Abstract 203: Supporting the Potential Use of the Thoracic Impedance Signal to Detect Return of Spontaneous Circulation
Background: During resuscitation, checking for a carotid pulse to recognize cardiac arrest or detect the return of spontaneous circulation (ROSC) has been shown to be both inaccurate and time-consuming. More recently, an abrupt sustained increase in end-tidal carbon dioxide (EtCO2) to a normal value (35 to 40 mmHg) has been accepted as an indicator of ROSC. During ROSC the thoracic impedance (TI) signal shows a circulation component (ICC) with small fluctuations with each heartbeat. Mean amplitude of 40.04 mΩ has been reported for the ICC in pulse-generating rhythms, and 6.03 mΩ in pulseless electrical activity.
Aim: To analyze the relationship between EtCO2 and ICC amplitude in order to assess the potential use of the TI for circulation detection during resuscitation.
Methods: A sample of 203 ROSC segments (mean duration 8.9±4.2 s) containing ECG, TI and capnography signals were extracted from 40 cardiac arrest episodes recorded by Tualatin Valley Fire & Rescue (Tigard, Oregon) using the Philips MRx devices. An adaptive scheme based on a least mean square algorithm was used to estimate the ICC from the TI using as reference the instants of the QRS complexes automatically detected in the ECG. The EtCO2 and the mean peak-to-trough amplitude of the ICC were computed per segment and their distributions analyzed. For all the segments, univariate linear regression was used to fit a model to predict the EtCO2 value, C, based on the amplitude of the ICC, A. The linearity was tested with the Pearson correlation coefficient, R.
Results: Mean values were 54±20 mmHg and 53.1±34.1 mΩ for EtCO2 and ICC amplitude respectively. High levels of EtCO2 were clearly associated with high ICC amplitudes, although the linearity between EtCO2 and ICC amplitude was low (R=-0.22).
Conclusion: High levels of EtCO2 are linked to high ICC amplitudes, which supports the potential use of TI signal as ROSC indicator in resuscitation scenarios where capnography is not available.
Author Disclosures: E. Alonso: None. E. Aramendi: Other Research Support; Modest; BexenCardio. U. Ayala: None. D. González-Otero: None. M. Daya: Research Grant; Modest; NIH-NHLBI. Consultant/Advisory Board; Modest; Unpaid consultant with Philips Healthcare. J.K. Russell: Employment; Significant; Philips Healthcare.
- © 2014 by American Heart Association, Inc.