Measurement of ventilation and cardiac related impedance changes with electrical impedance tomography

Grant, Caroline A, Pham, Trang, Hough, Judith, Riedel, Thomas, Stocker, Christian and Schibler, Andreas (2011) Measurement of ventilation and cardiac related impedance changes with electrical impedance tomography. Critical Care, 15 1: 1-9. doi:10.1186/cc9985

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Author Grant, Caroline A
Pham, Trang
Hough, Judith
Riedel, Thomas
Stocker, Christian
Schibler, Andreas
Title Measurement of ventilation and cardiac related impedance changes with electrical impedance tomography
Journal name Critical Care   Check publisher's open access policy
ISSN 1466-609X
Publication date 2011-01-25
Sub-type Article (original research)
DOI 10.1186/cc9985
Open Access Status DOI
Volume 15
Issue 1
Start page 1
End page 9
Total pages 9
Place of publication London, England, U.K.
Publisher BioMed Central Ltd.
Collection year 2012
Language eng
Formatted abstract
Introduction
Electrical impedance tomography (EIT) has been shown to be able to distinguish both ventilation and perfusion. With adequate filtering the regional distributions of both ventilation and perfusion and their relationships could be analysed. Several methods of separation have been suggested previously, including breath holding, electrocardiograph (ECG) gating and frequency filtering. Many of these methods require interventions inappropriate in a clinical setting. This study therefore aims to extend a previously reported frequency filtering technique to a spontaneously breathing cohort and assess the regional distributions of ventilation and perfusion and their relationship.

Methods
Ten healthy adults were measured during a breath hold and while spontaneously breathing in supine, prone, left and right lateral positions. EIT data were analysed with and without filtering at the respiratory and heart rate. Profiles of ventilation, perfusion and ventilation/perfusion related impedance change were generated and regions of ventilation and pulmonary perfusion were identified and compared.

Results
Analysis of the filtration technique demonstrated its ability to separate the ventilation and cardiac related impedance signals without negative impact. It was, therefore, deemed suitable for use in this spontaneously breathing cohort.

Regional distributions of ventilation, perfusion and the combined ΔZV/ΔZQ were calculated along the gravity axis and anatomically in each position. Along the gravity axis, gravity dependence was seen only in the lateral positions in ventilation distribution, with the dependent lung being better ventilated regardless of position. This gravity dependence was not seen in perfusion.

When looking anatomically, differences were only apparent in the lateral positions. The lateral position ventilation distributions showed a difference in the left lung, with the right lung maintaining a similar distribution in both lateral positions. This is likely caused by more pronounced anatomical changes in the left lung when changing positions.

Conclusions
The modified filtration technique was demonstrated to be effective in separating the ventilation and perfusion signals in spontaneously breathing subjects. Gravity dependence was seen only in ventilation distribution in the left lung in lateral positions, suggesting gravity based shifts in anatomical structures. Gravity dependence was not seen in any perfusion distributions.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2012 Collection
School of Medicine Publications
 
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Created: Fri, 25 Nov 2011, 13:30:44 EST by Matthew Lamb on behalf of School of Medicine