Comparison of physical properties of two exogenous surfactants: new parameter.

The pulmonary surfactant has essential physical properties for normal lung function. The most important property is the surface tension. In this work, it was evaluated the surface tension of two commercial exogenous surfactants used in surfactant replacement therapy, poractant alfa (Curosurf, Chiesi Farmaceuticals, Italy) and beractant (Survanta, Abbott Laboratories, USA) using new parameters. A Langmuir film balance (Minitrough, KSV Instruments, Finland) was used to measure surface tension of poractant alfa and beractant samples. For both samples, we prepared a solution of 1 mg/m dissolved in chloroform (100π`), which was applied over a subphase of milli-Q water (175 ml) in the chamber of the balance. The chamber has two moving barriers that can change its surface area between a maximal value of 112.5 cm 2 , and a minimal value of 22.5 cm 2, defining a balance cycle. Each surfactant had its surface tension evaluated during 20 balance cycles for three times. Four quantities were calculated from the experiment: Minimum Surface Tension (MTS), defined as the surface tension at minimal surface area during the first cycle; Mean Work Cycle (MWC), defined as the mean hysteresis area of the measured surface tension curve of the last 16 balance cycles; Critical Active Surface Area in Compression (CASAC) or in Expansion (CASAE), defined as the maximal chamber area where the surfactant is active on the surface in compression or expansion. The t-test was applied to verify for statistical significance of the results. Comproved with the MST is the same reported in literature, the differences between MWC, CASAC, and CASAE were statistically significant (p<0.001). The MWC, CASAC and CASAE were higher for poractant alfa than for beractant. A higher MWC for poractant alfa means higher elastic recoil of the lung in comparison with beractant. Using a different methodology, our results showed that poractant alfa is probably more effective in a surfactant replacement therapy than beractant due the use of poractant alfa in relation to the use of beractant in preterm infants with Respiratory Distress Syndrome (RDS).CNPqFAPES

Quasi-static assessment of the respiratory mechanics in rodents using a lung insufflator.

A avaliação da mecânica respiratória (AMR) busca descrever o comportamento mecânico do sistema respiratório, para melhor entender a sua fisiologia e a sua patofisiologia. O método quasi-estático é caracterizado pela AMR em condições nas quais a aceleração dos tecidos pode ser considerada desprezível. Esta dissertação de mestrado teve como objetivo avaliar a mecânica respiratória pelo método quasi-estático em roedores, utilizando um insuflador pulmonar para pequenos roedores (IPPR) construído no Laboratório de Engenharia Biomédica (LEB) da Escola Politécnica da Universidade de São Paulo (EPUSP). Uma extensa revisão da literatura sobre fisiologia e técnicas de AMR em humanos e roedores é apresentada. Uma documentação bastante detalhada sobre a implementação e o funcionamento do IPPR é fornecida, com o intuito de permitir que o dispositivo seja reproduzido. Testes de bancada foram executados, para avaliar o funcionamento do IPPR, e um protocolo experimental com modelo animal de doença, em ratos Wistar envenenados por Paraquat, foi realizado. Os resultados dos testes de bancada mostraram que o equipamento ainda carece de alguns ajustes, pois apresenta erros na indicação de volume, da ordem de 5%, mas que podem ser compensados na análise dos dados experimentais obtidos. No futuro, pretende-se sanar essa imprecisão, tornando o IPPR independente de um microcomputador com sistema operacional multitarefa. Os resultados da aplicação do modelo matemático exponencial, nos dados obtidos de curvas pressão-volume no protocolo experimental, trouxeram informações que estão de acordo com as características observadas no modelo animal de envenenamento por Paraquat.The assessment of respiratory mechanics (AMR) aims to describe the mechanical behavior of the respiratory system in order to better understand its physiology and pathophysiology. The quasi-static method is characterized by the AMR under conditions where the tissue\'s acceleration can be considered negligible. The purpose of this master degree dissertation was to assess the respiratory mechanics by quasistatic method in rats using a lung insufflator for small rodents (IPPR) implemented in the Biomedical Engineering Laboratory (LEB) of Escola Politécnica of University of São Paulo (EPUSP). Abroad literature review on AMR techniques and on physiology in humans and rodents was presented. A fairly detailed documentation of the assembly and the operation of the IPPR was provided in order to allow the device to be reproduced. Bench tests were conducted to evaluate the behavior of the IPPR, and an animal disease model by Paraquat poisoning protocol was performed in Wistar rats. The bench tests results showed that the equipment still needs some tweaking, because it presents errors in volume indication of the order of 5%, but these errors can be compensated in the analysis of the experimental data. In the future, there is an intention to correct this inaccuracy turning the IPPR independent of a multitask microcomputer operating system. The results of the mathematical exponential modeling applied on the pressure-volume curves in the experimental protocol are in good agreement with the characteristics observed on Paraquat poisoning animal model

Mechanical Measurements Of Two Exogenous Surfactants Using A Langmuir Film Balance:A Comparative Study

Rationale: The primary function of surfactant is to reduce the surface tension at air-liquid interface. In this study, the surface tension behavior of two commercial surfactants, poractant alfa (ChiesiFarmaceuticals,ltaly) and beractant (Abbott Laboratories,USA), were evaluated,using new parameters.\ud Methods: We used a Langmuir film balance (Minitrough,KSV lnstruments,Finland) to measure of surface tension of both poractant alfa and beractant samples. For both samples,we prepared a solution of 1 mg/mdl dissolved in chloroform. The solution (1uL) was applied over a subphase of milli-Q water (175 ml) in the chamber of the balance. The chamber has two moving barriers that can change its surface area between a maximum value of 112.5 cm2 anda minimum value of 22.5 cm2, defining a balance cycle.lhree sample's films were evaluated for each sample, during 20 balance cycles. Here quantify two new variables, which is the mean hysteresis area of the measured curve surface tension of the last 16 balance cycles,defined here as Mean Work Cycle (MWC), and the moment that the surfactant is active in the surface, this measure is defined here as Active Surface Area Critical in the compression (ASACC) and the expansion (ASACE). The test was applied to compare the statistical significance of the results.FAPES