Thoracic Electrical Impedance Tomography—The 2022 Veterinary Consensus Statement

Electrical impedance tomography (EIT) is a non-invasive real-time non-ionising imaging modality that has many applications. Since the first recorded use in 1978, the technology has become more widely used especially in human adult and neonatal critical care monitoring. Recently, there has been an increase in research on thoracic EIT in veterinary medicine. Real-time imaging of the thorax allows evaluation of ventilation distribution in anesthetised and conscious animals. As the technology becomes recognised in the veterinary community there is a need to standardize approaches to data collection, analysis, interpretation and nomenclature, ensuring comparison and repeatability between researchers and studies. A group of nineteen veterinarians and two biomedical engineers experienced in veterinary EIT were consulted and contributed to the preparation of this statement. The aim of this consensus is to provide an introduction to this imaging modality, to highlight clinical relevance and to include recommendations on how to effectively use thoracic EIT in veterinary species. Based on this, the consensus statement aims to address the need for a streamlined approach to veterinary thoracic EIT and includes: an introduction to the use of EIT in veterinary species, the technical background to creation of the functional images, a consensus from all contributing authors on the practical application and use of the technology, descriptions and interpretation of current available variables including appropriate statistical analysis, nomenclature recommended for consistency and future developments in thoracic EIT. The information provided in this consensus statement may benefit researchers and clinicians working within the field of veterinary thoracic EIT. We endeavor to inform future users of the benefits of this imaging modality and provide opportunities to further explore applications of this technology with regards to perfusion imaging and pathology diagnosis

Confluencias del río Maullín: modos de vida locales y conservación de la biodiversidad

The Maullín River is part of one of the main hydrographic basins in the Los Lagos region. From its origin in Lake Llanquihue to its mouth in the Pacific Ocean, this watercourse supports different riverside communities. Based on an ethnographic research, this article analyzes the different practices and ways of life historically deployed along the river, unraveling the relationships between humans and non-humans that are interwoven in its evolution. Likewise, the environmental problems that threaten its integrity and the different collective actions of defense and protection that lead to the creation of the Maullín River Wetlands Nature Sanctuary are identified. El río Maullín forma parte de una de las principales cuencas hidrográficas de la región de Los Lagos. Desde su origen en el lago Llanquihue hasta su desembocadura en el océano Pacífico, este curso de agua sostiene a distintas comunidades ribereñas. A partir de una investigación etnográfica, el presente artículo analiza las diferentes prácticas y modos de vida desplegadas históricamente a lo largo del río, desentrañando las relaciones entre humanos y no humanos que se entretejen en su devenir. Asimismo, se identifican los problemas ambientales que amenazan su integridad y las distintas acciones colectivas de defensa y protección que desembocan en la creación del Santuario de la Naturaleza Humedales del río Maullín.

Effects of continuous positive airway pressure administered by a helmet in cats under general anaesthesia

Objectives: The aim of this study was to evaluate the respiratory effects of non-invasive continuous positive airway pressure (CPAP) administered by a helmet in healthy cats under anaesthesia. Methods: Fifteen healthy male cats scheduled for castration were anaesthetised with medetomidine (20 µg/kg), ketamine (10 mg/kg) and buprenorphine (20 µg/kg) intramuscularly. When an adequate level of anaesthesia was achieved, a paediatric helmet was placed on all subjects. The helmet was connected to a Venturi valve supplied with medical air and cats received the following phases of treatments: 0 cmH2O (pre-CPAP), 5 cmH2O (CPAP) and 0 cmH2O (post-CPAP). Each treatment lasted 10 mins. At the end of each phase an arterial blood sample was drawn. The following data were also collected: mean arterial pressure, respiratory rate, heart rate and the anaesthesia level score (0 = awake, 10 = deep anaesthesia). The alveolar to arterial oxygen gradient (P[A-a]O2) and the venous admixture (Fshunt) were also estimated. Data were analysed with two-way ANOVA (P <0.05). Results: The arterial partial pressure of oxygen was higher (P <0.001) at CPAP (103.2 ± 5.1 mmHg) vs pre-CPAP (77.5 ± 7.4 mmHg) and post-CPAP (84.6 ± 8.1 mmHg). The P(A-a)O2 and the Fshunt were lower (P <0.001) at CPAP (4.4 ± 2.3 mmHg; 7.4 ± 3.1%) vs pre-CPAP (18.9 ± 6.4 mmHg; 22.8 ± 4.6%) and post-CPAP (15.6 ± 7.3 mmHg; 20.9 ± 4.6 %). No other parameters differed between groups. Conclusions and relevance: Non-invasive CPAP applied by a helmet improves oxygenation in cats under injectable general anaesthesia

Effects of two alveolar recruitment maneuvers in an "open-lung" approach during laparoscopy in dogs

ObjectivesThe aim of this study was to compare the effects of a sustained inflation alveolar recruiting maneuver (ARM) followed by 5 cmH(2)O of PEEP and a stepwise ARM, in dogs undergoing laparoscopic surgery. Materials and methodsTwenty adult dogs were enrolled in this prospective randomized clinical study. Dogs were premedicated with methadone intramuscularly (IM); anesthesia was induced with propofol intravenously (IV) and maintained with inhaled isoflurane in pure oxygen. The baseline ventilatory setting (BVS) was as follows: tidal volume of 15 mL/kg, inspiratory pause of 25%, inspiratory to expiratory ratio of 1:2, and the respiratory rate to maintain the end-tidal carbon dioxide between 45 and 55 mmHg. 10 min after pneumoperitoneum, randomly, 10 dogs underwent sustained inflation ARM followed by 5 cmH(2)O of PEEP (ARMi), while 10 dogs underwent a stepwise recruitment maneuver followed by the setting of the "best PEEP" (ARMc). Gas exchange, respiratory system mechanics, and hemodynamic were evaluated before the pneumoperitoneum induction (BASE), 10 min after the pneumoperitoneum (PP), 10 min after the recruitment (ARM), and 10 min after the pneumoperitoneum resolution (PostPP). Statistical analysis was performed with the ANOVA test (p < 0.05). ResultsStatic compliance decreased in both groups at PP (ARMc = 1.35 +/- 0.21; ARMi = 1.16 +/- 0.26 mL/cmH(2)O/kg) compared to BASE (ARMc = 1.78 +/- 0.60; ARMi = 1.66 +/- 0.66 mL/cmH(2)O/kg) and at ARM (ARMc = 1.71 +/- 0.41; ARMi = 1.44 +/- 0.84 mL/cmH(2)O/kg) and PostPP (ARMc = 1.75 +/- 0.45; ARMi = 1.89 +/- 0.59 mL/cmH(2)O/kg), and it was higher compared to PP and similar to BASE. The PaO2/FiO(2), in both groups, was higher at ARM (ARMc = 455.11 +/- 85.90; ARMi = 505.40 +/- 31.70) and PostPP (ARMc = 521.30 +/- 66.20; ARMi = 450.90 +/- 70.60) compared to PP (ARMc = 369.53 +/- 49.31; ARMi = 394.32 +/- 37.72)

Definition and clinical evaluation of a recruiting airway pressure based on the specific lung elastance in anesthetized dogs

Objective: To determine the specific lung elastance (SEL) in anesthetized dogs and to evaluate the efficacy of a SEL-based recruiting airway pressure (RPaw) at improving global and regional lung aeration. Study design: Retrospective and prospective clinical study. Animals: A total of 28 adult dogs were included in the retrospective study and six adult dogs in the prospective study. Methods: Retrospective study: SEL and SEL-based RPaw were determined using previously published data. In mechanically ventilated dogs undergoing thoracic computed tomography (CT), SEL was calculated as ΔPL/(VT/EELV), where ΔPL is the driving transpulmonary pressure, VT is the tidal volume and EELV is the end-expiratory lung volume. The ratio of lung to respiratory system elastance (EL/Ers) was determined. SEL and EL/Ers were used to calculate the SEL-based RPaw. Prospective study: dogs underwent thoracic CT at end-expiration and at end-inspiration using the SEL-based RPaw, and global and regional aeration was determined. For analysis of regional aeration, lungs were divided into cranial, intermediate and caudal regions. Regional compliance was also calculated. A p value <0.05 was considered significant. Results: The SEL and EL/Ers were 12.7 ± 3.1 cmH2O and 0.54 ± 0.07, respectively. The SEL-based RPaw was 29.1 ± 7.6 cmH2O. In the prospective study, the RPaw was 28.2 ± 1.3 cmH2O. During RPaw, hyperinflation increased (p = 0.0003) whereas poorly aerated (p < 0.0001) and nonaerated (p = 0.01) tissue decreased. Normally aerated tissue did not change (p = 0.265). Regional compliance was higher in the intermediate (p = 0.0003) and caudal (p = 0.034) regions compared with the cranial region. Aeration did not differ between regions (p > 0.05). Conclusions and clinical relevance: An SEL-based RPaw reduces poorly and nonaerated lung tissue in anesthetized dogs. In nonsurgical anesthetized dogs, an RPaw near 30 cmH2O is effective at improving lung aeration

Preliminary evaluation of the effects of a 1:1 inspiratory-to-expiratory ratio in anesthetized and ventilated horses

Objective: To describe some cardiorespiratory effects of an inspiratory-to-expiratory (IE) ratio of 1:1 compared with 1:3 in ventilated horses in dorsal recumbency. Study design: Randomized crossover experimental study. Animals: A total of eight anesthetized horses, with 444 (330–485) kg body weight [median (range)]. Methods: Horses were ventilated in dorsal recumbency with a tidal volume of 15 mL kg–1 and a respiratory rate of 8 breaths minute–1, and IE ratios of 1:1 (IE1:1) and 1:3 (IE1:3) in random order, each for 25 minutes after applying a recruitment maneuver. Spirometry, arterial blood gases and dobutamine requirements were recorded in all horses during each treatment. Electrical impedance tomography (EIT) data were recorded in four horses and used to generate functional EIT variables including regional ventilation delay index (RVD), a measure of speed of lung inflation, and end-expiratory lung impedance (EELI), an indicator of functional residual capacity (FRC). Results were assessed with linear and generalized linear mixed models. Results: Compared with treatment IE1:3, horses ventilated with treatment IE1:1 had higher mean airway pressures and respiratory system compliance (p < 0.014), while peak, end-inspiratory and driving airway pressures were lower (p < 0.001). No differences in arterial oxygenation or dobutamine requirements were observed. PaCO2 was lower in treatment IE1:1 (p = 0.039). Treatment IE1:1 resulted in lower RVD (p < 0.002) and higher EELI (p = 0.023) than treatment IE1:3. Conclusions and clinical relevance: These results suggest that IE1:1 improved respiratory system mechanics and alveolar ventilation compared with IE1:3, whereas oxygenation and dobutamine requirements were unchanged, although differences were small. In the four horses where EIT was evaluated, IE1:1 led to a faster inflation rate of the lung, possibly the result of increased FRC. The clinical relevance of these findings needs to be further investigated.Fil: Pittman, Ella. Cornell University. College of Veterinary Medicine. Department of Clinical Sciences; Estados UnidosFil: Martin-Flores, Manuel. Cornell University. College of Veterinary Medicine. Department of Clinical Sciences; Estados UnidosFil: Mosing, Martina. Murdoch University. School of Veterinary Medicine; AustraliaFil: Lorenzutti, Matias. Universidad Católica de Córdoba. Facultad de Ciencias Veterinarias. Pharmacology and Toxicology; ArgentinaFil: Retamal, Jaime. Pontificia Universidad Católica de Chile. Facultad de Medicina. Departamento de Medicina Intensiva; ChileFil: Staffieri, Francesco. “Aldo Moro” University of Bari. Department of Emergency and Organ Transplantation D.E.O.T. Section of Veterinary Clinics and Animal Production; ItaliaFil: Adler, Andy. Carleton University. Systems and Computer Engineering; CanadaFil: Campbell, Mark. Systems and Computer Engineering; CanadaFil: Araos, Joaquin. Cornell University. College of Veterinary Medicine. Department of Clinical Sciences; Estados Unido