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PubMed2000

Neurologic outcome of controlled compressed-air diving.

The authors compared the neurologic, neuropsychological, and neuroradiologic status of military compressed-air divers without a history of neurologic decompression illness and controls. No gross differences in the neuropsychometric test results or abnormal neurologic findings were found. There was no correlation between test results, diving experience, and number and size of cerebral MRI lesions. Prevalence of cerebral lesions was not increased in divers. These results suggest that there are no long-term CNS sequelae in military divers if diving is performed under controlled conditions.

Adult↗
PubMed2006

Extreme diving of beaked whales.

Sound-and-orientation recording tags (DTAGs) were used to study 10 beaked whales of two poorly known species, Ziphius cavirostris (Zc) and Mesoplodon densirostris (Md). Acoustic behaviour in the deep foraging dives performed by both species (Zc: 28 dives by seven individuals; Md: 16 dives by three individuals) shows that they hunt by echolocation in deep water between 222 and 1885 m, attempting to capture about 30 prey/dive. This food source is so deep that the average foraging dives were deeper (Zc: 1070 m; Md: 835 m) and longer (Zc: 58 min; Md: 47 min) than reported for any other air-breathing species. A series of shallower dives, containing no indications of foraging, followed most deep foraging dives. The average interval between deep foraging dives was 63 min for Zc and 92 min for Md. This long an interval may be required for beaked whales to recover from an oxygen debt accrued in the deep foraging dives, which last about twice the estimated aerobic dive limit. Recent reports of gas emboli in beaked whales stranded during naval sonar exercises have led to the hypothesis that their deep-diving may make them especially vulnerable to decompression. Using current models of breath-hold diving, we infer that their natural diving behaviour is inconsistent with known problems of acute nitrogen supersaturation and embolism. If the assumptions of these models are correct for beaked whales, then possible decompression problems are more likely to result from an abnormal behavioural response to sonar.

Activity Cycles↗
PubMed2006

Exogenous nitric oxide and bubble formation in divers.

PURPOSE: Prevention of bubble formation is a central goal in standard decompression procedures. Previously we have shown that exercise 20-24 h prior to a dive reduces bubble formation and increases survival in rats exposed to a simulated dive. Furthermore, we have demonstrated that nitric oxide (NO) may be involved in this protection; blocking the production of NO increases bubble formation while giving rats a long-lasting NO donor 20 h and immediately prior to a dive reduces bubble formation. This study determined whether a short-lasting NO donor, nitroglycerine, reduced bubble formation after standard dives and decompression in man. METHODS: A total of 16 experienced divers were randomly assigned into two groups. One group performed two dives to 30 m of seawater (msw) for 30 min breathing air, and performed exercise at an intensity corresponding to 30% of maximal oxygen uptake during the bottom time. The second group performed two simulated dives to 18 msw for 80 min breathing air in a hyperbaric chamber, and remained sedentary during the bottom period. The first dive for each diver served as the control dive, whereas the divers received 0.4 mg of nitroglycerine by oral spray 30 min before the second dive. Following the dive, gas bubbles in the pulmonary artery were recorded using ultrasound. RESULTS: The open-water dive resulted in significantly more gas bubbles than the dry dive (0.87 +/- 1.3 vs 0.12 +/- 0.23 bubbles per square centimeter). Nitroglycerine reduced bubble formation significantly in both dives from 0.87 +/- 1.3 to 0.32 +/- 0.7 in the in-water dive and from 0.12 +/- 0.23 to 0.03 +/- 0.03 bubbles per square centimeter in the chamber dive. CONCLUSION: The present study demonstrates that intake of a short-lasting NO donor reduces bubble formation following decompression after different dives.

Adult↗
PubMed2003

Alternobaric vertigo in sport SCUBA divers and the risk factors.

We investigated the eustachian tube function and the incidence of alternobaric vertigo (AV) in 29 sport self-contained underwater breathing apparatus (SCUBA) divers with, or without, some possible risk factors for AV. The divers had normal audiological and otoscopic findings at the pre-dive examination. We used the nine-step inflation/deflation tympanometric test and Toynbee test for evaluation of eustachian tube function, and the Valsalva manoeuvre for patency. Information on divers, their history, and their otolaryngologic examination were obtained in the pre-dive examination. Divers performed 1086 dives (mean 37, range: 3-100) during the observation period. Four divers (14 per cent) experienced AV during five dives (0.46 per cent), (one diver experienced AV two times). It was found that having an otitis media history or eustachian tube dysfunction determined with the nine-step inflation/deflation tympanometric test before diving, or difficulty in clearing ears during diving could be important risk factors for AV in sport SCUBA divers (p <.05). Divers with such findings seem to be more prone to AV and should pay rigorous attention to the precautions for prevention of AV.

Acoustic Impedance Tests↗
PubMed1977

Otologic and otoneurologic injuries in divers: clinical studies on nine commercial and two sport divers.

In the past two decades, we have seen a great increase in the number of injuries from commercial and sport diving. During this time, our knowledge of the physiology and pathophysiology of diving has also increased. As a result, we now can accurately diagnose and successfully treat many of these injuries. Of the commercial and sport divers examined as pateints in the Department of Otolaryngology at the University of Texas Medical Branch in Galveston, Tex., between September, 1974, and May, 1975, 11 showed positive otologic and otoneurologic findings which are reported herein. One patient was surgically explored for an oval window fistula. In localizing and classifying these injuries, we have utilized extensive and broad-based test batteries, which include complete history, otologic and otoneurologic physical examination, audiometry, a central auditory test battery, and a vestibular test battery. These tests are described. The findings in each of the divers are illustrated and analyzed. This article further describes the use of these test batteries, which were employed to localize otoneurologic pathology in this sample of injured divers. Based on these cases, we have expanded and modified Edmonds' classification of the etiology of vertigo related to diving. We feel that the test batteries which we describe, or similar tests, should be part of the otologic and otoneurologic workup of injuries divers.

Adult↗
PubMed1980

Scintigraphy versus radiography in the early diagnosis of experimental bone necrosis, with special reference to caisson disease of bone.

The early diagnosis of caisson disease of bone is hindered by the long delay which must elapse before an abnormality becomes apparent on a radiograph. The possible use of bone scintigraphy for this purpose was investigated. Necrosis of the bone and marrow was produced in rabbits by glass microspheres to simulate persistent gas-bubble emboli and then serial radiographs and scintigrams using 99mTc-diphosphonate were obtained. Regions of necrosis could be detected as "hot-spots" on the scintigrams as early as three weeks after the causative insult, which was many weeks before any abnormality could be detected on the radiographs. Histological examination of excised femora suggested that the scintigraphic abnormality might depend on the new bone formation during a reactive or repair process. It is suggested that scintigraphy may have clinical value in caisson disease.

Animals↗
PubMed1980

Regional distribution of circulating microspheres in the femur of the rabbit.

In an attempt to explain the distribution of lesions of caisson disease of bone in the human femur, the regional distribution of circulating microspheres which had been labelled with scandium-46 was studies in the femur of the rabbit. Microspheres with a diameter of 15 microns were equally distributed between the two ends of the bone and between the upper and lower halves of the shaft. However, microspheres with a diameter of 50 microns congregated in the upper end of the femur and in the lower half of the shaft, the two sites most commonly affected by caisson disease. A large percentage of the microspheres in the shaft, especially the larger spheres, were retained in the marrow. It is suggested that the microcirculation of the marrow may act as a filter and that the nature and distribution of its vessels determine the site of impaction of circulating emboli. This would explain why lesions of the shaft mainly affect the medulla of the bone and not the cortex.

Animals↗
PubMed1981

A study of old lesions of caisson disease of bone by radiography and bone scintigraphy.

A group of patients were studied 10 years after stopping work in a high-pressure environment. Radiographs of their long bones showed little change during the period, but only two of 12 scintigrams were normal. The 10 abnormal scintigrams contained 18 "hot-spots" which were not always associated with an abnormal radiographic appearance; the findings suggest that some lesions may never become visible on a radiograph. A reactive or repair process associated with these lesions may be prolonged and may not be beneficial, as structural failure of the joint may subsequently occur. Prognosis should therefore be guarded.

Adult↗
PubMed2005

Acute and chronic gas bubble lesions in cetaceans stranded in the United Kingdom.

The first evidence suggestive of in vivo gas bubble formation in cetacea, including eight animals stranded in the UK, has recently been reported. This article presents the pathologic findings from these eight UK-stranded cetaceans and two additional UK-stranded cetacean cases in detail. Hepatic gas-filled cavitary lesions (0.2-6.0 cm diameter) involving approximately 5-90% of the liver volume were found in four (two juvenile, two adult) Risso's dolphins (Grampus griseus), three (two adult, one juvenile) common dolphins (Delphinus delphis), an adult Blainville's beaked whale (Mesoplodon densirostris), and an adult harbour porpoise (Phocoena phocoena). Histopathologic examination of the seven dolphin cases with gross liver cavities revealed variable degrees of pericavitary fibrosis, microscopic, intrahepatic, spherical, nonstaining cavities (typically 50-750 microm in diameter) consistent with gas emboli within distended portal vessels and sinusoids and associated with hepatic tissue compression, hemorrhages, fibrin/organizing thrombi, and foci of acute hepato-cellular necrosis. Two common dolphins also had multiple and bilateral gross renal cavities (2.0-9.0 mm diameter) that, microscopically, were consistent with acute (n = 2) and chronic (n = 1) arterial gas emboli-induced renal infarcts. Microscopic, bubblelike cavities were also found in mesenteric lymph node (n = 4), adrenal (n = 2), spleen (n = 2), pulmonary associated lymph node (n = 1), posterior cervical lymph node (n = 1), and thyroid (n = 1). No bacterial organisms were isolated from five of six cavitated livers and one of one cavitated kidneys. The etiology and pathogenesis of these lesions are not known, although a decompression-related mechanism involving embolism of intestinal gas or de novo gas bubble (emboli) development derived from tissues supersaturated with nitrogen is suspected.

Animals↗
PubMed1987

Hyperbaric oxygen. A therapy in search of diseases.

The application of HBO to the therapy of various human diseases developed over a 300 year period. Like most of medicine, the basis of these applications was and continues to be pragmatic in nature, and involves uncritical and untested judgments. The possibility of risks has been understated and possible benefits have been overstated. Individual physicians offering HBO and organized groups, such as the Undersea Medical Society, advocating its use may well be highly motivated, well meaning, and sincerely convinced that HBO is an important therapeutic approach. It may be that, buried among the host of indications, will be some disorders for which HBO is uniquely and highly effective. If so, the present nonsystem for evaluating responses to HBO will require modification, so that these potentially valuable additions to therapeutics are not lost. Because of its almost global application to a wide variety of diseases, HBO therapy lends itself easily to medical adventurism (therapy in search of a disease) and economic exploitation. If there is some patient benefit to come from the experience of the last 300 years, changes in approach, initiated by baromedical devotees or by medicine generally, or resulting from pressures outside of medicine, will be required.

Decompression Sickness↗