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Measurements of Respiratory Carbon Dioxide
Mälardalen University, Department of Computer Science and Electronics.ORCID iD: 0000-0001-8704-402X
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [sv]

Koldioxid är en central parameter för metabolismen i alla levande varelser. Hos människan regleras koldioxidhalten främst genom andningen. Därför är det viktigt att kunna mäta och övervaka koldioxidhalten i fysiologiska applikationer så väl inom sportmedicin som inom vården, till exempel på intensivvårdsavdelningar. Dessa mätningar kräver adekvat mätutrustning.

Syftet med denna avhandling är att kritiskt granska föreslagna metoder för övervakning av andningsaktiviteten, att föreslå och utveckla förbättringar, samt att föreslå och utveckla nya applikationer för mätning av koldioxidhalten i utandningsluften med hjälp av en elektroakustisk sensor.

Mätning av koldioxid i utandningsluften har den fördelen över andra föreslagna metoder för andningsövervakning att den även ger information om förhållandet i arteriellt blod då partialtrycket för koldioxid i slutet av ett andetag är lika stort som i artärblod hos lungfriska personer.

Den föreslagna tekniken bygger på en elektroakustisk sensor som kan registrera och mäta koldioxidhalten i utandningsluften om fukt- och temperaturvariationer utjämnas med hjälp av filter. Den elektroakustiska sensorn består av en ultraljudssändare och en reflektor placerade i varsin ände av ett perforerat rör. Den elektriska impedansen i sensorn representerar molekylvikten inne i sensorkaviteten. Molekylmassan har ett linjärt förhållande till koldioxidhalten så länge övriga gaser hålls konstanta.

Det faktum att partialtrycket av koldioxid i slutet av ett andetag kan mätas med den elektroakustiska sensorn gör den användbar i flera kliniska situationer om andra gaser inte kan påverka mätningarna.

Partialtrycket av koldioxid i slutet av ett andetag har visat sig vara användbar som en indikator för mjölksyratröskeln då personens individuella mjölksyratröskel infaller då partialtrycket av koldioxid i slutet av ett andetag börjar minska. Det ger en ny applikation inom sportmedicin. På det sättet är det möjligt för en idrottare att mäta variationerna i sin mjölksyratröskel, i sin egen sport på daglig basis, vilket kan användas för att optimera arbetsintensiteten under träning och tävling. Trots att det elektroakustiska sensorsystemet inte är selektivt för koldioxid och därför påverkas även av förändringar i syre i utandningsluften har det visat sig fungera i denna applikation.

Place, publisher, year, edition, pages
2005. , 52 p.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 15
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Elektronik
Identifiers
URN: urn:nbn:se:mdh:diva-49ISBN: 91-88834-69-7 (print)OAI: oai:DiVA.org:mdh-49DiVA: diva2:121032
Public defence
2005-09-09, Västerås, 15:00
Opponent
Supervisors
Available from: 2005-11-15 Created: 2005-11-15 Last updated: 2013-12-03
List of papers
1. Critical review of non-invasive respiratory monitoring in medical care
Open this publication in new window or tab >>Critical review of non-invasive respiratory monitoring in medical care
2003 (English)In: Medical & Biological Engineering & Computing, Vol. 41, no 4, 377-383 p.Article in journal (Refereed) Published
Abstract [en]

Respiratory failure can be difficult to predict. It can develop into a life-threatening condition in just a few minutes, or it can build up more slowly. Thus continuous monitoring of respiratory activity should be mandatory in clinical, high-risk situations, and appropriate monitoring equipment could be life-saving. The review considers non-invasive methods and devices claimed to provide information about respiratory rate or depth, or gas exchange. Methods are categorised into those responding to movement, volume and tissue composition detection; air flow, and blood gas concentration. The merits and limitations of the methods and devices are analysed, considering information. content and their ability to minimise the rate of false alarms and false non-alarms. It is concluded that the field of non-invasive respiratory monitoring is still in an exploratory phase, with numerous reports on specific device solutions but less work on evaluation and adaptation to clinical requirements. Convincing evidence of the clinical usefulness of respiratory monitors is still lacking. Devices responding only to respiratory rate, and lacking information about actual gas exchange, will have limited clinical value. Furthermore, enhancement in specificity and sensitivity to avoid false alarms and non-alarms will be necessary to meet clinical requirements. Miniature CO2 sensors are identified as one route towards substantial improvement.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-4155 (URN)10.1007/BF02348078 (DOI)000184231800001 ()
Available from: 2005-11-15 Created: 2005-11-15 Last updated: 2013-12-03Bibliographically approved
2. Comparative Provocation Test of Respiratory Monitoring Methods
Open this publication in new window or tab >>Comparative Provocation Test of Respiratory Monitoring Methods
2002 (English)In: Journal of Clinical Monitoring and Computing, ISSN 1387-1307, Vol. 17, no 2, 97-103 p.Article in journal (Refereed) Published
Abstract [en]

Objective. The aim of this study was to compare clinically relevant performance of: 1) a prototype respiratory sensor based on capnometry with two alternative signal receptor fixations, 2) a fiberoptic humidity sensor and 3) human visual observation. Comparative provocation tests were performed on volunteers at the Post-Anesthesia Care Unit at Västerås Central Hospital. Methods. The experimental tests involved 10 healthy, voluntary test subjects, instructed to intersperse normal breathing with protocol provocations of breath holding, limb and head movements, and nasal oxygen supplement. The signal outputs from the three respiratory monitoring methods were recorded on a personal computer. The signal analysis included visual categorising of the signals and counting breath events. Recognising that none of the methods could act as reference, events were classified as "unanimous," "majority" or "minority" events depending on how many of the three methods that detected a breath. Results. The average total recording time was 37 minutes per subject. The respiratory rates varied from 6.5 to 19 breaths per minute, with a mean value of 11.4 breaths/minute. The breath hold duration ranged from 18 to 50 seconds. Discrepancies between the three methods were found in more than 20% of the marked events. The most frequent majority events were due to events not recorded by the observer who, on the other hand, contributed the least to minority events. The provocations made by the subjects during the measurement did not increase the rates of majority and minority events, compared to periods of no provocation. The fiberoptic device exhibited a large count of minority events but a smaller contribution to majority events than the capnometry prototype. Conclusions. The capnometry and fiberoptic sensors exhibit differences in responses that may be understood from basic principles. The importance of the physical application of the sensor to the patient was clearly observed. The optimum design remains to be found.

National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:mdh:diva-4156 (URN)10.1023/A:1016309913890 (DOI)2-s2.0-0035995224 (Scopus ID)
Available from: 2005-11-15 Created: 2005-11-15 Last updated: 2016-01-15Bibliographically approved
3. Gas sensor with electroacoustically coupled resonator
Open this publication in new window or tab >>Gas sensor with electroacoustically coupled resonator
2001 (English)In: Sensors and Actuators, ISSN 0925-4005, Vol. 78, 161-165 p.Article in journal (Refereed) Published
Abstract [en]

A new configuration for a gas sensor is demonstrated. The configuration consists of an electroacoustic element coupled to an acoustic resonator, such as Kundt's tube, exhibiting a resonance frequency that is related to the velocity of sound, which, in turn is a function of the molecular mass of the gas within the resonator. Electrical impedance measurements were performed, whereby a resonance peak attributable to the resonator was identified. Contributing effects to the quality factor, Q, of the resonance, was analyzed. Predictable shifts of the resonance frequency were observed when adding CO2 and He to air, and when varying the resonator length. Linearity within the experimental accuracy was confirmed. The new sensor configuration offers the potential advantages of smaller size, improved dynamic response, and lower cost. © 2001 Elsevier Science B.V. All rights reserved.

National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:mdh:diva-4157 (URN)10.1016/S0925-4005(01)00807-3 (DOI)000171071200025 ()2-s2.0-0035975052 (Scopus ID)
Available from: 2005-11-15 Created: 2005-11-15 Last updated: 2016-01-15Bibliographically approved
4. End tidal carbon dioxide measurement using an electro acoustic sensor
Open this publication in new window or tab >>End tidal carbon dioxide measurement using an electro acoustic sensor
2004 (English)In: Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings, 2004, 3452-3455 p.Conference paper, Published paper (Other academic)
Abstract [en]

End tidal carbon dioxide measurement with an electro-acoustic sensor is demonstrated. The sensor consists of an acoustic resonator coupled to a low cost electro-acoustic element. By simultaneous measurements with a reference sensor, the new device was tested on subjects performing exercise, hypo- and hyperventilation whereby the CO2 concentration ranged from 2.1 to 7.0 kPa. The output from the experimental device correlated well with the reference CO2 readings with a correlation coefficient of 0.976. Response time for expiration less than 0.8 seconds was noted. The new device could be useful in situations where selectivity to other gases is not important.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:mdh:diva-4158 (URN)10.1109/IEMBS.2004.1403969 (DOI)2-s2.0-11144263761 (Scopus ID)0-7803-8439-3 (ISBN)
Conference
26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC 2004; San Francisco, CA; United States; 1 September 2004 through 5 September 2004
Available from: 2005-11-15 Created: 2005-11-15 Last updated: 2015-07-27Bibliographically approved
5. Estimate the Individual Anaerobic Threshold by measuring End-tidal carbon dioxide
Open this publication in new window or tab >>Estimate the Individual Anaerobic Threshold by measuring End-tidal carbon dioxide
(English)In: Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:mdh:diva-4159 (URN)
Available from: 2005-11-15 Created: 2005-11-15 Last updated: 2015-08-17
6. A pilot study to estimate the lactate threshold using an electro acoustic sensor
Open this publication in new window or tab >>A pilot study to estimate the lactate threshold using an electro acoustic sensor
2005 (English)Conference paper, Published paper (Other academic)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:mdh:diva-4160 (URN)
Conference
FMBE, NBC'05 UMEÅ 13th Nordic-Baltic Conference on Biomedical Engineering & Medical Physics, p 249-250, Swedish Society for Medical Engineering and Medical Physics, Umeå, Sweden
Available from: 2005-11-15 Created: 2005-11-15 Last updated: 2014-10-07Bibliographically approved

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