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Does change in thoracic impedance measured via defibrillator electrode pads accurately detect ventilation breaths in
Kathryn Roberts1, Vijay Srinivasan, Dana E Niles
1Department of Nursing, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.
Insights
Changes in thoracic impedance (ΔTI) can accurately detect adequate rescue ventilations (≥ 7 ml/kg) in children. Both anterior-apical and anterior-posterior defibrillator pad positions showed similar detection rates for effective ventilation volumes.
Area of Science:
- Pediatric critical care medicine
- Biomedical engineering
- Cardiopulmonary resuscitation
Background:
- Current resuscitation guidelines recommend rescue ventilation tidal volumes of 7-10 ml/kg.
- Changes in thoracic impedance (ΔTI) have not been previously studied in children for detecting ventilation adequacy.
Purpose of the Study:
- To evaluate if ΔTI measured using standard anterior-apical (AA) defibrillator pad positions can accurately detect ventilations > 7 ml/kg in children.
- To compare the efficacy of the standard AA position with the alternative anterior-posterior (AP) position for ΔTI measurements.
Main Methods:
- Prospective, observational study involving 28 sedated children (6 months to 17 years) on mechanical ventilation.
- Thoracic impedance (TI) was measured using a Philips MRx defibrillator with standard electrode pads in both AA and AP positions.
- Ventilation volumes were simultaneously measured using a pneumotachometer for comparison.
Main Results:
- For ventilations ≥ 7 ml/kg, detection rates were high and similar for both positions: 95.1% for AA and 95.7% for AP (p=0.38).
- For ventilations < 7 ml/kg, detection rates were lower (80.0% for both positions), indicating potential missed shallow breaths.
- No significant difference in impedance measurements was found between the AA and AP pad positions.
Conclusions:
- Thoracic impedance changes measured via defibrillator pads can reliably detect adequate (≥ 7 ml/kg) ventilation volumes in mechanically ventilated children.
- Both AA and AP pad positions demonstrate similar accuracy, but may miss smaller ventilation volumes (< 7 ml/kg).
- The findings support the use of ΔTI as a tool to guide rescue ventilations during cardiopulmonary resuscitation (CPR) in pediatric patients.
Introduction:
Resuscitation guidelines recommend rescue ventilations consist of tidal volumes 7-10 ml/kg. Changes in thoracic impedance (ΔTI) measured using defibrillator electrode pads to detect and guide rescue ventilations have not been studied in children.
Aim:
We hypothesized that ΔTI measured via standard anterior-apical (AA) position can accurately detect ventilations with volume > 7 ml/kg in children. We also compared standard AA position with alternative anterior-posterior (AP) position.
Methods:
IRB-approved, prospective, observational study of sedated, subjects (6 months to 17 years) on conventional mechanical ventilation. Thoracic impedance (TI) was obtained via Philips MRx defibrillator with standard electrode pads for 5 min each in AA and AP positions. Ventilations were simultaneously measured by pneumotachometer (Novametrix CO(2)SMO Plus).
Results:
Twenty-eight subjects (median 4 years, IQR 1.7-9 years; median 16.3 kg, IQR 10.5-39 kg) were enrolled. Data were available for 21 episodes in AA position and 22 episodes in AP position, with paired AA and AP data available for 18. For ventilations with volume < 7 ml/kg, the defibrillator algorithm detected 80.0% for both AA and AP (p=0.99). For ventilations ≥ 7 ml/kg, detection was 95.1% for AA and 95.7% for AP (p=0.38).
Conclusions:
Changes in thoracic impedance obtained via defibrillator pads can accurately detect ventilations above 7 ml/kg in stable, mechanically ventilated children, corresponding to rescue ventilations recommended during CPR. Both AA and AP pad positions were less sensitive to detect smaller volumes (< 7 ml/kg) than higher volumes (≥ 7 ml/kg), suggesting that shallow ventilations during CPR might be missed. There were no differences in impedance measurements between standard AA pad position and commonly used alternative AP pad position.
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