Abstract: In order to keep a patient from being administered an incorrect anaesthetic, an erroneous concentration of an anaesthetic or a mixture of anaesthetics, an anaesthetic system can be equipped with a device for identifying anaesthetics in anaesthetic system. The device identifies anaesthetics by determining a parameter related to a physical property, such as density, of liquid anaesthetics. A floating body can be immersed in the anaesthetic fluid. The floating body then sinks to a depth which depends on the fluid's density. The identity of the anaesthetic can then be read off a measurement stick arranged on the floating body.

Abstract: For preventing a patient from being administered an erroneous anaesthetic, an incorrect concentration of anaesthetic or a mixture of anaesthetics, an anaesthetic system is equipped with a device capable of identifying anaesthetics in the anaesthetic system. A device for simple and reliable identification of anaesthetics does so by having a thermal element which varies the temperature of at least some of the anaesthetic to cause it to undergo a change in physical state, e.g., condensation from the gaseous state to the liquid state. A transition temperature at which the change in physical state occurred is determined and the anaesthetic is identified from the determined transition temperature. The condensation point temperature can be determined by sensing the capacitance between two conductors or sensing changes in the resonant behavior of an oscillating crystal.

Abstract: An anaesthetic system, which can be switched between an open system and a rebreathing system, includes a breathing circuit, a setting unit and a switching unit. When the breathing circuit is connected as a rebreathing system and a change in anaesthetic concentration or a change of anaesthetic type is initiated via the setting unit, the switching unit automatically sets the breathing circuit as an open system for a predetermined period of time, at the end of which the breathing circuit is automatically reset as a rebreathing system.

Abstract: A valve for controlling a gas or liquid flow, has an admission and a discharge with a valve seat, a valve part displaceable relative to the valve seat, and a seal therebetween, whereby the valve part presses the seal against the valve seat in one position and thus interrupts the flow. In order to obtain a valve of this type that has a simple structure and exhibits an extremely high sealing power over a comparatively long time span, a liquid having such properties that it is insoluble in the liquid or the gas that flows through the valve serves at least partially as a seal.

Abstract: In a method and apparatus for identifying the spatial distribution of electrical impedance within an examination subject, a source of electrical current is electrically connected to at least two feed electrodes which impress a feed current from the source in an examination region of a subject. The resulting magnetic field is measured at points outside the examination region, and an equivalent current density distribution is reconstructed within the examination region from the measured values of the magnetic field by an evaluation unit. A compensation conductor is connected to the current source. The current source delivers a compensation current, which flows in a direction opposite to the feed current, through the compensation conductor loop, so that the magnetic field generated by the feed current in the connecting lines is compensated. The evaluation unit identifies the spatial distribution of the impedance from the equivalent current density distribution.

Abstract: An apparatus for the in vivo intracardial acquisition of a measured signal corresponding to the physical activity of a subject has an optoelectronic arrangement measuring the blood oxygen content of the subject and a temperature sensor for measuring the blood temperature. The apparatus can be operated so that a measured signal can be obtained which is optionally dependent on the blood oxygen content and the blood temperature, dependent only on the blood oxygen content, or dependent only on the blood temperature.

Abstract: An implantable rate-responsive pacemaker is disclosed wherein two or more sensors indicative of physiological demand are utilized in a fashion designed to realize the advantages of both sensors in a circuit producing a rate command signal which is used to operate the pacemaker at an optimum pacing rate which will closely match physiological need of the patient. A rate matrix is used to produce a specific selected rate which is unique to the particular combination of sensor inputs which are being measured at the particular time. In the preferred embodiment, a plurality of rate matrices are provided, with the appropriate rate matrix to be used being selected by a switch matrix which monitors the logic-processed and time-processed signals from the sensors, the outputs of the processing circuitry being used to select a cell in the switch matrix which corresponds to the exact set of conditions currently being encountered by the sensors.

Abstract: An implantable rate-responsive pacemaker is disclosed wherein two or more sensors indicative of physiological demand are utilized in a fashion designed to realize the advantages of both sensors in a circuit producing a rate command signal which is used to operate the pacemaker at an optimum pacing rate which will closely match physiological need of the patient. A switch matrix monitors processed signals from the sensors to select a unique set of numerical coefficients indicated by the processed sensor signals. The selected set of numerical coefficients are used as weighting factors to weight the impact of each of the sensor signals in the calculation of a selected rate.

Abstract: A rate-responsive pacing method and system senses the minimum blood oxygen saturation in the right atrium of a patient's heart and uses such minimum blood oxygen saturation as a control parameter for indicating the muscular activity of a patient. Because the oxygen content of the venous blood in the right atrium varies significantly as venous blood from all parts of the body is introduced therein, evidencing differing levels of oxygen demand throughout the patient's body, the minimum oxygen content of the venous blood provides an accurate and reliable measure of those portions of the patient's body experiencing the greatest oxygen demand, i.e., experiencing muscular activity. A rate-responsive pacing system includes means for sensing the minimum oxygen content in the right atrium over a prescribed time interval, and using such minimum oxygen content as a control parameter for adjusting the rate of the pacemaker.

Abstract: A flexible, planar patch electrode for cardiac defibrillation is fabricated from conductive wire mesh covered on an insulation side by a flexible layer of insulation. The electrode provides a substantial electrical contact area of 2-4 square inches and is shaped to provide an essentially rectangular base region with a plurality of protrusions extending longitudinally therefrom. he protrusions may be readily flexed to follow natural heart contours and slots between protrusions may be positioned to avoid features such as arteries near the surface of the heart. Central attachment of a lead within the base region minimizes current density and corresponding I.sup.2 R energy losses.

Abstract: A medical apparatus for stimulating a physiological event in a patient, with the stimulation intensity being automatically adapted to the physical activity of the patient, includes respective sensors for monitoring the chronological curves of the temperature within the patient and at the body periphery of the patient. These temperature curves are used as a basis for determining the activity level of the patient, and for setting the stimulation intensity in accordance with that physical activity.

Abstract: A pacemaker has a sensor for deteching inertial and/or rotational movements of a patient in whom the pacemaker is implanted. The sensor has a hollow member with at least one freely moveable member therein, the freely moveable member generating a mechanical vibration upon movement thereof within the hollow member caused by movement or rotation of the patient. A transducer generates an electrical signal corresponding to the mechanical vibrations, the electrical signal being proportional to the movement. This electrical signal is used to vary the rate at which stimulation pulses are supplied to the patient by the pacemaker.

Abstract: An implantable lead has conductors wound in a multi-pole helix. The conductors are individually insulated by a first insulating material and the insulated conductors are embedded in, and axially separated from each other by a second tube-formed insulating material. The inner opening of the tube receives a helically wound stylet guide coil which may also be a multi-pole conductor arrangement. The conductors may be helically wound, multi-filament wires. Preferably, all helically wound arrangements in the lead are wound in the same direction so that the lead is still when rotating it in one direction and flexible when rotating it the other way.

Abstract: A body activity sensor in a rate adaptive pacer responds to myoelectrical signals in the patient's electrocardiogram (ECG). These myoelectrical signals are a measure of body activity and thus control the pulse generation rate of the pacer. Preferably, the myoelectrical signals are obtained by filtering out high frequency portions from the ECG and processing these filtered frequency portions.

Abstract: A cardiac pacer which generates pacing pulses at a predetermined pacing rate, includes a device for generating an alternating signal which is unable to pace the heart. The pacing pulses and the alternating signal are transmitted together to the heart. The alternating signal after transmittal to the heart is measured and processed such that a respiratory signal is obtained. The predetermined pacing rate is then varied dependent on the respiratory signal.

Abstract: A cardiac pacer, which generates pacing pulses at a predetermined basic pacing rate, includes a device for sensing physical activity and for generating a control signal dependent thereon, a device for varying the predetermined basic pacing rate independent on the control signal and a device for forcing the pacing rate back to a lower rate if the pacing rate runs at or above a predetermined high rate for a predetermined time period.

Abstract: A heart pacemaker for supplying pacing signals to a heart includes circuitry for controlling operation of the pacemaker in dependence upon the occurrence of heart sounds. The pacemaker includes a detector for such sounds and circuitry for generating a control signal therefrom which is supplied to the basic pacing circuitry.

Abstract: A heart pacemaker electrode for stimulating and detecting heart voltages, has an electrode head at the distal, heart-proximate end, which functions to both stimulate the heart by supplying pulses thereto, and to sense heart activity. The surface of the electrode head is divided into portions which, although electrically connected, exhibit different impedances. Once portion has a lower impedance, which primarily functions for stimulating the heart, and the other portion has a higher impedance which functions in combination with the portion of lower impedance during sensing. The electrode head thus in totality exhibits a low impedance for stimulating the heart, permitting a high current density to be achieved, while exhibiting an overall high impedance for sensing.

Abstract: A cardiac pacer which generates pacing pulses at a predetermined pacing rate includes a device for making a body activity measurement. The measured body activity signal is non-linearly amplified such that signal portions having higher amplitudes are more amplified than signal portions having lower amplitudes. The non-linearly amplified body activity signal is integrated over a period of time. The predetermined pacing rate is varied dependent on the integrated signal.

Abstract: An atrium controlled heart pacemaker has a switching stage which is controlled in dependence upon the appearance of atrial signals. The switching stage switches the heart pacemaker to a VVI mode for a predetermined number of stimulation pulses or natural ventricular events, or a predetermined time, upon the appearance of at least one atrial signal before a selected time limit. The time limit is derived from the difference between a smallest synchronous interval and the AV delay.