title: Noninvasive myocardial contractility monitoring with seismocardiography during simulated dives.
abstract: OBJECTIVE
  To determine if bradycardia during hyperbaric exposure is accompanied by a negative influence on myocardial contractility.
  
  
  METHODS
  Accelerometer-based registration of myocardial compression waves with Seismocardiography (SCG) for noninvasive contractility monitoring. Comparative pulmonary artery (PA) catheter study (9 ICU-patients, mean = 67ys) with ejection-fraction (EF) equivalent versus sum of g-values of contraction phase in SCG, and Preload (leg-positioning). Test with monitoring of changes in Contractility Index (ContrI) derived from the SCG-power spectrum (contraction phases, area under curve). Hyperbaric chamber study (0.6MPa dive-simulation) in 14 healthy divers. Quantitative SCG-(ContrI, power spectra) and ECG-recording.
  
  
  RESULTS
  Correlation between changes in EF (PA catheter) and in the g-values (SCG) was r(SP) = 0.87 (p < 0.0001). ContrI increased in the leg-positioning test parallel to preload increase, heart rate remained stable. During hyperbaric exposure (0.6MPa) heart rate decrease was highly significant (68 to 58 min(-1); p < 0.001), ContrI and power spectra remained nearly unchanged, SCG registration was noise free.
  
  
  CONCLUSIONS
  Hyperoxic bradycardia during simulated dives is not accompanied by impaired contractility measured with SCG, which is concordant to findings with invasive methods in current literature. SCG is suitable for noninvasive and stress free contractility monitoring and patient surveillance in a hyperbaric chamber.
authors.affiliation: German Naval Medical Institute, Kopperpahler Allee 120, 24119 Kronshagen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Koch
authors.forename: P
authors.initials: P
authors.lastname: McCormack
authors.forename: A
authors.initials: A
authors.lastname: Schwanecke
authors.forename: P
authors.initials: P
authors.lastname: Schnoor
authors.forename: C
authors.initials: C
authors.lastname: Buslaps
authors.forename: K
authors.initials: K
authors.lastname: Tetzlaff
authors.forename: H
authors.initials: H
authors.lastname: Rieckert
mesh_terms: D000328:Adult; D000368:Aged; D001273:Atmosphere Exposure Chambers; D001919:Bradycardia / Q000503:physiopathology*; D006328:Cardiac Catheterization; D004242:Diving / Q000502:physiology*; D006334:Heart Function Tests / Q000379:methods; D006801:Humans; D006931:Hyperbaric Oxygenation / Q000009:adverse effects; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D010865:Pilot Projects