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PubMed2001

Relationship between right-to-left shunts and cutaneous decompression illness.

The presence of a large right-to-left shunt is associated with neurological decompression illness after non-provocative dives, as a result of paradoxical gas embolism. A small number of observations suggest that cutaneous decompression illness is also associated with a right-to-left shunt, although an embolic aetiology of a diffuse rash is more difficult to explain. We performed a retrospective case--control comparison of the prevalence and sizes of right-to-left shunts determined by contrast echocardiography performed blind to history in 60 divers and one caisson worker with a history of cutaneous decompression illness, and 123 historical control divers. We found that 47 (77.0%) of the 61 cases with cutaneous decompression illness had a shunt, compared with 34 (27.6%) of 123 control divers (P<0.001). The size of the shunts in the divers with cutaneous decompression illness was significantly greater than in the controls. Thus 30 (49.2%) of the 61 cases with cutaneous decompression illness had a large shunt at rest, compared with six (4.9%) of the 123 controls (P<0.001). During closure procedures in 17 divers who had cutaneous decompression illness, the mean diameter of the foramen ovale was 10.9 mm. Cutaneous decompression illness occurred after dives that were provocative or deep in subjects without shunts, but after shallower and non-provocative dives in those with shunts. The latter individuals are at increased risk of neurological decompression illness. We conclude that cutaneous decompression illness has two pathophysiological mechanisms. It is usually associated with a large right-to-left shunt, when the mechanism is likely to be paradoxical gas embolism with peripheral amplification when bubble emboli invade tissues supersaturated with nitrogen. Cutaneous decompression illness can also occur in individuals without a shunt. In these subjects, the mechanism might be bubble emboli passing through an 'overloaded' lung filter or autochthonous bubble formation.

Case-Control Studies↗

PubMed1990

Nitrogen partial pressures in man after decompression from simulated scuba dives at rest and during exercise.

In 5 subjects arterial and central venous nitrogen partial pressures (PN2) were measured after decompression from a chamber dive following a decompression schedule for scuba diving. The simulated dives consisted of exposure to air at 6 bar for 30 min corresponding to a depth of 50 m. Afterward the subjects were decompressed with decompression stops at 2.5, 2.2, 1.9, 1.6, and 1.3 bar with a total decompression time of 67 min. In 3 of the subjects the measurements were repeated after they had exercised (workload 75 W) during bottom time. Immediately after decompression and every 40 min until Minute 240 arterial and central venous blood samples were analyzed for PN2 using a manometric Van Slyke apparatus. Venous PN2 remained elevated until 160 min after decompression, indicating still incomplete nitrogen washout for at least 2 h after decompression had been accomplished. We did not find any difference in PN2 values after decompression from dives at rest and after exercise. Applying a computer program based on a wide range of theoretical tissue half-times nitrogen elimination proved to be consistent with Haldanian theories when using our decompression profile. Our data confirm that nitrogen elimination is prolonged after decompression from simulated dives at rest and after exercise.

Adult↗

PubMed1996

Endoscopic decompression for acute colonic pseudo-obstruction.

BACKGROUND: Acute colonic pseudo-obstruction is often treated by colonoscopic decompression. Efficacy, safety, and outcome of endoscopic decompression was assessed. METHODS: Colonoscopic decompressions from 1988 to 1994 were reviewed. Resolution without further endoscopic intervention was defined as clinical success. RESULTS: Acute colonic pseudo-obstruction was diagnosed in 50 patients. Thirty-three cases followed surgery or trauma and 17 developed during severe medical illness. Orthopedic joint surgery was most common. Nineteen of 50 patients (38%) had severe underlying medical disease. Forty-one patients (82%) had one colonoscopic decompression with clinical success in 39 (95%). Nine patients (18%) required multiple (2 to 4) colonoscopic decompressions with clinical success in 5 (56%). A decompression tube positioned in the right colon (57%) and in the transverse colon (33%) had similar clinical success. In 8 procedures a decompression tube was not placed, with poor clinical success (25%). The overall clinical success of colonoscopic decompression was 88% (44 of 50). An endoscopic perforation occurred in 1 patient (2%). Overall hospital mortality was 30%. CONCLUSIONS: Colonoscopic decompression is effective and safe for acute colonic pseudo-obstruction that does not respond to conservative therapy. Most patients will respond to one colonoscopic decompression with decompression tube placement. Complete colonoscopy and cecal tube placement is unnecessary.

Acute Disease↗

PubMed1985

Current trends in orbital decompression.

A questionnaire was sent to members of the American Society of Ophthalmic Plastic and Reconstructive Surgery (ASOPRS) and the Orbital Society in regard to indications, surgical techniques and results of orbital decompression for Graves' disease. It was found that more than 60% of orbital decompressions were performed for mild to severe exophthalmos to correct corneal exposure or disfigurement. A total of 3.9% of these procedures were performed to relieve visual loss in compressive neuropathy. The large majority of decompressions were performed using antral-ethmoidal decompression via a translid or fornix approach. The amount of retrodisplacement was greatest with Kennerdell-Maroon or four-wall decompression and the least with lateral wall decompression. The antral-ethmoidal and three-wall decompression techniques gave an average of 4 to 6 mm of retrodisplacement. It was determined from the survey that antral-ethmoidal decompressions performed through the transantral approach were more likely to relieve the pressure in compressive neuropathy and also more likely to induce a worsening of muscle balance. In contrast, antral-ethmoidal decompressions performed via the translid approach were not as effective in relieving compressive neuropathy but had a much lower incidence of worsened muscle balance, and in fact, resulted in a higher incidence of improved muscle balance. The same trends were confirmed in the author's surgical practice, and an anatomic explanation is offered. The importance of creating nasoantral windows following decompression is emphasized. The risks of cerebrospinal fluid leakage and changes in eyelid positioning following decompression are described.

Combined Modality Therapy↗

PubMed1997

Transforaminal and posterior decompressions of the lumbar spine. A comparative study of stability and intervertebral foramen area.

STUDY DESIGN: Ten fresh, cadaveric, two-vertebrae, functional spinal units were used to study the pathoanatomy, intervertebral foraminal area, and flexibility changes after posterior and transforaminal decompression. OBJECTIVES: To determine the feasibility of an endoscopic transforaminal approach as an alternative to conventional approaches, to establish the adequacy of transforaminal decompression without destabilizing the spine, and to study the structural changes in the spine after decompressions. SUMMARY OF THE BACKGROUND DATA: Posterior decompression entails major dissection and excision of bone and ligaments to access the spinal canal. Posterior decompression may be complicated by acute or chronic spinal instability, and the adequacy of lateral decompression is highly subjective. METHODS: The functional spinal units were mounted in quick-setting epoxy blocks. Pre- and postoperative computed tomography scans were taken to study changes in the foraminal area. Pre- and postoperative flexibility and anatomic studies were performed to compare the results. RESULTS: A 45.5% increase in the intervertebral foraminal area was possible, there was no flexibility change, and minimal anatomic damage to the spine was noted after transforaminal decompression. A 34.2% increase in the intervertebral foraminal area and a significant increase in extension and axial rotation flexibility were noted after the posterior decompression. CONCLUSION: Transforaminal decompression produced a significantly larger increase in the intervertebral foraminal area than posterior decompression, without increasing the range of motion or neutral zone in any direction. Because there was no violation of the anatomic integrity of the spine in the transforaminal approach, the risk of surgically induced instability was minimized. Endoscopic transforaminal decompression is a feasible alternative to current approaches.

Adult↗

PubMed1987

Decompression of the spinal cord improves recovery after acute experimental spinal cord compression injury.

The value of decompression after spinal cord injury in patients is still an unresolved issue. It has previously been shown in our laboratory that functional recovery in rats after cord compression varied with both the force and time until decompression. However, the longest duration studied was only 15 minutes, which is far less than that usually encountered in clinical practice, and therefore, the present study was undertaken to determine the value of decompression after more prolonged periods of compression. A factorially designed experiment with five rats per cell was used with the clip compression injury model. Forces of 2.3, 16.9 or 53.0 gms were applied at C7-T1 until decompression was performed after 15, 60, 120, or 240 minutes of compression. Functional recovery was assessed weekly for 8 weeks using the inclined plane technique. Maximum and minimum performance limits were established in normal rats and rats with cord transection, respectively. Univariate analysis and multiple comparison tests were used to analyse the data. The major determinant of recovery was the force of the injury. For example, the animals injured by the 2.3 gm clip performed significantly better than those injured at higher forces for all times until decompression (p less than 0.0001), and there was a significant difference in recovery between the groups injured by the 16.9 and 53.0 gm clips, although only for the 15 minutes until decompression group (p less than 0.05). The time until decompression also affected recovery, but only for the lighter compression forces (2.3 and 16.9 gm). For example, animals decompressed after 60 minutes of 2.3 gm compression recovered significantly better than those decompressed after 240 minutes (p less than 0.05). Thus, if the initial injury force is small, decompression is beneficial even after prolonged injury.

Animals↗

PubMed2001

A randomized controlled trial of total colonic decompression after colonoscopy to improve patient comfort.

OBJECTIVES: Bloating occurring after colonoscopy may cause significant discomfort in some patients. We sought to determine whether total colonic decompression decreased bloating and improved comfort after colonoscopy. METHODS: Consecutive outpatients undergoing elective colonoscopy were randomized to total colonic decompression or to the control group after completion of the routine colonoscopy. The colonoscope was advanced again to the cecum and the air aspirated during withdrawal in patients randomized to decompression and the procedure was terminated without decompression in control patients. Pain and bloating was assessed in the recovery room and in 24-48 h using a five-point scale. RESULTS: Sixty-five patients were randomized to decompression and 61 were randomized to the control group. The baseline demographic and procedural characteristics were similar between the two groups, but decompression took significantly longer (median, 17 min vs 14 min, p = 0.0002). Seventy-five percent of the decompression group and 80% of the control group denied any pain during colonoscopy. Significantly fewer patients from the decompression group complained of bloating after the procedure (25% vs 59%, p < 0.001) when questioned in the recovery room. However, comparable patients complained of postprocedure bloating when questioned in 24-48 h after the procedure (45% of decompression group vs 47% of control group, p = 0.86). The nurse and the endoscopist were poor at predicting the patient's bloating and significantly overestimated the level of pain. CONCLUSIONS: Total colonic decompression does not significantly reduce bloating after colonoscopy when assessed 24-48 h after the procedure.

Abdominal Pain↗

PubMed2000

Reversal of dysthyroid optic neuropathy following orbital fat decompression.

AIMS: To document the successful treatment of five patients with dysthyroid optic neuropathy by orbital fat decompression instead of orbital bone decompression after failed medical therapy. METHODS: Eight orbits of five patients with dysthyroid optic neuropathy were selected for orbital fat decompression as an alternative to bone removal decompression. Treatment with systemic corticosteroids and/or orbital radiotherapy was either unsuccessful or contraindicated in each case. All patients satisfied clinical indications for orbital bone decompression to reverse the optic neuropathy. High resolution computerised tomographic (CT) scans were performed in all cases and in each case showed signs of enlargement of the orbital fat compartment. As an alternative to bone decompression, orbital fat decompression was performed on all eight orbits. RESULTS: Orbital fat decompression was performed on five patients (eight orbits) with optic neuropathy. Optic neuropathy was reversed in all cases. There were no cases of postoperative diplopia, enophthalmos, globe ptosis, or anaesthesia. All patients were followed for a minimum of 1 year. CONCLUSIONS: In a subset of patients with an enlarged orbital fat compartment and in whom extraocular muscle enlargement is not the solitary cause of optic neuropathy, fat decompression is a surgical alternative to bony decompression.

Adipose Tissue↗

PubMed1999

An evidence-based review of decompressive surgery in acute spinal cord injury: rationale, indications, and timing based on experimental and clinical studies.

OBJECT: The authors conducted an evidence-based review of the literature to evaluate critically the rationale and indications for and the timing of decompressive surgery for the treatment of acute, nonpenetrating spinal cord injury (SCI). METHODS: The experimental and clinical literature concerning the role of, and the biological rationale for, surgical decompression for acute SCI was reviewed. Clinical studies of nonoperative management of SCI were also examined for comparative purposes. Evidence from clinical trials was categorized as Class I (well-conducted randomized prospective trials), Class II (well-designed comparative clinical studies), or Class II (retrospective studies). Examination of studies in which animal models of SCI were used consistently demonstrated a beneficial effect of early decompressive surgery, although it is difficult to apply these data directly to the clinical setting. The clinical studies provided suggestive (Class III and limited Class II) evidence that decompressive procedures improve neurological recovery after SCI. However, no clear consensus can be inferred from the literature as to the optimum timing for decompressive surgery. Many authors have advocated delayed treatment to avoid medical complications, although good evidence from recent Class II trials indicates that early decompressive surgery can be performed safely without causing added morbidity or mortality. CONCLUSIONS: There is biological evidence from experimental studies in animals that early decompressive surgery may improve neurological recovery after SCI, although the relevant interventional timing in humans remains unclear. To date, the role of surgical decompression in patients with SCI is only supported by Class III and limited Class II evidence. Accordingly, decompressive surgery for SCI can only be considered a practice option. Furthermore, analysis of the literature does not allow definite conclusions to be drawn regarding appropriate timing of intervention. Hence, there is a need to conduct well-designed experimental and clinical studies of the timing and neurological results of decompressive surgery for the treatment of acute SCI.

Acute Disease↗

PubMed2000

Decompression scenarios in a new underground transportation system.

BACKGROUND: The risks of a public exposure to a sudden decompression, until now, have been related to civil aviation and, at a lesser extent, to diving activities. However, engineers are currently planning the use of low pressure environments for underground transportation. This method has been proposed for the future Swissmetro, a high-speed underground train designed for inter-urban linking in Switzerland. HYPOTHESIS: The use of a low pressure environment in an underground public transportation system must be considered carefully regarding the decompression risks. Indeed, due to the enclosed environment, both decompression kinetics and safety measures may differ from aviation decompression cases. METHOD: A theoretical study of decompression risks has been conducted at an early stage of the Swissmetro project. A three-compartment theoretical model, based on the physics of fluids, has been implemented with flow processing software (Ithink 5.0). Simulations have been conducted in order to analyze "decompression scenarios" for a wide range of parameters, relevant in the context of the Swissmetro main study. RESULTS: Simulation results cover a wide range from slow to explosive decompression, depending on the simulation parameters. Not surprisingly, the leaking orifice area has a tremendous impact on barotraumatic effects, while the tunnel pressure may significantly affect both hypoxic and barotraumatic effects. Calculations have also shown that reducing the free space around the vehicle may mitigate significantly an accidental decompression. CONCLUSION: Numeric simulations are relevant to assess decompression risks in the future Swissmetro system. The decompression model has proven to be useful in assisting both design choices and safety management.

Accidents↗

PubMed1996

Effects of various degrees of compression and active decompression on haemodynamics, end-tidal CO2, and ventilation during cardiopulmonary resuscitation of pigs.

UNLABELLED: The effects of various degrees of compression and active decompression during cardiopulmonary resuscitation were tested in a randomized cross-over-design during ventricular fibrillation in eight pigs using an automatic hydraulic chest compression device. Compared with 4/0 (compression/decompression in cm), mean carotid arterial blood flow rose by 60% with 5/0, by 90% with 4/2 and 4/3, and 105% with 5/2. Two cm active decompression increased mean brain and myocardial blood flow by 53% and 37%, respectively, as compared with 4/0. Increasing standard compression from 4 to 5 cm caused no further increase in brain or heart tissue blood flow whether or not combined with active decompression. Tissue blood flow remained unchanged or decreased when active decompression (4/3) caused that 50% of the pigs were lifted from the table due to the force required. Myocardial blood flow was reduced with 5/0 vs. 4/0 despite no reduction in end decompression coronary perfusion pressure ((aortic-right atrial pressure) (CPP), (7 +/- 8 mmHg with 4/0, 14 +/- 11 mmHg with 5/0)(NS)). End decompression CPP increased by 186% with 4/2 vs. 4/0, by 200% with 4/3, and by 300% with 5/2. Endo-tracheal partial pressure of CO2 was significantly increased during the compression phase of active decompression CPR compared with standard CPR. Active decompression CPR generated an significantly increased ventilation compared with standard CPR. CONCLUSION: Carotid and tissue blood flow, ventilation, and CPP increase with 2 cm of active decompression. An attempt to further increase the level of active decompression or increasing the compression depth from 4 to 5 cm did not improve organ blood flow.

Animals↗

PubMed1997

Intraoperative ultrasound for immediate evaluation of anterior cervical decompression and discectomy.

STUDY DESIGN: An evaluation of whether the immediate operative results can be improved in anterior cervical surgery in patients in whom disc fragments could remain hidden behind a vertebral body or far laterally in the foramen or in canal stenosis that involved a significant amount of a vertebral body. OBJECTIVES: To determine whether intraoperative ultrasonography can provide immediate evaluation of the decompression. SUMMARY OF BACKGROUND DATA: The anterior cervical approach has anatomic limitations that prevent good visualization of deep structures. Sequestered disc fragments can be hidden behind the bone of the vertebral body. Even careful preoperative measurements cannot ensure adequate length and width of decompression for stenotic lesions. METHODS: Three groups of patients were studied. Group 1 contained seven patients with soft disc herniations that were either behind the vertebral body or extended laterally into the neural foramen. Group 2 consisted of five patients with canal stenosis involving at least one third of the length of a vertebral body and causing myelopathic signs and symptoms. Group 3 consisted of four patients with radicular and cord symptoms. All were studied with either magnetic resonance imaging or computed tomography myelography or both. The size of the desired decompression was measured from these studies. A standard anterior decompression using magnification was performed that satisfied the surgeon's visual and tactile evaluation. The operative site was imaged ultrasonically and the decompression extended until preset imaging criteria were met. These criteria were clear root visualization for radiculopathy and good dural pulsations for stenotic lesions. RESULTS: Twelve of the 16 patients did not meet the set criteria on initial imaging, and 11 had their decompression extended. A hidden lateral disc fragment was found in one. In this selected group of 16 patients with complicated cervical pathology, 14 improved neurologically after the use of ultrasonic guidance intraoperatively. One error of interpretation was made. One patient who did not meet the ultrasonic decompression criteria and did not have the decompression extended did not improve after surgery. CONCLUSIONS: In complicated anterior cervical decompressions, intraoperative ultrasonic imaging provides immediate evaluation of the extent of the decompressive procedure and may improve the operative result.

Cervical Vertebrae↗

PubMed1996

Cardiopulmonary changes with moderate decompression in rats.

Sprague-Dawley rats were compressed to 616 kPa (a) for 120 min then decompressed at 38 kPa/min to assess the cardiovascular and pulmonary responses to moderate decompression stress. In one series of experiments the rats were chronically instrumented with Doppler ultrasonic probes for simultaneous measurement of blood pressure, cardiac output, heart rate, left and right ventricular wall thickening fraction, and venous bubble detection. Data were collected at baseline, throughout the compression/decompression protocol, and for 120 min post decompression. In a second series of experiments the pulmonary responses to the decompression protocol were evaluated in non-instrumented rats. Analyses included blood gases, pleural and bronchoalveolar lavage (BAL) protein and hemoglobin concentration, pulmonary edema, BAL and lung tissue phospholipids, lung compliance, and cell counts. Venous bubbles were directly observed in 90% of the rats where immediate post-decompression autopsy was performed and in 37% using implanted Doppler monitors. Cardiac output, stroke volume, and right ventricular wall thickening fractions were significantly decreased post decompression, whereas systemic vascular resistance was increased suggesting a decrease in venous return. BAL Hb and total protein levels were increased 0 and 60 min post decompression; pleural and plasma levels were unchanged. BAL white blood cells and neutrophil percentages were increased 0 and 60 min post decompression and pulmonary edema was detected. Venous bubbles produced with moderate decompression profiles give detectable cardiovascular and pulmonary responses in the rat.

Animals↗

PubMed1998

Ocular bubble formation as a method of assessing decompression stress.

Tear film bubble formation and ultrasound reflectivity of the lens-vitreous humor compartments were monitored following simulated dives in a hyperbaric chamber. the sensitivity of these methods in determining decompression stress was compared with the results of precordial Doppler ultrasound. In addition, the utility of these diagnostic techniques in testing decompression dive profiles was evaluated. Eleven divers completed two series of chamber dives according to the decompression schedule of the Professional Association of Diving Instructors. The first dive series comprised dives to 70 feet of seawater (fsw) for 15, 29, and 40 min. The second series comprised maximum duration no-stop decompression dives to 40 fsw for 140 min, 70 fsw for 40 min, 90 fsw for 25 min, and 120 fsw for 13 min. Before and immediately after each dive, the following measurements were obtained from each subject: eye surface tear film bubble counts with a slit-lamp microscope, lens and vitreous humor reflectivity using A- and B-mode ophthalmic ultrasonic scan, and precordial Doppler ultrasonic detection of venous gas bubbles. Tear film bubble assessment and ocular scanning ultrasound were observed to be more sensitive in detecting decompression stress than the conventional Doppler ultrasonic surveillance of the precordial region. In contrast to precordial Doppler ultrasonic surveillance, which failed to detect any significant changes in circulating bubbles, tear film bubble formation displayed a dose-response relationship with increasing duration of the 70-fsw dives. Reflectivity changes of the lens-vitreous humor interface were not significant until the no-stop decompression limit was reached. In addition, for each of the no-stop decompression limit dives, increases in the average tear film bubble formation and lens-vitreous humor interface reflectivity were similar. Ocular bubble observations may provide a practical and objective ocular bubble index for analyzing existing decompression schedules and predicting individual susceptibility to decompression sickness.

Adolescent↗

PubMed2000

Sigmoid stiffener for decompression tube placement in colonic pseudo-obstruction.

BACKGROUND AND STUDY AIMS: Decompression tube placement improves outcome in colonic pseudo-obstruction (CP) which is refractory to conservative measures, especially if the decompression tube is placed proximal to the hepatic flexure. We evaluate the ability of a sigmoid stiffener to facilitate more proximal colonoscopy and decompression tube placement. PATIENTS AND METHODS: A sigmoid stiffener is used in the standard fashion during colonoscopic decompression for pseudo-obstruction. After cecal wire placement, the colonoscope is withdrawn, leaving the stiffener and wire in place. By passing through the stiffener, an over-wire decompression tube can avoid sigmoid looping. We compared proximal extent of colonoscopy, tube position, endoscopy time, and patient outcomes using a sigmoid stiffener, with a control group of patients treated previously. Patients with colonic ischemia were excluded. RESULTS: Using this technique, nine consecutive colonoscopies and decompression tube placements reached the right colon. Significantly, only three of seven control colonoscopies and two control decompression tubes did so. However, improvements in procedural time and patient outcome did not reach statistical significance. No complications occurred. CONCLUSION: The use of a sigmoid stiffener during colonic decompression allows more proximal colonoscopy and decompression tube placement, with possible clinical benefit. We do not use this technique in the setting of left colon ischemia.

Adult↗

PubMed1998

Cervical arachnoid cysts after craniocervical decompression for Chiari II malformations: report of three cases.

OBJECTIVE AND IMPORTANCE: We describe three cases in which ventrally situated cervical arachnoid cysts led to spinal cord or cervicomedullary compression after repeat craniocervical decompression for Chiari II malformations. CLINICAL PRESENTATION: All three patients underwent craniocervical decompression when their Chiari malformations became symptomatic. The first patient developed chronic vertiginous spells and headache and was treated with repeated craniocervical decompression procedures during several years. Seven months after undergoing her third decompression procedure, she developed severe dizzy spells, which were determined to be of brain stem origin. The second patient had a small, asymptomatic arachnoid cyst anterior to the brain stem discovered at age 6 years. After undergoing repeat craniocervical decompression for headaches 8 years after undergoing his first procedure, the patient developed severe neck pain and acute quadraparesis. A third patient underwent repeat craniocervical decompression at age 14 years for cranial nerve dysfunction. Postoperatively, he acutely developed paresis of extraocular movements and incoordination of the upper extremities. All three patients were found to have anteriorly situated arachnoid cysts compressing the brain stem and/or cervical spinal cord. INTERVENTION AND TECHNIQUE: Fenestration of the arachnoid cyst or drainage with cystoperitoneal shunting adequately treated acute brain stem or cervical spinal cord compression. All three patients had achieved satisfactory relief from their acute symptoms of neural compression at their follow-up examinations. CONCLUSION: An association between spinal arachnoid cysts and neural tube defects has previously been reported. However, the development of previously undetected spinal arachnoid cysts after craniocervical decompression was unexpected. We hypothesize that extensive craniocervical decompression may alter the cerebrospinal fluid pressure dynamics in such a way that the anterior subarachnoid space, previously compressed, may dilate. Occasionally, because of perimedullary arachnoiditis, the cerebrospinal fluid may become loculated and act as a mass. Direct fenestration or shunting may successfully treat this problem, and less extensive craniocervical decompression may avoid it.

Adolescent↗

PubMed1990

Nitrogen partial pressures in man after decompression from simulated scuba dives.

In five subjects arterial and central venous nitrogen partial pressures (PN2) were measured after decompression from a chamber dive following a decompression schedule for scuba diving. The simulated dives consisted of exposure at rest to air at 6 bar for 30 min. corresponding to a depth of 50 m. Afterwards the subjects were decompressed with decompression stops at 2.5, 2.2, 1.9, 1.6 and 1.3 bar with a total decompression time of 73 min. Immediately after decompression and every 40 min. until the 240th min. arterial and central venous blood samples were analyzed for PN2 using a manometric Van Slyke apparatus. Venous PN2 remained elevated until 160 min. after decompression indicating still incomplete nitrogen wash-out at least two hours after decompression had been accomplished. Bubble formation is discussed as a cause for prolonged nitrogen elimination. Our data confirm that nitrogen elimination is prolonged after decompression from simulated dives at rest.

Arteries↗

PubMed1996

Decompressive craniectomy in a rat model of "malignant" cerebral hemispheric stroke: experimental support for an aggressive therapeutic approach.

Acute ischemia in the complete territory of the carotid artery may lead to massive cerebral edema with raised intracranial pressure and progression to coma and death due to uncal, cingulate, or tonsillar herniation. Although clinical data suggest that patients benefit from undergoing decompressive surgery for acute ischemia, little data about the effect of this procedure on experimental ischemia are available. In this article the authors present results of an experimental study on the effects of decompressive craniectomy performed at various time points after endovascular middle cerebral artery (MCA) occlusion in rats. Focal cerebral ischemia was induced in 68 rats using an endovascular occlusion technique focused on the MCA. Decompressive craniectomy was performed in 48 animals (in groups of 12 rats each) 4, 12, 24, or 36 hours after vessel occlusion. Twenty animals (control group) were not treated by decompressive craniectomy. The authors used the infarct volume and neurological performance at Day 7 as study endpoints. Although the mortality rate in the untreated group was 35%, none of the animals treated by decompressive craniectomy died (mortality 0%). Neurological behavior was significantly better in all animals treated by decompressive craniectomy, regardless of whether they were treated early or late. Neurological behavior and infarction size were significantly better in animals treated very early by decompressive craniectomy (4 hours) after endovascular MCA occlusion (p < 0.01); surgery performed at later time points did not significantly reduce infarction size. The results suggest that use of decompressive craniectomy in treating cerebral ischemia reduces mortality and significantly improves outcome. If performed early after vessel occlusion, it also significantly reduces infarction size. By performing decompressive craniectomy neurosurgeons will play a major role in the management of stroke patients.

Animals↗