Computational protocol: Unobtrusive Nocturnal Heartbeat Monitoring by a Ballistocardiographic Sensor in Patients with Sleep Disordered Breathing

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Protocol publication

[…] Overnight diagnostic PSG was performed with a digital polygraph of Schwarzer Brainlab (Schwarzer Brainlab, Software Version 4.00, Munich, Germany; Barcelona: Deltamed, Software version 2007 Paris, France). Noninvasive HR measurement was performed during polysomnography with a BCG foil (30 × 60 cm) of EmFit (EmFit Ltd. Vaajakoski, Finland). Electrical safety was approved by the VDE (“VDE Verband der Elektrotechnik, Elektronik, Informationstechnik e.V.”, Frankfurt, Germany) according to EN IEC 60601-1. [...] Distribution of the recorded ECG and BCG heartbeats showed right-sided outliers, leading to skewness to the left and increased kurtosis. In time-series analysis, considerable autocorrelation was present in the data. For such a big sample of auto-correlated measurements with inter-participant heterogeneity, conventional significance tests for normality are not valid. Therefore, we analysed the data predominantly with descriptive methods like histograms, Bland-Altman and scatter plots. Because of the outliers, Spearman rank correlation was preferred to the Pearson coefficient. To avoid outlier effects, in some cases we used the median to represent the central tendency of the recorded data. For qualitative analysis, all values are expressed in percentages and absolute numbers. Statistical analysis was performed with SPSS 24 (IBM Corp. Released 2016. IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY: IBM Corp.). ECG and BCG deflections were analysed and displayed with Signalplant 1.2.2.4 (MEDISIG – F. Plesinger; J. Jurco; 2013–2017; Institute of Scientific Instruments of the CAS; Czech Republic). Although our algorithm needs no training phase, the QI was calculated by comparing at least two consecutive heartbeats. Thus, we applied the algorithm to the complete BCG signal, but considered for statistical analysis only episodes of at least 10 consecutive heartbeats with a QI > 0.1. […]

Pipeline specifications

Software tools EMFit, SPSS
Applications Miscellaneous, cryo-EM