This invention relates to electromechanical transducers in general and more particularly to a transducer particularly adapted for use in the medical field.
Transducers have been employed in the medical field for quite some time. A very common type of transducer consists of resistive transducer elements which can be excited by AC or DC current. As such the transducers are commonly employed for the monitoring of blood pressure by use of catheters or a direct puncture technique. The type of transducers employed include bonded and unbonded strain wire bridges as well as silicon and piezoresistive elements.
The use of such transducers for monitoring blood pressure has substantially increased, and, therefore, it is apparent that there is a need for an economical unit. There is a further need to develop a unit which is readily compatible with electronic patient monitors which exist in the hospital. This relates to fabricating a transducer which has standard outputs in regard to its terminals so that the device can be utilized with conventional monitoring equipment found in a hospital. Although the application of pressure transducers for the measurement of blood pressure is most common, the same transducers can be used in many cases for the measurement of other fluid coupled physiological pressures such as intracranial, gastroenterological, uterine and bladder pressure. It is thus apparent that there is a need for an economical and reliable transducer which can operate in the various environments.
In any event, the use of a catheter or a direct puncture technique employing a transducer introduces a possible conductive pathway directly from the transducer to the heart of the patient. In view of the fact that such transducers are commonly employed with patients who may require defribillation with equipment generating voltages of 10,000 volts, it is important that such a transducer be well insulated both for patient safety and transducer serviceability. Although the conductivity of this pathway is significantly lower than that of other types of electrodes, it is necessary that the transducer be isolated or insulated to avoid any additional risk to the patient.
Apart from the above problems, is the problem of the continuous expansion of pressure measurement by the use of transducers and the fact that these measurements are conducted in a variety of locations throughout the hospital. Each of these locations within the same hospital may be supplied with different patient monitoring equipment. This fact necessitates that the hospital stock a large number of transducers made by various manufacturers to assure the availability of replacement devices for each specific monitor. Additional transducers must be kept on hold due to the use of gas sterilants which require significant aeration time. Also, as a patient is moved within the hospital, new transducers may have to be drawn from supply in order to accommodate the different pieces of equipment. At each point, the plumbing must be disconnected, the new transducer reconnected and the system flushed and debubbled. This procedure significantly affects the accuracy of the measurement and may contaminate the liquid column thus presenting an infection hazard to the patient, as well as being costly and inconvenient.
Apart from the above considerations, there remains the typical problem regarding handling and abuse of the transducer. Essentially based on many considerations, the transducers have to be relatively rugged in order to withstand large forces which may occur if they are dropped or otherwise mishandled.
Based on the nature of the field, presently there are a host of manufacturers which supply transducers of various configurations and operating characteristics for use in medical electronics. The devices presently supplied have various disadvantages which relate to the above noted problems. It is, therefore, an object of the present invention to provide an electrical medical transducer which is reliable and which provides electrical isolation for patient use.
It is a further object of the present invention to provide a medical transducer which is extremely rugged while capable of reliable operation with repeatable characteristics.