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Biomedical subjects

Y Melamed

Publications and source records attributed to Y Melamed.

At least 91 records · Page 5Linked to original sources
PubMed1992

Recovery of the hypoxic ventilatory drive of rats from the toxic effect of hyperbaric oxygen.

Hyperbaric oxygen (HBO) exposure reduces the hypoxic ventilatory drive (HVD), probably by damaging the carotid bodies. The recovery of the HVD from HBO exposure was studied. The HVD was calculated from whole body plethysmographic recordings of the ventilatory response to greater than 85% and 2% O2 in N2 mixtures. Five groups of rats were exposed to HBO for 9 h at pressures of 1.9, 2.0, 2.1, 2.2, and 2.4 ATA, respectively. Each rat underwent three control measurements on different days prior to HBO exposures and then at various intervals following the exposure. Postexposure HVD was reduced to 28% of control values in the high PO2s. Ninety percent recovery of pre-exposure HVD was evident by 12-48 h although in some animals exposed to relatively low PO2s (1.9 and 2.0 ATA) HVD stabilized at a level lower than 100%. The recovery of the HVD in percent during the first 4 d following exposure can be expressed as an exponential function of the time from the termination of HBO: HVD = 28 + 72(1 - exp-0.053t) (t in hours). This information may be of importance in cases of repeated exposures to HBO where one tries to avoid cumulative damage to the carotid bodies, and in the care of the poorly oxygenated patient after HBO treatment.

Air Pressure↗
PubMed1991

[Short-term psychiatric hospitalization in an emergency room unit].

Short-term psychiatric hospitalization, developed during the past 2 decades, needs thorough evaluation with regard to its advantages. It is important to be able to identify those patients who might be aided by such treatment. Therefore the psychiatric emergency room physician should have at hand a model which would enable quick and relatively accurate decisions in identifying such patients. Our work shows that they are either without previous psychiatric history or had been admitted for less than 2 months; that they had suffered from depression, anxiety, personality disorder or addiction; that they had a substantial support system; and that when they had been treated, there had been good compliance with prescribed medication. On the other hand, those who probably would not benefit from short-term psychiatric hospitalization had a history of psychiatric hospitalization of usually more than 2 months; were diagnosed as suffering from schizophrenia or affective disorder; lacked substantial family support; and had poor compliance with medication. This data may aid the physician during the initial interview in the psychiatric emergency room in deciding on further treatment. We also found that psychiatric emergency room diagnoses are usually reliable; and that those whose only diagnosis was "for observation" had a fair chance of a successful result after short-term hospitalization (discharge directly from the emergency room unit). We therefore presume that a sharper characterization of patients referred to the psychiatric emergency room may aid in tailoring the most suitable treatment for any particular patient, thus reserving short-term hospitalization only for those who would benefit the most.(ABSTRACT TRUNCATED AT 250 WORDS)

Emergency Service, Hospital↗
PubMed1991

Diving-related inner ear injuries.

Diving-related inner ear barotrauma (IEB) and inner ear decompression sickness (IEDS) most often result in permanent severe cochleovestibular deficits, unless immediate diagnosis is reached and the correct treatment is commenced early. Nine cases of sport-diving-induced inner ear injuries that were referred to the Israeli Naval Hyperbaric Institute between October 1987 and September 1989 are presented with regard to evaluation, treatment, and follow-up. The diagnosis was IEB in five divers and IEDS in four. Explorative tympanotomy was carried out with remarkable results in two patients with IEB, while the remaining three were relieved by bed rest alone. Three of the four IEDS patients were recompressed according to the extended US Navy Table 6 with good short-term results. The role of complete otoneurological evaluation in the decision-making process leading to the correct diagnosis and treatment is emphasized.

Adolescent↗
PubMed1991

Hyperbaric oxygen and scopolamine.

Scopolamine (Hyoscine), an anticholinergic compound is widely used for the prophylaxis and treatment of motion sickness and might be used with oxygen diving and hyperbaric oxygen therapy. We therefore decided to test the interaction of scopolamine with oxygen at high pressure. Thirty-six rats implanted with cortical EEG electrodes were injected subcutaneously with two doses of scopolamine (0.02 or 0.2 mg.kg-1), or the vehicle (saline), 30 min before exposure to 5 atm abs (0.5 MPa) oxygen. Electroencephalogram and heart rate were monitored continuously. Spectral analysis of the EEG was carried out, and the duration of the latent period before convulsions was determined. No significant difference was found in the duration of the latent period between the control rats receiving vehicle (saline) and rats injected with scopolamine (n = 12 for each group). Changes in background EEG activity and maximal dilation of the pupil were detected at both scopolamine doses. Heart rate significantly decreased at 0.02 mg.kg-1 and increased at the dose of 0.2 mg.kg-1 scopolamine. Our findings indicate that the duration of the latent period preceding hyperoxic seizures is not altered by scopolamine in rats; however, other side effects of the drug regarding visual and cardiovascular symptoms should be considered when scopolamine is used in combination with hyperbaric oxygen.

Animals↗
PubMed1991

Oxygen therapy in hemorrhagic shock.

Decreased oxygen delivery and cellular hypoxia are important factors in the pathophysiology of hemorrhagic shock. We studied the effects of 100% oxygen at 1 and 3 ATA (atmosphere absolute) in a severe model of hemorrhagic shock induced by bleeding 50% of the total blood volume in rats. Post-treatment with 100% oxygen at 1 and 3 ATA maintained mean arterial blood pressure (MABP) in hemorrhaged rats at significantly higher values compared to untreated controls (P less than 0.01 at 1 and 3 ATA). Treatment with oxygen attenuated the increase in plasma activities of the lysosomal hydrolase cathepsin D (P less than 0.05 at 1 ATA; P less than 0.01 at 3 ATA). Oxygen at 3 ATA also attenuated the plasma accumulation of free amino-nitrogen compounds (P less than 0.05). Furthermore, hyperoxia prevented the final increase in hematocrit (P less than 0.05 at 1 ATA; P less than 0.01 at 3 ATA). Hemorrhaged rats treated with oxygen also exhibited a significantly longer survival time (P less than 0.01 at both doses), and higher survival rates (50% at 1 ATA and 100% at 3 ATA; P less than 0.05 and P less than 0.01, respectively) than untreated shock rats. No significant effect on any of the above mentioned variables was found in hemorrhaged rats treated with 7% oxygen at 3 ATA (oxygen pressure 0.2 ATA), indicating that all salutary effects can be attributed to oxygen and not to the increased ambient pressure per se. Our results indicate that 100% oxygen in normobaric and hyperbaric conditions exerts important beneficial effects in hemorrhagic shock and may be a useful drug for the treatment of this condition.

Animals↗
PubMed1990

Sialolithiasis. A survey on 245 patients and a review of the literature.

245 patients with sialolithiasis, treated during a period of 20 years, were evaluated and the literature has been reviewed. The submandibular gland was involved in 231 patients, the parotid gland in 11 patients, and the sublingual gland only in 1 patient. There is some indication that patients with sialolithiasis are more prone to develop nephrolithiasis. A relationship with other systemic disorders could not be detected. Laser treatment seems to be a promising treatment modality for stone removal, even in acute phases.

Adolescent↗
PubMed1990

Vestibulo-ocular reflex as a parameter of seasickness susceptibility.

The vestibulo-ocular reflex (VOR) is known to be modulated in response to changing vestibular and optokinetic stimuli. The purpose of this study was to investigate possible relationships between VOR and future susceptibility and habituation to seasickness. Thirty candidates for future maritime service were exposed to a series of yaw axis smooth harmonic accelerations before and after 6 months of regular sailing, and their VOR gain and phase responses were recorded. Seasickness severity was estimated after 1 and 6 months of service by a questionnaire. We conclude that VOR gain at 0.01 Hz may serve as a physiologic correlate helping to predict seasickness susceptibility, and that the increase in phase lead at 0.02 Hz may mark the habituation process to sea conditions.

Acceleration↗
PubMed1990

Inner ear decompression sickness following a shallow scuba dive.

Inner Ear Decompression Sickness (IEDCS)--manifested by tinnitus, vertigo, nausea, vomiting, and hearing loss--is usually associated with deep air or mixed gas dives, and accompanied by other CNS symptoms of decompression sickness (DCS). Early recompression treatment is required in order to avoid permanent inner ear damage. We present an unusual case of a scuba diver suffering from IEDCS as the only manifestation of DCS following a short shallow scuba dive, successfully treated by U.S. Navy treatment table 6 and tranquilizers. This case suggests that diving medical personnel should be more aware of the possible occurrence of IEDCS among the wide population of sport scuba divers.

Adult↗
PubMed1989

Hyperbaric oxygenation for necrotizing (malignant) otitis externa.

Two patients with extensive necrotizing otitis externa have been treated by hyperbaric oxygenation. One patient had facial nerve palsy and the other suffered from skull base involvement. Due to severe side effects, the preferred combined intravenous antibiotic therapy was changed to monotherapy in one case and completely withdrawn in the second. This was done before the commencement of hyperbaric oxygenation, while the necrotizing infection was still active. Hyperbaric oxygenation therapy was followed by complete resolution of the necrotizing otitis externa, which did not recur. The pathogenesis of the disease and mechanisms by which hyperbaric oxygenation might be of benefit are described. We conclude that hyperbaric oxygenation should be considered as adjuvant therapy for necrotizing otitis externa whenever a therapeutic pressure chamber is available.

Aged↗
PubMed1989

Scuba diving.

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Diving↗
PubMed1989

Effects of hyperbaric oxygen in circulatory shock induced by splanchnic artery occlusion and reperfusion in rats.

We studied the effects of hyperbaric oxygen in a severe model of circulatory shock induced by occlusion and reperfusion of major splanchnic arteries (splanchnic artery occlusion (SAO) shock). Pentobarbital-anesthetized rats subjected to total occlusion of the superior mesenteric and the celiac arteries for 40 min developed a severe shock state, resulting in a uniformly fatal outcome after release of the occlusion. Exposure to hyperbaric oxygen at 2 ATA (atmosphere absolute) (1 ATA = 0.1 MPa) was initiated immediately after reperfusion. SAO shock rats exposed to hyperbaric oxygen maintained mean arterial blood pressure at significantly higher values throughout the postreperfusion period compared with untreated SAO shock rats (p less than 0.01), with final mean arterial blood pressures of 88 +/- 9 and 51 +/- 4 mmHg, respectively. Treatment with hyperbaric oxygen attenuated the increase in plasma activities of the lysosomal hydrolase cathepsin D (p less than 0.05), and diminished the increase of hematocrit (p less than 0.01 from untreated shock rats). Splanchnic occlusion shock rats treated with hyperbaric oxygen also exhibited a significantly higher survival rate than the untreated shock group (77 vs. 0%, respectively; p less than 0.01). Our results suggest that the beneficial effects of exposure to hyperbaric oxygen immediately after reperfusion of the splanchnic region outweigh its possible deleterious effect.

Animals↗
PubMed1989

Three-years' experience of transdermal scopolamine: long-term effectiveness and side-effects.

A study was carried out in 68 otherwise healthy male naval crew members to assess the long-term effectiveness and side-effects of routine transdermal scopolamine administration for the prevention of seasickness. The transdermal patches were applied to the mastoid process before each sailing and the subjects generally used 2 patches a week. Check-ups were made every 3 months over a period of 3 years. The average reported seasickness severity (on a scale of 0 to 7) after 6 months at sea prior to the administration of transdermal scopolamine was 5.64 +/- 0.11 (mean +/- S.E.M.), in comparison with 3.14 +/- 0.23 post-administration (p less than 0.001). A significant improvement was found in the self-estimated performance at sea whilst receiving the drug: 65.7% +/- 3.38% (mean +/- S.E.M.), compared to 25% +/- 2.24% beforehand (p less than 0.001). Contact dermatitis precluded the use of transdermal scopolamine in 3 (4.4%) subjects. The only other significant side-effect was dryness of mucous membranes. In conclusion, transdermal scopolamine was found to be effective in the prevention of seasickness and improvement of performance at sea during 3 years of follow-up and routine administration of the drug was not complicated either by severe side-effects or by performance disturbances.

Administration, Cutaneous↗
PubMed1988

Hyperoxic exposure affects the ventilatory response to hypoxia in awake rats.

We tested whether hyperbaric O2 (HBO) has an adverse effect on the hypoxic ventilatory drive. Four groups of rats were exposed for 550 min to O2 at 1.67, 1.90, and 2.15 ATA and to air at 1.90 ATA, respectively. Ventilatory parameters (frequency, tidal volume, and minute ventilation) were measured using whole-body plethysmography, before the hyperbaric exposure, immediately after the exposure, and up to 20 days after the exposure. Resting ventilation was not affected after exposure at 1.90 ATA to air or at 1.67 ATA to O2. HBO at 1.90 and 2.15 ATA caused a reduction of frequency and an elevation of tidal volume at different inspired gases: air, 5% CO2 balance O2, 80% O2, and 4.5% O2. However, minute ventilation on the day after the hyperoxic exposure was not different from the control at either air, 5% CO2, or 80% O2 but was markedly attenuated on the first three breaths at 4.5% O2. The hypoxic ventilation decreased to 48 +/- 13 (SD) and 32 + 11% after 1.90 and 2.15 ATA, respectively. The ventilatory parameters recovered in the days after HBO. We conclude that HBO reversibly depresses the hypoxic ventilatory drive, most probably by a direct effect on the carotid O2 chemoreceptors.

Animals↗
PubMed1988

Ventilatory response to transient hypoxia in O2 divers.

This study addresses the question of whether repeated acute exposure to hyperbaric oxygen, such as encountered in O2 diving, affects the peripheral oxygen chemosensors. Groups of nondivers, active O2 divers, and ex-O2 divers, as well as active air scuba divers, were given 1 or both of 2 tests that measure the ventilatory response to transient hypoxia. Results showed that all groups of divers have a mean response similar to or higher than that of nondivers as well as that of normal subjects, as reported in the literature. A repeat test on 10 diving candidates before and after 200 h of accrued O2 diving also did not show an impairment in the hypoxic ventilatory response. Oxygen diving within the established depth and time limits does not seem to cause cumulative damage to the peripheral O2 chemosensors.

Adult↗