Abstract: The assessment of clearance conditions in an operating turbine structure has provide difficult to achieve. The invention provides apparatus which enables the clearance between seal fins on rotating blades and adjacent fixed structure, to be observed during rotation, and comprises refracting prisms (30, 32) on the fixed structure arranged so as to straddle sealing fin (14) on the blades. The stage of blades on their associated disc are moved towards the fixed structure and light which is refracted through the prisms is obscured by the fins. In one embodiment, the ratio of obscured to unobscured light is utilised to generate electrical signals, which are then manipulated so as to indicate the magnitude of the clearance.

Abstract: According to the invention, methods and devices for increasing cardiopulmonary circulation induced by chest compression and decompression when performing cardiopulmonary resuscitation are provided. Cardiopulmonary circulation is increased according to the invention by impeding air flow into a patient's lungs to enhance the extent and duration of negative intrathoracic pressure during decompression of the patient's chest. Enhanced extent and duration of negative of intrathoracic pressure thus promotes venous blood flow into the heart and lungs from the peripheral venous vasculature. In one embodiment, impeding the air flow into the patient's lungs is accomplished by placing a ventilation tube in the patient's airway. The ventilation tube contains either a flow restrictive orifice disposed within or connected in series with a lumen of the ventilation tube, or a pressure-responsive valve within a lumen of the tube to impede the inflow of air.

Abstract: The subject apparatus integrates a two-channel defibrillator with a programmable stimulator to provide a means for assessing lethal ventricular tachyarrhythmias and determining defibrillation thresholds during implantable defibrillator procedures. The subject apparatus includes a number of features to aid doctors as well as improve patient care at substantially decreased patient risk. These features include an automatic charging circuit, as well as dual channel high voltage capacitor circuits to reduce the time in which a rescue shock can be delivered to a patient after an initial test defibrillation shock. Parameter storage is provided to allow the unit to be preprogrammed prior to the initiation of an electrophysiologic procedure. A microprocessor controlled display system provides the physician with information parameters regarding defibrillation shocks. This displayed information includes the energy delivered and the resistance in the patient.

Abstract: A method is disclosed for combined cardiac pacing and defibrillating with an implanted pacer/defibrillator having sensing and pacing leads connected to the atrium and the ventricle. P-waves and R-waves are sensed, and a V-V timer and a V-A timer are reset if an R-wave is sensed. If an R-wave is sensed during the V-V timer interval, a pacing stimulus to the ventricle is inhibited. If a P-wave is sensed during the V-A timer interval, a pacing stimulus to the atrium is inhibited. If an R-wave is sensed during the V-V timer interval, arrhythmia therapy is provided if an arrhythmia is determined to be present. If the sensed ventricular rate is greater than a selected tachycardia rate but is less than a selected fibrillation rate, than a determination is made whether the sensed atrial rate is greater than a selected fibrillation rate, and if so, the V-V and V-A timers are reset, but if the sensed atrial rate is not greater than a selected fibrillation rate, then arrhythmia therapy is provided.

Abstract: The subject invention integrates a two-channel defibrillator with a programmable stimulator to provide a means for assessing lethal ventricular tachyarrhythmias and determining defibrillation thresholds during implantable defibrillator procedures. The subject apparatus includes a number of features to aid doctors as well as improve patient care at substantially decreased patient risk. These features include an automatic charging circuit, as well as dual channel high voltage capacitor circuits to reduce the time in which a rescue shock can be delivered to a patient after an initial test defibrillation shock. Parameter storage is provided to allow the unit to be preprogrammed prior to the initiation of an electrophysiologic procedure. A microprocessor controlled display system provides the physician with information parameters regarding defibrillation shocks. This displayed information includes the energy delivered and the resistance in the patient.

Abstract: A method is disclosed for combined cardiac pacing and defibrillating with an implanted pacer/defibrillator having sensing and pacing leads connected to the atrium and the ventricle. P-waves and R-waves are sensed, and V--V timer and a V--A timer are reset if an R-wave is sensed. If an R-wave is sensed during the V--V timer interval, a pacing stimulus to the ventricle is inhibited. If a P-wave is sensed during the V--A timer interval, a pacing stimulus to the atrium is inhibited. In an R-wave is sensed during the V--V timer interval, arrhythmia therapy is provided if an arrhythmia is determined to be present. If the sensed ventricular rate is greater than a selected tachycardia rate but is less than a selected fibrillation rate, then a determination is made whether the sensed atrial rate is greater than a selected fibrillation rate, and if so, the V--V and V--A timers are reset, but if the sensed atrial rate is not greater than a selected fibrillation rate, then arrhythmia therapy is provided.

Abstract: In processing a priority queue, the elements are kept in an unsorted stack and are searched for the next highest priority element only after the highest priority element has been read from the holding register. Each time a new element is written into the queue, a comparison is made of the priority of the new element with the priority of the existing element in the holding register. If the new element has a higher priority, then the existing element in the holding register is written onto the top of the stack. Alternately, if the element in the holding register has the higher priority, then the new element is written onto the top of the stack. This assures that the holding register always contains the element having the highest priority. Therefore, a read of the priority queue by reading the contents of the holding register guarantees that the highest priority element is there and it can be accessed immediately without further searching the queue.

Abstract: A combination two-channel defibrillator and programmable pacing stimulator for assesses lethal ventricular tachyarrhythmias and determine defibrillation thresholds during implantable defibrillator procedures. A pair of switching transistors are provided to protect the pacing circuit when a defibrillation shock is delivered. These switching transistors provide symmetric voltage protection and prevent the defibrillation energy from being shunted back to the patient through the pacing leads.