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PubMed1994

Release of surfactant and a myelin proteolipid apoprotein in spinal tissue by decompression.

Two experiments have been performed on sections of bovine spinal cord, the first demonstrating that surface-active phospholipid (SAPL) and myelin proteolipid protein (PLP) are released by bubbles produced by decompression. Both phospholipid and proteolipid were found to be released in amounts increasing with the extent of decompression. The immediate recruitment of surfactant to the monolayer coating the pool surface indicated that the SAPL had been "carried" at the liquid-air interface of the bubbles. In the second study, electrophoresis was used to identify a major portion of the released proteolipid as the PLP much studied in recent times for its encephalitogenic properties. These findings are offered as a possible explanation for the demyelination often found in pathologic studies of divers and for the possible role of SAPL and PLP in stabilizing microbubbles/macronuclei during recompression, especially in relation to the practice of surface decompression.

Animals↗
PubMed1995

[Neurologic accident of decompression: a new indication of transesophageal echocardiography].

Decompression sickness in a 33-year-old SCUBA diver led to neurological lesions with brain damage. The existence of a patent foramen ovale detected with a transoesophageal contrast echocardiography suggested paradoxal gas embolism. This observation emphasizes the intest of transoesophageal contrast echocardiography in decompression sickness as discussed in the literature. Its widely utilization would permit a better understanding of the pathophysiology of decompression sickness. It also may help the physician in deciding whether or not to authorize further diving.

Adult↗
PubMed1993

Prevention of decompression sickness in current and future fighter aircraft.

United States Air Force oxygen regulators set to "NORMAL OXYGEN" deliver up to 60% nitrogen to the pilot at cockpit altitudes of 15,000 to 20,000 ft (4573-6096 m). Research chamber exposure to these altitudes while breathing 50% nitrogen has resulted in high grades of venous gas emboli. Expansion of existing gas emboli following an unplanned decompression to ambient aircraft altitude (e.g., loss of canopy) could result in rapid development of decompression sickness (DCS) symptoms. To reduce this potential problem, regulators in current fighters should be set to "100% OXYGEN" until descent from cruise to increase denitrogenation. The United States' Advanced Tactical Fighter and the European Fighter Aircraft may be designed to cruise above 50,000 ft (15,240 m), where cockpit altitudes exceed 20,000 ft with a 5-psi differential (psid) cockpit pressurization schedule. Increasing cockpit differential pressure to 7 psid while breathing 100% oxygen would greatly reduce the chance of significant emboli formation and the potential for DCS, but would slightly elevate the risks associated with pulmonary overpressure during rapid decompression.

Air Pressure↗
PubMed1993

Relationship between venous bubbles and hemodynamic responses after decompression in pigs.

We present a new pig model for studying relationships between venous gas bubbles and physiologic effects during and after decompression. Sixteen pigs were anesthetized to allow spontaneous breathing. Eight of them underwent a 30-min exposure to 5 bar (500 kPa) followed by a rapid decompression to 1 bar (2 bar/min); the remaining eight served as controls. The pigs were monitored for intravascular bubbles using a transesophageal echocardiographic transducer, and bubble count in the two-dimensional ultrasound image of the pulmonary artery was used as a measure of the number of venous gas bubbles. Effects on physiologic variables of the pulmonary and the systemic circulations were either measured or estimated. We detected venous bubbles in all pigs after decompression, but the interindividual variation was large. The time course of changes in the mean pulmonary artery pressure, in the pulmonary vascular resistance, in the arterial oxygen tension, and in the pulmonary shunt fraction followed the time course of the bubble count. In contrast, such a relationship to the number of venous gas bubbles was not found for the immediate increase in mean arterial pressure and for the changes in the other variables of the systemic circulation. We conclude that the number of venous gas bubbles, as evaluated by the bubble count in the ultrasound image of the pulmonary artery, is clearly related to changes in the variables of the pulmonary circulation in this pig model.

Animals↗
PubMed1996

A probabilistic model of hypobaric decompression sickness based on 66 chamber tests.

One consequence of the NASA tissue ratio (TR) model is that calculated probability of decompression sickness [P(DCS)] is constant in tests at different ambient pressures so long as the ratio of P1N2 to P2 is the same in each test; P1N2 is N2 pressure in the 360 minute half-time compartment, and P2 is ambient pressure after decompression. We test the hypothesis that constant P(DCS) is better described by TRs that decrease as P2 decreases. Data were from 66 NASA and USAF hypobaric chamber tests resulting in 211 cases of DCS in 1075 exposures. The response variable was presence or absence of DCS while at P2. Explanatory variables were P1N2, P2, exercise at P2, (yes or no), time to DCS (failure time), and time to end of test in those without DCS (censored time). Probability models were fitted using techniques from survival analysis. The log likelihood for the two parameter log logistic survival model was -846 with only failure and censored times, -801 when TR [P1N2/P2] plus exercise were added, and -663 when modified TR [(((P1N2+cl)/P2)-1)c2] plus exercise were added, where c1 and c2 are fitted parameters in the five parameter model. Constant P(DCS) was better described by TRs that decrease as P2 decreases; a conclusion supported by additional empirical observations, and bubble growth models that are independent of DCS data. Exercise increased the P(DCS) at P2. As a description of decompression "dose", the modified TR was superior to TR over a wider range of experimental conditions.

Adult↗
PubMed1996

[Decompression of the optic nerve sheath--results in the first 37 operated eyes].

The authors present results of optic nerve sheath decompression in 37 eyes. The decompression surgery was performed for progressive form of anterior ischemic optic neuropathy (AION) in 11 eyes, AION combined with central retinal vein occlusion in 2 eyes, low tension glaucoma in 7 eyes (+1 reoperation), central. retinal vein occlusion in 1 eye, optic nerve head drusen in 11 eyes, chronic optic disc edema in pseudotumor cerebri in 3 eyes, amiodarone optic neuropathy in 1 eye. Postoperative findings (visual acuity and visual field) are presented for each diagnosis. After surgery a transient double vision developed in 5 patients. We have not seen any other complications. Optic nerve sheath decompression is a controversial method of treatment for optic neuropathies. We advocate this method of treatment for vision-threatening optic neuropathies after thoroughly balanced assessment of possible risks and gains.

Adult↗
PubMed1997

Utility of Doppler-detectable microbubbles in the diagnosis and treatment of decompression sickness.

BACKGROUND: Doppler-detectable microbubbles (DMB) are frequently used to evaluate altitude decompression stress. However, the role of DMB in the therapy of decompression sickness (DCS) has not been examined. HYPOTHESIS: The ability of Doppler to detect microbubbles during decompression (Doppler test) may be used in the diagnosis of DCS, and to aid clinical decisions about treatment options for DCS. METHODS: We examined the data on DMB and symptoms from NASA Database on DCS (n = 516). The accuracy of Doppler test was obtained from the Receiver Operating Characteristic (ROC) for DMB (grades I through IV), and efficacy was obtained by calculating predictive or post-test probabilities. Threshold analysis was used to obtain the probabilities for testing and/or treatment decisions. RESULTS: The Doppler test was useful for both screening and confirming DCS, when different criteria (grade I for screening; grade IV for confirming) were used for a positive test. Calculation of predictive values and threshold analysis showed that: 1) early recompression was the therapy of choice when post-test probability of disease was > 0.25 in individuals with non-specific pain at altitude, and early recompression with 100% oxygen for 2 h at site level was optimal therapy when this probability was > 0.33; 2) hyperbaric therapy was optimal when post-test probability was > 0.04 in individuals with uncertain symptoms post-flight. CONCLUSIONS: The Doppler test was of greater utility in excluding DCS than confirming its presence, and was useful in making therapeutic decisions on DCS when confronted with non-specific symptoms at altitude.

Aerospace Medicine↗
PubMed1997

[Surgical treatment of therapy refractory Sudeck's dystrophy by transaxillary decompression of the neurovascular bundle and sympathectomy. On the pathogenesis of Sudeck's disease].

Since 1984, altogether nine cases of otherwise untreatable reflex sympathetic dystrophy (RSD) of the upper extremity were treated by transaxillary decompression of the neurovascular bundle with resection of the upper thoracic ganglia. This resulted in an immediate improvement of the local findings and the entire post-operative course of treatment as well as significantly improved functional results (seven excellent, one good, one fair). Average follow-up was 7.5 years. All patients returned to their original work. Clinical as well as intraoperative studies show that the acute edema of RSD is caused by a stenosis of the subclavian vein, which was proven in all cases by preoperative phlebography. Surgical decompression of the subclavian vein thus can result in an essential improvement of venous backflow and also significant improvement of the lesion-caused misproportion between increased arterial inflow and venous outflow with all resulting consequences for peripheral edema, subfascial pressure, microcirculation, perfusion of tissue and metabolism. By decompression of the subclavian artery and the lower plexus roots as well as by simultaneous transaxillary sympathectomy, the sympathetic efferents are drastically reduced or rather interrupted, leading to immediate improvement of the acute pain-syndrome. The so-called "individual predisposition" for RSD can mainly be attributed to a venous stenosis in the area of the subclavian vein and to an increase in sympathetic tonus by irritation of the lower parts of the brachial plexus and the postganglionic fibres accompanying the subclavian artery. The consequences for the pathogenesis of RSD are discussed in detail.

Adult↗
PubMed1977

[Effect of biliary decompression on the results of the surgical treatment of gunshot wounds of the liver].

The purpose of this study consisted in providing experimental grounds to prove the efficiency of the biliferous tract decompression at surgical treatment of gunshot wounds of the liver. The experiments were carried out on 39 dogs. It was ascertained that within 3 to 5 days after gunshot injury to the liver the conditions for normal bile discharge from the liver into the duodenum get hampered. The decompression of the biliferous system in the postoperative period resulted in the decrease of the severity and duration of posttraumatic bile decompression and exerted an appreciable effect upon the lowering of the lethality.

Animals↗
PubMed1997

[Management of trigeminal neuralgia by microvascular decompression].

The experience with a series of 28 posterior fossa exploration and microvascular decompression for trigeminal neuralgia is presented. All the patients were treated with carbamazepine previously and some of them were operated on by destructive methods. The diagnostic work-up consisted of an accurate history, CT or MRI in all cases, and recently (in 17 cases) the vascular compression of the trigeminal nerve was demonstrated directly by MR angiography in the plane of the trigeminal nerve. Microvascular decompression was performed through a suboccipital retromastoid craniotomy. At the operations 21 arterial, 4 venous, 2 combined (arterial + venous) and 1 arachnoid band compression were found. The mean follow up was 30 months. Immediate pain relief was achieved in all cases but one, and there were two recurrences 6 and 12 months later (both of them were venous compression), which have been controllable medically since then. There were 3 permanent hypaesthesia of the face (one of them loss of corneal reflex), 2 hypacusis, 1 cerebrospinal fluid leakage and 1 cerebellar edema as complications. Microvascular decompression is a safe and effective treatment for trigeminal neuralgia and advised if the medical treatment is failed, the patient suitable for general anaesthesia, and there is the evidence of vascular compression of trigeminal nerve on MR angiography.

Adult↗
PubMed1976

Biochemistry and hematology at decompression sickness: a case report.

A 24-year-old hospital corpsman, a volunteer in a series of dry chamber air dives to a simulated pressure equivalent to 188 FSWG (57.3 MSWG), developed left knee pain shortly after standard decompression. A tentative diagnosis of decompression sickness was made and recompression therapy was initiated with alleviation of pain occurring at 60 FSWG (18.3 MSWG). A U.S. Navy Treatment Table "5 (oxygen breathing) regimen was then selected and completed uneventfully. The subject had been undergoing biomedical evaluation for several days prior to diving; thus, a clinically diagnosed case of dysbarism with subsequent treatment was available for study. This individual was then monitored for a 10-d period. The acute phase of decompression sickness was characterized by a marked shortening of clotting time and a thrombocytopenia with accompanying increased platelet aggregates. The recovery phase was categorized by a variety of hematological and bio-chemical changes. Hemodilution, an elevated megathrombocyte index, and a tendency toward eosinopenia were evident for most of the 10-d observation period. Other persistent alterations detected during this period included a relative hyperglycemia, depressed urine Na+/K+, and increased ketosteroid excretion. These observations indicate that abatement of pain after treatment of dysbarism can be followed by the onset of a variety of biochemical and hematological changes. Moreover, complete recovery may require upwards of 10 d.

Adult↗
PubMedDate not supplied

[The effect of early decompression on the extent of changes in spinal cord microcirculation in experimental traumatic injury to the cord in rabbits].

The purpose of the study was the assessment of the effect of compression of the spinal cord after traumatic injury on spinal microcirculation disturbances and the evaluation in what degree early decompression of the cord reduces the degree of these changes. The experimental study was carried out on 20 rabbits. The injury to the cord was produced at the Th9-Th10 level with simultaneous compression causing vertebral canal narrowing by 1/3 of its width. The assessment was based on the results of microangiographic qualitative and quantitative studies. The animals were divided into 4 groups depending on the duration of cord compression 2, 4, 6 and 12 hours. In each group microcirculation studies were done 12 hours after decompression. Prolonged compression was found to increase the extent of microcirculation disturbances, which were most pronounced after 6 hours of compression. In the group of 12-hour compression microcirculation improvement was observed near the focal lesion. It is concluded that possibly early decompression up to 6 hours after trauma can reduce the degree of secondary damage caused by ischaemia.

Animals↗
PubMed1976

Incidence of decompression sickness in Navy low-pressure chambers.

This study reports the incidence of decompression sickness occurring in U. S. Navy altitude chambers in association with physiological training of aircrews for the period 1 Jan. 1972 to 31 Dec. 1975. There were 79 cases of decompression sickness in 88,520 altitude chamber exposures, an incidence of 0.089%. Among trainees, there were 22 cases in 73,561 exposures, an incidence of 0.029%. Among chamber inside observers, there were 57 cases in 14,959 exposures, an incidence of 0.38%. This 12-fold greater incidence among inside observers over trainees was statistically significant (p less than 0.01). Reasons for the increased incidence of decompression sickness among inside observers are discussed.

Altitude↗
PubMed1997

[Alteration in regional blood flow in minipigs' femur under inadequate decompression studied by isotopes washout method].

We studied the alteration in regional blood flow in minipigs' femur under inadequate decompression after hyperbaric air exposure. The animals were placed in the hyperbaric chamber and exposed to the pressure of 0.5 MPa for 1.5 h, which was reduced to atmosphere at an ascent rate of 0.03-0.04 MPa/min. Regional blood flow in the femur was measured by the isotopes washout method of inhaling 133Xe. The radioactivity was monitored by a multifunctional blood flowmeter interfaced to a minicomputer. Before exposure, the values of average blood flow (F) of femur on the left and right were 15.4 +/- 1.8 and 16.9 +/- 2.0 ml/100 g.min respectively. The values of blood flow (f1) of hematopoietic marrow were 19.1 +/- 2.0 and 21.3 +/- 2.0 ml/100 g.min (n = 7). After inadequate decompression, F values were reduced to 10.3 +/- 1.8 and 11.1 +/- 1.6 ml/100 g.min and f1 values reduced to 13.9 +/- 1.4 and 13.8 +/- 1.0 ml/100 g.min (n = 7), which were obviously lower than those before exposure (P < 0.05). This experiment showed that significant reduction in blood flow in the femur region occurred under inadequate decompression after the exposure of minipigs hyperbaric environment, suggesting that ischemia is a causative factor of osteonecrosis.

Animals↗
PubMed1998

[Choice of the mode of intubation and decompression of the small intestine in acute obstruction].

On the basis of case records analysis of 370 patients from 1107 with acute small bowel obstruction (ASBO) treated in hospital, the authors have classified methods of intubation and decompression of the small bowel and modes of the use of decompression probe. Classification of clinical course of ASBO is proposed for substantiation of application of various modes of intubation and decompression depending on the progression stage of ASBO and medical technology for treatment of such kind of patients.

Acute Disease↗
PubMed1986

Surgical decompression of the facial nerve in the treatment of chronic cluster headache.

The nervus intermedius (NI) appears to be the main conduit for the associated symptoms of cluster headache (CH) and perhaps for the pain as well. Subtle injury of the facial nerve and NI might initiate mechanisms responsible for CH. Five patients with chronic CH unresponsive to medication underwent surgical decompression of the root exit-entry zone of the facial nerve, and in two patients the trigeminal nerve root was also decompressed. In two patients, the pain syndrome was markedly relieved for as long as two years. In one patient, initial improvement was obscured by narcotic addiction. In two patients, the operation was a failure. The NI was identified as a separate bundle in only one of five patients and decompressions may not have affected that component of the facial nerve.

Adult↗
PubMed1977

Optic nerve decompression. A clinical pathologic study.

Decompression of the perioptic meninges for intractable chronic papilledema was done in a patient with a right parietal temporal glioblastoma multiforme. The patient died 39 days postoperatively. Histologic study of the optic nerves indicated fistulas in the dura compatible with cerebrospinal fluid (CSF) egress and maintenance of a normal subarachnoid space around the nerve. Two additional patients with unilateral optic nerve decompression producing bilateral resolution of papilledema were studied. We contend that egress of CSF was the principle mode of action in these three cases. How long the dural fistula remains patent is unknown. Reports in the literature show considerable variation in the effects of optic nerve decompression. Anatomic variation of the intracanalicular subarachnoid space together with differences in underlying pathologic condition, surgical technique, and patient response may explain discrepancies among the results reported.

Adolescent↗
PubMed1981

Transorbital decompression. Indications and results.

In a few patients with Graves' disease, visual loss related to an optic neuropathy develops. Clinical and radiologic evidence suggests that the mechanism of visual loss is optic nerve compression in the orbital apex. Steroids may offer improvement, but often the condition recurs unless high doses are maintained. Orbital decompression provides dramatic visual and cosmetic improvement in most cases. A transorbital approach suitable to the experienced orbital surgeon for decompression of the orbital floor and medial wall has been presented in a companion article. Results of this approach in 12 eyes with visual loss unmanageable by steroid therapy indicate a gratifying improvement in vision. Strabismus is the most frequent complication. Results with follow-up ranging from six to 18 months are encouraging and comparable to the results obtained with other methods of surgical decompression.

Adult↗