Outcome after treatment of neurological decompression illness is predicted by a published clinical scoring system.

BACKGROUND: After recompression therapy, some cases of neurological decompression illness (DCI) have a significant residual deficit. Boussuges et al. report a scoring system to predict sequelae using weighted historical and clinical indices at presentation which we applied to the British Hyperbaric Association (BHA) database of UK diving accidents, held at the Institute of Naval Medicine (INM). METHODS: A database search identified 234 cases of neurological DCI from the 2 yr, 1995-6. Of these, 217 case records contained sufficient data to apply the scoring system. Outcome was classified as severe sequelae (i.e., causing a functionally important deficit) or as mild/no sequelae. RESULTS: The median score in UK cases with severe sequelae was 13 (95% C.I. 11.5 to 14.5) and in cases with mild/no sequelae, 6 (95% C.I. 5.5 to 6.5). Significantly more cases with scores > 7 had severe sequelae than cases with scores < or = 7 (chi2, p < 0.0001). The sensitivity of a score > 7 (for severe sequelae) was 94% and the specificity was 65%. The positive predictive value of a score > 7 (for severe sequelae) was 18% and the negative predictive value of a score < or = 7 was 99%. CONCLUSIONS: When applied to the INM/BHA database a score of > 7 by this scoring system has a higher sensitivity and lower specificity for severe sequelae than reported by Boussuges et al. It has a higher predictive accuracy for successful outcome of treatment (99% vs. 89%) but a much lower predictive value for severe sequelae (18% vs. 86%). Convergence between this and other published scoring systems may allow derivation of a generic scoring system that could then be evaluated prospectively in multiple centers.

The management of elderly patients with femoral fractures. A randomised controlled trial of early intervention versus standard care.

OBJECTIVE: To determine the effect of an early intervention program in an acute care setting on the length of stay in hospital of elderly patients with proximal femoral fractures. SETTING: Acute orthopaedic ward of a large teaching hospital. DESIGN AND PARTICIPANTS: A randomised controlled trial comparing 38 Intervention patients with 33 Standard Care patients. INTERVENTION: Early surgery, minimal narcotic analgesia, intense daily therapy and close monitoring of patient needs via a multidisciplinary approach versus routine hospital management. MAIN OUTCOME MEASURES: Length of stay (LOS); deaths; level of independent functioning. RESULTS: Mean LOS was shorter in the Intervention group than in the Standard Care group (21 days v. 32.5 days; P < 0.01). After adjusting for other factors that could affect LOS (eg, age, sex, pre-trauma functional levels, pre-trauma comorbidity and postsurgical complications), the Intervention program was significantly predictive of shorter LOS (P = 0.01). The Intervention group did not experience greater numbers of deaths, deterioration in function or need for social support than the Standard Care group. CONCLUSION: This early intervention program in an acute care setting results in significantly shorter length of hospital stay for elderly patients with femoral fractures.

Cutaneous lesions in swine after decompression: histopathology and ultrastructure.

A detailed histopathologic description of skin lesions from a porcine model of decompression sickness (DCS) is presented. Pigs were dived in a dry chamber on a variety of profiles over an 11-mo period, with a 0.1-0.6 (10-60%) incidence of cutaneous lesions. The clinical appearance of the lesions evolved from irregular, sharply demarcated areas of erythema to violaceous and, eventually, darkly mottled macules. The lesions were biopsied under deep, sedative anesthesia. Histologic abnormalities were found in 91% (20/22) of the biopsies from clinically apparent cutaneous lesions. Vascular congestion was the most common finding. Focal areas of vasculitis were noted in 45% (10/22) of the lesions. Perivascular neutrophil infiltrates, edema, and occasionally, hemorrhage were also noted. Ultrastructural abnormalities were found in all of the lesions studied. Acute inflammation affecting the dermal vasculature was the most common finding. Platelets were rarely observed aggregating within vessels. The clinical and histologic features of cutaneous lesions in pigs after decompression are compared with previous accounts in humans. The model provides a useful tool for the study of cutaneous lesions in DCS and may be a means of exploring interventions in the disease.

Acute neurologic decompression illness in pigs: lesions of the spinal cord and brain.

A detailed histopathologic description of central nervous system lesions from a porcine model of neurologic decompression illness is presented. Pigs were dived in a dry chamber to 200 feet of seawater for 24 min before the start of decompression. Of 120 pigs, 40 (33.3%) were functionally unaffected and 80 (66.6%) developed neurologic decompression illness; 16 died, 64 survived. Petechial hemorrhages were grossly visible in the spinal cord of 73% of the survivors, 63% of the fatalities, and 3% of the clinically unaffected pigs. The thoracic part of the cord was most commonly involved. Histologic cord lesions were found in 75 (63%) pigs: 83% of decompression illness survivors, 81% of the fatalities, and 23% of those clinically unaffected. Morphologically, hemorrhagic lesions were the most common (54%). Other common findings included spongiosis (48%), axonal swelling and loss (39%), and myelin degeneration (35%). White matter hemorrhages in the spinal cord were generally more numerous and extensive than those affecting the gray matter; however, gray matter hemorrhage was associated with increasing disease severity. Brain lesions were present in 23% of pigs and were most frequent in fatalities. Cerebellar and brain stem hemorrhages were the most common brain lesions; the molecular layer of the cerebellum appeared particularly susceptible. Pigs were chosen because of their cardiovascular and gas exchange similarities to humans. The clinical and histopathologic features of the pig model were compared with previous accounts in animals and humans; the model was judged analogous to severe human decompression illness. The finding of occult brain and cord lesions in clinically unaffected pigs is discussed. The model provides a useful tool for the study of dysbaric lesions of the central nervous system. Its noninvasive nature may facilitate the study of nervous system injury and repair processes.

Spinal cord lipid levels in a porcine model of spinal cord decompression sickness.

Spinal cord lipid content was analyzed in 50 pigs that had experienced a simulated dive known to produce 20-80% incidence of neurologic decompression sickness (DCS). Using air and heliox as breathing mixtures, these animals underwent chamber dives ranging from 200-250 feet of seawater (fsw). These dives were designed to generate spinal cord DCS, which was detected by observing the animals for gross neurologic deficits. Using a standardized method, cylindrical samples of cord were cut from different spinal levels and analyzed for total lipid (TL) content, which produced two cervical, three thoracic, and two lumbar samples. All areas with gross hemorrhage were also sampled. The range of TL (mean) in milligrams per gram from the cervical, thoracic, and lumbar regions were 118-679 (319), 140-635 (366), and 109-658 (307), respectively. Although this implies that TL varies markedly between cords, values within each cord were fairly consistent (+/- 20% from cord mean). The difference in TL values between cord regions with and without hemorrhage was not significant (P > 0.1). This reveals that increased spinal cord TL levels, together with their presumed dissolved inert gas, do not play a major role in the location or incidence of spinal cord hemorrhages in pigs with clinical signs of spinal cord DCS.

Acute carpal tunnel syndrome in a diver: evidence of peripheral nervous system involvement in decompression illness.

Conclusive evidence for involvement of the peripheral nervous system in decompression illness is lacking. We report a case of decompression illness associated with shoulder pain and the clinical features of median nerve injury at the wrist. Initial recompression and hyperbaric oxygen treatment produced prompt relief of all symptoms and signs, but carpal tunnel syndrome subsequently recurred. Nerve conduction studies confirmed median nerve conduction delay at the wrist. Repeat measurements after treatment with hyperbaric oxygen showed electrophysiologic improvement that was consistent with improvement in symptoms. We believe this is the first objectively substantiated case of injury to the peripheral nervous system caused by decompression illness.

Neurological decompression illness in swine.

BACKGROUND: A porcine model of neurological decompression illness (DCI) and its treatment is described. METHODS: Pigs (wt. 16-22 kg) underwent a simulated dive to 200 feet of seawater (fsw) (612.6 kPa) for 24 min, then decompressed at 60 fsw/min-1 (183 kPa.min-1). Pigs that developed neurological DCI were sedated with diazepam, then treated by recompression on U.S. Navy Treatment Table 6. Functional outcome was assessed by treadmill running. At necropsy 24 h postdive, carcass density was measured by underwater weighing, and tissue samples including heart, spinal cord, and brain were taken for histopathological examination. RESULTS: Neurological DCI occurred in 73% of control animals and developed within 2-7 min in 50% of cases. Affected pigs had significantly earlier onset of skin DCI than unaffected pigs (means: 9.52 min vs. 17.9 min, p < 0.001). Only 16.4% of pigs made a full functional recovery after recompression treatment. Outcome at 24 h was not improved in 20 pigs randomized to receive adjunctive lidocaine infusion compared to 20 pigs that received saline alone. Following necropsy, 77% of cases had petechial hemorrhages grossly visible in the spinal cord. Multifocal, microscopic hemorrhages, predominantly of spinal cord white matter, were found in 86.6% of DCI cases. Neither weight, density, nor genetic predisposition were found to influence DCI risk. CONCLUSIONS: The model is analogous to severe, early-onset, neurological DCI in humans and allows prospective evaluation of risk reduction and treatment stratagems for this form of DCI. Many applied and basic science issues relevant to diving medicine may also be studied using the model, and adaptation to study hypobaric DCI and other clinical applications of hyperbaric oxygen is feasible.

Reduction of decompression illness risk in pigs by use of non-linear ascent profiles.

An established swine model of neurologic decompression illness (DCI) was adapted to investigate the influence of no-stop ascent profile shape on DCI risk after deep air and heliox dives. Pigs underwent a simulated air dive in a dry chamber to 200 fsw (613 kPa) for 24 min bottom time. They were then decompressed at either a linear rate of 20 fsw/min (61 kPa/min) or on a non-linear, fast-deep/slow-shallow profile. Both decompressions lasted 10 min. In the linear group, there were 11/20 cases of neurologic DCI, including 1 death and 8 severe cases, compared to 5/20 cases (1 severe) in the fast/slow group. Thirteen out of 20 from the linear group, vs. 6/20 of the non-linear group, had moderate or severe skin DCI affecting > 20% skin surface area. A similar study, but of paired, randomized, investigator-blind, and sequential design was performed with pigs breathing 80/20% heliox: Pigs were compressed to 250 fsw (766 kPa) for 8 min 50 s, then decompressed at either a linear 30 fsw/min (92 kPa/min), or on a fast/slow profile. Neurologic DCI occurred more frequently (P = 0.024) in the linear group (16/20; 1 death and 11 severe) than in the fast/slow group (8/20; 3 severe). Moderate or severe skin DCI affected 16/20 of the linear group compared to 3/20 of the fast/slow group (P = 0.0002). The study findings suggest that substantial reductions in DCI risk may be obtainable by manipulating the ascent profile after deep no-stop diving. This finding has potential application in both military and civil diving operations.

Exercise conditioning reduces the risk of neurologic decompression illness in swine.

During development of a pig model of neurologic decompression illness (DCI) we noted that treadmill-trained pigs seemed less likely to develop DCI than sedentary pigs. The phenomenon was formally investigated. Twenty-four immature, male, castrated, pure-bred Yorkshire swine were conditioned by treadmill running, while 34 control pigs remained sedentary. All pigs (weight 18.75-21.90 kg) were dived on air to 200 feet of seawater (fsw) in a dry chamber. Bottom time was 24 min. Decompression rate was 60 fsw/min. Pigs that developed neurologic DCI were treated by recompression. Pigs without neurologic signs were considered neurologically normal if they ran on the treadmill without gait disturbance at 1 and 24 h postdive. Of the 24 exercise-conditioned pigs, only 10 (41.7%) developed neurologic DCI, compared to 25 of 34 (73.5%) sedentary pigs (X2 = 5.97; P = < 0.015). Neither mean carcass density (adiposity) nor mean age were significantly different between groups. No patent foramen ovale was detected at necropsy. An additional control group of 24 pigs was dived to clarify the influence of weight. The results suggest that the risk of neurologic DCI is reduced by physical conditioning, and the effect is independent of differences in age, adiposity, and weight.

Aspects of neurological decompression illness: a view from Bethesda.

A minority of divers with neurological decompression illness (DCI) fail to improve with recompression treatment. This is particularly seen in cases where features of severe spinal cord injury develop soon after surfacing. Haemorrhage into the spinal cord is implicated in the pathogenesis of these cases, and evidence is presented that supports the view that the bleeding coincides with shrinkage of autochthonous bubbles. The role of hyperbaric oxygen therapy in the treatment of spinal cord DCI is discussed with reference to possible benefit in ischaemia-reperfusion (I-R) injury. Similarities and differences between the tissue injury of dysbaric and conventional spinal cord injury are outlined. The implications of advances in drug therapy for conventional spinal cord trauma are considered in the context of their potential application to treat neurological DCI.

Failure to prevent decompression illness in rats by pretreatment with a soluble complement receptor.

Controversy exists over the role of complement activation in the natural history of decompression illness (DCI), and whether an individual's predisposition to DCI might be influenced by susceptibility to activation of complement by intravascular gas bubbles. Treatment with a soluble complement receptor (sCR-1), which neutralizes activated complement components, is known to be beneficial in other complement-dependent disease processes. This study investigated the effect of treating rats with sCR-1 or saline before decompression from a dive profile known to produce a high incidence of DCI. No statistical difference in the incidence of DCI was observed between the 27 rats treated with sCR-1 and 26 control rats treated with saline. The study was unable to confirm the previously reported observation in rats of a positive correlation between DCI incidence and increasing weight.

High altitude headache: treatment with ibuprofen.

Up to half of those who ascend rapidly to altitudes of over 3,000 m may experience symptoms of acute mountain sickness (AMS) and of these some 95% may suffer from high altitude headache. We report the first controlled trial specifically to assess an oral drug therapy for this common symptom. Subjects were 21 members of mountaineering expeditions to similar altitudes in the Bolivian Andes and the Himalayas in Nepal. The study was of a randomized, placebo-controlled, double-blind, within-patient crossover design. Ibuprofen was significantly superior to placebo both in reducing headache severity and in speed of relief (a mean difference of 94 min in time to no/minimal headache). Only 14% of subjects who initially took ibuprofen felt the need for further medication compared to 83% of those who took placebo first (p = 0.02). Of the 11 subjects completing both phases of the crossover, 8 (73%) favored ibuprofen while the remainder had no preference (p = 0.004). No attributable adverse effects occurred. The results suggest that ibuprofen is a safe and effective treatment for high altitude headache.

Climatic and environmental factors in the aetiology of decompression sickness in divers.

As decompression sickness (DCS) may occur unexpectedly after 'safe' dives it was hypothesised that the weather and tidal factors could contribute to the risk. One hundred and seventy seven cases of DCS were identified from the Institute of Naval Medicine's diving accident records and allocated to a 'safe' group or control 'risky' group, depending on the dive profiles. Comparison of the prevailing environmental conditions between groups revealed significant differences in air temperature and windchill (p = < 0.001 for all dives) and for air minus water temperature (p = < 0.01 for all dives). The results imply that exposure to a cold thermal environment following diving, particularly when the air temperature is colder than the water temperature, may be a previously unrecognised risk factor for DCS.

Pneumothorax as a complication of recompression therapy for cerebral arterial gas embolism.

The danger from pneumothorax in patients who undergo compression chamber treatment for cerebral arterial gas embolism (CAGE) following pulmonary barotrauma is frequently emphasized. Two cases of CAGE treated by recompression after submarine escape tank training (SETT) accidents are described. Both were complicated by bilateral pneumothoraces but the first case, treated on an air table, required thoracentesis in the chamber, whereas the second case, treated on an oxygen table, escaped the need for in-chamber thoracentesis despite large pneumothoraces. Review of similar Royal Navy and United States Navy SETT accidents suggests that the danger from pneumothorax during recompression treatment of CAGE victims may be overstated. Modern management on oxygen-based therapeutic recompression tables may significantly reduce the risk. Thoracentesis while under pressure should be reserved for cases developing symptoms or signs of tension pneumothorax. Treatment options for these cases are discussed and a decision algorithm is proposed.

Carbon monoxide poisoning: forgotten not gone!

Carbon monoxide causes one third of all poisoning deaths in Britain. In this paper a modern scheme for the assessment and management of victims of carbon monoxide poisoning is outlined, the importance of the direct cellular toxicity of carbon monoxide and the rationale behind hyperbaric oxygen therapy are discussed, and a list of currently available hyperbaric facilities is given.