An in vivo image acquisition system for the evaluation of tracheal mechanics in rats.

Mechanical evaluation of tracheal grafts is of great relevance for transplant research. Although there are some publications demonstrating different techniques of tracheal mechanical evaluation, there is still no definitive or preferred protocol available. Here, we present a simple image processing acquisition system that can be used for in vivo experiments. Six male Wistar rats were submitted to orotracheal intubation and a longitudinal incision was made to expose the trachea. Images of tracheae were acquired from a video camera in different scenarios of bronchoconstriction using methacholine (MCh) (Basal, PBS, MCh 30 µg/kg, MCh 300 µg/kg, and postmetabolized) during imposed-inspiration and imposed-expiration. The area variation ratio (the ratio between areas during expiration vs. inspiration) was 1.1× for the Basal group, while the ratio for MCh 300 µg/kg was 6.5×. The area variation of imaged tracheae was statistically significant at the dose of MCh 300 µg/kg for imposed-inspiration versus imposed-expiration (P = .002). Likewise, elastance data of respiratory mechanics indicated a statistically significant difference at the dose of MCh 300 µg/kg for imposed-inspiration versus imposed-expiration (P = .026). Our image processing analysis protocol presented corresponding behavior when compared to mechanical parameters of the respiratory system. In addition, our image acquisition system was able to highlight the differences between imposed-inspiration and imposed-expiration. Image analysis of the tracheal area variation seems to be in agreement with the elastance of the respiratory system. Taken together, these observations may help future studies of tracheal transplantation for in situ assessment of graft patency.

Assessment of the mechanics of a tissue-engineered rat trachea in an image-processing environment.

OBJECTIVES: Despite the recent success regarding the transplantation of tissue-engineered airways, the mechanical properties of these grafts are not well understood. Mechanical assessment of a tissue-engineered airway graft before implantation may be used in the future as a predictor of function. The aim of this preliminary work was to develop a noninvasive image-processing environment for the assessment of airway mechanics. METHOD: Decellularized, recellularized and normal tracheas (groups DECEL, RECEL, and CONTROL, respectively) immersed in Krebs-Henseleit solution were ventilated by a small-animal ventilator connected to a Fleisch pneumotachograph and two pressure transducers (differential and gauge). A camera connected to a stereomicroscope captured images of the pulsation of the trachea before instillation of saline solution and after instillation of Krebs-Henseleit solution, followed by instillation with Krebs-Henseleit with methacholine 0.1 M (protocols A, K and KMCh, respectively). The data were post-processed with computer software and statistical comparisons between groups and protocols were performed. RESULTS: There were statistically significant variations in the image measurements of the medial region of the trachea between the groups (two-way analysis of variance [ANOVA], p<0.01) and of the proximal region between the groups and protocols (two-way ANOVA, p<0.01). CONCLUSIONS: The technique developed in this study is an innovative method for performing a mechanical assessment of engineered tracheal grafts that will enable evaluation of the viscoelastic properties of neo-tracheas prior to transplantation.

Efeitos da estimulação diafragmática transcutânea sincronizada em pacientes com doença pulmonar obstrutiva crônica (DPOC): um estudo piloto / Effects of transcutaneous diaphragmatic synchronized pacing in patients with chronic obstructive pulmonary disease (COPD)

A pesquisa descrita neste artigo teve por objetivo avaliar quali-quantitativamente os efeitos da estimulação diafragmática transcutânea sincronizada em portadores de DPOC. Para isso, desenvolveu-se um sistema de estimulação elétrica controlado pelo sinal respiratório, a partir das variações de temperatura durante os eventos de inspiração e expiração, medidas por meio de dois termistores do tipo NTC inseridos dos lados interno e externo de uma máscara de respirador. Seis voluntários portadores de DPOC, de ambos os sexos, com idade entre 56 e 71anos, foram submetidos a 10 sessões estimulatórias de 20 minutos. O padrão do sinal estimulatório continha pulsos com duração de 90μs e repouso de 400μs, gerados em intervalos regulares e modulados em bursts com período ativo de 1470μs e inativo de 600μs, apresentando perfil trapezoidal com tempos de subida, descida e platô de 500ms cada. Todos os pacientes foram submetidos a uma avaliação inicial contendo: teste de força muscular respiratória avaliada por meio de PImáx e PEmáx, teste de função pulmonar e aplicação do questionário de qualidade de vida SGRQ. Após 10 sessões, houve um aumento na força muscular inspiratória em todos os pacientes, onde a PImáx sofreu um incremento médio de 66,67± 12,11cmH2O para 91,67 ± 25,03 cmH2O, a PEmáx de 92,50 ± 10,84 cmH2O para 116,67 ± 8,16 cmH2O. Também observou-se melhora da qualidade de vida no domínio sintoma, de 49,10± 19,40 para 28,60± 25,20; no domínio atividade, de 83,40± 12,50 para 67,57± 18,80; no domínio impacto, de 54,10± 11,34 para 38,00± 27,07; e escore total, de 65,50± 7,60 para 44,47± 22,31. A partir desses resultados, concluiu-se que a estimulação elétrica diafragmática sincronizada pode promover resultados positivos em portadores de DPOC.

The research described in this paper has the goal of evaluating the effects of transcutaneous diaphragmatic synchronized pacing in patients with COPD. In order to achieve the experimental protocol, it has been developed a system for electrical stimulation triggered by the respiratory signal obtained from the temperature variations during inspiration and expiration events, using two NTC thermistors coupled inside and outside of a respirator mask. It was studied six volunteers with COPD, of both sexes, aged between 56 to 71 years, who were submitted to 10sessions of 20minutes. The stimulatory parameters were set to: active phase of the pulse of 90μs, and inactive phase of 400μs, generated at regular intervals and modulated in bursts with active and inactive periods of 1470μs and 600μs, respectively; presenting trapezoidal envelope with rise time, fall time and plateau of 500ms. All patients underwent an initial assessment including: test of respiratory muscle strength seen through the MIP and MEP tests, lung function test and application of SGRQ quality of life questionnaire. After 10 sessions, there is an increasing inspiratory muscle strength in all patients, where MIP has an average increase of 66.67± 12.11cmH2O to 91.67 ± 25.03 cmH2O, MEP from 92.50 ± 10.84 cmH2O to 116.67 ± 8.16 cmH2O, and also observed a better quality of life in the symptom domain of 49.10± 19.40 to 28.60± 25.20, in the activity domain of 83.40± 12.50 to 67.57± 18.80, and in the impact domain of 54.10± 11.34 to 38.00± 27.07 and total score of 65.50± 7.60 to 44.47± 22.31. Therefore, we concluded that the transcutaneous diaphragmatic synchronized pacing can promote positive outcomes in patients with COPD.