Patent Application
20160045155
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I. Field of the Invention
This invention relates generally to methods of conducting sleep studies on patients to assess apnea and more particularly to a method for assessing respiratory effort that obviates the need for conventional RIP Belts.
II. Discussion of the Prior Art
In conducting sleep studies on patients suspected of episodes of sleep apnea, it is customary to apply a number of sensors to the patient for detecting such things as respiratory air flow, snoring, rapid eye movement, leg twitches, heart rate, and respiratory effort. Conventionally, respiratory inductance plesmography belts (RIP belts) are used to monitor respiratory effort. The RIP belts incorporate a body encircling band incorporating a somewhat sinusoidally bent wire. A high frequency signal is applied and as the patient breathes, chest or abdominal movement causes a measurable modulation of the applied signal that is delivered over electrical leads to a polysomnograph (PSG) machine, along with outputs from the other sensors where by abnormal sleep events can be assessed. Such RIP Belts have been found to suffer from a number of problems, not the least of which is the breakage of the undulating inductance wire that necessitates a redo of the sleep study. Additionally, RIP belts have the potential to reverse polarity of the output waveform should the patient move so as to fold the elastic RIP belt a certain way. Cleaning the reusable belt can also be problematic as water will affect and corrode the embedded wire over time.
Dymedix Corporation of Shoreview, Minn. introduced to the market a respiratory effort belt to replace a RIP Belt. Instead of a variable inductance element, it incorporated a piezoelectric element that generates a measurable signal when subjected to changes in force on the element as the patient's chest and/or abdomen changes in circumference due to breathing. The piezoelectric element in the Dymedix belt is a strip of polyvinylidene fluoride (PVDF) polymer disposed on a predetermined surface of the body-encircling belt. The film is metalized on its two major surfaces and electrical leads are conductively attached to the metallization to convey signals to a PSG machine. Further information may be obtained from published U.S. Patent Application No. 2008/0275356A1. The present invention provides a method of assessing respiratory effort of a patient that eliminates the need for a belt configuration in conducting a sleep study.
A method of detecting, identifying, monitoring and assessing a sleeping patient's respiratory effort involves the steps of providing a sensor comprising a flat strip of PVDF polymer having a metallized layer on its opposed major surfaces to which are conductively attached a pair of insulated electrical leads. The metallized strip and the distal end portions of the leads are sandwiched between a layer of double sided adhesive tape and a layer of single sided adhesive tape. This construction allows the sensor to be adhesively affixed to the patient's skin on the chest and/or abdominal area. The proximal ends of the leads are then connected to a physiological data collection device, such as a PSG machine or a home sleep test (HST) monitor or other suitable physiological data collection device whereby electrical signals due to changes in thoracic or abdominal circumference resulting from breathing are generated and analyzed for purposes of screening or diagnosing sleep disordered breathing abnormalities.
The foregoing features, objects and advantages of the invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment, especially when considered in conjunction with the accompanying drawings in which:
Referring to
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As the patient breathes, the circumference of the chest and abdominal areas will expand during inhalation and will fall during exhalation. The resulting stretching and recovery of the PVDF polymer layer 12 causes a voltage to be applied to the leads 22 and 24 creating a signal proportional to the force exerted on the transducer. The signal is recorded and/or displayed for analysis by a medical professional who can then assess the patient's respiratory effort.
It will be immediately recognized that the need for a body encircling belt is obviated. Upon completion of the sleep study, the sensor may be readily removed from the patient and disposed of.
It is apparent that there has been provided in accordance with this invention a disposable sensing device for sensing respiratory effort. While the invention has been described in combination with a specific embodiment thereof, it should be evident that many modifications and variations will become apparent to those skilled in the art from what is described herein. Accordingly, it is intended to embrace all such alternatives, modification and variations as fall within the spirit and broad scope of the appended claims.
