Ventilation distribution assessed with electrical impedance tomography and the influence of tidal volume, recruitment and positive end-expiratory pressure in isoflurane-anesthetized dogs

Aline M Ambrosio; Tatiana P A Carvalho-Kamakura; Keila K Ida; Barbara Varela; Felipe S R M Andrade; Lara L Facó; Denise T Fantoni

doi:10.1016/j.vaa.2016.06.003

Ventilation distribution assessed with electrical impedance tomography and the influence of tidal volume, recruitment and positive end-expiratory pressure in isoflurane-anesthetized dogs

Vet Anaesth Analg. 2017 Mar;44(2):254-263. doi: 10.1016/j.vaa.2016.06.003. Epub 2017 Jan 11.

Authors

Aline M Ambrosio¹, Tatiana P A Carvalho-Kamakura², Keila K Ida³, Barbara Varela², Felipe S R M Andrade², Lara L Facó², Denise T Fantoni¹

Affiliations

¹ Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil; Laboratory of Medical Investigation 8, Posgraduate Program in Anesthesiology, Medical School, University of São Paulo, São Paulo, Brazil.
² Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.
³ Laboratory of Medical Investigation 8, Posgraduate Program in Anesthesiology, Medical School, University of São Paulo, São Paulo, Brazil. Electronic address: keila.ida@ulg.ac.be.

PMID: 28457827
DOI: 10.1016/j.vaa.2016.06.003

Abstract

Objective: To examine the intrapulmonary gas distribution of low and high tidal volumes (V_T) and to investigate whether this is altered by an alveolar recruitment maneuver (ARM) and 5 cmH₂O positive end-expiratory pressure (PEEP) during anesthesia.

Study design: Prospective randomized clinical study.

Animals: Fourteen client-owned bitches weighing 26 ± 7 kg undergoing elective ovariohysterectomy.

Methods: Isoflurane-anesthetized dogs in dorsal recumbency were ventilated with 0 cmH₂O PEEP and pressure-controlled ventilation by adjusting the peak inspiratory pressure (PIP) to achieve a low (7 mL kg^-1; n = 7) or a high (12 mL kg^-1; n = 7) V_T. Ninety minutes after induction (T90), an ARM (PIP 20 cmH₂O for 10 seconds, twice with a 10 second interval) was performed followed by the application of 5 cmH₂O PEEP for 35 minutes (RM35). The vertical (ventral=0%; dorsal=100%) and horizontal (right=0%; left=100%) center of ventilation (CoV), four regions of interest (ROI) (ventral, central-ventral, central-dorsal, dorsal) identified in electrical impedance tomography images, and cardiopulmonary data were analyzed using two-way repeated measures anova.

Results: The low V_T was centered in more ventral (nondependent) areas compared with high V_T at T90 (CoV: 38.8 ± 2.5% versus 44.6 ± 7.2%; p = 0.0325). The ARM and PEEP shifted the CoV towards dorsal (dependent) areas only during high V_T (50.5 ± 7.9% versus 41.1 ± 2.8% during low V_T, p = 0.0108), which was more distributed to the central-dorsal ROI compared with low V_T (p = 0.0046). The horizontal CoV was centrally distributed and cardiovascular variables remained unchanged throughout regardless of the V_T, ARM, and PEEP.

Conclusions and clinical relevance: Both low and high V_T were poorly distributed to dorsal dependent regions, where ventilation was improved following the current ARM and PEEP only during high V_T. Studies on the role of high V_T on pulmonary complications are required.

Keywords: pressure-controlled ventilation; pulmonary atelectasis; pulmonary gas exchange; respiratory mechanics.

Publication types

Randomized Controlled Trial

MeSH terms

Anesthetics, Inhalation*
Animals
Dogs
Electric Impedance*
Female
Isoflurane*
Positive-Pressure Respiration / methods
Positive-Pressure Respiration / veterinary*
Prospective Studies
Tidal Volume / physiology
Time Factors
Tomography / methods
Tomography / veterinary

Substances

Anesthetics, Inhalation
Isoflurane