title: Analyzing Seismocardiogram Cycles to Identify the Respiratory Phases.
abstract: the objective of this study was to develop a method to identify respiratory phases (i.e., inhale or exhale) of seismocardiogram (SCG) cycles. An SCG signal is obtained by placing an accelerometer on the sternum to capture cardiac vibrations.
  
  
  
  SCGs from 19 healthy subjects were collected, preprocessed, segmented, and labeled. To extract the most important features, each SCG cycle was divided to equal-sized bins in time and frequency domains, and the average value of each bin was defined as a feature. Support vector machines was employed for feature selection and identification. The features were selected based on the total accuracy. The identification was performed in two scenarios: leave-one-subject-out (LOSO), and subject-specific (SS).
  
  
  
  time-domain features resulted in better performance. The time-domain features that had higher accuracies included the characteristic points correlated with aortic-valve opening, aortic-valve closure, and the length of cardiac cycle. The average total identification accuracies were 88.1% and 95.4% for LOSO and SS scenarios, respectively.
  
  
  
  the proposed method was an efficient, reliable, and accurate approach to identify the respiratory phases of SCG cycles.
  
  
  
  The results obtained from this study can be employed to enhance the extraction of clinically valuable information such as systolic time intervals.
authors.forename: Vahid
authors.initials: V
authors.lastname: Zakeri
authors.forename: Alireza
authors.initials: A
authors.lastname: Akhbardeh
authors.forename: Nasim
authors.initials: N
authors.lastname: Alamdari
authors.forename: Reza
authors.initials: R
authors.lastname: Fazel-Rezai
authors.forename: Mikko
authors.initials: M
authors.lastname: Paukkunen
authors.forename: Kouhyar
authors.initials: K
authors.lastname: Tavakolian
mesh_terms: D061725:Accelerometry / Q000379:methods*; D000328:Adult; D000465:Algorithms; D001450:Ballistocardiography / Q000379:methods*; D003198:Computer Simulation; D006801:Humans; D008297:Male; D008954:Models, Biological; D009991:Oscillometry / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D015656:Respiratory Mechanics / Q000502:physiology*; D012680:Sensitivity and Specificity; D060388:Support Vector Machine