Electrical impedance tomography to measure lung ventilation distribution in healthy horses and horses with left-sided cardiac volume overload

Muriel Sacks; David P Byrne; Nicolas Herteman; Cristy Secombe; Andy Adler; Giselle Hosgood; Anthea L Raisis; Martina Mosing

doi:10.1111/jvim.16227

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. doi: 10.1111/jvim.16227. Epub 2021 Aug 4.

Authors

Muriel Sacks¹, David P Byrne¹, Nicolas Herteman², Cristy Secombe¹, Andy Adler³, Giselle Hosgood¹, Anthea L Raisis¹, Martina Mosing¹

Affiliations

¹ School of Veterinary Medicine, Murdoch University, Perth, Australia.
² Equine Clinic, Department for Equine Medicine, Vetsuisse Faculty, University of Zurich, Zürich, Switzerland.
³ Systems and Computer Engineering, Carleton University, Ottawa, Canada.

Abstract

Background: Left-sided cardiac volume overload (LCVO) can cause fluid accumulation in lung tissue changing the distribution of ventilation, which can be evaluated by electrical impedance tomography (EIT).

Objectives: To describe and compare EIT variables in horses with naturally occurring compensated and decompensated LCVO and compare them to a healthy cohort.

Animals: Fourteen adult horses, including university teaching horses and clinical cases (healthy: 8; LCVO: 4 compensated, 2 decompensated).

Methods: In this prospective cohort study, EIT was used in standing, unsedated horses and analyzed for conventional variables, ventilated right (VAR) and left (VAL) lung area, linear-plane distribution variables (avg-max VΔZ_Line , VΔZ_Line ), global peak flows, inhomogeneity factor, and estimated tidal volume. Horses with decompensated LCVO were assessed before and after administration of furosemide. Variables for healthy and LCVO-affected horses were compared using a Mann-Whitney test or unpaired t-test and observations from compensated and decompensated horses are reported.

Results: Compared to the healthy horses, the LCVO cohort had significantly less VAL (mean difference 3.02; 95% confidence interval .77-5.2; P = .02), more VAR (-1.13; -2.18 to -.08; P = .04), smaller avg-max VΔZL_Line (2.54; 1.07-4.00; P = .003) and VΔZL_Line (median difference 5.40; 1.71-9.09; P = .01). Observation of EIT alterations were reflected by clinical signs in horses with decompensated LCVO and after administration of furosemide.

Conclusions and clinical importance: EIT measurements of ventilation distribution showed less ventilation in the left lung of horses with LCVO and might be useful as an objective assessment of the ventilation effects of cardiogenic pulmonary disease in horses.

Keywords: EIT; center of ventilation; congestive heart failure; furosemide; pulmonary edema; pulmonary hypertension.

MeSH terms

Animals
Cardiac Volume*
Electric Impedance
Horses
Lung* / diagnostic imaging
Prospective Studies
Tomography, X-Ray Computed