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Abstract

Table of contents

Introduction

The need for non-invasive monitoring devices has proliferated in recent years and has led to this

development of the ThereNIM- a non invasive respiratory monitoring device. Non-invasive monitoring

devices have various uses in the medical field and hospitals. At a basic level, non-invasive monitoring

is considered the monitoring by not using obtrusive mechanisms like attached sensors and electrodes.

Most times hospitals find themselves faced with cost burdens of newer non invasive mechanism.

Furthermore, these mechanisms are not always completely accurate and may still be invasive in some

manner. The hurdle that all ways to monitor the human body's vital statistics is that most patients do

not simply lie down without ever moving. The movement of the patient affects the measurements of

these devices and this problem is prevalent in all of medical monitoring.

Many devices have been implemented to non-invasively monitor and circumvent the problem

mentioned above. Some of the devices that have been recently introduced include video monitoring,

actigraphy watches and motility sensors placed in beds. The drawback of most of these tracking

devices is the cost. Actigraphy watches tend to be the cheapest of these methods however, these

watches must be tied onto the wrist and are still in contact with the patient. Another device that claims

to be non-invasive is the Masimo Rainbow Acoustic Monitoring device. There is an acoustic transducer

placed unobtrusively on the patient's neck to continuously monitor the respiration rate of an individual.

This method is still not completely non-contact and is not cost efficient.

This method of tracking chest wall movement involves using capacitance and electric fields to detect

body movements. This method allows the doctors or researchers to continuously monitor the change in

motion of the patient's chest without touching them. The cost efficiency of this method is one of the

key highlights since it can be manufactured well within a hundred dollars without the addition of a

computer. Current methods cost well in the hundreds and even thousands of dollars.

The basis for the design of this method stems from a musical instrument invented by Russian Physicist

Leon Theremin in 1919. It is considered the world's first electronic instrument and can be played

without any contact. The Theremin works based off 3 oscillators built inside. On the outside are 2

antennas, one to control pitch and one to control volume. The ThereNIM device is based off of this

same basic principle. It is a variation of the oscillator combinations. The underlying principle behind

the operation of this device is that as the body or hand approaches an antenna, the capacitance

increases in the circuit. This circuit is reflected across the variable oscillator and reduces the frequency.

This causes an audible frequency difference between oscillators and the frequency of this not depends

on distance of the human body. Another elementary principle is the concept of heterodyning. This is

the concept that as two separate frequencies are inputed into a mixer, only the lower frequencies are

taken out. Essentially what occurs is that the difference between both frequencies is the only

transmitted signal while the sum of both frequencies is discarded. The heterodyne principle consists of

beating of both frequencies. When two sound waves of different frequency approach your ear, the

alternating constructive and destructive interference causes the sound to be alternatively soft and loud -

a phenomenon which is called "beating" or producing beats. The beat frequency is equal to the absolute

value of the difference in frequency of the two waves. Using these basic principles that make up the

Theremin, the ThereNIM was developed as a monitoring device. This device is a novel application of

an idea that had been only used in the arts.

This model with multiple oscillators beating was selected for various reasons. Most of the other sensors

were far too expensive and much less changeable. Other sensing devices like lasers and photoelectics,

infrared, ultraviolet, and others have a major drawback. These techniques are generally used for

detection of an object. They provide monochromatic results. An example is using lasers as security

devices in banks. These lasers detect if an object or person is in the range or not. There is no way to

detect movement. Only two possibilities exist. This method of heterodyning oscillators used in the

ThereNIM has the possibility of detecting movement of an object. The human body's respiratory

motion is not definite and does not exist between two acute points. Rather, the chest movement of each

individual is unique and has its own pattern. This is the root reason behind choosing this model for

implementation as it is unique in its abilities.

This method employs a form of capacitive sensing to detect changes in body movement. It then

converts this to a frequency which is emitted as a sound. This sound can be recorded to be converted

into a frequency graph that can show any abnormalities or changes in the breathing rates. This device is

intended to provide a retrospective view on a patient's body function rather than instantaneous results.

Thus it will only provide a relative view of the patients breathing and not the exact amount of

breathing.

Purpose/goals

The purpose of this project is to smoothly and efficiently detect continuous respiratory movement over

a period of time. The ThereNIM device must do this through all obstructions and impedances. The goal

of this project is to combine concepts of passive capacitance, heterodyning, and beating to track the

changes in respiratory activity over time in a contact less manner. The ThereNIM project intends to

overcome the problems of physical movement excluding respiratory ballistic movement by using

multiple antennas. This project intends to devise a cheaper method of sensing by avoiding the use of

highly sensitive sensors and turning towards a simpler constructable alternative.

Project description

This project involves creating a device that is able to efficiently track the changes the respiratory

system's movement causes on the human body. This ballistic effect is detected by using the body as a

capacitive device adding capacitance to an electric field. By doing this, the frequencies emitted by the

oscillator on which the capacitors are connected to change. This change in frequency is audible and this

change in frequency can be plotted over time. Using this, the doctors can detect change over time in

respiratory activity without actually detected the movement. Two antennas are used as sensors and

these two detect changes in the body movement. When an individual tosses or turns, his body is closer

to one antenna than the other. Yet, the sum of the distance will still be the same so the effect of tossing

around in sleep is blocked.

Applications

For patients who are victims of burn accidents, patients who are frail elders or delicate infants, it is not

possible to attach electrodes and other sensors. Similarly in sleep research the need for non-contact

monitors has been growing. These “contact free” devices are used for measuring sleep quality data.

The patients who are in need of the ThereNIM are not minorities. In America alone, there are 450,000

burn victims annually visiting hospitals and more than 18 million Americans affected by sleep apnea.

The thousands of patients in the Post Anesthetic Care Unit (PACU) are also in need of a non-invasive

monitoring device. These patients are observed critically by doctors for signs of respiratory depression.

All anesthetic drugs relax the muscles to the point that there is a loss of airway potency putting patients

in risk of hyperventilation. It is crucial for post anesthetical patients to be observed after going through

a procedure because hyperventilation of this sort is a life threatining condition. Many patients have

expressed discomfort and dislike towards most continuous monitoring devices in hospitals today.

Having multiple electrodes pinched into their skin repels these patients. Manual and instantaneous

methods of monitoring have not been accurate or precise enough to be acceptable for use because of

the wide margin of error. Additionally the cost of un-obtrusive monitoring devices is far too exorbitant

to be accepted by hospitals and clinics globally. Thus, here stands the global need for a novel non-

invasive respiratory monitoring device that is not only cheap but also effective to diagnose and save the

millions of ill patients in this world. This project has a wide scope for use in hospitals, clinics, and

labaratories. The ThereNIM explores the use of capacitive sensing. The research behind the theremin

musical instrument has been limited to improving its musical capabilities. This project explores this

idea and opens the gate for further implementation.

Materials: ·CMOS 4093, 4077 chips·TTL chips – 74LS266, 74LS132·3-chip voltage regulator (5v)- (Lm7805)·100pF 500v 5% capacitors·3.25x2.125 half sized bread board·Potentiometer 25k 25 turn 5 Watt·1μF 25 volts radial capacitors·10k Ohm .25 Watt 5% resistor ·15 K Ohm .25 watt 5% resistors·Monolithic capacitors 1nF 63 V·Multiple other resistors of lesser value (1.5 Ohms)·.0001 μF capacitors·Assorted jumpers and/or staples and spare CAT5 wire·9 volt power supply·Battery connector clips·Oscilloscope·Frequency counter·precision mini Screwdrivers·Scissors·Pliers·Copper wire·diagonal wire cutters·optional: Electric precision screw driver·Multimeter·Mini Guitar amplifier or other amplifying device·Speakers or headphones to connect to amplifying device·Computer with microphone ·Audacity program on computer·

·Methodology·