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Biomedical subjects

P Eberhard

Publications and source records attributed to P Eberhard.

At least 19 recordsLinked to original sources
PubMed1995

[Progressive fragmentation of a bipartite patella: apropos of a case].

PURPOSE OF THE STUDY: Progressive dissolution of the supero-lateral fragment of a bipartite patella is reported. MATERIAL AND METHODS: The patient, a 44 year old professor of gymnastics, was examined for long standing anterior knee pain. For many years, his daily activities included forceful knee flexion exercises. Serial radiographs, between 1986 and 1990, revealed a progressive fragmentation of the accessory ossification center and accompanying calcific deposits in the lateral patellar retinaculum. RESULTS: Surgical excision of the calcific mass and accessory ossification center relieved the painful symptomatology completely, allowing the patient full normal function at one year's follow-up. DISCUSSION: The pathological findings were compatible with a dystrophic calcinosis associated with detritic synovitis. A pathogenic mechanism is hypothesized for this unusual and progressive course of a common condition: Repetitive trauma, in this case forceful knee flexion exercises, shear microscopic bony fragments of the poorly vascularized accessory ossification center. These microscopic fragments act as deposits of an apatite crystal which go on to induce the secondary soft tissue calcifications seen in our patient.

Adult↗
PubMed1990

[Bilateral congenital absence of the anterior cruciate ligament and the internal menisci of the knee. A case report].

Bilateral congenital absence of the anterior cruciate ligament associated with the absence of the medial meniscus is reported in a 34-year-old-woman. The simultaneous absence may be explained by a common embryological mesenchymal origin of the anterior cruciate ligament and the menisci. This absence was at the origin of an abnormal development of the condyles and especially of the tibial epiphysis which was tipped over in flexum. Treatment consisted of a central ligamentous plasty associated with a lateral plasty, a medial plasty and a closing anterior tibial osteotomy. The result was good.

Adult↗
PubMed1988

[The natural history of rupture of the posterior cruciate ligament].

A study has been made in a series of 45 patients, 36 of whom were re-examined and 11 of whom replied to a questionnaire, of the fate of knees that had suffered a rupture of the posterior cruciate ligament which had not had a primary or secondary repair. The follow-up was between 5 and 44 years, with a mean of 15 years. In the 36 who were reviewed, 21 showed an isolated posterior laxity, 8 a postero-lateral laxity and 7 a postero-medial laxity. Even though the posterior cruciate ligament is the strongest ligament in the knee, an isolated rupture of the ligament is often well tolerated after a mean period of adaptation of 12 months. This functional tolerance is remarkable since it allows a return to sporting activity, even at high level. However, the disturbance of the kinematics of the knee resulting from the loss of the posterior cruciate ligament leads, after an average of 25 years, to osteoarthritis, either medial tibio-femoral or generalised depending on the morphological features of the patient. These findings have stimulated us to repair fresh lesions in young persons, especially in the presence of combined lesions but care needs to be exercised about the indications for surgery in chronic laxities during the first year of adaptation.

Adaptation, Physiological↗
PubMed1986

[Cancer of kidney with venous invasiveness: prognosis. Apropos of 238 renal excisions with 64 cases of venous invasiveness].

About a series of 238 surgically managed renal cell carcinoma with 64 venous invasion's cases (without no lost of follow-up) the prognosis is bad: post-operative mortality: 12,5%. Overall uncorrected five-years actuarial survival: 25%. But 42% of these patients with venous invasion had associated lymph node invasion and-or visceral metastasis. About 37 cases with only venous extension five-years actuarial survival reaches 45,9%. The inferior vena cava (I.V.C.) extension is the worst. Five american data reports some cases (5 to 18 cases) with near half and half surviving patients. In this series about 14 isolated I.V.C. invasion, only 4 patients are surviving with no evidence of disease but 2 have more than six years and fourteen years follow-up.

Actuarial Analysis↗
PubMed1982

Electrochemical sensors for invasive and non-invasive monitoring of blood gases.

The need for continuous monitoring of blood gases in critically ill patients has become more and more evident during the past years. Electrochemical sensors appear to be most appropriate for such measurements because of their simplicity, ease of use and low cost. Intravascular sensors and skin surface sensors for pO2 and pCO2 are available today in different degrees of technical maturity. In the case of intravascular sensors, the use of surface heparinisation techniques may lead to considerable functional improvements. In the case of skin surface sensors, a reliable method for simultaneous measurement of cutaneous blood flow is needed. Laser doppler flowmetry appears to be a promising method for this purpose.

Blood Gas Analysis↗
PubMed1982

Monitoring of PCO2 by skin surface sensors.

The methodology of cutaneous PCO2 measurement and the results of the first clinical studies performed with a newly developed sensor are reported. The in vitro data of the sensor are: sensitivity 55 mV/decade; response time tau 90% = 50 s; drift less than 10% per 24 h; no measurable interference by oxygen and anesthetic gases. At a sensor temperature of 44 degrees C, the correlation between arterial PCO2 and cutaneous PCO2 is significant, with correlation coefficients above 0.95 both in case of neonates and adult patients. The cutaneous PCO2 is, however, consistently higher than arterial PCO2, and a correction of the cutaneous PCO2 value needs to be performed. At 44 degrees C, the time lag between changes of cutaneous PCO2 and arterial PCO2 is about 2-3 min as estimated from capnometric measurements. At lower sensor temperatures, the correlation between arterial and cutaneous PCO2 is still good; however, the physiological response time of the cutaneous PCO2 measurement becomes prohibitively long.

Adult↗
PubMed1981

Interference of anesthetic gases at skin surface sensors for oxygen and carbon dioxide.

Several variables may account for the response of electrochemical skin surface PO2 sensors to anesthetic gases: cathode material and size, pH of the electrolyte and membrane material. These variables cannot be chosen arbitrarily and their influence has been tested with two types of sensors. In one type (LSC), a large size cathode (mm range) and a membrane with low permeability for oxygen such as mono-axially oriented polyethylene is used. The other type (MC) contains one or more microcathodes (micron range) and a membrane which is highly permeable for oxygen such as Teflon PTFE. With the LSC sensor, the N2O interference current is smaller than 5% of the air current when the sensor is polarized at --600 mV. The interference current with 2% halothane is smaller than 3% of the air current. With the MC sensor, the N2O interference may be up to 40% of the current in air when the sensor is polarized at --800 mV. The magnitude of this interference depends considerably on the silver deposition on the platinum cathode. At --600 mV the N2O interference is negligible. However, at this polarization voltage, the sensor is not operated within the limiting current plateau of oxygen. The interference current with 2% halothane may be up to 30% of the current in air. With both types of sensors there was no measurable interference by 2% enflurane. The authors conclude that to reduce the interference of anesthetic gases at skin surface sensors for oxygen to a reasonable level, it is necessary to use a membrane with low permeability for oxygen and a polarization voltage of approximately --600 mV. These two conditions can be fulfilled optimally only with a sensor design in which a large size cathode is used. At Stowe-Severinghaus type skin surface sensors for PCO2, there is no measurable interference by N2O, halothane or enflurane.

Anesthetics↗
PubMed1979

An electrochemical sensor for continuous intravascular oxygen monitoring.

The intravascular PO2 sensor described in this paper essentialal routine use. The small dimensions of the sensor permit its introduction into the vessel through a conventional guiding catheter size 4 F or larger. With 5 F catheters, simultaneous blood sampling and/or blood pressure measurement is possible. The accuracy and stability of the sensor permit continuous PO2 measurement to be performed over several days.

Animals↗
PubMed1978

Normal and malignant melanin-containing pigment cells of xiphophorine fish as studied with formaldehyde-induced fluorescence.

Embryonic skin and eyes, and melanomas of xiphophorine fish were investigated by fomaldehyde-induced fluorescence in order to test whether the pigment cells in these tissues may be identified by a specific green-yellow fluorescence. Skin of pigmented fish embryos showed no fluorescence in the black pigment cells (melanocytes and melanophores), while skin of albino embryos showed a green-yellow fluorescence in all cells which correspond to the black pigment cells of pigmented embryos. The skin of both pigmented and albino embryos showed a bright orange fluorescence in the red pigment cells (pterinophores). No fluorescence was observed in the retinal pigment epithelium of pigmented embryos, while a green-yellow fluorescence was observed in the pigment epithelium of albino embryos. Neither the melanotic melanomas of pigmented fish nor the amelanotic melanomas of albino fish showed any specific fluorescence.

Animals↗
PubMed1978

Reliability of cutaneous oxygen measurement by skin sensors with large-size cathodes.

The oxygen partial pressure may be measured cutaneously by directly heated PO2 sensors attached to the surface of the skin. The use of a large-size cathods (diameter 4 mm) allows one to obtain an average PO2 value over a sufficiently large skin area. The permeability of the membrane for oxygen has to be kept low to prevent a disturbance of the oxygen profile in the cutaneous tissue as a result of the oxygen consumption of the sensor. When using of 6 micrometer Mylar membrane, the current can be limited by the diffusion of oxygen through the membrane and is a measure of the arterialized cutaneous PO2. One effect of using membrane of low permeability is that the response time of the sensor is long (tau 90% = ca 45 sec). The reliability of correctly reproducing cPO2 variations by sensors having different response times may be evaluated by determining the transfer function of the membrane which allows the calculation of the frequency characteristics for various membranes. The cutaneous tissue layer also acts as a filter for rapid PO2 fluctuations. The characteristic of this filter is essentially similar to that of a "slow" membrane such as Myler 6 micrometer. The information gained by using a "rapid" membrane such as Telfon 13 micrometer is negligible. In 490 comparative measurements in newborns performed with sensors heated to 44 degree C, the correlation between arterial PO2 and cutaneously measured PO2 is significant (correlation coefficient = 0.934) and the regression line does not deviate significantly from the identity line.

Blood Gas Analysis↗
PubMed1978

A fast stabliization technique for oxygen sensors with low cathode current densities.

After application of the polarization voltage to a newly prepared oxygen sensor, an initial stabilization of several minutes to a few hours is required. The electrochemical phenomena accounting for this stabilization process are discussed. By far the slowest reaction is the change of the oxidation state of the noble metal cathode after application of the polarization voltage. During this process, reduction of surface oxides at the cathode causes a transient current. The contribution of this reaction to the total current is proportionately higher in the case of oxygen sensors with low cathode current densities (large cathode, membrane of low oxygen permeability) than in the case of sensors with microcathodes. For the first type of sensor, a technique has been developed which allows acceleration of this surface reaction by passing a high constant current across the cathode. With this technique, the stabilization time can be considerably shortened in a reproducible manner, and the sensor is ready to be used within 15 to 30 min of its preparation. This time is comparable to the stabilization time needed for sensors with microcathodes.

Blood Gas Analysis↗
PubMed1978

Measurement of heated skin O2 diffusion conductance and PO2 sensor induced O2 gradient.

A large cathode heated transcutaneous PO2 electrode was used to measure the resistance of skin to diffusion of O2 from the capillary bed to the surface. With a non-O2-consuming tcPO2 electrode, one would read ideal tcPO2, Pi, which approximates PaO2 between 50 and 100 mmHg due to approximate cancellation of the rise by heating and the fall by skin O2 consumption. When a large cathode tcPO2 electrode is used, its O2 consumption causes a PO2 gradient across skin resistance, Rs, which depends on electrode membrane resistance RM (with Mylar), or RT (with Telfon). Surface PO2 will fall below Pi, and assuming no change in capillary PO2: PT/Pi = RT/(RT + Rs) and PM/Pi = RM/(RM + Rs) (1) 12 micrometer Telfon is 50 times as permeable to O2 as 6 micrometer Myler. When an electrode, covered alternately with these two membranes, was mounted on the same skin site in six subjects, the mean observed PT/PM was about 0.3. Substituting in equation (1) yields RT/Rs = 0.4, Rm/Rs = 20, and PM/Pi = 0.95. Using the known O2 permeability of Teflon, we computed skin O2 conductance to be 6.6 pmol O2/(cm2 .s .kPa), or 15 nl O2/(cm2 .s .atm). This method thus provides a way of determining ideal tc PO2 and stirring effect, phi, of other electrodes and various membranes.

Blood Gas Analysis↗