Regional distribution of ventilation in horses in dorsal recumbency during spontaneous and mechanical ventilation assessed by electrical impedance tomography: a case series

Martina Mosing, Charlotte Marly-Voquer, Paul MacFarlane, David Bardell, Stephan H. Böhm, Regula Bettschart-Wolfensberger, Andreas D. Waldmann

Research output: Contribution to journalArticle (Academic Journal)peer-review

10 Citations (Scopus)

Abstract

Objective

To evaluate the regional distribution of ventilation in horses during spontaneous breathing and controlled mechanical ventilation (CMV) using electrical impedance tomography (EIT).

Study design

Prospective, experimental case series.

Animals

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 PaCO2 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 (DO2) 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 DO2 also decreased.

Conclusions and clinical relevance

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.
Original languageEnglish
Pages (from-to)127-132
Number of pages6
JournalVeterinary Anaesthesia and Analgesia
Volume44
Issue number1
Early online date23 Feb 2017
DOIs
Publication statusPublished - 2017

Keywords

  • anaesthesia
  • controlled mechanical ventilation
  • distribution of ventilation
  • electrical impedance tomography
  • horse
  • lung aeration

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