Regional ventilation distribution and dead space in anaesthetized horses treated with and without continuous positive airway pressure: novel insights by electrical impedance tomography and volumetric capnography

Objective: The aim of this study was to evaluate the effect of continuous positive airway pressure (CPAP) on regional distribution of ventilation and dead space in anaesthetized horses. Study design: Randomized, experimental, crossover study. Animals: A total of eight healthy adult horses. Methods: Horses were anaesthetized twice with isoflurane in 50% oxygen and medetomidine as continuous infusion in dorsal recumbency, and administered in random order either CPAP (8 cmH2O) or NO CPAP for 3 hours. Electrical impedance tomography (and volumetric capnography (VCap) measurements were performed every 30 minutes. Lung regions with little ventilation [dependent silent spaces (DSSs) and nondependent silent spaces (NSSs)], centre of ventilation (CoV) and dead space variables, as well as venous admixture were calculated. Statistical analysis was performed using multivariate analysis of variance and Pearson correlation. Results: Data from six horses were statistically analysed. In CPAP, the CoV shifted to dependent parts of the lungs (p < 0.001) and DSSs were significantly smaller (p < 0.001), while no difference was seen in NSSs. Venous admixture was significantly correlated with DSS with the treatment time taken as covariate (p < 0.0001; r = 0.65). No differences were found for any VCap parameters. Conclusions and clinical relevance: In dorsally recumbent anaesthetized horses, CPAP of 8 cmH2O results in redistribution of ventilation towards the dependent lung regions, thereby improving ventilation-perfusion matching. This improvement was not associated with an increase in dead space indicative for a lack in distension of the airways or impairment of alveolar perfusion

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

Monitoring changes in distribution of pulmonary ventilation by functional electrical impedance tomography in anaesthetized ponies

Objective To assess changes in the distribution in pulmonary ventilation in anaesthetized ponies using Electrical Impedance Tomography (EIT). Study design Prospective experimental study Animals Eight adult ponies geldings Methods General anaesthesia was induced and maintained using isoflurane in oxygen with volume-controlled ventilation [tidal volume (10 mL kg-1), respiratory rate (8 – 12 breaths minute-1)] to maintain end-tidal carbon dioxide between 35 and 40 mmHg (4.66–5.32 kPa). Regional distribution of ventilation was assessed with EIT (plane of 5th to 6th intercostal space) at 30, 60 and 90 minutes after intubation. The resulting functional images were divided into four regions of interest (ROI, A - D) to determine 1) the ratio of tidal volume distribution between dependent to non-dependent lung (D/ND), 2) changes in distribution within the lungs in latero-lateral direction. The centre of ventilation (COV) was calculated. The dimension of the chest in latero-lateral (W) and dorso-ventral (H) direction was measured at the height of the withers and the W/H ratio was calculated. The influence of time on D/ND ratio, COV and ROI A – D were analysed with ANOVA followed by post-hoc Bonferroni tests. Pearson correlation coefficient and the coefficient of determination (r2) were calculated to evaluate the relationship between W/H ratio and D/ND ratio, and COV. Statistical significance was set at p < 0.05. Results The median D/ND ratio (T30 to T90) was 0.67 (0.40 -1.01) and for COV 31.15% (11.20-45.20), confirming the expected uneven distribution of ventilation. The D/ND ratio had a moderate negative correlation with the W/H ratio (r = -0.68, r2 = 0.46, p = 0.000), while the COV did not correlate with the W/H ratio (r = -0.04). Conclusion and clinical relevance: Uneven ventilation in mechanically ventilated right laterally recumbent anaesthetised ponies occurs within thirty minutes and changed little over the following 60 minutes

Lessons to learn from EORTC study 08981: A feasibility study of induction chemoradiotherapy followed by surgical resection for stage IIIB non-small cell lung cancer

The present EORTC phase II feasibility study in stage IIIB (T4-N3) NSCLC was conducted to investigate whether an induction regimen with concurrent chemoradiotherapy followed by surgery after restaging by re-mediastinoscopy and/or fluorodeoxyglucose-positron emisson tomography (FDG-PET) was feasible in a multicenter setting. Unfortunately, the study closed prematurely because of poor accrual. The combination of more stringent selection criteria, the incorrect prevailing view of Ethical Boards that a tri-modality approach is too toxic, competing studies in the participating centers and the fact that patients with N3 disease could only be enrolled if a re-mediastinoscopy could be performed, underlie the low accrual. Although this study illustrates that the conduct of a tri-modality study across Europe appeared to be difficult at that time, the number of centers with highly qualified and experienced specialists involved in this kind of multi-modality approaches is rapidly increasing. Future initiatives should, therefore, certainly be encouraged. Minimally invasive procedures such as EUS and EBUS should preferably be used for up-front mediastinal staging, mediastinoscopy with or without EUS should preferably be reserved for restaging, and especially right-sided pneumonectomies should be avoided. Though evident, the feasibility to complete this kind of studies within a reasonable time period is still a condition sine qua non

Quality assurance of thoracic radiotherapy in EORTC 08941: a randomised trial of surgery versus thoracic radiotherapy in patients with stage IIIA non-small-cell lung cancer (NSCLC) after response to induction chemotherapy.

Contains fulltext : 50144.pdf (publisher's version ) (Closed access)The aim of this study was to investigate the improvement of quality of radiotherapy and compliance to the protocol amendment of EORTC study 08941. The radiotherapy-specific data were analysed from 154 patients with stage IIIA-N2 Non-Small-Cell Lung Cancer who were actually irradiated after response to 3 cycles of platinum-based induction chemotherapy. The parameters of quality, assessed in 93 patients before and in 61 after protocol amendment, included: time interval between last chemotherapy course and start of thoracic radiotherapy, the use of a 3-D planning CT, dose and fractionation scheme to the primary tumour, the involved and uninvolved mediastinum, duration of radiotherapy and toxicity. A significant improvement of all quality parameters was noted, except for the overall treatment time, which decreased slightly. Protocol amendment resulted in an improvement of the quality and the compliance of most observed parameters, at the cost of some increase in overall treatment time. The latter reflects logistical problems rather than poor compliance