Monitoring of tidal ventilation by electrical impedance tomography in anaesthetised horses

Mosing, Martina; Waldmann, Andreas D.; Raisis, Anthea L.; Böhm, Stephan H.; Drynan, Eleanor A.; Wilson, Keely A T

doi:10.1111/evj.12998

Cited by 23 publications

(44 citation statements)

References 23 publications

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“…This study is in agreement with previous work showing a linear relationship in several species exists between VT EIT and VT Spiro using no PEEP [3,8,10] and indirectly PEEP [11,27,28]. Linearity was stable when breathing amplitude, extremes in lung volume and anthropometric characteristics varied [27,29].…”

Section: Discussionsupporting

confidence: 92%

“…This relationship was persistent over a range of volumes and different lung states produced by increasing PEEP. Commercially available spirometry in sedated, anesthetised or non-compliant subjects requires tubing and equipment in addition to ventilatory equipment [10,15]. Specific circumstances such as; high flow rates or longterm use, CPAP helmets or where subjects can deteriorate quickly even when on oxygen, prevent accurate measurements with spirometry and capnography.…”

Section: Discussionmentioning

confidence: 99%

“…The electrical current flows either side of the electrode plane creating an image area of the lung up to 10 cm in both directions from the electrode plane [5,7]. Impedance change (△Z) has been shown to have a direct relationship with tidal volume (VT) measured via spirometry in healthy people, pigs, small ruminants, dogs and horses with no positive end-tidal expiratory pressures (PEEP) applied [3,[7][8][9][10][11][12][13][14]. This relationship has not been established in cattle and has yet to be challenged with alterations in lung state via the application of PEEP.…”

Section: Introductionmentioning

confidence: 99%

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Effects of PEEP on the relationship between tidal volume and total impedance change measured via electrical impedance tomography (EIT)

Brabant

Crivellari

Hosgood

et al. 2021

J Clin Monit Comput

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Electrical impedance tomography (EIT) is used in lung physiology monitoring. There is evidence that EIT is linearly associated with global tidal volume (VT) in clinically healthy patients where no positive end-expiratory pressure (PEEP) is applied. This linearity has not been challenged by altering lung conditions. The aim of this study was to determine the effect of PEEP on VT estimation, using EIT technology and spirometry, and observe the stability of the relationship under changing lung conditions. Twelve male castrated cattle (Steer), mean age 7.8 months (SD ± 1.7) were premedicated with xylazine followed by anaesthesia induction with ketamine and maintenance with halothane in oxygen via an endotracheal tube. An EIT belt was applied around the thorax at the level of the fifth intercostal space. Volume controlled ventilation was used. PEEP was increased in a stepwise manner from 0 to 5, 10 and 15 cmH 2 O. At each PEEP, the VT was increased stepwise from 5 to 10 and 15 mL kg −1. After a minute of stabilisation, total impedance change (VT EIT), using EIT and VT measured by a spirometer connected to a flow-partitioning device (VT Spiro) was recorded for the following minute before changing ventilator settings. Data was analysed using linear regression and multi variable analysis. There was a linear relationship between VT EIT and VT Spiro at all levels of PEEP with an R 2 of 0.71, 0.68, 0.63 and 0.63 at 0, 5, 10 and 15 cmH 2 O, respectively. The variance in VT EIT was best described by peak inspiratory pressure (PIP) and PEEP (adjusted R 2 0.82) while variance in VT Spiro was best described by PIP and airway deadspace (adjusted R 2 0.76). The relationship between VT EIT and VT Spiro remains linear with changes in tidal volume, and stable across altered lung conditions. This may have application for monitoring and assessment in vivo.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of PEEP on the relationship between tidal volume and total impedance change measured via electrical impedance tomography (EIT)

Brabant

Crivellari

Hosgood

et al. 2021

J Clin Monit Comput

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“…The global impedance changes—representing the volume signal in arbitrary units (AU) —is calculated as the sum of all pixels within the entire EIT image. The tidal volume‐related electrical impedance tomography factor VT EIT is calculated by subtracting the impedance distribution at start of inspiration by the impedance distribution at end of inspiration (Figure B, C) . Global and regional gas flow was calculated as the first derivative of this global and regional impedance change (Figure B, C).…”

Section: Methodsmentioning

confidence: 99%

“…Further details on EIT technology and image reconstruction can be found elsewhere . The total impedance change during inspiration and expiration corresponds with the inspired and expired volume . Peak inspiratory (InF global ) and peak expiratory (ExF global ) global flow can be evaluated by calculating the first derivative of the EIT volume signal .…”

Section: Introductionmentioning

confidence: 99%

Evaluation of histamine‐provoked changes in airflow using electrical impedance tomography in horses

Secombe

Waldmann

Hosgood

et al. 2020

Equine Veterinary Journal

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Background Electrical impedance tomography (EIT) generates thoracic impedance images of the lungs and has been used to assess ventilation in horses. This technique may have application in the detection of changes in airflow associated with equine asthma. Objectives The objective was to determine if histamine‐induced airflow changes observed with flowmetric plethysmography (Δflow) could also be explained using global and regional respiratory gas flow signals calculated from EIT signals. Study design Experimental in vivo study. Methods Six horses, sedated using detomidine were fitted with a thoracic EIT belt and flowmetric plethysmography hardware. Saline (baseline = BL) and increasing concentrations of histamine (C1‐4) were nebulised into the face mask until a change in breathing pattern was clinically confirmed and Δflow increased greater or equal to 50%. After nebulisation Δflow and EIT images were recorded over 3 minutes and peak global inspiratory (InFglobal) and expiratory (ExFglobal) flow as well as peak regional expiratory and inspiratory flow for the dorsal and the ventral area of the right and left lungs were evaluated. Delta flow, InFglobal and ExFglobal at subsequent concentrations were indexed to baseline (yi = Ci/BL−1). Indexed and nonindexed variables were evaluated for a difference from baseline at sequential histamine doses (time). Multiple linear regression assessment of variance in delta flow was also investigated. Results Consistent with histamine‐provoked increases in Δflow, the global flow indices increased significantly. A significant increase in regional inspiratory flow was seen in the right and left ventral lung and dorsal right lung. Multiple regression revealed that the variance in ExFglobal, and right and left ventral expiratory flow best explained the variance in Δflow (r2 = .82). Main limitations Low number of horses and horses were healthy. Conclusions Standardised changes in airflow during histamine challenge could be detected using EIT gas flow variables.

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Performance evaluation of electrode design and material for a large animal electrical impedance tomography belt

et al. 2022

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Background: Electrical impedance tomography (EIT) produces lung ventilation images via a thoracic electrode belt. Robust electrode design and material, providing low electrode skin contact impedance (SCI), is needed in veterinary medicine. The aim of this study was to compare three EIT electrode designs and materials. Methods: Simulations of cylindrical, rectangular and spiked electrode designs were used to evaluate electrode SCI as a function of electrode size, where skin contact was uneven. Gold-plated washers (E GW ), zinc-plated rivets (E ZR ) and zinc-galvanised spikes (E ZS ) were assigned randomly on two interconnected EIT belts. Gel was applied to the cranial or caudal belt and placed on 17 standing cattle. SCI was recorded at baseline and 3, 5, 7, 9 and 11 minutes later. Results: Simulations that involved electrodes with a greater skin contact area had lower and more uniform SCI. In cattle, SCI decreased with all electrodes over time (p < 0.01). Without gel, no difference was found between E GW and E ZS , while SCI was higher for E ZR (p < 0.03). With gel, SCI was lower in E GW and E ZR (p < 0.026), with the SCI in E GW being the lowest (p < 0.01). Limitations: Low numbers of animals and static electrode position may affect SCI. Conclusions: Electrode design is important for EIT measurement, with larger electrode designs able to compensate for the use of less conductive materials. Gel is not necessary to achieve acceptable SCI in large animals.

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Monitoring of tidal ventilation by electrical impedance tomography in anaesthetised horses

Abstract: The EIT can be used to quantify changes in tidal volume.

Cited by 23 publications

References 23 publications

Effects of PEEP on the relationship between tidal volume and total impedance change measured via electrical impedance tomography (EIT)

Effects of PEEP on the relationship between tidal volume and total impedance change measured via electrical impedance tomography (EIT)

Evaluation of histamine‐provoked changes in airflow using electrical impedance tomography in horses

Performance evaluation of electrode design and material for a large animal electrical impedance tomography belt

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