Transthoracic Impedance Measured with Defibrillator Pads-New Interpretations of Signal Change Induced by Ventilations

Per Olav Berve; Unai Irusta; Jo Kramer-Johansen; Tore Skålhegg; Håvard Wahl Kongsgård; Cathrine Brunborg; Elisabete Aramendi; Lars Wik

doi:10.3390/jcm8050724

Transthoracic Impedance Measured with Defibrillator Pads-New Interpretations of Signal Change Induced by Ventilations

J Clin Med. 2019 May 22;8(5):724. doi: 10.3390/jcm8050724.

Authors

Per Olav Berve^{1

2}, Unai Irusta³, Jo Kramer-Johansen^{4

5}, Tore Skålhegg^{6

7}, Håvard Wahl Kongsgård⁸, Cathrine Brunborg⁹, Elisabete Aramendi¹⁰, Lars Wik^{11

12}

Affiliations

¹ National Advisory Unit for Prehospital Emergency Medicine (NAKOS), Oslo University Hospital-Ullevål and University of Oslo, P.O. Box 4956 Nydalen, N-0424 Oslo, Norway. poberve@gmail.com.
² Prehospital Clinic, Ambulance Department, Oslo University Hospital-Ullevål, P.O. Box 4956 Nydalen, N-0424 Oslo, Norway. poberve@gmail.com.
³ Communications Engineering Department, University of the Basque Country UPV/EHU, Alameda Urquijo S/N, 48013 Bilbao, Spain. unai.irusta@ehu.eus.
⁴ National Advisory Unit for Prehospital Emergency Medicine (NAKOS), Oslo University Hospital-Ullevål and University of Oslo, P.O. Box 4956 Nydalen, N-0424 Oslo, Norway. jo.kramer-johansen@medisin.uio.no.
⁵ Prehospital Clinic, Ambulance Department, Oslo University Hospital-Ullevål, P.O. Box 4956 Nydalen, N-0424 Oslo, Norway. jo.kramer-johansen@medisin.uio.no.
⁶ Prehospital Clinic, Ambulance Department, Oslo University Hospital-Ullevål, P.O. Box 4956 Nydalen, N-0424 Oslo, Norway. toretang911@hotmail.com.
⁷ Prehospital Clinic, Airambulance Department, Oslo University Hospital-Ullevål, P.O. Box 4956 Nydalen, N-0424 Oslo, Norway. toretang911@hotmail.com.
⁸ National Advisory Unit for Prehospital Emergency Medicine (NAKOS), Oslo University Hospital-Ullevål and University of Oslo, P.O. Box 4956 Nydalen, N-0424 Oslo, Norway. haavard.kongsgaard@gmail.com.
⁹ Oslo Centre for Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital-Ullevål, P.O. Box 4956 Nydalen, N-0424 Oslo, Norway. UXBRUC@ous-hf.no.
¹⁰ Communications Engineering Department, University of the Basque Country UPV/EHU, Alameda Urquijo S/N, 48013 Bilbao, Spain. elisabete.aramendi@ehu.eus.
¹¹ National Advisory Unit for Prehospital Emergency Medicine (NAKOS), Oslo University Hospital-Ullevål and University of Oslo, P.O. Box 4956 Nydalen, N-0424 Oslo, Norway. lars.wik@medisin.uio.no.
¹² Prehospital Clinic, Ambulance Department, Oslo University Hospital-Ullevål, P.O. Box 4956 Nydalen, N-0424 Oslo, Norway. lars.wik@medisin.uio.no.

Abstract

Compressions during the insufflation phase of ventilations may cause severe pulmonary injury during cardiopulmonary resuscitation (CPR). Transthoracic impedance (TTI) could be used to evaluate how chest compressions are aligned with ventilations if the insufflation phase could be identified in the TTI waveform without chest compression artifacts. Therefore, the aim of this study was to determine whether and how the insufflation phase could be precisely identified during TTI. We synchronously measured TTI and airway pressure (Paw) in 21 consenting anaesthetised patients, TTI through the defibrillator pads and Paw by connecting the monitor-defibrillator's pressure-line to the endotracheal tube filter. Volume control mode with seventeen different settings were used (5-10 ventilations/setting): Six volumes (150-800 mL) with 12 min^-1 frequency, four frequencies (10, 12, 22 and 30 min^-1) with 400 mL volume, and seven inspiratory times (0.5-3.5 s ) with 400 mL/10 min^-1 volume/frequency. Median time differences (quartile range) between timing of expiration onset in the Paw-line (Paw_EO) and the TTI peak and TTI maximum downslope were measured. TTI peak and Paw_EO time difference was 579 (432-723) m s for 12 min^-1, independent of volume, with a negative relation to frequency, and it increased linearly with inspiratory time (slope 0.47, R 2 = 0.72). Paw_EO and TTI maximum downslope time difference was between -69 and 84 m s for any ventilation setting (time aligned). It was independent ( R 2 < 0.01) of volume, frequency and inspiratory time, with global median values of -47 (-153-65) m s , -40 (-168-68) m s and 20 (-93-128) m s , for varying volume, frequency and inspiratory time, respectively. The TTI peak is not aligned with the start of exhalation, but the TTI maximum downslope is. This knowledge could help with identifying the ideal ventilation pattern during CPR.

Keywords: cardiopulmonary resuscitation (CPR); peak inspiration pressure; pulmonary barotrauma; pulmonary injury; transthoracic impedance; ventilation; ventilation pattern.

Abstract

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