Assessment of the patterns of lung deflation after bronchoscopic insertion of endobronchial one-way valves using electrical impedance tomography in pigs

• Grant number: 14/17747-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): December 01, 2014
• Effective date (End): November 30, 2015
• Field of knowledge: Health Sciences - Medicine - Surgery
• Principal Investigator: Paulo Francisco Guerreiro Cardoso
• Grantee: Christopher Kengo Nagao
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Emphysema is characterized by a progressive destruction of the lung parenchyma with consequent loss of elastic recoil and dynamic hyperinflation, ultimately resulting in dyspnea and limited exercise capacity. Endoscopic treatment by means of endobronchial one-way valves has been proposed as a way to promote volume reduction. Such devices are capable of producing lung deflation enabling diaphragmatic remodelling, improvement both in lung function and exercise capacity as well as in quality of life. Insofar, the best clinical results with such devices are related to the presence of poor collateral ventilation, high heterogeneity between the affected lobes and in the presence of lobar atelectasis following the procedure.Despite the experience accumulated with the EBV-Zephyrone way valves for emphysema (Pulmonx, Redwood City-CA, EUA), there are pending issues regarding patient selection, criteria for functional response to therapy, the best methods for pre and post-procedural assessment, as well as predictive fators for a successful outcome. To date there have been no methods capable of providing accurate and reliable data on lung deflation during the procedure. This issue is particularly important for determining the correct anatomical location for valve placement, for early detection of pneumothorax and for the confirmation of the findings provided by the measurement of collateral ventilation. The possibility of a bedside, non-invasive, radiation-free imaging method that can be used both during and after the procedure may render the procedure safer and more effective. Electrical impedance tomography (TIE) has emerged as a method able to fulfill all such requirements and therefore it can be potentially applicable in the evaluation of such patients. To the best of our knowledge, there are no studies specifically aimed for the use of TIE in the assessment of lung deflation. It is therefore necessary to establish an animal model to assess the patterns of lung deflation and to pave the ground for future clinical application of TIE for the assessment of patients submitted to endoscopic lung volume reduction for emphysema. Swine are notorious for having poor collateral ventilation between lung lobes which turns it into the ideal model for both the detection the measurement the of lung deflation. Preliminary unpublished data from our laboratory provided the proof of principle that TIE is able to detect lung deflation accurately, reliably and in a timely fashion. This study was designed to test the TIE as a method for the assessment lung deflation following lobar occlusion with one-way valves in pigs under mechanical positive pressure ventilation. The issues targeted are: (1) the correlation between the measurement of lung deflation obtained by means of the selective lobar occlusion with a baloon-catheter with a built-in flow-pressure transducer and the concomitant measurement of deflation provided by the TIE; (2) the detection and quantitative assesssment of lung deflation caused by selective lobar occlusion with one-way endobronchial valves as measured by the TIE; (3) whether lung deflation as detected by TIE can be altered by different inspired oxygen fractions. (AU)