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Elektrische Impedanztomographie zum Lungenmonitoring des Hundes
Elektrische Impedanztomographie zum Lungenmonitoring des Hundes
Electrical impedance tomography (EIT) is a radiation free technique which takes advantage of the different electrical conductivities of different tissues. Its main field of application is lung ventilation monitoring through real time imaging of the lung air content. The aim of the present study was to evaluate the feasibility of collecting EIT information on a sample of dogs with different thoracic shapes under clinical conditions by connecting an electrode belt without fur clipping. The EIT data obtained were compared to CT measurements. In this prospective study, 15 pulmonarily healthy dogs that underwent a CT examination for a different reason (for example orthopedic affection), were anesthetized and ventilated in a pressure-controlled mode at three different positive end-expiratory pressure levels (PEEP of 0 cmH2O, 5 cmH2O and 10 cmH2O) for five breaths each, with a peak inspiratory pressure of 15 cmH2O (PIP 15) in sternal recumbency. The ventilation was recorded with a commercial EIT device applied around the thorax. Subsequently, the ventilation regime was repeated and a computed tomography scan (CT) of the same thoracic segment was performed for each PEEP level. The tidal volume (Vt) was recorded. For the collection of EIT data the sum of regional impedance changes was recorded for the last three breaths of each PEEP level. The impedance value of the entire lung (global) was recorded and the ventilated area was quartered into four regions of interests (ROI). A CT image could be selected with the fewest adjacent organs (heart, liver). Lung tissue was selected to obtain the mean Hounsfield-Units (HU) for the entire lung. As in the EIT analysis, the lungs were divided into four ROIs and the mean of HU for each ROI was recorded. EIT recordings via the electrode belt were possible without clipping. There was a significant correlation for the parameters of aeration as measured by EIT and CT for both the entire ventilated lung and the corresponding ROIs. The increasing PEEP resulted in a proportional increase of the impedance, and there was a negative correlation between EIT and Vt. The better ventilated dorsal ROIs could be identified using both EIT and CT. An intra-assay coefficient of variation showed a good reproducibility for lung ventilation in anesthetized dogs in the EIT. The results show that EIT is a reliable method for evaluating the ventilation of dogs in a clinical setting. Further clinical studies are needed to assess whether EIT can also provide valuable information for evaluating non-sedated dogs, different body positions or dogs with pulmonary pathologies.
Lung function, general anaesthesia, positive end-expiratory pressure
Gloning, Simon
2017
German
Universitätsbibliothek der Ludwig-Maximilians-Universität München
Gloning, Simon (2017): Elektrische Impedanztomographie zum Lungenmonitoring des Hundes. Dissertation, LMU München: Faculty of Veterinary Medicine
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Abstract

Electrical impedance tomography (EIT) is a radiation free technique which takes advantage of the different electrical conductivities of different tissues. Its main field of application is lung ventilation monitoring through real time imaging of the lung air content. The aim of the present study was to evaluate the feasibility of collecting EIT information on a sample of dogs with different thoracic shapes under clinical conditions by connecting an electrode belt without fur clipping. The EIT data obtained were compared to CT measurements. In this prospective study, 15 pulmonarily healthy dogs that underwent a CT examination for a different reason (for example orthopedic affection), were anesthetized and ventilated in a pressure-controlled mode at three different positive end-expiratory pressure levels (PEEP of 0 cmH2O, 5 cmH2O and 10 cmH2O) for five breaths each, with a peak inspiratory pressure of 15 cmH2O (PIP 15) in sternal recumbency. The ventilation was recorded with a commercial EIT device applied around the thorax. Subsequently, the ventilation regime was repeated and a computed tomography scan (CT) of the same thoracic segment was performed for each PEEP level. The tidal volume (Vt) was recorded. For the collection of EIT data the sum of regional impedance changes was recorded for the last three breaths of each PEEP level. The impedance value of the entire lung (global) was recorded and the ventilated area was quartered into four regions of interests (ROI). A CT image could be selected with the fewest adjacent organs (heart, liver). Lung tissue was selected to obtain the mean Hounsfield-Units (HU) for the entire lung. As in the EIT analysis, the lungs were divided into four ROIs and the mean of HU for each ROI was recorded. EIT recordings via the electrode belt were possible without clipping. There was a significant correlation for the parameters of aeration as measured by EIT and CT for both the entire ventilated lung and the corresponding ROIs. The increasing PEEP resulted in a proportional increase of the impedance, and there was a negative correlation between EIT and Vt. The better ventilated dorsal ROIs could be identified using both EIT and CT. An intra-assay coefficient of variation showed a good reproducibility for lung ventilation in anesthetized dogs in the EIT. The results show that EIT is a reliable method for evaluating the ventilation of dogs in a clinical setting. Further clinical studies are needed to assess whether EIT can also provide valuable information for evaluating non-sedated dogs, different body positions or dogs with pulmonary pathologies.