Decompression Illness In Divers Research Articles

Decompression Illness in Divers With or Without Patent Foramen Ovale : A Cohort Study.

In previous studies, the prevalence of patent foramen ovale (PFO) has been reported to be higher in scuba divers who experienced decompression illness (DCI) than in those who did not. To assess the association between PFO and DCI in scuba divers. Prospective cohort study. Tertiary cardiac center in South Korea. One hundred experienced divers from 13 diving organizations who did more than 50 dives per year. Participants had transesophageal echocardiography with a saline bubble test to determine the presence of a PFO and were subsequently divided into high- and low-risk groups. They were followed using a self-reported questionnaire while blinded to their PFO status. All of the reported symptoms were adjudicated in a blinded manner. The primary end point of this study was PFO-related DCI. Logistic regression analysis was done to determine the odds ratio of PFO-related DCI. Patent foramen ovale was seen in 68 divers (37 at high risk and 31 at low risk). Patent foramen ovale-related DCI occurred in 12 divers in the PFO group (non-PFO vs. high-risk PFO vs. low-risk PFO: 0 vs. 8.4 vs. 2.0 incidences per 10000 person-dives; P= 0.001) during a mean follow-up of 28.7 months. Multivariable analysis showed that high-risk PFO was independently associated with an increased risk for PFO-related DCI (odds ratio, 9.34 [95% CI, 1.95 to 44.88]). The sample size was insufficient to assess the association between low-risk PFO and DCI. High-risk PFO was associated with an increased risk for DCI in scuba divers. This finding indicates that divers with high-risk PFO are more susceptible to DCI than what has been previously reported and should consider either refraining from diving or adhering to a conservative diving protocol. Sejong Medical Research Institute.

Patent Foramen Ovale-A Not So Innocuous Septal Atrial Defect in Adults.

Patent foramen ovale (PFO) is a common congenital atrial septal defect with an incidence of 15–35% in the adult population. The development of the interatrial septum is a process that begins in the fourth gestational week and is completed only after birth. During intrauterine life, the foramen ovale allows the passage of highly oxygenated blood from the right to the left atrium and into the systemic arteries, thus bypassing the pulmonary circulation. In 75% of the general population, the foramen ovale closes after birth, and only an oval depression, called fossa ovalis, remains on the right side of the interatrial septum. Patent foramen ovale can be associated with various clinically important conditions, including migraine and stroke, or decompression illness in divers. The aim of this review is to summarize the PFO developmental and anatomical features and to discuss the clinical risks associated with this atrial septal defect in adults.

Inspiratory and expiratory resistance cause right-to-left bubble passage through the foramen ovale.

A patent foramen ovale (PFO) is linked to increased risk of decompression illness in divers. One theory is that venous gas emboli crossing the PFO can be minimized by avoiding lifting, straining and Valsalva maneuvers. Alternatively, we hypothesized that mild increases in external inspiratory and expiratory resistance, similar to that provided by a SCUBA regulator, recruit the PFO. Nine healthy adults with a Valsalva‐proven PFO completed three randomized trials (inspiratory, expiratory, and combined external loading) with six levels of increasing external resistance (2–20 cmH2O/L/sec). An agitated saline contrast echocardiogram was performed at each level to determine foramen ovale patency. Contrary to our hypothesis, there was no relationship between the number of subjects recruiting their PFO and the level of external resistance. In fact, at least 50% of participants recruited their PFO during 14 of 18 trials and there was no difference between the combined inspiratory, expiratory, or combined external resistance trials (P > 0.05). We further examined the relationship between PFO recruitment and intrathoracic pressure, estimated from esophageal pressure. Esophageal pressure was not different between participants with and without a recruited PFO. Intrasubject variability was the most important predictor of PFO patency, suggesting that some individuals are more likely to recruit their PFO in the face of even mild external resistance. Right‐to‐left bubble passage through the PFO occurs in conditions that are physiologically relevant to divers. Transthoracic echocardiography with mild external breathing resistance may be a tool to identify divers that are at risk of PFO‐related decompression illness.

Patent foramen ovale (PFO): is there life before death in the presence of PFO?

Patent foramen ovale (PFO) is an embryologic remnant with incomplete postnatal adhesion of the cardiac atrial septum primum and secundum. After birth, the prevalence of PFO decreases from about 35% at young to approximately 20% at old age. PFO has been associated with numerous conditions such as decompression illness in divers, migraine, high-altitude pulmonary oedema, cerebrovascular and coronary ischaemia, and obstructive sleep apnoea syndrome. PFO is the cause of intermittent atrial right-to-left shunt, and it can be the source of cardiac paradoxical embolism. So far, randomized controlled trials have not documented a reduced rate of cerebrovascular recurrent events in patients receiving PFO device closure as compared to those on medical treatment. The purpose of this article was to critically evaluate evidence on the pathophysiologic, clinical as well as prognostic relevance of PFO.

Patent Foramen Ovale and Thromboembolic Complications

The foramen ovale, an atrial septal defect which is essential in the fetal circulation, remains patent through adulthood in approximately 25% of the general population and so it represents the most common persistent abnormality of fetal origin. Patent foramen ovale (PFO) allows interatrial right-to-left blood shunting during those periods of the cardiac cycle in which the right atrial pressure exceeds the left one. An increasing number of pathological manifestations of PFO has been recently identified; among these, paradoxical systemic embolism, refractory hypoxemia in patients with right ventricular myocardium infarction or severe pulmonary disease, orthostatic oxygen desaturation in the rare platypnea-orthodeoxia syndrome, neurological decompression illness in divers, high altitude pilots and astronauts, and finally, migraine headache with aura. Nowadays many techniques allow to detect a PFO. In this study we investigated each of them, assessing their potential diagnostic role even in comparison with the main features of the other methods.

Åpent foramen ovale og trykkfallssyke hos dykkere

About 25 % of the population has patent foramen ovale, and the condition has been assumed to be a causal factor in decompressive illness. Transcatheter closure is possible and is associated with a relatively low risk, but it has not been clarified whether there is an indication for assessment and treatment of the condition in divers. The present study explored a possible relationship between a patent foramen ovale and the risk for decompression illness in divers, if there are categories of divers that should be screened for the condition and what advice should be given to divers with this condition. The review is based on literature identified through a search in Pubmed and the authors' long clinical experience in the field. The risk of decompression illness for divers with a persistent foramen ovale is about five times higher than that in divers without this condition, but the absolute risk for decompression illness is only 2.5 after 10,000 dives. A causal association has not been shown between patent foramen ovale and decompression illness. Even if closure of patent foramen ovale may be done with relatively small risk, the usefulness of the procedure has not been documented in divers. We do not recommend screening for patent foramen ovale in divers because the absolute risk of decompression illness is small and transcatheter closure is only indicated after decompression illness in some occupational divers.

Patent Foramen Ovale: Where Are We in 2009?

Patent Foramen Ovale (PFO) is present in 20 - 25% of the population, and is known to be associated with a number of clinical syndromes. However, it is less clear that there is a causal (or contributory) role for the PFO in the development of thromboembolic stroke, systemic thromboembolization, decompression illness in divers, hypoxemia with obstructive sleep apnea, or migraine headaches. On-going and new randomized prospective trials are testing these relationships and are attempting to prove therapeutic benefit to closing the defects. This paper will review the existing literature on PFO, and will attempt to clarify some of the outstanding clinical management issues.

Patent foramen ovale closure: A new therapy for migraine

Migraine is a recurrent disabling disorder predominantly affecting middle-aged women. Migraine occurs with or without aura symptoms. Several studies have shown an increased prevalence of right-to-left shunts (RLSs) in migraine with aura. The overwhelming majority of these shunts were due to a patent foramen ovale (PFO). Furthermore, migraine with aura is more prevalent in clinical entities associated with a RLS, e.g. cryptogenic stroke, decompression illness in divers, or in patients with hereditary hemorrhagic teleangiectasia and pulmonary arteriovenous fistulas. Retrospective studies have consistently shown that shunt closure was associated with a significant reduction in migraine frequency. Its beneficial effect seemed to exceed the efficacy of conventional migraine therapy. Several randomized clinical trials to prospectively assess the benefit of shunt closure in migraine patients have been initiated. The only one completed, the MIST trial (Migraine Intervention with STARFLEX Technology), showed a significant reduction of migraine with aura after device implantation, compared with controls. However, the benefit of PFO closure was more modest than expected. This review recapitulates the current data regarding PFO closure and migraine with aura and summarizes in brief the current knowledge regarding migraine pathophysiology and the link to a RLS.

Patent Foramen Ovale and Migraine—Bringing Closure to the Subject

There is increasing interest in the relationship between migraine and patent foramen ovale (PFO). PFO is more common in migraineurs with aura, and migraine with aura is more prevalent in patients with PFO. Retrospective analyses of PFO closure for stroke prevention and decompression illness in divers have suggested that migraineurs with and without aura may derive significant benefit from PFO closure, but to date no prospective, randomized, sham-controlled study to confirm this has been completed. Herein we review published data regarding the relationship between migraine and PFO and discuss the rationale, justification, and important factors to consider in the conduct of prospective, controlled, clinical trials designed to evaluate the efficacy and safety of percutaneous device closure of PFO for migraine prevention.

Patent Foramen Ovale: A Primer for Headache Physicians

Evidence continues to mount relating the patent foramen ovale (PFO), a small flap‐valve in the wall separating the right and left atria of the heart, and number of neurologic syndromes including thromboembolic stroke, migraine headache, and decompression illness in divers. With increasing focus on the migraine relationship, both industry and patients are looking to neurologists for additional information about this cardiac defect. This review will examine the PFO in detail: its role in the fetal circulation, the formation of the atrial septum, the disease processes felt to be associated with it and their probable mechanisms, current closure techniques, and upcoming trials of these techniques.

Hazards of percutaneous PFO closure

Please see the article by Christen et al. (doi: 10.1016/j.euje.2005.08.002 ) to which this editorial pertains. In 2004, an estimated 2000–3000 patients underwent percutaneous closure of a patent foramen ovale (PFO). Given the range of potential indications (such as prevention of cryptogenic stroke, decompression illness in divers, platypnea–orthodeoxia syndrome, and migraine headaches) and the perception of PFO closure being an easy and safe procedure,1 the number of patients with percutaneously implanted PFO closure devices will continue to grow. The first attempt to percutaneously close an interatrial defect was undertaken in 1974 and reported by King and colleagues in 1976.2 In the following years, several different devices were developed and re-modified to facilitate this technique. It began with the Clamshell occluder from Rashkind,3 later modified into the CardioSEAL and then the StarFLEX device. Other models soon followed including the Buttoned device,4 the ASDOS device,5 the Monodisk,6 the Angel-Wings device,7 the Amplatzer ASD occluder8 and the Helex device.9 Although these devices were initially intended for atrial septal defect closure, they could also be used for closure of PFO, an idea first evoked by Bridges in 1992.10 Soon thereafter, devices dedicated exclusively for percutaneous PFO closure entered the market, namely the Amplatzer PFO occluder and the PFOStar (now Cardiastar) device. Part of the reasoning to favour percutaneous PFO closure over open heart surgery promises a safer and of course, less …

Decompression Illness in Divers: A Review of the Literature

Neurologists may be consulted to diagnose and treat the severe neurologic injuries that can occur in divers with decompression illness (DCI). Subclinical bubbles form during normal diving activity. DCI, a diffuse and multifocal process, results when bubbles cause symptoms by exerting mass effect in tissues, or obstructing venous or arterial flow. The lower thoracic spinal cord is a commonly affected area of the central nervous system. The most commonly described form of brain DCI is cerebral arterial gas embolism with middle cerebral artery or vertebrobasilar distribution involvement. Bubbles exert secondary damage to the vascular endothelium, causing activation of numerous biochemical cascades. Divers can develop DCI on very short dives or in shallow water, even when adhering to protocols. DCI should be strongly considered when divers experience pain after diving. Any neurologic symptoms after a dive are abnormal and should be attributed to DCI. Even doubtful cases should be treated immediately with hyperbaric oxygen (HBO), after a chest x-ray to rule out pneumothorax. The Divers Alert Network should be contacted for emergency consultation. Delay to treatment can worsen outcome; however, the overwhelming majority of divers respond to HBO even days to weeks after injury. Although DCI is a clinical diagnosis, magnetic resonance imaging, somatosensory evoked potentials, single-photon emission tomography, and neuropsychologic testing help to document disease and monitor response to therapy. Divers should be treated with HBO until they reach a clinical plateau. Complete relief of symptoms occurs in 50% to 70% of divers; 30% have partial relief.

Transcatheter closure of patent foramen ovale using the Amplatzer septal occluder to prevent recurrence of neurological decompression illness in divers

OBJECTIVELarge flap valve patent foramens may cause paradoxical thromboembolism and neurological decompression illness in divers. The ability of a self expanding Nitinol wire mesh device (Amplatzer septal occluder) to produce...

Effects of a patent foramen ovale on arterial saturation during exercise and on cardiovascular responses to deep breathing, Valsalva manoeuvre, and passive tilt: relation to history of decompression illness in divers.

To determine whether the presence of a patent foramen ovale could result in significant arterial desaturation and affect the responses of heart rate and blood pressure to physiological manoeuvres and to determine whether responses differed between those with and those without prior clinical events associated with a patent foramen ovale. Blind controlled study. Teaching hospital. Divers with a large patent foramen ovale shown by contrast echocardiography and divided into those who had neurological decompression illness that started within 30 minutes of surfacing (group 1), those who had no history of decompression illness (group 2), and age and sex matched control divers who had no evidence of intracardiac shunts (group 3). The change in percentage haemoglobin oxygen saturation during treadmill exercise and the response of heart rate and blood pressure to physiological manoeuvres. There were no significant differences between the three groups but two divers in group 1 showed clinically important desaturation during exercise and unusual blood pressure and heart rate responses to passive tilt. These divers were notable for having the greatest number of episodes and the most severe single episode of spinal cord decompression illness. A large patent foramen ovale may be associated with clinically significant arterial desaturation and unusual responses of heart rate and blood pressure in some healthy subjects.

Neurologic and psychologic manifestations of decompression illness in divers.

It has been widely accepted that the neurologic sequelae of decompression illness are confined to the spinal cord. Of 10 divers who gave a history of an episode of decompression illness involving the central nervous system, we found that eight had unequivocal neurologic deficits implicating multiple supraspinal lesions. Seven of these neurologically impaired divers completed a battery of neuropsychologic tests that revealed severe deficits in all cases. The findings show that diffuse and multiple central nervous system lesions result from decompression illness and demonstrate the importance and close correlation of thorough neurologic and neuropsychologic tests in assessment following diving accidents.