Claus-Martin Muth

Decompression illness, iatrogenic gas embolism, and carbon monoxide poisoning: the role of hyperbaric oxygen therapy.

Decompression Illness and Iatrogenic Gas EmbolismHyperbaric oxygen therapy (HBOT) is the treatment of choice in medical emergencies in which gas bubbles released in the tissues lead to profound disturbances of physiological processes and tissue injury. There are two major pathways for gas bubble dis

DNA damage after long-term repetitive hyperbaric oxygen exposure.

A single exposure to hyperbaric oxygen (HBO), i.e., pure oxygen breathing at supra-atmospheric pressures, causes oxidative DNA damage in humans in vivo as well as in isolated lymphocytes of human volunteers. These DNA lesions, however, are rapidly repaired, and an adaptive protection is triggered against further oxidative stress caused by HBO exposure. Therefore, we tested the hypothesis that long-term repetitive exposure to HBO would modify the degree of DNA damage. Combat swimmers and underwater demolition team divers were investigated because their diving practice comprises repetitive long-term exposure to HBO over years. Nondiving volunteers with and without endurance training served as controls. In addition to the measurement of DNA damage in peripheral blood (comet assay), blood antioxidant enzyme activities, and the ratio of oxidized and reduced glutathione content, we assessed the DNA damage and superoxide anion radical (O(2)(*-)) production induced by a single ex vivo HBO exposure of isolated lymphocytes. All parameters of oxidative stress and antioxidative capacity in vivo were comparable in the four different groups. Exposure to HBO increased both the level of DNA damage and O(2)(*-) production in lymphocytes, and this response was significantly more pronounced in the cells obtained from the combat swimmers than in all the other groups. However, in all groups, DNA damage was completely removed within 1 h. We conclude that, at least in healthy volunteers with endurance training, long-term repetitive exposure to HBO does not modify the basal blood antioxidant capacity or the basal level of DNA strand breaks. The increased ex vivo HBO-related DNA damage in isolated lymphocytes from these subjects, however, may reflect enhanced susceptibility to oxidative DNA damage.

Scuba diving and the heart. Cardiac aspects of sport scuba diving

Zusammenfassung.Tauchen mit autonomem Tauchgerät hat sich zu einem beliebten Freizeitsport entwickelt, und es gibt zunehmend Hinweise darauf, dass nicht nur junge, gesunde Menschen, sondern auch solche mit vorbestehenden kardiovaskulären Erkrankungen diese Aktivität aufnehmen. Zur sicheren Ausübung dieses Sports ist nicht unbedingt eine athletische Kondition notwendig, aber die physikalischen Besonderheiten der Umgebung unter Wasser haben physiologische Auswirkungen auf den Organismus und erfordern eine gewisse medizinische Fitness. Dem Herz-Kreislauf-System kommt dabei eine zentrale Bedeutung im Rahmen der Risikoabschätzung bei der Beurteilung der medizinischen Tauchtauglichkeit zu. Die immersionsbedingte Erhöhung von kardialer Vor- und Nachlast führt zu einer besonderen Belastung des Herzens, welche im Fall einer Vorschädigung fatale Konsequenzen haben kann. Venöse Mikrogasblasen können bei Vorliegen eines kardialen Rechts-links-Shunts in das arterielle System gelangen und zur arteriellen Gasembolie führen. Es ist daher wichtig, Tauchkandidaten medizinisch zu untersuchen und bei Vorliegen von kardiovaskulären Kontraindikationen auf die bestehenden Risiken hinzuweisen.Abstract.Diving with self-contained underwater breathing apparatus (scuba) has become a popular recreational sports activity throughout the world. A high prevalence of cardiovascular disorders among the population makes it therefore likely that subjects suffering from cardiovascular problems may want to start scuba diving.Although scuba diving is not a competitive sport requiring athletic health conditions, a certain medical fitness is recommended because of the physical peculiarities of the underwater environment. Immersion alone will increase cardiac preload by central blood pooling with a rise in both cardiac output and blood pressure, counteracted by increased diuresis. Exposure to cold and increased oxygen partial pressure during scuba diving will additionally increase afterload by vasoconstrictive effects and may exert bradyarryhthmias in combination with breath-holds. Volumes of gas-filled body cavities will be affected by changing pressure (Figure 1), and inert gas components of the breathing gas mixture such as nitrogen in case of air breathing will dissolve in body tissues and venous blood with increasing alveolar inert gas pressure. During decompression a free gas phase may form in supersaturated tissues, resulting in the generation of inert gas microbubbles that are eliminated by the venous return to the lungs under normal circumstances.Certain cardiovascular conditions may have an impact on these physiological changes and pose the subject at risk of suffering adverse events from scuba diving. Arterial hypertension may be aggravated by underwater exercise and immersion. Symptomatic coronary artery disease and symptomatic heart rhythm disorders preclude diving. The occurrence of ventricular extrasystoles according to Lown classes I and II, and the presence of atrial fibrillation are considered relative contraindications in the absence of an aggravation following exercise. Asymptomatic subjects with Wolff-Parkinson-White syndrome may be allowed to dive, but in case of paroxysmal supraventricular tachycardia they must refrain from diving. Pacemakers will fail with increasing pressure, but some manufacturers have proven their products safe for pressure equivalents of up to 30 m of seawater, so that patients may dive uneventfully when staying within the 0–20 m depth range. Significant aortic or mitral valve stenosis will preclude diving, whereas regurgitation only will not be a problem. Right-to-left shunts have increasingly gained attention in diving medicine, since they may allow venous gas microbubbles to spill over to the arterial side of the circulation enabling the possibility of arterial gas embolism. Significant shunts thus preclude diving. The highly prevalent patent foramen ovale is considered a relative contraindication only when following certain recommendations for safe diving (Table 2). Metabolic disorders are of concern, since adiposity is associated with both, higher bubble grades in Doppler ultrasound detection after scuba dives when compared to normal subjects, and an increased epidemiologic risk of suffering from decompression illness. In conclusion, cardiovascular aspects are important in the assessment of fitness to dive, and certain cardiovascular conditions preclude scuba diving. Any history of cardiac disease or abnormalities detected during the routine medical examination should prompt to further evaluation and specialist referral.

Should children dive with self‐contained underwater breathing apparatus (SCUBA)?

Diving with self‐contained underwater breathing apparatus (SCUBA) has become a popular recreational activity in children and adolescents. This article provides an extensive review of the current literature.

Efficacy of ventilation and ventilation adjuncts during in-water-resuscitation—A randomized cross-over trial ☆

INTRODUCTION Drowning is a common cause of death in young adults. The 2010 guidelines of the European Resuscitation Council call for in-water-resuscitation (IWR). There has been controversy about IWR amongst emergency and diving physicians for decades. The aim of the present study was assessing the efficacy of IWR. METHODS In this randomized cross-over trial, nineteen lifeguards performed a rescue manoeuvre over a 100 m distance in open water. All subjects performed the procedure four times in random order: with no ventilation (NV) and transportation only, mouth-to-mouth ventilation (MMV), bag-mask-ventilation (BMV) and laryngeal tube ventilation (LTV). Tidal volumes, ventilation rate and minute-volumes were recorded using a modified Laerdal Resusci Anne manikin. Furthermore, water aspiration and number of submersions of the test mannequin were assessed, as well as the physical effort of the lifeguard rescuers.One lifeguard subject did not complete MMV due to exhaustion and was excluded from analysis. RESULTS NV was the fastest rescue manoeuvre (advantage ∼40s). MMV and LTV were evaluated as efficient and relatively easy to perform by the lifeguards. While MMV (mean 199 ml) and BMV (mean 481 ml) were associated with a large amount of aspirated water, aspiration was significantly lower in LTV (mean 118 ml). The efficacy of ventilation was consistently good in LTV (Vt=447 ml), continuously poor in BMV (Vt=197) and declined substantially during MMV (Vt=1,019 ml initially and Vt=786 ml at the end). The physical effort of the lifeguards was remarkably higher when performing IWR: 3.7 in NV, 6.7 in MMV, 6.4 in BMV and 4.8 in LTV as measured on the 0-10 visual analogue scale. CONCLUSION IWR in open water is time consuming and physically demanding. The IWR training of lifeguards should put more emphasis on a reduction of aspiration. The use of ventilation adjuncts like the laryngeal tube might ease IWR, reduce aspiration of water and increase the efficacy of ventilation during IWR.

Effectiveness and Safety of In-Water Resuscitation Performed by Lifeguards and Laypersons: A Crossover Manikin Study

Abstract Objective. Drowning is associated with a high mortality and morbidity and a common cause of death. In-water resuscitation (IWR) in the case of drowning accidents has been recommended by certain resuscitation guidelines in the last several years. IWR has been discussed controversially in the past, especially with regard to the delay of chest compressions, effectiveness of ventilation, and hazard to the rescuer. The aim of the present study was to assess the effectiveness and safety of IWR. Methods. In this crossover manikin study, 21 lifeguards and 21 laypersons performed two rescue procedures in an indoor swimming pool over a 50-meter distance: In random order, one rescue procedure was performed with in-water ventilation and one without. Tidal and minute volumes were recorded using a modified Laerdal Resusci Anne (Laerdal Medical, Stavanger, Norway) and total rescue duration, submersions, water aspiration by the victim, and physical effort were assessed. Results. IWR resulted in significant increases in rescue duration (lifeguards: 106 vs. 82 seconds; laypersons: 133 vs. 106 seconds) and submersions (lifeguards: 3 vs. 1; laypersons: 5 vs. 0). Furthermore, water aspiration (lifeguards: 112 vs. 29 mL; laypersons: 160 vs. 56 mL) and physical effort (lifeguards: visual analog scale [VAS] score 7 vs. 5; laypersons: VAS score 8 vs. 6) increased significantly when IWR was performed. Lifeguards achieved significantly better ventilation characteristics and performed both rescue procedures faster and with lower side effects. IWR performed by laypersons was insufficient with regard to both tidal and minute volumes. Conclusions. In-water resuscitation is associated with a delay of the rescue procedure and a relevant aspiration of water by the victim. IWR appears to be possible when performed over a short distance by well-trained professionals. The training of lifeguards must place particular emphasis on a reduction of submersions and aspiration when IWR is performed. IWR by laypersons is exhausting, time-consuming, and inefficient and should probably not be recommended. Key words: drowning; near-drowning; hypoxia; ventilation, artificial; respiration, artificial; resuscitation, in-water

Effects of a media campaign on resuscitation performance of bystanders: a manikin study

Objective Cardiac arrest is associated with a poor outcome if cardiopulmonary resuscitation (CPR) is delayed. Nevertheless, CPR performance by laypersons in witnessed cardiac arrest is frequently poor. The present study evaluated the effect of a media campaign on CPR performance. Participants and methods CPR performance of 1000 individuals who did not have any medical background was evaluated using a resuscitation manikin. The media campaign consisted of flyers, posters, and electronic advertisement. Five hundred individuals were evaluated before the media campaign and 500 individuals after the media campaign. Age and male/female ratio were comparable within each of the groups. Premedia campaign performance was compared with postmedia campaign performance with respect to chest compressions and ventilation metrics. Results Chest compression depth and total compression work were significantly higher after the media campaign: median depth 51 mm postcampaign versus 45 mm precampaign (P<0.001), median cumulative compression work postcampaign 4176 versus 2462 mm precampaign (P<0.001). Tidal volumes and ventilation work were significantly lower following the media campaign, but did not differ between participants who had acknowledged exposure to the campaign and those who did not. Ventilation performance was generally poor across the two groups both before and after the media campaign. Conclusion A simple and cost-efficient media campaign appears to enhance the performance of chest compressions. Ventilation performance and the rate of CPR performance were not increased by the campaign.

Commentaries on Viewpoint: Why predominantly neurological DCS in breath-hold divers?

TO THE EDITOR: Schipke and Tetzlaff (5) suggest breath-hold diving may recruit intrapulmonary arteriovenous anastomoses (IPAVA), providing a pathway for venous gas emboli to become arterialized leading to transient neurological injury consistent with transient ischemic attacks. To be a valid hypothesis there must be evidence of microbubbles in the right ventricle, left ventricle, carotid, or cerebral arteries of breath-hold divers after a typical dive profile with common dive times and surface intervals. Only one study could find evidence of microbubbles in the pulmonary infundibulum in a single subject (2) who had never even had symptoms of decompression sickness! With no evidence of arterialized microbubbles, the suggestion of IPAVA recruitment is premature. The recruitment of IPAVA by hypoxia is equally controversial, owing in part to an invalidated measurement technique that lacks a quantifiable assessment of IPAVA blood flow and involves a contrast agent that is susceptible to changes in transit time, blood gases, barometric pressure, and blood viscosity (1). Alternatively, we wondered if the dive profile of commercial breath-hold divers could be a sufficient intermittent hypoxic stimulus predisposing divers to the same cerebrovascular dysfunction observed in obstructive sleep apnea patients with similar presentations on neuroimaging studies (4). Progressive cerebrovascular dysfunction may underlie acute neurological injury, particularly if breath-hold diving acutely increases cerebrovascular transmural wall stress (through increased cerebral blood volume). The presence of vasogenic edema in breath-hold divers with neurological injury (3) supports a role for the breakdown of the blood-brain barrier, rather than gas emboli from IPAVA recruitment.

[Hyperbaric therapy and diving medicine - diving medicine - present state and prospects].

The diving accident (decompression incident, DCI) occurs in the decompression phase of dives. The DCI can either be caused by an arterial gas embolism (AGE) subsequent to a pulmonary barotrauma or by the formation of inert gas bubbles subsequent to a reduction of ambient pressure during the ascent from depth. In contrast to the traditional assumption that decompression incidents only occur if decompression rules are neglected, recent data indicate that a vast amount of diving accidents occur even though divers adhered to the rules. Hence, there is a large inter- and intraindividual variability in the predisposition for diving accidents. Within the past few years, the molecular understanding of the pathophysiology of diving accidents has improved considerably. It is now well accepted that pro-inflammatory and pro-coagulatory mechanisms play a central role. Moreover, microparticles are increasingly discussed in the pathogenesis of diving accidents. These new molecular findings have not yet resulted in new therapeutic approaches. However, new approaches of preconditioning before the dive have been developed which are intended to reduce the risk of diving accidents. The symptoms of a diving accident show a large variability and range. They reach from pruritus over tension in the female breast, marbled skin and pain in the joints to severe neurological disability like paraplegia or hemiplegia. Furthermore, pulmonary symptoms can be a result of a pulmonary gas embolism and/or a tension pneumothorax. Extreme cases can also manifest as generalized, difficult-to-treat seizures, loss of consciousness or even death. The evidence-based therapy of diving accidents consists of an immediate application of 100% inspiratory O2. This can be performed via a demand valve, face mask with reservoir bag or ventilation bag connected to a reservoir bag. Fluid substitution is performed by i. v. infusion of 500-1000ml/h of cristalloids. If consciousness is not impaired, the diver is positioned in a supine position, in case of impaired or absent consciousness in a lateral recovery position. Especially in severe cases of DCI a fast transfer to a qualified hyperbaric center and the earliest possible hyperbaric O2-therapy is essential.

Oxylator and SCUBA dive regulators: useful utilities for in-water resuscitation

Introduction In water resuscitation has been reported to enhance the outcome of drowning victims. Mouth-to-mouth ventilation during swimming is challenging. Therefore, the efficacy of ventilation utilities was evaluated. Methods Ventilation was assessed with the Oxylator ventilator, as well as the consecutive self-contained underwater breathing apparatus (SCUBA) regulators using an anaesthetic test lung: Poseidon Cyklon 5000, Poseidon XStream, Apeks TX 100, Spiro Arctic, Scubapro Air2 and Buddy AutoAir. Results Oxylator, Apeks TX 100, Arctic and Buddy AutoAir delivered reliable peak pressures and tidal volumes. In contrast, the ventilation parameters remarkably depended on duration and depth of pressing the purge button in Poseidon Cyklon 5000, Poseidon XStream and Scubapro Air2. Critical peak pressures occurred during ventilation with all these three regulators. Discussion The use of Poseidon Cyklon 5000, Poseidon XStream and Scubapro Air2 regulators is consequently not recommended for in-water ventilation. With the limitation that the devices were tested with a test lung and not in a human field study, Apeks TX 100, Spiro Arctic and Buddy AutoAir might be used for emergency ventilation and probably ease in-water resuscitation for the dive buddy of the victim. Professional rescue divers could be equipped with the Oxylator and an oxygen tank to achieve an early onset of efficient in-water ventilation in drowning victims.