ABSTRACT
OBJECTIVE: To develop a simple, robust, safe and efficient invasive mechanical ventilator that can be used in remote areas of the world or war zones where the practical utility of more sophisticated equipment is limited by considerations of maintainability, availability of parts, transportation and/or cost. METHODS: The device implements the pressure-controlled continuous mandatory ventilation mode, complemented by a simple assist-control mode. Continuous positive airway pressure is also possible. The consumption of compressed gases is minimized by avoiding a continuous flow of oxygen or air. Respiratory rates and inspiration/expiration time ratios are electronically determined, and an apnea/power loss alarm is provided. RESULTS: The pressure profiles were measured for a range of conditions and found to be adjustable within a ± 2.5cmH2O error margin and stable well within this range over a 41-hour period. Respiratory cycle timing parameters were precise within a few percentage points over the same period. The device was tested for durability for an equivalent period of four months. Chemical and biological tests failed to identify any contamination of the gas by volatile organic compounds or microorganisms. A ventilation test on a large animal, in comparison with a well established ventilator, showed that the animal could be adequately ventilated over a period of 60 minutes, without any noticeable negative aftereffects during the subsequent 24-hour period. CONCLUSION: This ventilator design may be viable, after further animal tests and formal approval by the competent authorities, for clinical application in the abovementioned atypical circumstances.
OBJETIVO: Desenvolver um ventilador mecânico invasivo simples, resistente, seguro e eficiente que possa ser utilizado em áreas remotas do mundo ou zonas de guerra, em que a utilidade prática de equipamentos mais sofisticados é limitada por questões de manutenção, disponibilidade de peças, transporte e/ou custo. MÉTODOS: O dispositivo implementa o modo de ventilação mandatória contínua com pressão controlada, complementado por um simples modo assisto-controlado. Pode-se também utilizar a pressão positiva contínua nas vias aéreas. Ao se evitar o fluxo contínuo de oxigênio ou ar, minimiza-se o consumo de gases comprimidos. As taxas respiratórias e as relações de tempo de inspiração e expiração são determinadas eletronicamente. Além disso, conta com um alarme de apneia/falta de energia. RESULTADOS: Os perfis de pressão foram medidos para uma série de condições, sendo considerados ajustáveis dentro de uma margem de erro de ± 2,5cmH2O, e foram considerados bem estáveis dentro dessa variação durante um período de 41 horas. Os parâmetros de tempo do ciclo respiratório foram precisos dentro de alguns pontos percentuais durante o mesmo período. O dispositivo foi testado quanto à durabilidade por um período equivalente a 4 meses. Os testes químicos e biológicos não conseguiram identificar qualquer contaminação do gás por compostos orgânicos voláteis ou micro-organismos. Em comparação com um ventilador bem estabelecido, o teste de ventilação em um animal de grande porte mostrou que este poderia ser ventilado adequadamente durante um período de 60 minutos, sem quaisquer efeitos negativos perceptíveis durante o período subsequente de 24 horas. CONCLUSÃO: Este projeto de ventilador pode ser viável após novos testes em animais e aprovação formal pelas autoridades competentes, para aplicação clínica nas circunstâncias atípicas anteriormente mencionadas.
Subject(s)
Continuous Positive Airway Pressure , Ventilators, Mechanical , Animals , Humans , Respiration, ArtificialABSTRACT
RESUMO Objetivo: Desenvolver um ventilador mecânico invasivo simples, resistente, seguro e eficiente que possa ser utilizado em áreas remotas do mundo ou zonas de guerra, em que a utilidade prática de equipamentos mais sofisticados é limitada por questões de manutenção, disponibilidade de peças, transporte e/ou custo. Métodos: O dispositivo implementa o modo de ventilação mandatória contínua com pressão controlada, complementado por um simples modo assisto-controlado. Pode-se também utilizar a pressão positiva contínua nas vias aéreas. Ao se evitar o fluxo contínuo de oxigênio ou ar, minimiza-se o consumo de gases comprimidos. As taxas respiratórias e as relações de tempo de inspiração e expiração são determinadas eletronicamente. Além disso, conta com um alarme de apneia/falta de energia. Resultados: Os perfis de pressão foram medidos para uma série de condições, sendo considerados ajustáveis dentro de uma margem de erro de ± 2,5cmH2O, e foram considerados bem estáveis dentro dessa variação durante um período de 41 horas. Os parâmetros de tempo do ciclo respiratório foram precisos dentro de alguns pontos percentuais durante o mesmo período. O dispositivo foi testado quanto à durabilidade por um período equivalente a 4 meses. Os testes químicos e biológicos não conseguiram identificar qualquer contaminação do gás por compostos orgânicos voláteis ou micro-organismos. Em comparação com um ventilador bem estabelecido, o teste de ventilação em um animal de grande porte mostrou que este poderia ser ventilado adequadamente durante um período de 60 minutos, sem quaisquer efeitos negativos perceptíveis durante o período subsequente de 24 horas. Conclusão: Este projeto de ventilador pode ser viável após novos testes em animais e aprovação formal pelas autoridades competentes, para aplicação clínica nas circunstâncias atípicas anteriormente mencionadas.
ABSTRACT Objective: To develop a simple, robust, safe and efficient invasive mechanical ventilator that can be used in remote areas of the world or war zones where the practical utility of more sophisticated equipment is limited by considerations of maintainability, availability of parts, transportation and/or cost. Methods: The device implements the pressure-controlled continuous mandatory ventilation mode, complemented by a simple assist-control mode. Continuous positive airway pressure is also possible. The consumption of compressed gases is minimized by avoiding a continuous flow of oxygen or air. Respiratory rates and inspiration/expiration time ratios are electronically determined, and an apnea/power loss alarm is provided. Results: The pressure profiles were measured for a range of conditions and found to be adjustable within a ± 2.5cmH2O error margin and stable well within this range over a 41-hour period. Respiratory cycle timing parameters were precise within a few percentage points over the same period. The device was tested for durability for an equivalent period of four months. Chemical and biological tests failed to identify any contamination of the gas by volatile organic compounds or microorganisms. A ventilation test on a large animal, in comparison with a well established ventilator, showed that the animal could be adequately ventilated over a period of 60 minutes, without any noticeable negative aftereffects during the subsequent 24-hour period. Conclusion: This ventilator design may be viable, after further animal tests and formal approval by the competent authorities, for clinical application in the abovementioned atypical circumstances.
ABSTRACT
BACKGROUND: Mesenchymal stem/stromal cells have unique properties favorable to their use in clinical practice and have been studied for cardiac repair. However, these cells are larger than coronary microvessels and there is controversy about the risk of embolization and microinfarctions, which could jeopardize the safety and efficacy of intracoronary route for their delivery. The index of microcirculatory resistance (IMR) is an invasive method for quantitatively assessing the coronary microcirculation status. OBJECTIVES: To examine heart microcirculation after intracoronary injection of mesenchymal stem/stromal cells with the index of microcirculatory resistance. METHODS: Healthy swine were randomized to receive by intracoronary route either 30x106 MSC or the same solution with no cells (1% human albumin/PBS) (placebo). Blinded operators took coronary pressure and flow measurements, prior to intracoronary infusion and at 5 and 30 minutes post-delivery. Coronary flow reserve (CFR) and the IMR were compared between groups. RESULTS: CFR and IMR were done with a variance within the 3 transit time measurements of 6% at rest and 11% at maximal hyperemia. After intracoronary infusion there were no significant differences in CFR. The IMR was significantly higher in MSC-injected animals (at 30 minutes, 14.2U vs. 8.8U, p = 0.02) and intragroup analysis showed a significant increase of 112% from baseline to 30 minutes after cell infusion, although no electrocardiographic changes or clinical deterioration were noted. CONCLUSION: Overall, this study provides definitive evidence of microcirculatory disruption upon intracoronary administration of mesenchymal stem/stromal cells, in a large animal model closely resembling human cardiac physiology, function and anatomy.
Subject(s)
Coronary Circulation , Coronary Vessels/cytology , Coronary Vessels/physiology , Mesenchymal Stem Cell Transplantation , Microcirculation , Animals , Female , Hemodynamics , Humans , Male , SwineABSTRACT
INTRODUCTION: The index of microcirculatory resistance (IMR) enables/provides quantitative, invasive, and real-time assessment of coronary microcirculation status. AIMS: The primary aim of this study was to validate the assessment of IMR in a large animal model, and the secondary aim was to compare two doses of intracoronary papaverine, 5 and 10 mg, for induction of maximal hyperemia and its evolution over time. METHODS: Measurements of IMR were performed in eight pigs. Mean distal pressure (Pd) and mean transit time (Tmn) were measured at rest and at maximal hyperemia induced with intracoronary papaverine, 5 and 10 mg, and after 2, 5, 8 and 10 minutes. Disruption of the microcirculation was achieved by selective injection of 40-µm microspheres via a microcatheter in the left anterior descending artery. RESULTS: In each animal 14 IMR measurements were made. There were no differences between the two doses of papaverine regarding Pd response and IMR values - 11 ± 4.5 U with 5 mg and 10.6 ± 3 U with 10 mg (p=0.612). The evolution of IMR over time was also similar with the two doses, with significant differences from resting values disappearing after five minutes of intracoronary papaverine administration. IMR increased with disrupted microcirculation in all animals (41 ± 16 U, p=0.001). CONCLUSIONS: IMR provides invasive and real-time assessment of coronary microcirculation. Disruption of the microvascular bed is associated with a significant increase in IMR. A 5-mg dose of intracoronary papaverine is as effective as a 10-mg dose in inducing maximal hyperemia. After five minutes of papaverine administration there is no significant difference from resting hemodynamic status.
