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Article: A non-contact Vital Signs Monitor

TitleA non-contact Vital Signs Monitor
Authors
KeywordsReferences (1) View In Table Layout
Issue Date2000
Citation
Critical Reviews in Biomedical Engineering, 2000, v. 28 n. 1-2, p. 173-178 How to Cite?
AbstractThe expansion and contraction of the lungs and heart result in movement of the chest wall that can be detected and monitored to determine respiration and heart rate. A prototype noncontact Vital Signs Monitor (VSM) has been developed which uses very low power, high frequency Doppler radar to detect these motions. Digital signal processing (DSP) techniques, imbedded in the VSM, are used to extract heart and respiration rate information from the resultant waveform. A 10-GHz prototype VSM was developed for the Air Force in the mid-1980s using analog technology. The objective was to assess a fallen soldier's clinical condition at distances up to 100 meters before committing resources to assist that individual. An updated and improved version of the original VSM was developed in 1997. This device was designed to operate at shorter distances, use a higher frequency carrier, and provide more specific heart and respiration rate information using digital signal prdcessing techniques. The VSM radar system is a straightforward homodyne receiver. It operates using frequency modulated continuous wave (FM-CW) transmission, which allows for very low power levels. The safe human power density exposure level at its operating frequency of 35 GHz is 10 mW/cm2. A simple approximation using uniform distribution and an antenna aperture of 2 cm by 3 cm gives a power density at the antenna face of 0.017 mW/cm2, nearly a factor of 1000 below the safe level. When the VSM's antenna is trained on the chest wall of a subject, the VSM is capable of measuring and distinguishing minute movements resulting from the mechanical activity of the heart and lungs. As the subject's chest wall moves, the exact phase of the return signal changes. To avoid the possibility of phase-related dead spots, two signals differing in phase by 90 degrees are used to demodulate the signal to baseband (DC). The two resulting 'time-varying DC' signals represent the sine and cosine of a phase angle corresponding to the changing position of the target, in this case the motion of the chest wall. The current VSM operates at a frequency of 35 GHz with a corresponding wavelength of only 8.6 mm. This provides a response sensitive enough to detect the small motions caused by cardiac function. The Vital Signs Monitor has several possible application areas. The fact that it is noncontacting would make it especially attractive for monitoring patients in burn units, NICUs, or trauma centers, where attaching electrodes is either inconvenient or not feasible. Results to date indicate a strong correlation between the cardiac component of the motion signal and an electrocardiogram (ECG). With careful signal processing and analysis, it may be possible to extract clinically useful information about cardiac condition, function, or performance from the surface-motion waveform. This could provide a safe, inexpensive, and painless addition to the diagnostic and monitoring tools currently available to cardiologists. Although there are technical obstacles to overcome in filtering gross motions of the subject, the VSM offers significant advances over conventional methods of measuring heart and respiration rate. | In the mid-1980s, a 10-GHz prototype Vital Signs Monitor (VSM) was developed using analog technology to assess a fallen soldier's clinical condition at distances up to 100 meters before committing resources to assist that individual. An updated and improved version of the original VSM was developed in 1997. This device was designed to operate at shorter distances, use a higher frequency carrier, and provide more specific heart and respiration rate information using digital signal processing techniques.
Persistent Identifierhttp://hdl.handle.net/10722/90701
ISSN
2001 Impact Factor: 0.292
2015 SCImago Journal Rankings: 0.587
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorMatthews, Gen_HK
dc.contributor.authorSudduth, Ben_HK
dc.contributor.authorBurrow, Men_HK
dc.date.accessioned2010-09-17T10:07:00Z-
dc.date.available2010-09-17T10:07:00Z-
dc.date.issued2000en_HK
dc.identifier.citationCritical Reviews in Biomedical Engineering, 2000, v. 28 n. 1-2, p. 173-178en_HK
dc.identifier.issn0278-940Xen_HK
dc.identifier.urihttp://hdl.handle.net/10722/90701-
dc.description.abstractThe expansion and contraction of the lungs and heart result in movement of the chest wall that can be detected and monitored to determine respiration and heart rate. A prototype noncontact Vital Signs Monitor (VSM) has been developed which uses very low power, high frequency Doppler radar to detect these motions. Digital signal processing (DSP) techniques, imbedded in the VSM, are used to extract heart and respiration rate information from the resultant waveform. A 10-GHz prototype VSM was developed for the Air Force in the mid-1980s using analog technology. The objective was to assess a fallen soldier's clinical condition at distances up to 100 meters before committing resources to assist that individual. An updated and improved version of the original VSM was developed in 1997. This device was designed to operate at shorter distances, use a higher frequency carrier, and provide more specific heart and respiration rate information using digital signal prdcessing techniques. The VSM radar system is a straightforward homodyne receiver. It operates using frequency modulated continuous wave (FM-CW) transmission, which allows for very low power levels. The safe human power density exposure level at its operating frequency of 35 GHz is 10 mW/cm2. A simple approximation using uniform distribution and an antenna aperture of 2 cm by 3 cm gives a power density at the antenna face of 0.017 mW/cm2, nearly a factor of 1000 below the safe level. When the VSM's antenna is trained on the chest wall of a subject, the VSM is capable of measuring and distinguishing minute movements resulting from the mechanical activity of the heart and lungs. As the subject's chest wall moves, the exact phase of the return signal changes. To avoid the possibility of phase-related dead spots, two signals differing in phase by 90 degrees are used to demodulate the signal to baseband (DC). The two resulting 'time-varying DC' signals represent the sine and cosine of a phase angle corresponding to the changing position of the target, in this case the motion of the chest wall. The current VSM operates at a frequency of 35 GHz with a corresponding wavelength of only 8.6 mm. This provides a response sensitive enough to detect the small motions caused by cardiac function. The Vital Signs Monitor has several possible application areas. The fact that it is noncontacting would make it especially attractive for monitoring patients in burn units, NICUs, or trauma centers, where attaching electrodes is either inconvenient or not feasible. Results to date indicate a strong correlation between the cardiac component of the motion signal and an electrocardiogram (ECG). With careful signal processing and analysis, it may be possible to extract clinically useful information about cardiac condition, function, or performance from the surface-motion waveform. This could provide a safe, inexpensive, and painless addition to the diagnostic and monitoring tools currently available to cardiologists. Although there are technical obstacles to overcome in filtering gross motions of the subject, the VSM offers significant advances over conventional methods of measuring heart and respiration rate. | In the mid-1980s, a 10-GHz prototype Vital Signs Monitor (VSM) was developed using analog technology to assess a fallen soldier's clinical condition at distances up to 100 meters before committing resources to assist that individual. An updated and improved version of the original VSM was developed in 1997. This device was designed to operate at shorter distances, use a higher frequency carrier, and provide more specific heart and respiration rate information using digital signal processing techniques.en_HK
dc.languageengen_HK
dc.relation.ispartofCritical Reviews in Biomedical Engineeringen_HK
dc.subjectReferences (1) View In Table Layouten_HK
dc.titleA non-contact Vital Signs Monitoren_HK
dc.typeArticleen_HK
dc.identifier.emailBurrow, MF:mfburr58@hku.hken_HK
dc.identifier.authorityBurrow, MF=rp1306en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.pmid10999382-
dc.identifier.scopuseid_2-s2.0-0033818356en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0033818356&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume28en_HK
dc.identifier.issue1-2en_HK
dc.identifier.spage173en_HK
dc.identifier.epage178en_HK
dc.identifier.isiWOS:000089248200030-

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