Regional distribution of ventilation in horses in dorsal recumbency during spontaneous and mechanical ventilation assessed by electrical impedance tomography: a case series.
Abstract: To evaluate the regional distribution of ventilation in horses during spontaneous breathing and controlled mechanical ventilation (CMV) using electrical impedance tomography (EIT). Methods: Prospective, experimental case series. Methods: Four anaesthetized experimental horses. Methods: Horses were anaesthetized with isoflurane in an oxygen-air mixture and medetomidine continuous rate infusion, placed in dorsal recumbency with an EIT belt around the thorax, and allowed to breathe spontaneously until PaCO reached 13.3 kPa (100 mmHg), when volume CMV was started. For each horse, the EIT signal was recorded for at least 2 minutes immediately before (T1), and at 30 (n = 3) or 60 (n = 1) minutes after the start of CMV (T2). The centre of ventilation (CoV), dependent silent spaces (DSS) (likely to represent atelectatic lung areas), non-dependent silent spaces (NSS) (likely to represent lung areas with low ventilation) and total ventilated area (TVA) were evaluated. Cardiac output (CO) was measured and venous admixture and oxygen delivery (DO) were calculated at T1 and T2. Data are presented as median and range. Results: After the initiation of CMV, the CoV moved ventrally towards the non-dependent lung by 10% [from 57.4% (49.6-60.2%) to 48.3% (41.9-54.4%)]. DSS increased [from 4.1% (0.2-13.9%) to 18.7% (7.5-27.5%)], while NSS [21.7% (9.4-29.2%) to 9.9% (1.0-20.7%)] and TVA [920 (699-1051) to 837 (662-961) pixels] decreased. CO, venous admixture and DO also decreased. Conclusions: In spontaneously breathing anaesthetized horses in dorsal recumbency, ventilation was essentially centred within the dependent dorsal lung regions and moved towards non-dependent ventral regions as soon as CMV was started. This shows a major lack of ventilation in the dependent lung, which may be indicative of atelectasis.
Copyright © 2016 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.
Publication Date: 2017-02-23 PubMed ID: 27483208DOI: 10.1111/vaa.12405Google Scholar: Lookup
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- Journal Article
- Anesthesia
- Case Reports
- Clinical Pathology
- Clinical Study
- Clinical Symptoms
- Diagnosis
- Diagnostic Technique
- Disease Diagnosis
- Disease Treatment
- Equine Diseases
- Equine Health
- Experimental Methods
- Horses
- Imaging Techniques
- In Vivo
- Lung Health
- Physiology
- Respiratory Health
- Veterinary Medicine
- Veterinary Procedure
- Veterinary Research
Summary
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This research studied how the distribution of ventilation in horses changes between natural breathing and controlled mechanical ventilation. The study found that under anesthesia, the center of ventilation shifted, there was increased silent areas in dependent areas, indicative of collapsed lung tissue, and limited ventilation in non-dependent areas.
Research Design and Methodology
- The study was a prospective, experimental examination of four anesthetized horses.
- Anesthesia was administered through a mix of isoflurane and oxygen-air along with a continuous infusion of medetomidine.
- The horses were positioned on their backs and an electrical impedance tomography (EIT) belt was wrapped around their chests for measurements.
- Spontaneous breathing was allowed until the partial pressure of carbon dioxide reached 13.3 kPa, at which point volume controlled mechanical ventilation (CMV) was initiated.
- EIT signals were recorded two minutes prior to, and then at 30 (3 horses) or 60 (1 horse) minutes after the start of CMV.
Assessment Criteria
- The researchers assessed the center of ventilation (CoV), dependent silent spaces (areas likely to represent collapsed lung areas or atelectasis), non-dependent silent spaces (areas with low ventilation), and total ventilated area.
- Also measured were the cardiac output (CO), venous admixture and oxygen delivery (DO).
Study Findings
- The initiation of mechanical ventilation (CMV) resulted in the center of ventilation moving ventrally (towards the belly) by 10%.
- Efficient ventilation areas (DSS) also increased, indicating more areas of collapsed lung tissue.
- In contrast, the areas of low ventilation (NSS) and total ventilated area (TVA), decreased.
- Cardiac output, venous admixture, and oxygen delivery also decreased with the initiation of CMV.
Conclusions
- The study found that in anesthetized horses laying on their backs, the center of ventilation, which is typically in the dorsal lung regions (closer to the back), shifted towards the ventral regions (the belly) as soon as mechanical ventilation started.
- The evident lack of ventilation in the dependent lung areas might be indicative of atelectasis or collapsed lung tissue, a potentially dangerous condition in horses under anesthesia.
Cite This Article
APA
Mosing M, Marly-Voquer C, MacFarlane P, Bardell D, Böhm SH, Bettschart-Wolfensberger R, Waldmann AD.
(2017).
Regional distribution of ventilation in horses in dorsal recumbency during spontaneous and mechanical ventilation assessed by electrical impedance tomography: a case series.
Vet Anaesth Analg, 44(1), 127-132.
https://doi.org/10.1111/vaa.12405 Publication
Researcher Affiliations
- Equine Department, Section of Anaesthesiology, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
- Equine Department, Section of Anaesthesiology, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland. Electronic address: chm062@mail.usask.ca.
- Langford Veterinary Services, University of Bristol, Bristol, UK.
- School of Veterinary Science, Leahurst Campus, University of Liverpool, Neston, UK.
- Swisstom AG, Landquart, Switzerland.
- Equine Department, Section of Anaesthesiology, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
- Swisstom AG, Landquart, Switzerland.
MeSH Terms
- Anesthesia / methods
- Anesthesia / veterinary
- Anesthetics, Inhalation
- Animals
- Electric Impedance
- Horse Diseases / physiopathology
- Horses
- Isoflurane
- Lung / physiology
- Medetomidine
- Patient Positioning / methods
- Patient Positioning / veterinary
- Prospective Studies
- Pulmonary Atelectasis / physiopathology
- Pulmonary Atelectasis / veterinary
- Respiration
- Respiration, Artificial / methods
- Respiration, Artificial / veterinary
- Tomography
Citations
This article has been cited 10 times.- Sacks M, Raidal S, Catanchin CSM, Hosgood G, Mosing M. Impact of sedation, body position change and continuous positive airway pressure on distribution of ventilation in healthy foals.. Front Vet Sci 2022;9:1075791.
- Andrade FSRM, Ambrósio AM, Rodrigues RR, Faccó LL, Gonçalves LA, Garcia Filho SG, Dos Santos RT, Rossetto TC, Pereira MAA, Fantoni DT. The optimal PEEP after alveolar recruitment maneuver assessed by electrical impedance tomography in healthy horses.. Front Vet Sci 2022;9:1024088.
- Brabant OA, Byrne DP, Sacks M, Moreno Martinez F, Raisis AL, Araos JB, Waldmann AD, Schramel JP, Ambrosio A, Hosgood G, Braun C, Auer U, Bleul U, Herteman N, Secombe CJ, Schoster A, Soares J, Beazley S, Meira C, Adler A, Mosing M. Thoracic Electrical Impedance Tomography-The 2022 Veterinary Consensus Statement.. Front Vet Sci 2022;9:946911.
- Moreno-Martinez F, Byrne D, Raisis A, Waldmann AD, Hosgood G, Mosing M. Comparison of Effects of an Endotracheal Tube or Facemask on Breathing Pattern and Distribution of Ventilation in Anesthetized Horses.. Front Vet Sci 2022;9:895268.
- Kozłowska N, Wierzbicka M, Jasiński T, Domino M. Advances in the Diagnosis of Equine Respiratory Diseases: A Review of Novel Imaging and Functional Techniques.. Animals (Basel) 2022 Feb 4;12(3).
- Herteman N, Mosing M, Waldmann AD, Gerber V, Schoster A. Exercise-induced airflow changes in horses with asthma measured by electrical impedance tomography.. J Vet Intern Med 2021 Sep;35(5):2500-2510.
- Sacks M, Byrne DP, Herteman N, Secombe C, Adler A, Hosgood G, Raisis AL, Mosing M. Electrical impedance tomography to measure lung ventilation distribution in healthy horses and horses with left-sided cardiac volume overload.. J Vet Intern Med 2021 Sep;35(5):2511-2523.
- Crivellari B, Raisis A, Hosgood G, Waldmann AD, Murphy D, Mosing M. Use of Electrical Impedance Tomography (EIT) to Estimate Tidal Volume in Anaesthetized Horses Undergoing Elective Surgery.. Animals (Basel) 2021 May 10;11(5).
- Brabant O, Crivellari B, Hosgood G, Raisis A, Waldmann AD, Auer U, Adler A, Smart L, Laurence M, Mosing M. Effects of PEEP on the relationship between tidal volume and total impedance change measured via electrical impedance tomography (EIT).. J Clin Monit Comput 2022 Apr;36(2):325-334.
- Ambrisko TD, Schramel JP, Auer U, Moens YPS. Impact of four different recumbencies on the distribution of ventilation in conscious or anaesthetized spontaneously breathing beagle dogs: An electrical impedance tomography study.. PLoS One 2017;12(9):e0183340.
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