ieee sensors journal, vol. 14, no. 9,...

IEEE SENSORS JOURNAL, VOL. 14, NO. 9, SEPTEMBER 2014 3245

Simplified Structural Textile Respiration SensorBased on Capacitive Pressure Sensing Method

Se Dong Min, Member, IEEE, Yonghyeon Yun, Member, IEEE, and Hangsik Shin, Member, IEEE

Abstract— We propose a simplified structural textile capacitiverespiration sensor (TCRS) for respiration monitoring system. TheTCRS is fabricated with conductive textile and Polyester, and ithas a simple layered architecture. We derive the respiration bythe distance changes between two textile plates in the TCRS,which measures the force from the abdominal diameter changeswith the respiratory movement. To evaluate the reliability ofTCRS, both linearity test and comparison test were carried out.Three times of tensile experiment were performed to confirmthe linearity of change in capacitance by the distance change.The result shows that the coefficient of determination (R2) ofproposed TCRS is 0.9933. For comparative study, 16 subjectswere participating in the experiment. As a result, the pro-posed respiratory rate detection system using TCRS successfullymeasures respiration compared with nasal airflow detection(R = 0.9846, p < 0.001). In Bland–Altman analysis, the upperlimit agreement is 0.5018 respirations per minute and lower limitof the agreement is −0.5049 respirations per minute. From theseresults, we confirmed that the TCRS could be used for monitoringof unconscious persons, avoiding the uncomfortness of subjects.Monitoring respiration using TCRS offers a promising possibilityof convenient measurement of respiration rates. In particular,this technology offers a potentially inexpensive implementationthat could extend applications to consumer home-healthcare andmobile-healthcare products.

Index Terms— Capacitive sensor, conductive textile,non-invasive monitoring, respiration measurement, wearablesensor.

I. INTRODUCTION

THERE has been increasing an importance of healthcaresince our life circumstance has changed in many ways,

such as the aged population society has come, the interest in anindividual’s health care has increased [1], [2]. On that score,healthcare services have been developed for patient centeredand high quality care technology [3], [4]. Also, there has beena move towards preventing chronic or acute diseases by early

Manuscript received March 10, 2014; accepted May 17, 2014. Date ofpublication June 17, 2014; date of current version July 29, 2014. This workwas supported in part by the Soonchunhyang University Research Fundunder Grant 20120676 and in part by the Chonnam National University. Theassociate editor coordinating the review of this paper and approving it forpublication was Prof. Chirosree RoyChaudhuri.

S. D. Min is with the Department of Medical IT Engineering, Soonchun-hyang University, Asan-si 336-745, Korea (e-mail: [email protected]).

Y. Yun is with the Department of Convergence Biomedical Engi-neering, Daelim University College, Anyang-si 431-715, Korea (e-mail:[email protected]).

H. Shin is with the Department of Biomedical Engineering, Chon-nam National University, Yeosu 550-749, Korea (e-mail: [email protected]).

Color versions of one or more of the figures in this paper are availableonline at http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/JSEN.2014.2327991

monitoring and diagnosis [2]. These changes accelerate thedevelopment of health-related products and systems that areconvenient and economical. For example, research on signalsfrom human body measurement technology without subject’sinconvenience, unconstrained and non-invasive systems thatare located on the patient or user and connected to the patientor user without wire [5]–[7], becomes the key solution forthe realization of ubiquitous healthcare. The requirement forsuch systems is that they are designed for long-term and dailyhealth monitoring where patient or user located [7].

To guarantee user’s comfort and higher quality of life, theforegoing monitoring systems need to be based on flexibleand smart technologies. Moreover, this system should enhanceuser’s motivation and consciousness. One of the stimulatingchallenges is the trial to acquire the most realistic health statusin a natural environment using textile materials. This approachspecifically minimizes the interaction between the sensingsystem and the user activity. These functions will be realizedby a wearable sensor system that is integrated into clothingor installed in our living space, and this type of systems mustbe able to monitor a person’s vital signs and activities duringdaily life [8]–[10]. For this reason the use of sensing textilematerials is gaining more and more attention [11].

Nowadays, several conductive fabrics have been used as asensor and electrode in the form of fiber and yarn, and utilizedto sense clothes measures the vital data with the conductiveand piezoresistive characteristics of electro-conductive fabric[12]–[16]. In the most of textile sensor, textile sensing patternare connected to signal acquisition device, and recorded sig-nals will be stored and transmitted to other remote monitoringsystem. Conductive textile based measurement has alreadytried to measure the critical physiological signals such aselectrocardiogram (ECG), electromyogram (EMG), respira-tion, activity pattern, and temperature [15], [16]. Moreover,the prototypes of textile-based belt-type capacitive respirationsensor were developed and have tried to be applied forrespiration monitoring [13], [14].

Among these signals, respiration is one of the most crit-ical indicators of the physiological state and it should workproperly in every moment of human life because respira-tory arrest could fatally damage the human body. Though thisimportance of the respiration, respiratory disease such as lowerrespiratory tract infections, chronic obstructive pulmonarydisease, tuberculosis and lung cancer still remain as major tenleading causes of death worldwide. World Health Organization(WHO) reports that nearly 5 percent of the human populationis suffering a respiratory disease like sleep apnea syndrome

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3246 IEEE SENSORS JOURNAL, VOL. 14, NO. 9, SEPTEMBER 2014

and about 30 percent of people in their seventies are reportedto have a respiratory disease in industrialized developed lands[17], [18]. Also, according to the World Health Report 2000of the WHO, the top five respiratory diseases account for17.4 percent of all deaths and 13.3 percent of all Disability-Adjusted Life Years [18]. To treat respiratory disease,continuous respiration monitoring surely helpful in respiratorydisease management, however reliable methods of respirationmonitoring hardly exist for home and ambulatory monitoring.For this, latest approaches based on textile-based solutionmay be a promising approach for comfortable and practicalrespiration monitoring because the textile based respirationsensor is relatively low-cost, easy of use and it has simplifiedstructure compared with current solution.

In this paper, we propose the simplified structural textilebased sensor for minimal constrained respiration monitoringusing conductive textile. We measure capacitance changesfrom the abdominal displacement in breathing and estimateinhalation and exhalation phase with signal processing. Then,estimated respiration was compared with reference signal thatobtained by nasal thermocouples to validate its feasibility.

II. MATERIALS AND METHODS

A. Capacitive Respiration Sensor

The capacitive respiration sensor is implemented with a thinplate (diaphragm), usually metal or metal-coated quartz, as oneplate of a capacitor [19]. It is generally built with spacing-change sensors, governed by the usual equation

C = ε0εrA

d(1)

where ε0 is the electric constant, εr is the relative static per-mittivity, A is cross-sectional area, d is the distance betweenplates. When the plates are parallel and displaced by �d , thechange in capacitance �C is

�C = −C

d�d (2)

Hence as dimensions are scaled to sub-millimeter siliconsize, the capacitance scales linearly, but the percent change incapacitance with displacement does not change. The capacitiverespiration sensor is displacing piezoresistive pressure sensorbecause of lower power requirements, less temperature, andlower drift [19]. The plate is exposed to the process pressureon one side and to a reference pressure on the other. Changesin force cause it to deflect and change the capacitance. Fig. 1(c)shows the change of the distance between plates and areacaused by force from inhalation. Because inhalation generatesthe centrifugal force, plates are pushed and get nearer. Also,centrifugal force stretch the textile sensor, therefore the area ofsensor can be varied with Young’s modulus, and it makes thechange of capacitance. The change may or may not be linearwith force and is typically a few percent of the total capaci-tance. Using it to control the frequency of an oscillator or tovary the coupling of an AC signal can monitor the capacitance.It is a good practice to keep the signal-conditioning electronicsclose to the sensor in order to mitigate the adverse effectsof stray capacitance. From the physiological characteristic,

Fig. 1. Abdominal circumference changes in every respiration: (a) Ininhalation, abdominal circumference is increased and it put force on the TCRS.(b) In exhalation, abdominal circumference is decreased and force of TCRS isdecreased. �d means the distance or diameter changes of subject’s body fromrespiratory movement. (c) The distance between plates is varied by respiration.In inhalation, outward force is generated and it makes the distance betweenplates shorter and the area larger.

abdominal and chest muscle moves by respiration mechanism.The movement of muscle makes an amount of force tothe outward. Fabricated TCRS uses this principal caused byabdominal movement, which transfers the force or pressureto TCRS. This force or pressure leads to distance changebetween conductive textile electrodes (see Fig. 1). Finally,inhalation and exhalation could be determined by capacitancevariation derived from the changes of chest and abdominalcircumference.

B. Design of Textile Capacitive Respiration Sensor

Belt type textile capacitive respiration sensor (BTCRS)consists of a basic five-layered structure forming a capacitancewith a non-conducting woven interlining as shown in Fig. 2.Electro-conductive fabric, W-290-PCN, was produced by AjinElectron (Busan, Republic of Korea). The base material ofW-290-PCN is Polyester and Ni-Cu-Ni plated as shown inFig. 3(a). Moreover, W-290-PCN is produced by an elec-troless plating method in order to be stronger the platingadhesive property. To achieve a characteristic of capacitor,two electric conductive fabrics have been wounded twice bya non-conducting woven interlining. Polyester woven fusibleinterlining (100 %) was used as an insulator between electricfabrics. Also, Fig. 3(b) shows the fabricated BTCRS, elasticfabric and snap button attached to the each end of the TCRS tofit in every size of body surface. The dimension of the BTCRSis 830 mm × 38.6 mm × 1.35 mm (width × height × thick-ness). The property of this material is represented in Table 1.

MIN et al.: SIMPLIFIED STRUCTURAL TEXTILE RESPIRATION SENSOR 3247

Fig. 2. (a) Construction of five layered belt-type capacitive textile forcesensor (BTCRS). BTCRS has repeated structure of conductive layer andinsulation layer. (b) Fabricated BCTFS with snap button. Dimensing ofBTCRS is 830 mm × 38.6 mm × 1.35 mm (width × height × thickness).

Fig. 3. Plating structure of electro-conductive fabric, W-290-PCN.

TABLE I

THE PROPERTY OF ELECTRO-CONDUCTIVE FABRIC (W-290-PCN)

Compared with previous research which uses 9 layer based onsilver coated conductive textile, 3D textile and water-repellentfabric [13], proposed TCRS is assembled with lesser layersusing cost-effective material.

C. Sensing Module of BTCRS

Analog front end for measurement circuit was implementedwith auto-balancing bridge [20], high impedance precisionrectifier [21] and 2nd order Butterworth low pass filter with10 Hz cut-off frequency to measure the capacitance changeof the textile pressure sensor. To validate the implementedacquisition module, we examine the output by changing thecapacitance from 0.01 nF to 1 nF, and the result shows thatthe output amplitude (V) is proportionally increased with thecapacitance changes. Schematic of designed circuit network isrepresented in Fig. 4.

D. System Configuration

BTCRS based respiration measurement system is consistedwith the textile, analog front end, data acquisition moduleand signal processing and analysis algorithm. To record therespiratory activity, participants wear the BTCRS on theirabdominal site, and the nasal thermocouple, TSD202A, BiopacSystem inc. (USA), is attached on the subject’s philtrumfor a reference respiration measurement. The experimentalsetup for respiration measurement using BTCRS is shownin Fig. 5.

MP150 (Biopac, U.S.A) was used to convert the analogoutput of the TCRS to the digital signal and Acknowledge3.8.1 was used for the real-time monitoring and data stor-ing. Every data were sampled with 100 Hz sampling fre-quency ( fs). MATLAB 7.3 (The MathWorks, Inc., Natick,MA, USA) was used for a signal processing and extracting therespiratory component of the recorded signal. SPSS Statistics20 (IBM, USA) and Sigmaplot 12 (Systat Software, Inc. USA)are used for a statistical analysis.

E. Signal Processing

Because the signal measured by BTCRS system con-tains frequency noise aside from the respiration signal range(0.1 Hz–0.5 Hz), we use a moving average filter to removehigh frequency noise. The moving average filter operates byaveraging a number of points from the input signal to produceeach point in the output signal. In the equation for movingaverage filtering is shown in (3).

y[i ] = 1

M

M−1∑

i=0

x[i + j ] (3)

where x[ ] is the input signal, y[ ] is the output signal, andM is the number of points in the average. In this paper, weset the fs/2 points for averaging.

Then, inflection points of inhalation to exhalation weredetected by using a zero crossing method [22] with filteredsignal. Inflection point detection is a key parameter in therespiration signal because peaks mean the number of breaths.Moreover, inflection point to near inflection point means aperiod of respiration, and respiration rate could be derivedfrom the time interval of each inflection point.

F. Feasibility Test

To validate the feasibility of BTCRS based respiration mea-surement system, feasibility test was designed and performed.Sixteen subjects were participated in experiments, and there isno reported any cardiovascular and respiratory diseases. Theage of the subjects ranged from 24 to 36 years old, with amean age of 30.06 years old. The body mass index (BMI)of the subjects ranged from 19.73 to 30.09 kg/m2, with amean BMI of 24.74 kg/m2. Respiration test was carried out in3-minute duration, and the average of the respiration ratesvaried from 5 to 17.7 breaths per minute with a mean of9.94 breaths per minute.

As a reference method of respiration measurement nasalthermocouple is attached near below the subject’s nose and


Fig. 4. Schematic of analog front end of the TCRS: (a) Auto-balancing bridge. (b) High impedance precision rectifier. (c) Butterworth second low-pass filter(cut-off freq. = 10 Hz).

Fig. 5. Experimental setup.

simultaneously record respiration with a BTCRS system forcomparative analysis. Subjects wear BTCRS on their waistcentered on navel. BTCRS was fastened without room betweenbody and BTCRS.

Comparative study is carried out in two different viewpoints.First is that the recorded respirations were compared withthe result of the BTCRS to evaluate the detection perfor-mance of BTCRS system, and the second is the accuracy ofBTCRS system was evaluated by comparing measured respi-ration rate between nasal thermocouple and BTCRS system.Bland-Altman plot was used to compare two competitiveresults and find the similarity.

III. EXPERIMENTAL RESULTS

A. Characteristic of TCRS

To see the capacitance change by change of force orpressure, analog push-pull gauge, FB-20K, manufactured byIMADA (Japan) was used. Three times of tensile experi-ment that modeled as respiration mechanism performed by

Fig. 6. TCRS characteristic curve from tensile experiment. Coefficient ofdetermination is R2 = 0.9933 for whole range. (Trend line is fitted by powerlaw equation.)

increasing the force from 0 to 3 N with 0.2 N increment.This experiment is a modeling to confirm the increment offorce makes two plates of capacitor closer which causes thechange of capacitance. The result shows that the appliedforce is closely related to the capacitance change of theTCRS. Coefficient of determination by power law fitting isR2 = 0.9933. These results are described in Fig. 6.

B. Characteristic of BTCRS

Respiration measurement with BTCRS is performed byraw signal measurement of abdominal movement, signalenhancement and noise removal and inflection point detec-tion in order. Measured respiration is compared withthe reference respiration method, the nasal airflow detec-tion. Fig. 7 represents the procedure of respiration mea-surement using BTCRS compared with nasal thermo-


Fig. 7. Comparison of measured respiratory signals: (a) measured respirationfrom nasal thermocouple, (b) measured respiration from BTCRS, (c) movingaverage filtered nasal thermocouple signal, (d) moving average filtered BTCRSsignal, (e) result of inflection point detection (nasal), and (f) result of inflectionpoint detection (BTCRS).

Fig. 8. Comparison respiration rates between BTCRS and Nasal thermocou-ple (BPM: Breath Per Minute).

couple. Fig. 7(a) and (d) shows recorded raw signalfrom BTCRS and nasal thermocouple, respectively. Inthis figure, much noise is found in BTCRS comparedwith the raw signal measured by nasal thermocouple.Fig. 7(b) and (e) is the result of the moving average filteringof nasal thermocouple and BTCRS, respectively. Especially,in Fig. 7(e), we can find that the noise component definitelydecreases in BTCRS signal. Fig. 7(c) and (f) shows the peakdetection result of both signals. From these figures, we canknow that respiration component can be successfully derivedfrom BTCRS after signal processing stages.

C. Performance Evaluation

Respiration measured by BTCRS was evaluated by com-paring with Nasal thermocouples in two different viewpoints;comparison of respiration rates and Bland-Altman Analysis.Respiration rate is obtained with the time differences betweenadjacent peaks and respiration number is obtained by countingthe number of peaks. Fig. 8 shows the similarity between twodifferent methods graphically. In this figure, we could find

Fig. 9. Bland-Altman plot between BCTRS and Nasal thermocouple forvalidation of respiration detection performance of BCTRS (Bias = −0.0015,SD = 0.2568, Limits of Agreement = −0.5049 to 0.5018).

that the proposed BTCRS method has linear characteristiccompared with the respiration of nasal airflow. As a resultof paired t-test, it was shown that the correlation coeffi-cient of measured respirations is slightly different accord-ing to subject, however the correlation coefficient was veryhigh and significant (R = 0.9846, p < 0.001) for wholesubjects.

Bland-Altman analysis is typically used to compare mea-surement techniques against a reference value. In Bland-Altman analysis, bias means an average difference, and limitsof Agreement means 2 standard deviation that describes therange of 95% of comparison points. In our experimental result,bias is −0.0015 bpm, SD is 0.2568 bpm, and limit of theagreement is −0.5049 to 0.5018 bpm. Fig. 9 is the graphicalrepresentation of Bland-Altman analysis, Bland-Altman plot.From this figure, we can find that the result of the proposedBTCRS method is very similar to the reference respirationmeasurement technique, nasal airflow detection.

IV. DISCUSSION

From the several experiments, we try to confirm the charac-teristic of BTCRS and its availability for practical respirationmeasurement. In the first experiment, we try to find thephysical characteristic of BTCRS using push-pull gauge andwe found that the capacitance generated from BTCRS showsalmost linear against applying pressure. From this result weconfirm that the proposed BTCRS has a proper characteristicin pressure measurement in the specified range.

We carried out another experiment to make sure the avail-ability of BTCRS in practical respiration measurement. Thisexperiment was performed with sixteen subjects, and the resultof BTCRS was compared with the result of the referencerespiration method, nasal airflow detection method. To guar-antee the statistical significance, measured respiration wasvalidated its significance with paired t-test and Bland-Altmananalysis. From the result of significance test, we found thatthe BTCRS measured respiration is highly correlated withreference method (R = 0.9846, p < 0.001). Moreover inBland-Altman analysis we also found that the respiration ratemeasurements from the BTCRS are between −0.5049 bpm


above and 0.5018 bpm below the rate measured with thenasal thermal sensor with 95% confidence. The differencebetween respiration rates calculated with BTCRS signal andthe nasal thermal sensor has a mean of −0.0015 bpm anda standard deviation of 0.2568 bpm. These results mean thatthe proposed BTCRS has only 0.0015 differences of breathper minute compared with reference respiration measurementtechnique, and the difference is allowed within around 1 breathper minute. These analyses signify that the proposed methodhas high similarity with reference method, and it implies thatthe BTCRS would be enough to apply to practical application.

V. CONCLUSION

One key parameter in the clinical monitoring of patients isthe number of breaths per minute, known as the respiratoryrate. Many heart and lung diseases, especially pneumonia,affect respiratory rate. Therefore, monitoring of the respira-tory rate is an important diagnostic method in planning ofmedical care.

This paper presents respiration measurement and monitoringwith a developed BTCRS. The developed sensors are linearwith sufficient resolution to measure a wide range of breathingand from different subjects. From the experimental results,proposed method shows very high significance compared withexisting methods, and it implies that the BTCRS has thepossibility for respiration measurement as a kind of surrogatemethods. In case of belt type textile capacitive respirationsensor for breathing monitoring, it was easily allowed to everysubject since it has been manufactured with a textile as cloths.Moreover, there may be performance difference in respirationmonitoring by measuring position, respiration could be suc-cessfully measured in arbitrary location of abdomen becauseBTCRS is an elastic band, however it should be fasten.

Another advantages of the developed TCRS are cost-effectiveness. Indeed, the price of the electro-conductive fabricthat used in this research, W-290-PCN, could be purchasedfewer than 5 dollars per unit area (1 m2). Moreover, this designresults in low manufacturing costs since all used componentsare available off the shelf and no special materials have to beinvented unlike resistive textile sensors where specific, resis-tance changing materials have to be used. Therefore, it couldbe any pattern or shape for user friendly and be embedded intounderwear, belt loops, trousers and sportswear. Furthermore,the design can be scaled to almost any size depending uponthe subject’s size and where it could be located.

Most of the future work on the BTCRS lies with theimprovement of the belt design as cloths which people weareveryday. Further work is required to solve the wirelessinstrumentation system on the sensor belt. It has been plannedto use a modular wireless sensor node developed for wearablehealth monitoring applications.

REFERENCES

[1] M. Leavitt, “Medscape’s response to the institute of medicine report:Crossing the quality chasm: A new health system for the 21st century,”MedGenMed, vol. 3, no. 2, p. 2, Mar. 2001.

[2] S. Warren, R. L. Craft, and B. Bosma, “Designing smart health caretechnology into the home of the future,” in Proc. Workshops FutureMed. Devices, Home Care Technol. 21st Century, 1999, p. 667.

[3] R. Wootton, “Telemedicine: A cautious welcome,” Brit. Med. J.,vol. 313, p. 1375, Nov. 1996.

[4] R. Harrison, W. Clayton, and P. Wallace, “Can telemedicine be usedto improve communication between primary and secondary care?” Brit.Med. J., vol. 313, p. 1377, Nov. 1996.

[5] H. Heathfield, D. Pitty, and R. Hanka, “Evaluating information tech-nology in health care: Barriers and challenges,” Brit. Med. J., vol. 316,p. 1959, Apr. 1998.

[6] N. Oliver and F. Flores-Mangas, “HealthGear: A real-time wearablesystem for monitoring and analyzing physiological signals,” in Proc.Int. Workshop Wearable Implant. BSN, Apr. 2006, pp. 4–64.

[7] A. Lymeris and D. E. De Rossi, Wearable Ehealth Systems for Per-sonalised Health Management: State of the Art and Future Challenges,vol. 108. Amsterdam, The Netherlands: Ios Press, 2004.

[8] P. Corbishley and E. Rodríguez-Villegas, “Breathing detection: Towardsa miniaturized, wearable, battery-operated monitoring system,” IEEETrans. Biomed. Eng., vol. 55, no. 1, pp. 196–204, Jan. 2008.

[9] F. H. Wilhelm, M. C. Pfaltz, and P. Grossman, “Continuous elec-tronic data capture of physiology, behavior and experience in reallife: Towards ecological momentary assessment of emotion,” Interact.Comput., vol. 18, no. 2, pp. 171–186, Mar. 2006.

[10] V. Gramse, A. De Groote, and M. Paiva, “Novel concept for anoninvasive cardiopulmonary monitor for infants: A pair of pajamaswith an integrated sensor module,” Ann. Biomed. Eng., vol. 31, no. 2,pp. 152–158, 2003.

[11] R. Paradiso, C. Belloc, G. Loriga, and N. Taccini, “Wearable healthcaresystems, new frontiers of e-textile,” Studies Health Technol. Informat.,vol. 117, pp. 9–16, Nov. 2005.

[12] C. T. Huang, C. L. Shen, C. F. Tang, and S. H. Chang, “A wearableyarn-based piezo-resistive sensor,” Sens. Actuators A, Phys., vol. 141,no. 2, pp. 396–403, Feb. 2008.

[13] T. Hoffmann, B. Eilebrecht, and S. Leonhardt, “Respiratory monitoringsystem on the basis of capacitive textile force sensors,” IEEE SensorsJ., vol. 11, no. 5, pp. 1112–1119, May 2011.

[14] C. R. Merritt, H. T. Nagle, and E. Grant, “Textile-based capacitivesensors for respiration monitoring,” IEEE Sensors J., vol. 9, no. 1,pp. 71–78, Jan./Feb. 2009.

[15] M. Pacelli, G. Loriga, N. Taccini, and R. Paradiso, “Sensing fabricsfor monitoring physiological and biomechanical variables: E-textilesolutions,” in Proc. 3rd IEEE/EMBS Int. Summer School Med. DevicesBiosensors, Sep. 2006, pp. 1–4.

[16] A. Dittmar, N. Taccini, G. Loriga, and R. Paradiso, “Knitted bioclothesfor health monitoring,” in Proc. Conf. Annu. Int. Conf. IEEE Eng. Med.Biol. Soc., 2003, pp. 2165–2168.

[17] T. Kotani et al., “An analysis of chest wall and diaphragm motions inpatients with idiopathic scoliosis using dynamic breathing MRI,” Spine,vol. 29, no. 3, pp. 298–302, Feb. 2004.

[18] N. Khaltaev, “WHO strategy for prevention and control of chronicobstructive pulmonary disease,” Exp. Lung Res., vol. 31, no. 1,pp. 55–56, Sep. 2005.

[19] L. K. Baxter, Capacitive Sensors: Design and Applications, vol. 1. NewYork, NY, USA: Wiley, 1996.

[20] X. Zhu et al., “Real-time monitoring of respiration rhythm andpulse rate during sleep,” IEEE Trans. Biomed. Eng., vol. 53, no. 12,pp. 2553–2563, Dec. 2006.

[21] C. W. Wang, A. Ahmed, and A. Hunter, “Vision analysis in detectingabnormal breathing activity in application to diagnosis of obstructivesleep apnoea,” in Proc. 28th IEEE Annu. Int. Conf., EMBS, Sep. 2006,pp. 4469–4473.

[22] S. Tachakra, X. Wang, R. S. Istepanian, and Y. Song, “Mobile e-health:The unwired evolution of telemedicine,” Telemed. J. E-Health, vol. 9,no. 3, pp. 247–257, 2003.

Se Dong Min was born in Seoul, Korea, in 1975. He received the M.S. andPh.D. degrees in electrical and electronic engineering from the Department ofElectrical and Electronics Engineering, Yonsei University, Seoul, in 2004 and2010, respectively. He is currently an Assistant Professor with the Departmentof Medical IT Engineering, Soonchunhyang University, Asan, Korea. Hisresearch area includes biomedical signal instrumentation and processing,healthcare sensor application, and mobile healthcare technologies.


Yonghyeon Yun received the B.S. degree in electronic engineering fromthe Seoul National University of Science and Technology, Seoul, Korea, in1998, and the M.S. and Ph.D. degrees in biomedical engineering from YonseiUniversity, Seoul, in 2002 and 2011, respectively. He was a Research Scientistwith the Korea Research Institute of Standards and Science, Deajeon, Korea,from 1999 to 2011. He was a Post-Doctoral Research Fellow with the Divisionof Cardiology, Severance Hospital, Yonsei University Health System, Seoul,from 2011 to 2013. Since 2013, he has been with the faculty of the DaelimUniversity College, as an Assistant Professor of Convergence BiomedicalEngineering. His current interests include medical ultrasound, biomedicalsignal processing and instrumentation, and u-healthcare applications.

Hangsik Shin is an Assistant Professor with Chonnam National University,Yeosu, Korea. He received the M.S. and Ph.D. degrees in electrical andelectronic engineering from the Department of Electrical and Electronics Engi-neering, Yonsei University, Seoul, Korea, in 2005 and 2010, respectively. Hisresearch area includes biomedical signal processing, physiological modelingand computer simulation, u-healthcare and mobile healthcare technologies.

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