• 한국방사선학회논문지
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• 제9권7호
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• pp.425-431
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• 2015

응급상황에서 중환자에게 시행되는 인공호흡 과정 중 호흡기류를 측정할 수 있도록 개발된 센서의 계측 정확도를 평가하였다. 호흡기류 센서의 압력-기류 특성식을 산출하였으며, 인공호흡시에 인가되는 호흡기류신호와 유사한 6가지 파형을 표준기류생성시스템으로 생성하여 호흡기류 센서에 가하면서 기류신호를 측정하였다. 이 기류신호로부터 일회호흡용적과 최대기류값을 산출하였으며, 이를 표준기류생성시스템에 부착되어 있고 물리적으로 오차가 없는 선형변위센서로부터 측정한 용적신호에서 산출한 표준값과 비교하였다. 일회호흡용적의 상대오차는 3% 이내이었으며, 최대기류값은 약 5% 정도로서 충분히 정확한 기류 계측이 가능함을 확인하였다. 따라서 실제 응급상황에서 호흡기류 센서로 적용하여 응급 중환자의 호흡신호와 호흡주기별 진단변수들을 실시간으로 모니터링 할 수 있는 시스템에 활용 가능할 것으로 사료된다.

• 전기학회논문지
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• 제62권6호
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• pp.833-839
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• 2013

Cardiopulmonary resuscitation (CPR) is performed by thoracic compression and artificial ventilation for the patient under emergent situation to maintain at least the minimum level of respiration and blood circulation for life survival. Good quality CPR requires monitoring respiration, however, traditional respiratory air flow transducers cannot be used because the transducer elements are facing the whole area perpendicular to the flow axis. The present study developed a new air flow transducer conveniently applicable to CPR. Specially designed "sensing rod" samples the air velocity at 3 different locations of the flow cross-section, then transforms into average dynamic pressure by the Bernoulli's law. The symmetric structure of the sensing holes of the sensing rod enables bi-directional measurement simply by taking the difference in pressure by a commercial differential pressure transducer. Both inspiratory and expiratory flows were obtained with symmetric measurement characteristics. Quadratic curve fitting provided excellent calibration formula with a correlation coefficient>0.999 (P<0.0001) and the mean relative error<1%. The present results can be usefully applied to accurately monitor the air flow rate during CPR.

• 대한의용생체공학회:의공학회지
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• 제30권5호
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• pp.393-400
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• 2009

The present study developed a new technique with no physical object on the flow stream but enabling the air flow measurement and easily incorporated with the devices for cardiopulmonary resuscitation(CPR) procedure. A turbulence chamber was formed in the middle of the respiratory tube by locally enlarging the cross-sectional area where the flow related turbulence was generated inducing energy loss which was in turn converted into pressure difference. The turbulence chamber was simply an empty enlarged air space, thus no physical object existed on the flow stream, but still the flow rate could be evaluated. Computer simulation demonstrated stable turbulence formation big enough to measure. Experiment was followed on the proto-type transducer, the results of which were within ${\pm}5%$ error compared to the simulation data. Both inspiratory and expiratory flows were obtained with symmetric measurement characteristics. Quadratic curve fitting provided excellent calibration formula with a correlation coefficient>0.999(P<0.0001) and the mean relative error<1%. The present results can be usefully applied to accurately monitor the air flow rate during CPR.

• 센서학회지
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• 제18권4호
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• pp.294-300
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• 2009

Cardiopulmonary resuscitation(CPR) is performed by artificial ventilation and thoracic compression for the patient under emergent situation to maintain at least the minimum level of respiration and blood circulation for life survival. Quality of the pre-hospital CPR not only significantly affects the patient's survival rate but also minimizes side effects caused by CPR. Good quality CPR requires monitoring respiration, however, traditional respiratory air flow transducers cannot be used because the transducer elements are located on the flow axis. The present study developed a new technique with no physical object on the flow stream but enabling the air flow measurement and easily incorporated with the CPR devices. A turbulence chamber was formed in the middle of the respiratory tube by locally enlarging the cross-sectional area where the flow related turbulence was generated inducing energy loss which was in turn converted into pressure difference. The turbulence chamber was simply an empty enlarged air space, thus no physical object was placed on the flow stream, but still the flow rate could be evaluated. Both inspiratory and expiratory flows were obtained with symmetric measurement characteristics. Quadratic curve fitting provided excellent calibration formula with a correlation coefficient>0.999 (P<0.0001) and the mean relative error<1 %. The present results can be usefully applied to accurately monitor the air flow rate during CPR.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1971-1972
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• 2008

Cardiopulmonary resuscitation(CPR) is an important clinical technique performing artificial ventilation and chest compression on a patient under emergent situation before arriving in hospital. Since the quality of CPR significantly affects the survival rate, it would be of great advantage to monitor respiration in real time during CPR. However, currently applied respiratory air flow transducers are difficult to apply with sensing elements in the middle of the flow axis. The present study developed a new turbulent air flow transducer conveniently applicable to CPR. Abrupt changes in diameter of the flow tube generated turbulence in air flow, thereby pressure difference was obtained to estimate the air flow rate, with no physical object on the flow plane. Expiration and inspiration were separated by the direction of the pressure difference, resulting in good symmetry. Pressure-flow relationship was tested on a quadratic model, which provided accurate enough estimation results. Therefore, the present turbulent air flow transducer seemed appropriate to monitor respiration during CPR.

• 대한의용생체공학회:의공학회지
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• 제36권4호
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• pp.115-122
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• 2015

A standard air flow generator system was developed to generate air flows of various levels simultaneously applied to two different air flow transducer modules. Axes of two identical standard syringes for spirometer calibration were connected with each other and driven by a servo-motor. Linear displacement transducer was also connected to the syringe axis to accurately acquire the volume change signal. The user can select either sinusoidal or square waveform of volume change and manually input any volume as well as maximal flow rate levels ranging 0~3 l and 0~15 l/s, respectively. Various volume and flow levels were input to operate the system, then the volume signal was acquired followed by numerical differentiation to obtain the air flow signal. The measured volumes and maximal air flow rates were compared with the user input data. The relative errors between the user-input and the measured stroke volumes were all within 0.5%, demonstrating very accurate driving of the system. In case of the maximal flow rate, relatively large error was observed when the syringe was driven very fast within a very short time duration. However, except for these few data, most measured flow rates revealed relative errors of approximately 2%. When the measure and user-input stroke volume and maximal flow rate data were analyzed by linear regression analysis, respectively, the correlation coefficients were satisfactorily higher than 0.99 (p < 0.0001). These results demonstrate that the servo-motor controls the syringes with enough accuracy to generate standard air flows. Therefore, the present system would be very much practical for calibration process as well as performance evaluation and comparison of two different air flow transducer modules.

• 전기학회논문지
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• 제61권9호
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• pp.1350-1357
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• 2012

Medical system for personal health management recently changes its paradigm from hospital service to self home care based on ubiquitous technology for healthcare anywhere at any time. The present study developed a wireless bio-signal measurement system for patients to self manage pulmonary disease and benign prostate hyperplasia(BPH), both of which are chronic diseases with increasing frequency in modern society. Velocity-type respiratory air flow transducer adapted to develop respiratory module for pulmonary disease management was simplified in structure to measure uni-directional flow since most important diagnostic parameters are evaluated on the expiratory flow signal only. Standard weight measurement technique was introduced to obtain urinary flow signal for BPH management. Three load cell signals were acquired for averaging to minimize noise, followed by accuracy evaluation. Transmission and receiver modules were also developed with user program for wireless communication. Averaged relative errors were 2.05 and 1.02% for respiratory volume and maximal flow rate, respectively, and the relative error was 2.17% for urinary volume, demonstrating that both modules enabled very accurate measurements. Wireless communication distance was verified within 15m, long enough for home care application. The present system allows the user to select a necessary measurement module on a particular health demand and to immediately provide the self-test results, thus better quality health care would be possible.

• 한국산학기술학회논문지
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• 제10권5호
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• pp.1082-1090
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• 2009

노력성 폐활량(FVC) 검사시 호식기류의 최대값인 최고호기유량(PEF)은 호흡기능의 평가에 매우 중요하게 활용되는 진단 매개변수이다. PEF는 검사 초기에 매우 짧은 순간에 크게 증가하는 양상을 띠기 때문에 호흡기류센서의 동특성이 충분하지 않은 경우 측정오차가 발생한다. 본 연구에서는 노력성 호식기류 상의 초기 상승속도($S_r$)를 산출하고 $S_r$ 값에 기초하여 센서 출력값을 보정하는 새로운 기법을 제안하였다. 미국 흥부학회(ATS)에서 제공하는 표준 기류신호 파형 26개를 생성하여(F) 속도계측형 호흡기류센서로 통과시키며 센서 출력신호(N)를 축적하였다. F의 최대값인 PEF와 N의 최대값인 $N_{PEF}$, 간에는 당초 예상했던 대로 2차함수 관계가 성립하였으나(상관계수 0.9997), ATS파형 #2 및 26은 상당한 이탈을 보였다(상대오차>10%). $N_{PEF}$의 상대오차와 $S_r$간의 관계를 분석하여 상호 선형적인 관계를 얻었으므로, 이를 이용하여 보정한 결과 PEF 상대오차의 99% 신뢰구간이 약 2.5% 이었다. 이는 국제표준인 ATS의 오차한계인 10%의 1/4 이내로써 매우 정확한 보정이 이루어졌다. 따라서 본 연구에서 제안하는 보정기법은 호흡기류센서 교정시 매우 유용하리라 판단된다.

• 센서학회지
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• 제16권1호
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• pp.24-32
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• 2007

Conductive rubber material was molded in a belt shape to measure respiration. Its resistivity was approximately $0.03{\;}{\Omega}m$ and the resistance-displacement relationship showed a negative exponent. The temperature coefficient was approximately $0.006{\;}k{\Omega}/^{\circ}C$ negligible when practically applied on the abdomen. The conductive rubber belt was applied on a normal male's abdomen with the dimensional change measured during resting breathing. The abdominal signal was differentiated ($F_{m}$) and compared with the accurate standard air flow rate signal ($F_{s}$) obtained by pneumotachometry. $F_{m}$ and $F_{s}$ differed in waveform, but the start and end timings of each breaths were clearly synchronized, demonstrating that the respiratory frequency could be accurately estimated before further processing of $F_{m}$. $F_{m}-F_{s}$ loop showed a nonlinear hysteresis within each breath period, thus 6 piecewise linear approximation was performed, leading to a mean relative error of 14 %. This error level was relatively large for clinical application, though customized calibration seemed feasible for monitoring general variation of ventilation. The present technique would be of convenient and practical application as a new wearable respiratory transducer.

• 센서학회지
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• 제17권2호
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• pp.133-142
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• 2008

Respiration is induced by muscular contraction of the chest and abdomen, resulting in the abdominal volume change. Thus, continuous measurement of the abdominal dimension enables to monitor breathing activity. Conductive rubber cord has been previously introduced and tested to develop wearable application for respiratory measurements. The present study implemented wireless wearable respiratory monitoring system with the conductive rubber cord in the patient's pants. Signal extraction circuitry was developed to obtain the abdominal circumference changes reflecting the lung volume variation caused by respiratory activity. Wireless transmission was followed based on the zigbee communication protocol in a size of 65mm${\times}$105mm easily put in pocket. Successful wireless monitoring of respiration was performed in that breathing frequency was accurately estimated as well as different breathing patterns were easily recognized from the abdominal signal. $CO_2$ inhalation experiment was additionally performed in purpose of quantitative estimation of tidal volume. Air mixed with $0{\sim}5%\;CO_2$was inhaled by 4 normal males and the respiratory air flow rate, abdominal dimension change, and end tidal $CO_2$ concentration were simultaneously measured in steady state. $CO_2$ inhalation increased the tidal volume in normal physiological state with a correlation coefficient of 0.90 between the tidal volume and the end tidal $CO_2$ concentration. The tidal volume estimated from the abdominal signal linearly correlated with the accurate tidal volume measured by pneumotachometer with a correlation coefficient of 0.88 with mean relative error of approximately 8%. Therefore, the tidal volume was accurately estimated by measuring the abdominal dimension change.