Monitoring Breathing Signals in Sleep

Apnea Patients Using LabVIEW

Allison Campbell, Bearden High School

Peixing Liu

Abstract - A program was developed that continuously monitors the simulated

breathing signals (from the DAQ card) of sleep apnea patients. If the signal is equal

to or less than the threshold value that is set at 0.2 volts for longer than 20 seconds,

the code will trigger an alarm that would awake the sleep apnea conditioned child in

the hospital bed. The LabVIEW Front Panel is where the caregiver(s) and hospital

staff can easily monitor the child’s current breathing signals. The LabVIEW Block

Diagram (Back Panel) consists of all the technical programing.

I. INTRODUCTION

Sleep apnea is a sleep disorder, in which a patient’s breathing stops and restarts

repeatedly. There are two types of this disorder, Obstructive Sleep Apnea and Central

Sleep Apnea. Obstructive Sleep Apnea occurs when the airway collapses (see Figure 1),

which prevents the patient from inhaling properly, therefore diminishing the patient’s

oxygen supply. Central Sleep Apnea occurs when the brain, usually an underdeveloped

one of an infant, neglects to send signals to the respiratory system during sleep. Both

forms of sleep apnea are a danger to patients. Sleep apnea affects over 40 million people

nationwide, and it is one of the leading causes of death in infants. Each pause in breathing

is called an apnea. Figure 2 shows the connection to other serious health risks, such as

stroke, diabetes, depression, etc.

Figure 1

About ninety percent of sleep apnea patients are unaware of their condition. The

symptoms of sleep apnea can be extremely frustrating to the patients because they do not

know their struggles are caused by sleep apnea (see Figure 3).

Figure 2

Infants who have Central Sleep Apnea require constant monitoring. Even with

today’s technology, medical staff struggle to visualize breathing signals and to be able to

adjust limits/thresholds that can provide early warnings prior to disastrous outcomes.

With this system, personnel will be able to set a threshold and visualize real time

breathing signal as needed.

II. LITERATURE REVIEW

Currently, there are three methods and devices used to treat sleep apnea.

Figure 3

1) Continuous Positive Airway Pressure (CPAP) is delivered by means of a mask during

sleep and a motor blows air into the mask through a large cannula (see Figure 4).

2) The Mandibular Advancement Device (MAD), which is the most widely used

mouth device, is similar to a mouth guard (see Figure 5). It eases the lower jaw forward

to open the airway.

Figure 4

3) Less commonly used is the Tongue Retaining Device, which holds the tongue in

place to keep the airway open (see Figure 6).

Figure 5

Figure 6

III. METHOD

The goal of this project was to design a program using LabVIEW software to

continuously monitor the sleep apnea patient’s breathing signals by means of voltage.

First, the DAQ card needs to be programed and generate a simulated signal as an

analogue system that emits a range of signal values in the form of a sine wave, whereas a

digital system can only emit two values. An analogue signal ranges from any value

between one and zero, unlike a digital signal that can only be one or zero. The threshold

value is what the signal value is being compared to. Depending on the individual patient,

the threshold value can be set at any value. A value of 0.2 was chosen as the threshold.

Then, the program continuously (with a While Loop) sampled the signal array and

displayed the sampling on the Front Panel as a visual waveform graph for caregivers and

physicians to view and monitor the real time breathing signals. To compare the signal to

the threshold system (a constant), the signal needs to be converted from an array to an

element. Also, inside the While Loop is a timing system that activates the alarm system

when the signal is equal to or less than the threshold and when this lasts greater than

twenty seconds. In order to apply both requirements of the alarm, an “AND” icon joined

the two comparisons. (See Figure 7)

IV. RESULTS

At the conclusion of the project timeframe, the programming was successful. A

simulated signal was produced and was screened continuously by a timing system. Then,

comparison icons were used to control the alarm activation, which fulfills the purpose of

this research project to provide caregivers with adequate warning and control with the

front panel (see Figure 8).

Figure 7

V. DISCUSSION

With the core programming completed, the simulated signal that was generated in

the virtual instrument leads one to believe that it is feasible for using the National

Instruments’s LabVIEW program to collect and display sleep apnea data in real time on a

monitor. Since this has proven to be possible in terms of technology, looking into the cost

of a final product may be just as important. Medical, or for that matter all, products need

Figure 8

to be simple to use, with well layout user interface, and the software needs to be robust.

Use of Control-Alt-Delete to reset the medical devise is not acceptable. In other words,

more work is needed to ensure that the software code will not hang when the user presses

a button that is not intended. The user interface screen needs to be developed and tested.

Proper sensors need to be selected and tested for long-term reliability, or it will be

necessary to select a disposable type of sensors, depending on cost structure, sanitary

considerations, etc. If all these are completed, this program could potentially be utilized

in hospitals to monitor the breathing signals of sleep apnea patients.

VI. CONCLUSION

These results have opened the door for physicians, nurses, and caregivers to many

possibilities to monitor all patients’ real time signals, not just sleep apnea. Now, clinical

trials could be organized performed in hopes of testing this program with sensors to be

attached to the patient and connected to the monitor.

VII. ACKNOWLEDGEMENTS

Thank you to the University of Tennessee CURENT Department of Electrical

Engineering and Computer Science and Dr. Chen for providing this opportunity for

students to learn and gain valuable experience in this field. In addition, special thanks to

Mr. Wills who provided the needed extra assistance and support to all the participants in

this program. He was extremely helpful and patient while guiding students throughout the

program.

This work was supported in part by the Engineering Research Center 

Program of the National Science Foundation and the Department of Energy 

under NSF Award Number EEC-1041877 and the CURENT Industry Partnership

Program.

VIII. REFERENCES

Obstructive Sleep Apnea. Digital image. Mayo Foundation for Medical Education and

Research, n.d. Web. 20 July 2015.

Sleep Apnea Statistics and Risks. Digital image. Associations to Sleep Apnea, n.d. Web.

20 July 2015.

Sleep Apnea Symptoms. Digital image. N.p., n.d. Web. 20 July 2015.

"Sleep Apnea Mouth Devices: CPAP, Mouth Guards, Mandibular Advancement, and

More." WebMD. WebMD, n.d. Web. 19 July 2015.

Continuous Positive Airway Pressure (CPAP) Machine. Digital image. McKesson

Corporation And/or One of Its Subsidiaries., 2014. Web. 20 July 2015.

How MAD Works. Digital image. N.p., 2015. Web. 20 July 2015.

How Oral Appliances Work. Mandibular Repositioning Appliances Tongue Retaining

Device (TRD). Digital image. Dental Sleep Medicine. N.p., n.d. Web. 20 July

2015.