Regional distribution of ventilation in horses in dorsal recumbency during spontaneous and mechanical ventilation assessed by electrical impedance tomography: a case series |
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| Institution: | 1. Institute of Electronics and Informatics Engineering of Aveiro (IEETA), Departamento de Electrónica, Telecomunicações e Informática, Universidade de Aveiro, Aveiro, Portugal;2. Esthesys Ltd, London, UK;3. Hospital Veterinário do Porto (HVP), Porto, Portugal;4. Research Center for Biosciences & Health Technologies, Universidade Lusófona de Humanidade e Tecnologia, Lisboa, Portugal;5. Rede de quimica e tecnologia (REQUIMTE), Faculdade de farmácia da universidade do porto (FFUP), Porto, Portugal;6. Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAD), Veterinary Sciences Department, University of Trás-os-Montes and Alto Douro (UTAD), Quinta de Prados, 5001-801 Vila Real, Portugal;7. Institute of Molecular and Cell Biology (IBMC), Porto, Rua do Campo Alegre, n° 823, 4150-180 Porto, Portugal;8. Departamento de Ciências e Tecnologia, Universidade Aberta, Delegação do Porto, Portugal;9. Centro de Investigação Clínica em Anestesiologia, Serviço de Anestesiologia, Centro Hospitalar do Porto, Portugal |
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| Abstract: | ObjectiveTo evaluate the regional distribution of ventilation in horses during spontaneous breathing and controlled mechanical ventilation (CMV) using electrical impedance tomography (EIT).Study designProspective, experimental case series.AnimalsFour anaesthetized experimental horses.MethodsHorses 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.ResultsAfter 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 relevanceIn 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. |
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| Keywords: | anaesthesia controlled mechanical ventilation distribution of ventilation electrical impedance tomography horse lung aeration |
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