Prevalence of patent foramen ovale (PFO) and MRI-lesions in mild neurological decompression sickness (type B-DCS/AGE).

BACKGROUND: Neurological decompression sickness (DCS/AGE) may cover two variants with either severer and probably central nervous (Type A) or milder and sometimes doubtful neurological symptoms (Type B). The pathophysiology of the Type B-DCS/AGE might be different from the Type A-variant. In Type A-DCS/AGE a higher PFO-prevalence (patent foramen ovale) points towards an embolic origin of the Type A-symptomatology. This is not necessarily expected for the Type B-DCS/AGE if the pathophysiology here is micro-embolic or even non-embolic. METHODS: 18 patients with Type B-DCS/AGE were tested against matched controls for presence and size of a PFO with echocardiography and transcranial ultrasound with echo-contrast. Prevalence and number of Type A-brain lesions were visualized by cranial MRI as possible sequelae from gas-embolic events. RESULTS: PFO-prevalence in both groups, the patients with Type B-DCS/AGE (5/18) as well as the controls (7/18) was similar to published PFO-prevalences in normals without any difference between patients and controls (p = 0.725). Also the number of MRI-lesions (ACFs) was the same for Type B-DCS/AGE cases (15 ACFs in 5 patients) and controls (37 ACFs in 8 divers). CONCLUSION: Indirect findings suggesting embolic brain injuries are found with similar frequency in patients with Type B-DCS/AGE and normal controls, which is in contrast to data about Type A-DCS/AGE. This is compatible with different pathophysiological mechanisms involved in the Type A- and Type B-DCS/AGE.

Viewpoint: the type A- and the type B-variants of Decompression Sickness.

BACKGROUND: Symptoms of neurological decompression incidents (DCS/AGE) can be severe or mild. It is unknown if these differences of symptom presentation represent different clinical entities or if they represent just the spectrum of DCS/AGE. METHODS: 267 cases with DCS/AGE were compared retrospectively and classified into two subgroups, the Type A-DCS/AGE for cases with a severe and often stroke-like symptomatology and the Type B-DCS/AGE for those with milder and sometimes even doubtful neurological symptoms. The main outcome measures were the number of hyperbaric treatments (HTs) needed and the clinical outcome. RESULTS: 42 patients with DCS/AGE were classified as Type A- and 225 patients met the criteria for a Type B-DCS/AGE. Patients with Type A-lesions were more severely affected, needed more hyperbaric treatments and had a less favorable outcome than patients with the Type B-variant. CONCLUSIONS: The Type A- and the Type B-DCS/AGE are likely to be different entities with better clinical outcome in the Type B-variant and possibly significant differences in the underlying pathophysiologies of both variants. Future studies with a particular focus on the up to now inadequately investigated Type B-DCS/AGE are necessary to elucidate such differences in the pathophysiology.

Memory deficits at 0.6 MPa ambient air pressure.

We investigated the effects of an elevated ambient air pressure of 0.6 MPa on verbal memory performance. Twenty-four experienced divers were compressed in a dry hyperbaric chamber to pressures equivalent to 0.5 meters of seawater (msw) (n = 12) and 50 msw (n = 12). Verbal memory was assessed by free recall and recognition of visually presented word lists. The testing procedure specified learning and testing at surface, learning at surface and testing at depth, learning and testing at depth, and learning at depth and testing at surface. Non-specific stress was assessed by measurement of salivary cortisol, heart rate, and subjective stress before, during, and after the dives. The 50-msw dive group showed a significant decrease of free recall performance when the material was learned at depth (P < 0.01). However, only postdive recall of material learned at depth remained significantly impaired (P < 0.05), whereas recognition performance was normal. For both groups no significant effects of depth on the investigated stress indices were obtained. These results are taken as evidence that inert gas narcosis may interfere with encoding and/or retrieval of verbal information, although the possibility that other stressors in the hyperbaric environment contributed to these deficits cannot be eliminated entirely.

Computed tomography of the chest in diving-related pulmonary barotrauma.

Arterial gas embolism due to barotrauma of the lungs is a severe complication in compressed air diving. Precipitating factors are often missed on plain chest radiology. This study was conducted to detect occult lung disease predisposing to the development of pulmonary barotrauma in conditions associated with a change in ambient pressure. During the past 4 years, 11 patients who have suffered pulmonary barotrauma with or without subsequent development of cerebral or spinal arterial gas embolism underwent computed tomography of the chest several days post-injury. Examinations were conducted either using the conventional technique (n = 7) or, more recently, in the spiral mode (n = 4). Chest radiographs were available in all cases. In five patients CT revealed subpleural emphysematous blebs or cysts that were not detected by conventional radiography. Follow-up studies performed in two of these cases several months post-injury showed that the cystic lesions did not resolve. We assume that the lung cysts or blebs are preexisting conditions which caused pulmonary barotrauma. Computed tomography of the chest, preferably in the spiral mode, is recommended in any case of suspected pulmonary barotrauma in order to evaluate the possibility of pre-existing pathology and to predict future fitness to dive.

Pulmonary barotrauma of a diver using an oxygen rebreathing diving apparatus.

A 22-yr-old healthy male diver performed a dive using a closed circuit oxygen rebreathing apparatus according to normal procedure. After the dive he developed clinical symptoms of mediastinal emphysema. A chest X-ray taken 1 d after the dive showed a discrete "tram track" sign in the left paracardial region. Spiral volumetric computed tomography of the chest 4 d postinjury detected a small subpleural emphysematous bulla next to the left ventricle, the pneumomediastinum being absorbed in the meantime. Clinical outcome of pulmonary decompression barotrauma in the case of oxygen rebreathing may be different from that in compressed air diving, due to the altered gas physics. The necessity for computed tomography of the chest is emphasized, preferably using the spiral mode, in any case of suspected pulmonary barotrauma.

[Diving-associated pulmonary barotrauma as a rare differential diagnosis in internal medicine-pneumologic ambulatory care]. / Tauchassoziiertes pulmonales Barotrauma als seltene Differentialdiagnose in der internistisch-pneumologischen Ambulanz.

Arterial gas embolism due to pulmonary barotrauma (PBT) is a well known fatal complication in compressed air diving. Pulmonary damage is often missed in conventional diagnostic radiology. We present two cases of PBT in recreational divers, in which pre and post accidental chest x-rays were negative but chest-CT showed peripheral bullae in the lower lung lobes preferably responsible for PBT, Chest-CT is recommended in any case of suspected PBT to evaluate the possibility of preexisting pathology in order to predict further diving fitness.

Exercise effects on central venous nitrogen tensions after simulated non-decompression dives.

In five subjects we examined the effect of exercise on the pattern of central venous (right atrial) N2 tensions (PVN2) after ascent from simulated non-decompression dives. The dives consisted of exposure to air at 3 bar for 20 min with 10 min of exercise (workload 75 W) at depth to achieve near-complete N2 saturation of the muscles. After the dive the subjects rested or, on another day, exercised for 30 min (workload 100 W) starting 10 min after completing the ascent. Blood samples taken every 10 min until the 60th min and 90 min after the dive were analyzed for PVN2 using a manometric Van Slyke apparatus. The amount of N2 eliminated was estimated from the PVN2 by adapting the Fick principle. Immediately after the ascent, PVN2 were 950 +/- 39 and 942 +/- 27 mmHg, respectively, in the rest and experiment series. In the rest experiments PVN2 continuously decreased to 606 +/- 8 mmHg 90 min after the dive, remaining significantly higher (P < 0.05) than before the dive. Exercise caused the PVN2 to increase beyond the corresponding levels of the rest experiments (P < 0.05 at 20 and 30 min exercise). After the exercise PVN2 rapidly declined, reaching predive levels 60 min after the ascent. Exercise increased N2 elimination to 970 +/- 143 ml, whereas it had been 311 +/- 61 ml (P < 0.05) in the corresponding phase of the rest experiments. We conclude that if extensive supersaturation and bubble formation can be avoided, such as probably was the case in our shallow non-decompression dives, exercise after the ascent accelerates N2 elimination.

[Successful treatment with hyperbaric oxygen following severe cerebro-arterial gas embolism]. / Erfolgreiche Langzeitbehandlung mit hyperbarem Sauerstoff nach schwerer zerebroarterieller Gasembolie.

We report on a patient suffering from a severe cerebral arterial gas embolism associated with decompression from a simulated high pressure chamber dive. Treatment with hyperbaric oxygen (HBO) commenced immediately after the accident and was continued subsequently for 8 weeks with a total of 49 HBO-sessions. Despite initial transitory amaurosis and flaccid tetraplegia lasting for two weeks the patient made a near complete recovery except for circumscript numbness and paraesthesia confined to the left tibia and palm. This case underscores the need to consider patients with cerebral arterial gas embolism for HBO treatment and the potential value of a subsequent long-term HBO therapy.

[Hyperbaric oxygen therapy--an adjuvant therapeutic procedure with problem cases in reconstructive bone surgery]. / Die hyperbare Sauerstofftherapie--Ein adjuvantes Therapieverfahren bei Problemfällen in der knöchernen Wiederherstellungschirurgie.

Prolonged and compromised wound-healing, i.e. in scar tissue or after irradiation, often causes problems, especially when free transplants, for example for bony reconstruction of the mandible after resection of tumor, are used. Hyperbaric Oxygen Therapy (HBO) means breathing of pure (100%) oxygen under increased athmospherical pressure. HBO induces high oxygen partial pressure in all tissues and also has an antioedematous effect, causes activation of fibroblasts and macrophages, stimulates angioneogenesis and has a bacteriostatic and bacteriocidic effect. We used HBO since 1991 in 27 patients, nine of them underwent bony reconstruction of the mandible. In our opinion HBO is a very helpful tool in the management of problem-wound-healing, assisting the classical surgical principles.