Early detection of hemorrhagic hypovolemia by muscle oxygen pressure assessment: preliminary report.

Skeletal muscle PO2 was studied during graded hemorrhagic shock in Labrador dogs by means of a polarographic needle PO2 electrode. Compared to hemodynamic, blood gas, biochemical, and hematologic variables, a shift to the left of the cumulative histogram of skeletal muscle PO2 was the earliest and most sensitive indicator of impaired skeletal muscle oxygenation. The mean arterial blood pressure and the mean of the medians of the skeletal muscle PO2, respectively, were as follows: during the control period 125 and 38.1 mm Hg, during the imminent shock period 143 and 24.5 mm Hg, and during the shock period 89 and 5.1 mm Hg. This electrode is suitable for clinical use.

Multichannel biotelemetry.

A summary of considerations for design and application of multichannel biotelemetry systems is given. The advantages but also the problems of wired, wireless, combined and storage telemetry are discussed in connection with its application. Modulation and multiplexing techniques are described extensively; however, this review focuses not only on the transmission of biological data but also on the important aspects of connection of the transmission equipment to the biological subject and display of the biological information. The topic of multichannel biotelemetry is rounded off by a few additional subjects such as telecontrol, information source and classification.

Biotelemetry, based on optical transmission.

Biotelemetry has developed as a reliable alternative to continuous monitoring of physiological variables under realistic circumstances of data assessment. For incorporation in clinical routine the lack of an adequate number of biotelemetry frequencies forms a severe disadvantage. This paper shows a way to circumvent the problem, namely by using infrared light as the carrier for the transmission system. Use of infrared light is limited to indoor applications, and a number of additional restrictions have to be accepted, but on the other hand infrared telemetry opens new possibilities not known to radiotelemetry, especially suited for clinical applications.

Modern patient care using biotelemetry: its potential and technical realization at present and in the future.

Incorporation of biotelemetry has a number of advantages, such as reduction of the impediment of the information source (patient, subject or animal) reduction of the psychological effects on the information source, reduction of measuring artifacts, reduction of the risk for electroshock, reduction of the complexity of monitoring of physiological variables, as well as a potential reduction of the total cost of patient care. Therefore, biotelemetry may be incorporated advantageously not only in areas where this technique is absolutely needed (sport, work, function control during realistic circumstances of activity), but also in other areas such as patient monitoring during intensive care and in the operating room. There have been a number of drawbacks in biotelemetry for application in patient monitoring in the past mainly due to the problem of frequency allocations and regulations, but with the newly developed infrared systems future applications of biotelemetry in clinical monitoring seems promising.

[Biotelemetry in anesthesia and intensive care (author's transl)]. / La télémesure en anesthésie et réanimation.

Biotelemetry and patient monitoring are two fields closely related, and should contribute to the contiuous measurement of physiological parameters from patients with little impediment. In anesthesia the requirement of minimal impediment is less important. Here wireless transmission has two advantages of great importance, namely: minimization of the risk of electricl shock by the incorporation of batteries and a complete separation of the patient and the recording equipment, and the possibility of connecting the patient to the measuring equipment before transporting him into the operating theatre. The telemetry of several parameters, especially of the cardiovascular and respiratory system is described, including the telemetry of blood-pressure, blood flow, cardiac output, ECG and arterial PO2, as well as respiratory flow, respiratory PO2 and its derived values, such as tidal volume, ventilation and oxygen uptake.

[Monitoring of arterial oxygen pressure (author's transl)]. / Monitorage de la pression partielle d'oxygène artérielle.

Arterial partial pressure of oxygen (PaO2) can be measured continuously either directly in the blood (in an artery or in an arterio-venous shunt), or indirectly, using the transcutaneous method or by measuring respiratory oxygen. Construction of miniaturized PO2 electrodes according to the polarographic principle (1.2 and 2 mm in diameter) with ring-shaped cathodes, allowing fast assession of arterial PO2 with little sensitivity to blood flow, and its clinical application are described. An exhausting investigation of the electrod properties, including in vivo parameters allowed continuous monitoring of PaO2 either directly in the radial artery or more often in an arterio-venous shunt under clinical routine circumstances in a large number of patients up to 24 hours. The recordings obtained with both methods are identical and show three types of oscillations.

Muscle oxygen tension, hemodynamics, and oxygen transport after extracorporeal circulation.

In eight patients who underwent elective coronary bypass operation, skeletal muscle PO2 was measured with a polarographic needle electrode as an index of peripheral tissue perfusion to study recovery after extracorporeal circulation. Measurements of skeletal muscle PO2 and O2 supply to the tissues were obtained immediately after ICU admission and after 2, 4, 8, and 16 h. During the first 2 h, mean arterial BP was high, mixed venous PO2 decreased, the arteriovenous O2 difference increased, and skeletal muscle PO2 decreased. The P50 of the O2 dissociation curve on ICU admission was decreased and thereafter increased to a maximal value at 8 h, and normalized again after 16 h. After the initial decrease, the median of the skeletal muscle PO2 returned to normal values, but decreased again after 16 h. The results showed that, during the first 4 h postoperatively, microcirculatory changes occurred despite normal cardiovascular and respiratory variables.