Clinical paperDoes change in thoracic impedance measured via defibrillator electrode pads accurately detect ventilation breaths in children?☆
Introduction
Studies of adults and children experiencing cardiac arrest demonstrate that providers frequently deliver poor quality cardiopulmonary resuscitation (CPR) in both in-hospital and out-of-hospital settings.1, 2, 3, 4, 5, 6 Specifically, over-ventilation during CPR is common and related to poor outcomes from cardiac arrest.7, 8 Published guidelines recommend that rescue ventilations consist of tidal volumes per kilogram bodyweight (Vts) of 7–10 ml/kg for optimal CPR and emphasize the importance of avoiding over-ventilation during CPR.9, 10 While there is evidence to suggest that CPR feedback/prompt devices to guide compressions and ventilations may improve skill acquisition and retention by providers, it is not known if such devices improve actual patient outcomes during CPR.11
Recent improvements in defibrillator and monitor technology make it feasible to provide audiovisual feedback on quality of CPR to providers in both adult and pediatric settings.12, 13, 14, 15 While studies in adults have demonstrated that changes in thoracic impedance (ΔTI) measured by defibrillator electrode pads are accurate in measuring presence and rate of ventilations delivered during CPR,16, 17 it is unknown if this technology is feasible to detect and guide rescue ventilations in children.
In this study, we investigated the relationship between tidal volume (Vt) and changes in thoracic impedance (TI) in children. We hypothesized that impedance would be predictive of tidal volume in a clinically useful way, and in particular, delta-TI could allow accurate detection of tidal volumes less than, equal to, or greater than 7 ml/kg. Thus, as our primary objective, we tested whether delta-TI measured through standard anterior–apical (AA) defibrillator electrode pad placement can accurately detect ventilations of >7 ml/kg in children. We also compared the AA position with the commonly used alternative anterior–posterior (AP) position to detect similar ventilations.
Section snippets
Methods
This prospective observational study was approved by the Institutional Review Board at the Children's Hospital of Philadelphia. Data were collected in compliance with the guidelines of the Health Insurance Portability and Accountability Act to ensure subject confidentiality. Parental/guardian informed consent and, if capable, child assent was obtained from all subjects.
Results
A total of 28 subjects met eligibility criteria and were enrolled in the study. Table 1 displays subject demographics and admission diagnosis. Median age was 4 years (range 6 months to 17 years; IQR 1.7–9). Three subjects were excluded due to irregular and dyssynchronous breathing patterns that resulted in both CO2SMO + and MRx signals that were too noisy to analyze. Simultaneous CO2SMO+ and MRx recordings (see Fig. 1 for an example) were available for 21 subjects in the AA position and for 22
Discussion
Our study is the first to examine the feasibility and accuracy of changes in thoracic impedance (using standard defibrillator electrode pads) to detect ventilations and quantify tidal volumes in the pediatric age group. We also examined the impact of different pad positions (AA vs. AP) to determine if there were differences in estimation of ventilation volumes. In addition to verifying that defibrillator electrode pads could accurately detect guideline recommended ventilations in the 7–10 ml/kg
Conclusions
This study demonstrates that changes in thoracic impedance obtained via defibrillator pads can accurately detect and guide ventilations in stable, mechanically ventilated children, corresponding to rescue ventilations recommended during cardiopulmonary resuscitation. The observed variability in the thoracic impedance coefficient between subjects precludes the use of a single average impedance coefficient to accurately estimate tidal volumes. As lower tidal volume provides less impedance change
Conflict of interest
The authors acknowledge the following potential conflicts of interest. Dana Niles and Vinay Nadkarni receive unrestricted research grant support from the Laerdal Foundation for Acute Care Medicine. Mette Stavland, Joar Eilevstjønn and Jon Nysæther were employed by Laerdal Medical during this work.
Acknowledgments
We wish to thank Stephanie Tuttle MBA, Raymond Matthews RRT, and the staff of the pediatric intensive care unit and perioperative complex at CHOP for their support and contributions to this study. We also thank Robert Berg MD for his support on the manuscript.
References (19)
- et al.
Is CPR quality improving? A retrospective study of out-of-hospital cardiac arrest
Resuscitation
(2007) - et al.
Effect of implementation of new resuscitation guidelines on quality of cardiopulmonary resuscitation and survival
Resuscitation
(2009) - et al.
Quantitative analysis of chest compression interruptions during in-hospital resuscitation of older children and adolescents
Resuscitation
(2009) - et al.
The use of CPR feedback/prompt devices during training and CPR performance: a systematic review
Resuscitation
(2009) - et al.
Leaning is common during in-hospital pediatric CPR, and decreased with automated corrective feedback
Resuscitation
(2009) - et al.
Quality of out-of-hospital cardiopulmonary resuscitation with real time automated feedback: a prospective interventional study
Resuscitation
(2006) - et al.
CPR quality improvement during in-hospital cardiac arrest using a real-time audiovisual feedback system
Resuscitation
(2007) - et al.
Transthoracic impedance used to evaluate performance of cardiopulmonary resuscitation during out of hospital cardiac arrest
Resuscitation
(2008) - et al.
Quality of cardiopulmonary resuscitation during in-hospital cardiac arrest
JAMA
(2005)
Cited by (11)
A novel technique to assess the quality of ventilation during pre-hospital cardiopulmonary resuscitation
2018, ResuscitationCitation Excerpt :A number of clinical and laboratory investigations showed a nearly linear relationship between tidal volume and thoracic bioimpedance [13,14]. In addition, studies also suggest that tidal volumes of about 4 mL/kg or about 300 mL produce a bioimpedance waveform amplitude of about 0.5 Ω across different devices [7,18,19,22,23]. We confirmed a similar relation between a tidal volume of 300 mL measured by a ventilator and 0.5 Ω amplitude in the bioimpedance waveform recorded simultaneously by the LP12, which were the devices used by our EMS agencies at the time of our study (right panel in Fig. 1).
Reliability and accuracy of the thoracic impedance signal for measuring cardiopulmonary resuscitation quality metrics
2015, ResuscitationCitation Excerpt :As a limitation, the volume of the ventilations was not considered in this approach. Although the guidelines recommend ventilations of 7–10 ml/kg of tidal volume, only the use of a flow monitoring system would provide such information.29,32 Our method unifies the detection of both CCs and ventilations in a single temporal method based on different preprocessing and adaptive thresholding, but common feature extraction.
- ☆
“A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2010.07.010”.