<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0188-9532</journal-id>
<journal-title><![CDATA[Revista mexicana de ingeniería biomédica]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. mex. ing. bioméd]]></abbrev-journal-title>
<issn>0188-9532</issn>
<publisher>
<publisher-name><![CDATA[Sociedad Mexicana de Ingeniería Biomédica]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0188-95322016000200091</article-id>
<article-id pub-id-type="doi">10.17488/rmib.37.2.3</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Respiratory Rate Detection by a Time-Based Measurement System]]></article-title>
<article-title xml:lang="es"><![CDATA[Detección de frecuencia respiratoria mediante un sistema de medida basado en el tiempo]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Sifuentes]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Cota-Ruiz]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[González-Landaeta]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad Autónoma de Ciudad Juárez Departamento de Ingeniería Eléctrica y Computación ]]></institution>
<addr-line><![CDATA[ Chihuahua]]></addr-line>
<country>México</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>08</month>
<year>2016</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>08</month>
<year>2016</year>
</pub-date>
<volume>37</volume>
<numero>2</numero>
<fpage>91</fpage>
<lpage>99</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0188-95322016000200091&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0188-95322016000200091&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0188-95322016000200091&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract: This paper proposes a system that converts a time-modulated signal from a resistive sensor into a digital signal with the goal to estimate the respiratory rate of a subject. To detect breathing, a known method based on a nasal thermistor, which detects temperature changes near the nostrils, is used. In this work, the thermistor mounted in a Wheatstone bridge, forms a RC circuit which is connected directly to a microcontroller, without using any analog circuit or analog-digital converter. Thus, whenever the subject breathes, it causes a fractional change in resistance x (&#8710;R/R 0) on the thermistor, and this produces a time-modulated signal that is directly digitized with the microcontroller. Measurements were made on 23 volunteers, obtaining changes of x &gt; 0.01. The temperature resolution was 0.2 °C, and the time response was 0.8 s, mainly limited by the thermistor properties; these features were enough to obtain a well-defined waveform of the breathing, from which was easy to estimate the respiratory rate by a compact, low cost and low power consumption system. Unlike interface circuits based on voltage or current amplitude, with this kind of interface, the self-heating of the sensor is avoided since the thermistor does not require any voltage or bias current.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Resumen: Este trabajo propone un sistema que convierte una señal modulada en tiempo, proveniente de un sensor resistivo, en una señal digital con el fin de estimar la frecuencia respiratoria de un sujeto. Para detectar la respiración se utilizó el método basado en un termistor nasal, el cual detecta los cambios de temperatura cerca de las fosas nasales. En este trabajo, el termistor, montado en un puente de Wheatstone, forma un circuito RC que se conecta directamente a un microcontrolador, sin necesidad de usar ningún circuito analógico, ni conversor analógico-digital. Así, cada vez que el sujeto respire, provoca un cambio fraccional de resistencia x (&#8710;R/R 0) en el termistor, y esto produce una señal modulada en tiempo que se digitaliza directamente con el microcontrolador. Se hicieron medidas en 23 voluntarios, obteniendo cambios de x &gt; 0.01. Se obtuvo una resolución en temperatura de 0.2 °C y un tiempo de respuesta de 0.8 s, limitado principalmente por las propiedades del termistor utilizado. Estas características demostraron ser suficientes para obtener una forma de onda de la respiración bien definida, de la cual es sencillo estimar la frecuencia respiratoria mediante un sistema compacto, de bajo costo y bajo consumo de energía. A diferencia de los circuitos de interfaz basado en la amplitud de tensión o corriente, con este tipo de interfaz se evita el autocalentamiento del sensor, ya que el termistor no requiere ningún voltaje o corriente de polarización.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[time-based measurements]]></kwd>
<kwd lng="en"><![CDATA[Wheatstone bridge sensors]]></kwd>
<kwd lng="en"><![CDATA[respiratory rate]]></kwd>
<kwd lng="en"><![CDATA[temperature measurement]]></kwd>
<kwd lng="en"><![CDATA[nasal thermistor]]></kwd>
<kwd lng="es"><![CDATA[medidas basadas en el tiempo]]></kwd>
<kwd lng="es"><![CDATA[sensores en puente de Wheatstone]]></kwd>
<kwd lng="es"><![CDATA[frecuencia respiratoria]]></kwd>
<kwd lng="es"><![CDATA[medida de temperatura]]></kwd>
<kwd lng="es"><![CDATA[termistor nasal]]></kwd>
</kwd-group>
</article-meta>
</front><back>
<ref-list>
<ref id="B1">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Estimation of breathing rate from respiratory sinus arrhythmia: comparison of various methods]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Schäfer]]></surname>
<given-names><![CDATA[A.]]></given-names>
</name>
</person-group>
<source><![CDATA[Ann. of Biomed. Eng.]]></source>
<year>2008</year>
<volume>36</volume>
<numero>3</numero>
<issue>3</issue>
<page-range>476-85</page-range></nlm-citation>
</ref>
<ref id="B2">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Multiparameter respiratory rate estimation from the photoplethysmogram]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Karlen]]></surname>
<given-names><![CDATA[W.]]></given-names>
</name>
</person-group>
<source><![CDATA[IEEE Trans. on Biomed. Eng.]]></source>
<year>2013</year>
<volume>60</volume>
<numero>7</numero>
<issue>7</issue>
<page-range>1946- 1953</page-range></nlm-citation>
</ref>
<ref id="B3">
<nlm-citation citation-type="confpro">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Chan]]></surname>
<given-names><![CDATA[A. M.]]></given-names>
</name>
</person-group>
<source><![CDATA[Ambulatory respiratory rate detection using ECG and triaxial accelerometer]]></source>
<year>2013</year>
<conf-name><![CDATA[ 35Conf. of the IEEE Eng. in Med. and Biol. Soc.]]></conf-name>
<conf-date>2013</conf-date>
<conf-loc>Osaka </conf-loc>
<page-range>4058-61</page-range></nlm-citation>
</ref>
<ref id="B4">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Respiration during sleep in children]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Carskadon]]></surname>
<given-names><![CDATA[M. A.]]></given-names>
</name>
</person-group>
<source><![CDATA[Western Journal of Medicine]]></source>
<year>1978</year>
<volume>128</volume>
<page-range>477- 481</page-range></nlm-citation>
</ref>
<ref id="B5">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Standards and indications for cardiopulmonary sleep studies in children]]></article-title>
<collab>American Thoracic Socienty</collab>
<source><![CDATA[Am. J Respir. Crit. Care Med.]]></source>
<year>1996</year>
<volume>153</volume>
<numero>2</numero>
<issue>2</issue>
<page-range>866- 878</page-range></nlm-citation>
</ref>
<ref id="B6">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Reliability of Sleep Strip as a screening test in obstructive sleep apnea patients]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Dinç]]></surname>
<given-names><![CDATA[A. E.]]></given-names>
</name>
</person-group>
<source><![CDATA[Eur. Arch. of Otorhinolaryngol.]]></source>
<year>2014</year>
<volume>271</volume>
<numero>10</numero>
<issue>10</issue>
<page-range>1-6</page-range></nlm-citation>
</ref>
<ref id="B7">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Overnight Polysomnography versus Respiratory Polygraphy in the Diagnosis of Pediatric Obstructive Sleep Apnea]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Tan]]></surname>
<given-names><![CDATA[H. L.]]></given-names>
</name>
</person-group>
<source><![CDATA[Sleep]]></source>
<year>2014</year>
<volume>37</volume>
<numero>2</numero>
<issue>2</issue>
<page-range>255-60</page-range></nlm-citation>
</ref>
<ref id="B8">
<nlm-citation citation-type="book">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Pallàs-Areny]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
<name>
<surname><![CDATA[Webster]]></surname>
<given-names><![CDATA[J. G.]]></given-names>
</name>
</person-group>
<source><![CDATA[Sensors and Signal Conditioning]]></source>
<year>2001</year>
<edition>2</edition>
<page-range>94-109</page-range><publisher-loc><![CDATA[New York ]]></publisher-loc>
<publisher-name><![CDATA[John Wiley & Sons]]></publisher-name>
</nlm-citation>
</ref>
<ref id="B9">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Determination of heart rate using a high-resolution temperature measurement]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Cuadras]]></surname>
<given-names><![CDATA[A.]]></given-names>
</name>
<name>
<surname><![CDATA[Casas]]></surname>
<given-names><![CDATA[O.]]></given-names>
</name>
</person-group>
<source><![CDATA[IEEE Sensors J.]]></source>
<year>2006</year>
<volume>6</volume>
<numero>3</numero>
<issue>3</issue>
<page-range>836-43</page-range></nlm-citation>
</ref>
<ref id="B10">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Direct interface circuit to linearise resistive sensor bridges]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Sifuentes]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
</person-group>
<source><![CDATA[Sensors and Actuators A]]></source>
<year>2008</year>
<volume>147</volume>
<numero>1</numero>
<issue>1</issue>
<page-range>210-5</page-range></nlm-citation>
</ref>
<ref id="B11">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[A simple, efficient interface circuit for piezoresistive pressure sensors]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Jordana]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
<name>
<surname><![CDATA[Pallàs-Areny]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
</person-group>
<source><![CDATA[Sensors and Actuators A]]></source>
<year>2006</year>
<volume>127</volume>
<numero>1</numero>
<issue>1</issue>
<page-range>69-73</page-range></nlm-citation>
</ref>
<ref id="B12">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Wireless magnetic sensor node for vehicle detection with optical wake-up]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Sifuentes]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
</person-group>
<source><![CDATA[IEEE Sensors J.]]></source>
<year>2011</year>
<volume>11</volume>
<numero>8</numero>
<issue>8</issue>
<page-range>1669-76</page-range></nlm-citation>
</ref>
<ref id="B13">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Medical Physics and Biomedical Engineering]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Brown]]></surname>
<given-names><![CDATA[B. H.]]></given-names>
</name>
</person-group>
<source><![CDATA[Institute of Physics]]></source>
<year>2001</year>
<page-range>548-77</page-range><publisher-loc><![CDATA[Madison ]]></publisher-loc>
</nlm-citation>
</ref>
<ref id="B14">
<nlm-citation citation-type="confpro">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Toba]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
</person-group>
<source><![CDATA[Non-Invasive Measurement System for Human Respiratory Condition and Body Temperature]]></source>
<year>1994</year>
<conf-name><![CDATA[ Int. Conf. on MFI]]></conf-name>
<conf-date>1994</conf-date>
<conf-loc>Las Vegas, NV </conf-loc>
<page-range>770-83</page-range></nlm-citation>
</ref>
<ref id="B15">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Heat Transfer Evaluation of the Nasal Thermistor Technique]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Storck]]></surname>
<given-names><![CDATA[K.]]></given-names>
</name>
</person-group>
<source><![CDATA[IEEE Trans. On Biomed. Eng.]]></source>
<year>1996</year>
<volume>43</volume>
<numero>12</numero>
<issue>12</issue>
<page-range>1187-91</page-range></nlm-citation>
</ref>
<ref id="B16">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[Accuracy of thermistors and thermocouples as flow-measuring devices for detecting hypopnoeas]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Farre]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
</person-group>
<source><![CDATA[Eur. Respir. J.]]></source>
<year>1998</year>
<volume>11</volume>
<numero>1</numero>
<issue>1</issue>
<page-range>179-82</page-range></nlm-citation>
</ref>
<ref id="B17">
<nlm-citation citation-type="confpro">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Sifuentes]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
</person-group>
<collab>IEEE</collab>
<source><![CDATA[Improved direct interface circuit for resistive full-and half-bridge sensors]]></source>
<year>2007</year>
<conf-name><![CDATA[ 4Int. Conf. on Electrical and Electronics Engineering]]></conf-name>
<conf-date>2007</conf-date>
<conf-loc> </conf-loc>
<page-range>197-200</page-range><publisher-loc><![CDATA[Mexico ]]></publisher-loc>
</nlm-citation>
</ref>
<ref id="B18">
<nlm-citation citation-type="journal">
<article-title xml:lang=""><![CDATA[The art of directly interfacing sensors to microcontrollers]]></article-title>
<person-group person-group-type="author">
<name>
<surname><![CDATA[Reverter]]></surname>
<given-names><![CDATA[F.]]></given-names>
</name>
</person-group>
<source><![CDATA[Low Power Electronics and Applications J.]]></source>
<year>2012</year>
<volume>2</volume>
<numero>4</numero>
<issue>4</issue>
<page-range>265-81</page-range></nlm-citation>
</ref>
<ref id="B19">
<nlm-citation citation-type="book">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Reverter]]></surname>
<given-names><![CDATA[F.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Direct interface circuits for sensors]]></article-title>
<person-group person-group-type="editor">
<name>
<surname><![CDATA[Nihtianov]]></surname>
<given-names><![CDATA[S.]]></given-names>
</name>
<name>
<surname><![CDATA[Luque]]></surname>
<given-names><![CDATA[A.]]></given-names>
</name>
</person-group>
<source><![CDATA[Smart Sensors and MEMS: Intelligent Devices and Microsystems for Industrial Applications]]></source>
<year>2014</year>
<page-range>27-62</page-range><publisher-name><![CDATA[Woodhead Publishing]]></publisher-name>
</nlm-citation>
</ref>
<ref id="B20">
<nlm-citation citation-type="">
<collab>Measurement Specialties</collab>
<source><![CDATA[LDT1-028K Shielded Piezo Sensors]]></source>
<year>2009</year>
<page-range>1-3</page-range><publisher-loc><![CDATA[Hampton, VA ]]></publisher-loc>
</nlm-citation>
</ref>
</ref-list>
</back>
</article>
