast bubbles were injected in the cubital vein at rest and exercise. The individual propensity for transpulmonary bubble passage was evaluated echocardiographically. The same subjects performed a standard air dive followed by an echosonographic assessment of VGE generation (graded on a scale of 0–5) and distribution. Twenty-three of thirty-four subjects allowed th...
Pre-Dive Exercise and Post-Dive Evolution of Venous Gas Emboli
Aviation, Space, and Environmental Medicine, 2012
Background: Recent studies have indicated that exercise before diving signifi cantly reduces the number of circulating bubbles and the risk of decompression sickness. However, the most effective time delay between exercise and dive is not clear; the present aim was to resolve this. Methods: In a hyperbaric chamber, 10 men were compressed to 18 m for 100 min, then decompressed as per Royal Navy Table 11. Each subject performed three dives: a control dive and two after exercise performed either 24 h or 2 h before diving. Exercise consisted of 40 min submaximal work on a cycle ergometer. Venous gas emboli (VGE) were evaluated using precordial Doppler ultrasound immediately on surfacing, with measurements made at 5-min intervals for 30 min, and at 15-min intervals for at least 2.5 h total using the Kisman Masurel (KM) scale. Results: Exercise either 24 or 2 h prior to a dive did not reduce the median number of circulating VGE (median maximum KM grade: control, 2 1 ; for both exercise dives, 3). Bubbles disappeared from the circulation faster after the control dive than the exercise dives. Time to median KM Doppler scores of zero were: control:120 min; 2-h group: 225 min; 24-h group: 165 min. Conclusion: Cycling exercise prior to diving did not reduce the number of circulating VGE in comparison to control, in contrast to recent studies. A number of factors may be responsible for these fi ndings, including type of exercise performed, wet diving experience, and disparity in Doppler measurement techniques.
Detection Of Venous Gas Emboli After Repetitive Breath-Hold Dives: Case Report
2016
Introduction: Neurological symptoms after breath-hold (BH) diving are often referred to as "Taravana" and considered a form of decompression sickness. However, the presence of "high" gas embolism after BH diving has never been clearly shown. This study showed high bubble formation after BH diving. Materials and methods: We performed transthoracic echocardiography on a 53-year-old male spearfishing diver (180 cm; 80 kg; BMI 24.7) 15 minutes before diving and at 15-minute intervals for 90 minutes after diving in a 42-meter-deep pool. Number of dives, bottom time and surface intervals were freely determined by the diver. Dive profiles were digitally recorded for depth, time and surface interval, using a freediving computer. Relative surface interval (surface interval/diving time) and gradient factor were calculated. Results: High bubble grades were found in all the recorded echocardiograms. From the first to third recording (45 minutes), Grade 4 Eftedal-Brubakk (EB) bubbles were observed. The 60-, 75and 90-minute recordings showed a reduction to Grades 3, 2 and 1 EB. Mean calculated GF for every BH dive was 0.22; maximum GF after the last dive was 0.33. Conclusions: High bubble grades can occur in BH diving, as confirmed by echocardiographic investigation. Ordinary methods to predict inert gas super-saturation may not able to predict Taravana cases.
Exercise-induced intrapulmonary shunting of venous gas emboli does not occur after open-sea diving
Journal of Applied Physiology, 2005
Dujić, Ž eljko, Ivan Palada, Ante Obad, Darko Duplančić, Alf O. Brubakk, and Zoran Valic. Exercise-induced intrapulmonary shunting of venous gas emboli does not occur after open-sea diving. arterializations of venous gas emboli can lead to neurological damage after diving with compressed air. Recently, significant exercise-induced intrapulmonary anatomical shunts have been reported in healthy humans that result in widening of alveolar-to-arterial oxygen gradient. The aim of this study was to examine whether intrapulmonary shunts can be found following strenuous exercise after diving and, if so, whether exercise should be avoided during that period. Eleven healthy, military male divers performed an open-sea dive to 30 m breathing air, remaining at pressure for 30 min. During the bottom phase of the dive, subjects performed mild exercise at ϳ30% of their maximal oxygen uptake. The ascent rate was 9 m/min. Each diver performed graded upright cycle ergometry up to 80% of the maximal oxygen uptake 40 min after the dive. Monitoring of venous gas emboli was performed in both the right and left heart with an ultrasonic scanner every 20 min for 60 min after reaching the surface pressure during supine rest and following two coughs. The diving profile used in this study produced significant amounts of venous bubbles. No evidence of intrapulmonary shunting was found in any subject during either supine resting posture or any exercise grade. Also, short strenuous exercise after the dive did not result in delayed-onset decompression sickness in any subject, but studies with a greater number of participants are needed to confirm whether divers should be allowed to exercise after diving. decompression sickness; echocardiography; maximal oxygen consumption; human Note that diver 7 did not show any bubbles during the observation period, so he was excluded from cyclic ergometer procedure and further analysis.
Venous gas emboli are involved in post-dive macro, but not microvascular dysfunction
European journal of applied physiology, 2017
Previous studies have shown vascular dysfunction of main conductance arteries and microvessels after diving. We aim to evaluate the impact of bubble formation on vascular function and haemostasis. To achieve this, we used a vibration preconditioning to influence bubble levels without changing any other parameters linked to the dive. Twentty-six divers were randomly assigned to one of three groups: (1) the "vibrations-dive" group (VD; n = 9) was exposed to a whole-body vibration session 30 min prior the dive; (2) the "diving" group (D; n = 9) served as a control for the effect of the diving protocol; (3) The "vibration" protocol (V; n = 8) allowed us to assess the effect of vibrations without diving. Macro- and microvascular function was assessed for each subject before and after the dive, subsequently. Bubble grades were monitored with Doppler according to the Spencer grading system. Blood was taken before and after the protocol to assess any change of ...
Venous bubble count declines during strenuous exercise after an open sea dive to 30 m
Aviation, space, and environmental medicine, 2006
The effect of post-dive exercise on bubble formation remains controversial, although the current practice of divers and aviators is to avoid strenuous exercise after diving. Previously, we have shown that exercising 24 h before a dive, or during a decompression stop, significantly reduces bubble formation in man. The objective of this study was to determine whether a short period of strenuous post-dive exercise promotes venous bubble formation. Seven male military divers performed an open-sea field dive to a maximum depth of 30 m for 30 min. At maximum depth, subjects performed mild underwater fin swimming, followed by standard decompression. Diving was followed by a post-dive exercise session consisting of short, strenuous incremental upright cycle ergometry, up to 85% of maximal oxygen uptake, for about 10 min. Subjects were monitored for venous gas bubbles in the right heart with an echo-imaging system starting 20 min post-dive while in the supine position, during cycle ergometry...
2014
The use of portable 2D echocardiography and 'frame-based' bubble counting as a tool to evaluate diving decompression stress. Diving and Hyperbaric Medicine. 2014 March;44(1):5-13.) Introduction: 'Decompression stress' is commonly evaluated by scoring circulating bubble numbers post dive using Doppler or cardiac echography. This information may be used to develop safer decompression algorithms, assuming that the lower the numbers of venous gas emboli (VGE) observed post dive, the lower the statistical risk of decompression sickness (DCS). Current echocardiographic evaluation of VGE, using the Eftedal and Brubakk method, has some disadvantages as it is less well suited for large-scale evaluation of recreational diving profiles. We propose and validate a new 'frame-based' VGE-counting method which offers a continuous scale of measurement. Methods: Nine 'raters' of varying familiarity with echocardiography were asked to grade 20 echocardiograph recordings using both the Eftedal and Brubakk grading and the new 'frame-based' counting method. They were also asked to count the number of bubbles in 50 still-frame images, some of which were randomly repeated. A Wilcoxon Spearman rho calculation was used to assess test-retest reliability of each rater for the repeated still frames. For the video images, weighted kappa statistics, with linear and quadratic weightings, were calculated to measure agreement between raters for the Eftedal and Brubakk method. Bland-Altman plots and intra-class correlation coefficients were used to measure agreement between raters for the frame-based counting method. Results: Frame-based counting showed a better inter-rater agreement than the Eftedal and Brubakk grading, even with relatively inexperienced assessors, and has good intra-and inter-rater reliability. Conclusion: Frame-based bubble counting could be used to evaluate post-dive decompression stress, and offers possibilities for computer-automated algorithms to allow near-real-time counting.
Diving and hyperbaric medicine, 2014
Germonpré P, Papadopoulou V, Hemelryck W, Obeid G, Lafère P, Eckersley RJ, Tang M-X, Balestra C. The use of portable 2D echocardiography and 'frame-based' bubble counting as a tool to evaluate diving decompression stress. Diving and Hyperbaric Medicine. 2014 March;44(1):5-13.) Introduction: 'Decompression stress' is commonly evaluated by scoring circulating bubble numbers post dive using Doppler or cardiac echography. This information may be used to develop safer decompression algorithms, assuming that the lower the numbers of venous gas emboli (VGE) observed post dive, the lower the statistical risk of decompression sickness (DCS). Current echocardiographic evaluation of VGE, using the Eftedal and Brubakk method, has some disadvantages as it is less well suited for large-scale evaluation of recreational diving profi les. We propose and validate a new 'frame-based' VGE-counting method which offers a continuous scale of measurement. Methods: Nine 'raters' of varying familiarity with echocardiography were asked to grade 20 echocardiograph recordings using both the Eftedal and Brubakk grading and the new 'frame-based' counting method. They were also asked to count the number of bubbles in 50 still-frame images, some of which were randomly repeated. A Wilcoxon Spearman rho calculation was used to assess test-retest reliability of each rater for the repeated still frames. For the video images, weighted kappa statistics, with linear and quadratic weightings, were calculated to measure agreement between raters for the Eftedal and Brubakk method. Bland-Altman plots and intra-class correlation coeffi cients were used to measure agreement between raters for the frame-based counting method. Results: Frame-based counting showed a better inter-rater agreement than the Eftedal and Brubakk grading, even with relatively inexperienced assessors, and has good intra-and inter-rater reliability. Conclusion: Frame-based bubble counting could be used to evaluate post-dive decompression stress, and offers possibilities for computer-automated algorithms to allow near-real-time counting.
Aerobic exercise before diving reduces venous gas bubble formation in humans
The Journal of Physiology, 2004
We have previously shown in a rat model that a single bout of high-intensity aerobic exercise 20 h before a simulated dive reduces bubble formation and after the dive protects from lethal decompression sickness. The present study investigated the importance of these findings in man. Twelve healthy male divers were compressed in a hyperbaric chamber to 280 kPa at a rate of 100 kPa min −1 breathing air and remaining at pressure for 80 min. The ascent rate was 9 m min −1 with a 7 min stop at 130 kPa. Each diver underwent two randomly assigned simulated dives, with or without preceding exercise. A single interval exercise performed 24 h before the dive consisted of treadmill running at 90% of maximum heart rate for 3 min, followed by exercise at 50% of maximum heart rate for 2 min; this was repeated eight times for a total exercise period of 40 min. Venous gas bubbles were monitored with an ultrasonic scanner every 20 min for 80 min after reaching surface pressure. The study demonstrated that a single bout of strenuous exercise 24 h before a dive to 18 m of seawater significantly reduced the average number of bubbles in the pulmonary artery from 0.98 to 0.22 bubbles cm −2 (P = 0.006) compared to dives without preceding exercise. The maximum bubble grade was decreased from 3 to 1.5 (P = 0.002) by pre-dive exercise, thereby increasing safety. This is the first report to indicate that pre-dive exercise may form the basis for a new way of preventing serious decompression sickness.