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PubMed2002

Evolution of relation P1(P2) describing saturation decompressions after air hyperbaric expositions.

The basic problem in decompression is the limit of maximum tolerable change of pressure after diving. Due to the number of parameters involved in decompression models (bottom time, ambient pressure, exposition profile, content of breathing mixtures, properties of inert gases) the number of possible solutions is theoretically unlimited. Since the beginning of modern decompression models the starting point has been direct saturation decompression using air. The generally accepted form of solution is the linear relation between tolerable pressure P2 after saturation exposition to pressure P1 described by the equation in the form P1 = P2 x A + B, where A and B are parameters obtained by experiments. Since the introduction of this equation values of parameters have been changing in order to decrease the rate of decompression illness. The aim of this study was to analyse and interpret the trend of those changes. Sixteen published models, including the one developed in our center, were compared and gradual change of parameters was identified. This trend should result in safer decompression systems.

Decompression↗
PubMed2003

Increased oxygen before and during decompression reduces bubble formation in rats.

The aim of this study was to test the hypothesis that increased oxygen partial pressure shortly before and during decompression from hyperbaric pressures would decrease venous gas bubble formation. Bubbles were detected by an ultrasound Doppler technique in conscious, freely moving rats. All rats were exposed twice to 6 bar for 2 hours. In exposure A, the breathing gas mixture was 1 bar O2 and 5 bar N2. In exposure B, the breathing gas was changed to 2 bar O2 and 4 bar N2, 5 min prior to decompression. The decompression rate was 0.1 bar x s(-1) in both groups. Significantly fewer bubbles were detected after decompression in exposure B compared to A. The angiotensin converting enzyme (ACE) concentration in serum was measured as an indicator of possible damage to the pulmonary endothelium induced by bubbles. However, no correlation between ACE and bubble amount was found. In conclusion, this study in conscious rats indicates that safer decompression may be obtained by increasing the oxygen partial pressure before and during decompression.

Animals↗
PubMedDate not supplied

Delayed effect of nitric oxide synthase inhibition on the survival of rats after acute decompression.

AIM: The formation of bubbles in the blood stream together with the ensuing sickness after rapid decompression is assumed to depend on the physiological condition of the vascular system. In order to gain insight into the vascular function of nitric oxide in acute decompression sickness, the effects of the nitric oxide synthase inhibition by N(omega)-nitro-L-arginine methyl ester was studied in rats. METHODS: Wistar rats under anaesthesia were exposed to hyperbaric conditions for two hours and decompressed approximately 2.5 hours after a single subcutaneous injection of N(omega)-nitro-L-arginine methyl ester. Scalar doses and different pressures were tested. RESULTS: The fraction of the rats that died after decompression was greater in rats treated with N(omega)-nitro-L-arginine methyl ester at doses greater than 8 mg Kg-1 body weight compared to untreated rats. CONCLUSION: Although we have not excluded effects of nitric oxide synthase inhibition on distribution of perfusion and therefore inert gas elimination from tissue during decompression as a factor, this result highlights a delayed benefit of nitric oxide synthase activity in preventing death in acute decompression sickness.

Animals↗
PubMedDate not supplied

Decompression tables and dive-outcome data: graphical analysis.

We compare outcomes of experimental air dives with prescriptions for ascent given by various air decompression tables. Among experimental dives compiled in the U.S. Navy Decompression Database, many profiles that resulted in decompression sickness (DCS) have longer total decompression times (TDTs, defined as times spent at decompression stops plus time to travel from depth to the surface) than profiles prescribed by the U.S. Navy table; thus, the divers developed DCS despite spending more time at stops than the table requires. The same is true to a lesser extent for the table used by the Canadian forces. A few DCS cases occurred in profiles having longer TDTs than those of the VVal-18 table and a table prepared at the University of Pennsylvania. The TDTs for 2.2% risk according to the probabilistic NMRI'98 Model are often far longer than TDTs of experimental dives that resulted in DCS. This analysis dramatizes the large differences among alternative decompression instructions and illustrates how the U.S. Navy table provides too little time at stops when bottom times are long.

Decompression↗
PubMed1994

Cerebral imaging of decompression injury patients with 18-F-2-fluoro-2-deoxyglucose positron emission tomography.

The objective assessment of the extent of cerebral insult and the effects of therapy in decompression injury patients has proven to be difficult by most imaging modalities. In this pilot study we evaluated the ability of 18-F-2-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) to identify metabolic brain abnormalities in decompression injury patients. Twenty-two patients who were evaluated at our institution for decompression accidents were evaluated with FDG-PET. Four of the 22 patients had no neurologic symptoms and no neurologic findings on clinical exam at the time of the FDG-PET study. No statistically significant correlations were found between the presence of symptoms and the demonstration of abnormalities on the PET study and no statistically significant correlation was found between the location of the decompression injury and the demonstration of abnormalities on the PET study. We conclude that FDG-PET imaging of the brain cannot reliably identify cerebral abnormalities in patients with decompression injuries and would be of limited benefit for monitoring therapy in patients with decompression illness.

Adult↗
PubMed1997

Exercise during decompression reduces the amount of venous gas emboli.

To determine the effects of moderate, intermittent exercise during decompression on the Doppler detectable amount of venous gas emboli (VGE), 29 healthy male volunteers performed 44 wet (8 degrees +/- 2 degrees C) dives to 45 msw (450 kPa) for 30 min with standard air decompression. During compression and the bottom period, all subjects were inactive; during decompression, 28 remained inactive, 11 performed leg exercise, and 5 did arm exercise. Intermittent exercise was controlled at approximately 50% of each subject's arm or leg aerobic capacity. At 30-min intervals after surfacing, subjects were monitored with a Doppler ultrasonic bubble detector. The Doppler scores were used to calculate the Kisman Integrated Severity Score (KISS). The KISS were log transformed (with zeroes being equivalent to log 0.01) and analyzed with a one-way analysis of variance. No significant differences (P < or = .05) between mean KISS scores after arm or leg exercise were observed, thus these data were pooled and compared to those of the inactive controls. The mean pooled KISS after exercising during decompression were significantly lower than those of the inactive controls. Moderate, intermittent exercise during decompression apparently reduces the amount of Doppler-detectable VGE after diving. The incidence rate of decompression sickness in both groups was not significantly different (P < 0.05).

Adult↗
PubMed1993

Spinal cord decompression sickness in sport diving.

OBJECTIVE: To summarize 16 years' experience in the diagnosis and treatment of spinal cord decompression sickness in Israel. DESIGN: The survey data were collected firsthand by physicians trained in underwater diving medicine. SETTING: The Israeli Naval Medical Institute, Israel's national hyperbaric referral center. PATIENTS: Sixty-eight sport divers diagnosed as having spinal cord decompression sickness. INTERVENTIONS: Hydration and 100% oxygen breathing until the patient reached the hyperbaric chamber. All patients received recompression therapy on US Navy treatment tables using oxygen, except for six who were treated by Comex Treatment Table CX-30, which uses helium in addition to oxygen. MAIN OUTCOME MEASURES: Neurological examination after the completion of recompression therapy. RESULTS: Forty-one percent of the dives were performed within the decompression limits of the US Navy standard decompression tables. Risk factors were fatigue, circumstances suggesting dehydration, and extreme physical effort. The most common presenting symptoms were paresthesias, weakness of the legs, lower back pain, or abdominal pain. Full recovery was achieved in 79% of the patients. Spinal symptoms appeared immediately on surfacing in six of the eight patients who continued to have multiple neurological sequelae. CONCLUSIONS: United States Navy air decompression tables appear not to be completely safe for sport divers. Even mild spinal symptoms identified on surfacing should be treated vigorously. High-pressure oxygen-helium therapy seems to be a promising alternative in cases of severe spinal cord decompression sickness.

Adult↗
PubMed1982

The permeability alteration of brain and spinal cord vasculature to horseradish peroxidase during experimental decompression sickness as compared to the alteration in permeability induced by hyperosmolar solution.

The permeability of microvasculature in the cerebral cortex, neostriatum, and spinal cord to i.v. injected horseradish peroxidase (HRP) has been investigated in rats following experimental compression to 6.1 bars (abs.) air for 90 min, and subsequent decompression to the ambient pressure in 1 min. For comparison, 1 ml of 2.0 M urea was injected into the right common carotid artery of rats during 15 s. After exposure to compression-decompression, under the light microscope focal leaky areas were found in all the regions examined. The leakage was most prominent in the grey matter of the spinal cord, and the cerebral cortex. In decompressed rats, arterioles were most often the site of peroxidase extravasation, whereas extravasation of HRP was less frequently displayed by capillaries and venules. In urea-treated rats, capillaries and venules frequently displayed extravasation of HRP as well. Parenchymal cells accumulated the trace adjacent to the leaky areas. Under the electron microscope, the extravasation of HRP was associated with peroxidase-containing pleomorphic vesicular structures in the endothelium, both in decompressed and urea-injected rats. Moreover, in contrast to decompressed rats, the junctions between endothelial cells were penetrated by the trace in urea-treated rats. Accordingly, the results indicate that during decompression sickness the pathway for the extravasation of proteins is through vesicular transfer, whereas the injection of hyperosmolar urea induces extravasation, both through vesicular transfer and junctions between the endothelial cells.

Animals↗
PubMed1999

Radiographic changes after colonoscopic decompression for acute pseudo-obstruction.

PURPOSE: Colonoscopy has been the principal tool for decompression in acute colonic pseudo-obstruction, known as Ogilvie's syndrome. The objectives of this study were to determine the immediate effect of colonoscopy on the cecal diameter (measured on supine radiographs) and to delineate possible correlations in the diameters of dilated segments of the colon. METHODS: The charts and radiographs of 24 patients who had colonoscopic decompression for acute colonic pseudo-obstruction between 1992 and 1997 at the San Diego Veterans Affairs Medical Center and the University of California, San Diego Hospitals were reviewed. We measured cecal, transverse, descending, and sigmoid colon diameters on serial radiographs up to the point of clinical resolution. RESULTS: Mean +/- standard deviation cecal diameter change (between initial and post-decompression films) was -2+/-3.4 cm at four hours and -2.2+/-3.3 cm one day after decompression. On the daily radiographs between colonoscopic decompression and clinical resolution, there was a close correlation between the diameter of the cecum and that of the transverse colon (P<0.05). There was no correlation between the cecal diameter and that of the descending or sigmoid colon. CONCLUSIONS: Colonoscopic decompression only causes a small decrease in cecal size in the patient with acute colonic pseudo-obstruction. Dilation patterns of the cecum and transverse colon are significantly correlated in acute colonic pseudo-obstruction. This correlation provides additional support to the contention that the same pathophysiology affects these two segments of the colon.

Acute Disease↗
PubMed2004

Sacral fractures with neurological injury: is early decompression beneficial?

During a 6-year period, 177 patients with a displaced sacral fracture were treated at our level-one trauma centre. At the initial presentation, 13 patients demonstrated a neurological deficit as a result of their sacral fracture. Six patients underwent surgical decompression, and seven patients were managed without surgical decompression. All patients were re-assessed at an average follow-up of 27.1 (range 12-84) months using the modified SOFCOT Index and the SF-36. Patients undergoing surgical decompression had a significantly better neurological improvement as measured by the modified SOFCOT Index (p=0.014). Moreover, patients undergoing surgical decompression had a significantly better physical function than the patients that were managed without surgical decompression, as measured by the SF-36 (p=0.044). We therefore believe that patients undergoing surgical decompression achieve better neurological improvement and better functional results.

Adolescent↗
PubMed2001

[Treatment of retinal vein occlusion. Vitrectomy with arteriovenous decompression and dissection of the internal limiting membrane].

BACKGROUND: Our therapeutical armamentarium for functional improvement after branch retinal vein occlusion (BRVO) is still limited and the efficacy is uncertain. Recently, surgical decompression of the vein at the arteriovenous crossing (AV decompression) has again been proposed as a suitable form of treatment. MATERIAL AND METHODS: A total of 40 patients with BRVO were treated in our department from August 1999 to February 2001 with AV decompression and 22 patients with comparable BRVO who refused this surgical intervention served as control. The surgical procedure consisted of a standard pars plana vitrectomy and separation of the overlying artery from the vein using microscissors. In 13 cases dissection of the internal limiting membrane was additionally performed. Assessment of visual acuity, fluorescein angiography and multifocal ERG in 7 patients was performed preoperatively and 6 weeks after surgery. RESULTS: The surgical procedure and postoperative course were uneventful. In most of the treated eyes, visual acuity improved and fluorescein angiography revealed capillary reperfusion. Functional results in patients with AV-decompression were highly significantly better than in the control group. CONCLUSION: Our results with surgical decompression of branch retinal vein occlusions demonstrate the therapeutical effect of surgical AV-decompression in BRVO. Further experience is necessary before some open questions can be answered.

Aged↗
PubMed2005

Frequency specific hearing improvement in microvascular decompression of the cochlear nerve.

BACKGROUND: Microvascular compressions of the cochlear nerve can lead to hearing loss. Due to the tonotopic organization of the cochlear nerve any focal compression of the cochlear nerve will result in a frequency specific hearing loss. Decompressing the cochlear nerve could result in a frequency specific hearing improvement, without improving overall hearing. METHOD: Thirty one patients underwent microvascular decompression operations of the vestibulocochlear nerve for vertigo or tinnitus. Preoperative audiograms were substracted from postoperative audiograms obtained 2 years after microvascular decompression. The frequencies of maximal hearing improvement postoperatively were determined. FINDINGS: Of the 31 patients studied, 19 had improvements of 5 dB or more at one or more frequencies postoperatively, and 15 patients had improvements of 10 dB or more. Three patients had improvements of 25 dB or more postoperatively. The postoperative hearing improvement was frequency-specific and related to the anatomical location of the vascular contact on the auditory nerve. The improvement of hearing becomes diluted when the difference between pre- and postoperative hearing thresholds are averaged over all audiometric frequencies. We therefore present results for each frequency that was tested. CONCLUSIONS: Microvascular decompression of the cochlear nerve can improve hearing in selected patients. The improvement seems too small to justify decompressive surgery for the sole purpose of hearing improvement, but it could be considered if associated short vertigo spells, ipsilateral tinnitus, otalgia and cryptogenic hemifacial spasm are present. Decompression should be performed early, before BAEP changes become noticeable. 3D-MRI could become a valuable tool for selecting good surgical candidates.

Adult↗
PubMed2001

Safety and efficacy of early surgical decompression of the thoracic outlet for Paget-Schroetter syndrome.

The surgical treatment of Paget-Schroetter syndrome has evolved to include early thrombolytic therapy and an interval period of anticoagulation, followed by late surgical decompression of the thoracic outlet. More recently, we have developed an abbreviated course of therapy in which the thrombolytic therapy is followed by early surgical decompression during the same admission, then a period of anticoagulation. We compared early surgical decompression with the standard management protocol to determine safety and efficacy of the early treatment algorithm. Nine patients were treated with lysis and early operation. These were compared with the preceding nine consecutive patients treated with lysis and staged operation. Demographic data, risk factors, duration of thrombosis, lytic therapy, time to surgery, operative variables, and postoperative complications were analyzed. Our results showed that thrombolysis followed by early operation does not result in increased perioperative morbidity or mortality. Early surgical decompression of the thoracic outlet during the same admission as lysis is as safe and efficacious as the traditional (staged decompression) approach to Paget-Schroetter syndrome. Lysis followed by early surgical decompression should be considered a new standard of care in the management of Paget-Schroetter syndrome.

Adult↗
PubMed2005

Prospective, randomized trial comparing intraoperative colonic irrigation with manual decompression only for obstructed left-sided colorectal cancer.

BACKGROUND: This is a prospective, randomized, controlled trial comparing the outcome of intraoperative colonic irrigation with that of manual decompression for acutely obstructing colorectal cancers distal to the splenic flexure. METHODS: All patients admitted to our department from June 1999 to August 2002 with obstructing left-sided colorectal cancers were recruited. Patients were randomized intraoperatively and were excluded if deemed unsuitable for segmental resection and primary anastomosis. Twenty-five patients were randomized to receive colonic irrigation and twenty-eight to receive manual decompression. Perioperative parameters and outcome including mortality and anastomotic leak were recorded. RESULTS: Both groups of patients were comparable in terms of gender and age. The time taken for mobilization, decompression, and irrigation in the colonic irrigation group (median, 31 minutes) was significantly longer than that for the manual decompression group (median, 13 minutes) (P; = 0.0005). However, the total time of the operation was similar for both groups. Times for recovery of bowel function, of wound infection, and until discharge from the hospital were also similar. In the manual decompression group there were two cases of anastomotic leak (8 percent, 2/25) requiring reoperation but none (0/24) in the colonic irrigation group. However, this difference was not statistically significant. CONCLUSION: Manual decompression of proximal colon without irrigation is as safe as colonic irrigation in one-stage surgical management of obstructing left-sided colorectal cancer.

Adult↗
PubMed2005

Characteristics and outcomes of strabismus surgery after orbital decompression for thyroid eye disease.

PURPOSE: To compare characteristics and outcomes of strabismus surgery in patients who have undergone orbital decompression for thyroid eye disease with those who have not. SUBJECTS AND METHODS: A chart review of all patients with thyroid eye disease requiring strabismus surgery in one physician's practice. RESULTS: There were 36 patients in the decompression group (DG) and 14 patients in the no-decompression group (NDG). There was a significantly greater amount of preoperative esotropia in the DG ( P = 0.02). There was an increased incidence of A-pattern in the DG ( P = 0.09). There was a slightly higher number of operated muscles in the DG ( P = 0.005). A good or excellent outcome was achieved in 93% of the NDG and in 94% of the DG ( P = 0.83). DISCUSSION: Previous studies suggest that patients requiring orbital decompression have a more complex thyroid eye disease and a lower success rate after strabismus surgery. Our findings suggest that this is not necessarily the case, and the difference in surgical success rates between the studies may in part be due to orbital decompression technique or indication. CONCLUSION: In this series, using a fixed suture technique, outcomes of strabismus surgery in patients with thyroid eye disease who underwent orbital decompression are similar to those who did not.

Adult↗
PubMedDate not supplied

Effect of subacromial decompression on laxity of the acromioclavicular joint: biomechanical testing in a cadaveric model.

Subacromial decompression is a well-accepted treatment for impingement syndrome when nonoperative therapies have failed. However, recent clinical data have raised concern that arthroscopic subacromial decompression may lead to laxity of the acromioclavicular joint and, potentially, predispose patients to late postoperative acromioclavicular joint pain. Our goal was to determine whether subacromial decompression with co-planing of the distal clavicle alters the laxity, or compliance, of the acromioclavicular joint in a cadaveric model. Eighteen cadaveric shoulders were dissected and tested in a specially designed rig, driven by a hydraulic materials testing machine. One hundred-Newton loads were applied to the distal clavicle in the superior, posterior, and anterior directions, while acromioclavicular joint motion was recorded with a 3-dimensional infrared optical measurement system. Acromioplasty was performed with a posterior-referenced cutting block technique and included co-planing of the distal clavicle in all specimens. Joint compliance before and after subacromial decompression was compared with the paired t test. Subacromial decompression increased anteroposterior compliance by 13%, from 8.8 +/- 2.9 mm (mean +/- SD) in the intact joint to 9.9 +/- 3.1 mm (P =.001). Subacromial decompression increased superior compliance by 32%, from 3.1 +/- 1.5 mm in the native specimen to 4.1 +/- 1.8 mm (P =.03). These observations may have implications for the technique of acromioplasty. Although the immediate result of acromioplasty with co-planing appears to be an increase in the compliance of the acromioclavicular joint, the clinical significance of these findings has yet to be determined.

Acromioclavicular Joint↗
PubMed2005

[Early detection of asymptomatic dysbaric osteonecrosis of the shoulder after type 1 decompression sickness: a case report].

INTRODUCTION: Dysbaric osteonecrosis is a rare illness in professional divers and compressed-air workers. The correlation between dysbaric osteonecrosis and previous decompression sickness with osteoarthromuscular pain (type 1 decompression sickness) remains a controversial subject. The probability for ischemic lesions detected with MRI to turn into osteonecrosis after decompression sickness is still not established. EXEGESIS: The authors report the case of a military diver declared definitely medically unfit to dive after the occurrence of advanced dysbaric osteonecrosis of the shoulder, eight months after decompression sickness treated with hyperbaric oxygen, in the same area. A close link between those two events and the requirement for monitoring the follow-up of acute type 1 decompression sickness are discussed. CONCLUSION: Every decompression sickness with osteoarthromuscular pain should be early examined with MRI in order to screen osteomedullar damages liable to worse with diving and change subsequently in bone necrosis.

Adult↗
PubMed2003

Optic neuropathy of Graves disease: results of transantral orbital decompression and long-term follow-up in 215 patients.

PURPOSE: To review demographic characteristics, clinical features, and long-term outcomes of patients with optic neuropathy of Graves disease after transantral orbital decompression. DESIGN: Retrospective analysis of noncomparative interventional case series; long-term follow-up by questionnaire. METHODS: Medical record data (preoperative and postoperative assessments) were collected from patients who had transantral orbital decompression to treat Graves optic neuropathy. Responses to two follow-up questionnaires concerning patient satisfaction were evaluated. Statistical analysis (reflected as P values) compared preoperative and early postoperative (< or =182 days) data. RESULTS: Between November 1969 and May 1989, 215 patients underwent transantral orbital decompression for Graves optic neuropathy. In 205 eyes with visual acuity of 20/40 or worse before decompression, visual acuity improved by 3 Snellen lines or more in 110 (54%) (P <.001). Of 291 eyes with visual field defects preoperatively, 120 (41%) had resolution, and 126 (43%) had improvement postoperatively (P <.001). Proptosis was reduced in 350 eyes by 4.4 +/- 2.3 mm (mean +/- SD) (P <.001). In 104 eyes, disk edema resolved in 72 (69%) and improved in 28 (27%). Responses to questionnaires mailed in 1990 and 2000 showed that 76% and 88% of respondents, respectively, were subjectively satisfied with the results of orbital decompression. CONCLUSIONS: Transantral orbital decompression appeared to be effective in treating optic neuropathy of Graves disease. Patient satisfaction was high at 10-year and 20-year follow-up.

Decompression, Surgical↗