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Author:Paalasmaa, Joonas
Title:Respiratory latent variable model for mechanically measured heartbeats
Hengityksen piilomuuttujamalli mekaanisesti mitatuille sydämenlyönneille
Publication type:Master's thesis
Publication year:2010
Pages:(6) + 43      Language:   eng
Department/School:Informaatio- ja luonnontieteiden tiedekunta
Main subject:Informaatiotekniikka   (T-61)
Supervisor:Kaski, Samuel
Instructor:Leen, Gayle
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  5782   | Archive
Keywords:ballistocardiography
respiration
latent variable model
heart rate
heartbeat
ballistokardiografia
hengitys
piilomuuttujamalli
syketaajuus
sydämenlyönti
Abstract (eng): In this thesis, a latent variable model for the respiratory variation of mechanically measured heartbeats is presented.
The effect of respiration on heartbeats in a mechanically measured cardiac signal was noticed already in the first respiratory ballistocardiography studies in the 1920s.
The effect was described as a modulation of the heartbeat amplitude, and that view has persisted.
Although a reasonable approximation, amplitude modulation is not an accurate description of the respiratory effect.
In the model presented here, the respiratory variation is described with a linear latent variable model, where the direction of variation can be distinct from the direction of amplitude.
The model was evaluated with seven ballistocardiograms from three healthy test subjects.

Based on a Bayesian information criterion analysis, it was found to describe the variation accurately in all the cases.
As the modelling of the heartbeat shape is improved, existing heartbeat detection methods can be made more accurate by applying the proposed model.
Abstract (fin): Tässä diplomityössä esitetään lineaarinen piilomuuttujamalli, joka kuvaa hengityksen aiheuttamaa sykemuodon vaihtelua.
Hengityksen vaikutus sydämen mekaanista toimintaa mittaavaan signaaliin huomattiin jo 1920-luvulla ensimmäisissä ballistokardiografisissa tutkimuksissa, jotka keskittyivät hengityksen vaikutuksen mittaamiseen.
Kyseisissä tutkimuksissa todettiin, että hengitys aiheuttaa sykemuodon amplitudin vaihtelua.
Vaikka amplitudin vaihtelu onkin kohtuullinen approksimaatio, se ei kuvaa hengityksen aiheuttamia sykemuodon muutoksia tarkasti.
Esitetty uusi malli kuvaa sykemuodon vaihtelun joustavammin, jolloin myös muutkin kuin amplitudin muutokset ovat mahdollisia.

Piilomuuttujamallin tarkkuutta arvioitiin kolmelta koehenkilöltä mitattujen seitsemän ballistokardiogrammin perusteella.
Malli on Bayesilaiseen informaatiokriteeriin perustuvan arvioinnin perusteella tarkka.
Piilomuuttujamalli parantaa sykemuodon mallinnusta, joten sitä voidaan soveltaa olemassa olevien sykkeentunnistusmenetelmien parantamiseksi.
ED:2010-10-12
INSSI record number: 41044
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