Computational fluid dynamics improvements and in vitro tests of a proposed transventricular axial blood pump

Heart failure is a chronic disease that affects thousands of people around the world, being characterized by the inability of one's heart to adequately pump their blood according to their body's needs. Its treatment may be performed through heart transplant. However, ventricular assist devices (VADs) can be used as a way to assist the patient while they wait for a transplant or as destination therapy, with them being responsible for the patients increase in the life expectancy. These devices are pumps that help supply the adequate cardiac output to the body. But the procedures used to implant this kind of device, the size and geometry of the pump are vital for the surgery success and assurance safety patient recuperation. Because of that many important researches center try to find pump geometry that comply these characteristics and comply human blood physiology. Then the reduction in size of these systems, which increases their reliability, biocompatibility and robustness, is essential to the complete implantation of the VADs, which is the main focus of the current state of art.

Safety control architecture for ventricular assist devices

ABSTRACT: In patients with severe heart disease, the implantation of a ventricular assist device (VAD) may be necessary, especially in patients with an indication for heart transplantation. For this, the Institute Dante Pazzanese of Cardiology (IDPC) has developed an implantable centrifugal blood pump that will be able to help a diseased human heart to maintain physiological blood flow and pressure. This device will be used as a totally or partially implantable VAD. Therefore, performance assurance and correct specification of the VAD are important factors in achieving a safe interaction between the device and the patient's behavior or condition. Even with reliable devices, some failures may occur if the pumping control does not keep up with changes in the patient's behavior or condition. If the VAD control system has no fault tolerance and no system dynamic adaptation that occurs according to changes in the patient's cardiovascular system, a number of limitations can be observed in the results and effectiveness of these devices, especially in patients with acute comorbidities. This work proposes the application of a mechatronic approach to this class of devices based on advanced control, instrumentation, and automation techniques to define a method to develop a hierarchical supervisory control system capable of dynamically, automatically, and safely VAD control. For this methodology, concepts based on Bayesian networks (BN) were used to diagnose the patient's cardiovascular system conditions, Petri nets (PN) to generate the VAD control algorithm, and safety instrumented systems to ensure the safety of the VAD system.

Implantable centrifugal blood pump with dual impeller and double pivot bearing system: electromechanical actuator, prototyping, and anatomical studies.

An implantable centrifugal blood pump has been developed with original features for a left ventricular assist device. This pump is part of a multicenter and international study with the objective to offer simple, affordable, and reliable devices to developing countries. Previous computational fluid dynamics investigations and wear evaluation in bearing system were performed followed by prototyping and in vitro tests. In addition, previous blood tests for assessment of normalized index of hemolysis show results of 0.0054±2.46 × 10⁻³ mg/100 L. An electromechanical actuator was tested in order to define the best motor topology and controller configuration. Three different topologies of brushless direct current motor (BLDCM) were analyzed. An electronic driver was tested in different situations, and the BLDCM had its mechanical properties tested in a dynamometer. Prior to evaluation of performance during in vivo animal studies, anatomical studies were necessary to achieve the best configuration and cannulation for left ventricular assistance. The results were considered satisfactory, and the next step is to test the performance of the device in vivo.

Specification of supervisory control systems for ventricular assist devices.

One of the most important recent improvements in cardiology is the use of ventricular assist devices (VADs) to help patients with severe heart diseases, especially when they are indicated to heart transplantation. The Institute Dante Pazzanese of Cardiology has been developing an implantable centrifugal blood pump that will be able to help a sick human heart to keep blood flow and pressure at physiological levels. This device will be used as a totally or partially implantable VAD. Therefore, an improvement on device performance is important for the betterment of the level of interaction with patient's behavior or conditions. But some failures may occur if the device's pumping control does not follow the changes in patient's behavior or conditions. The VAD control system must consider tolerance to faults and have a dynamic adaptation according to patient's cardiovascular system changes, and also must attend to changes in patient conditions, behavior, or comportments. This work proposes an application of the mechatronic approach to this class of devices based on advanced techniques for control, instrumentation, and automation to define a method for developing a hierarchical supervisory control system that is able to perform VAD control dynamically, automatically, and securely. For this methodology, we used concepts based on Bayesian network for patients' diagnoses, Petri nets to generate a VAD control algorithm, and Safety Instrumented Systems to ensure VAD system security. Applying these concepts, a VAD control system is being built for method effectiveness confirmation.

Characteristics of COPD patients admitted to the ICU of a referral hospital for respiratory diseases in Brazil.

OBJECTIVE: To report data regarding COPD patients admitted to the ICU of a referral hospital for respiratory diseases, including outcomes and treatment evaluation. METHODS: Study of a series of patients with respiratory failure and COPD admitted to the ICU of Nereu Ramos Hospital, located in the city of Florianópolis, Brazil, between October of 2006 and October of 2007. Data related to demographics, causes of hospitalization, pharmacological treatment, ventilatory support, length of hospital stay, in-hospital complications, ICU mortality, and 28-day mortality were obtained from the medical charts of the patients. Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were calculated. Mortality at 18 months was assessed by subsequent telephone calls. RESULTS: During the study period, 192 patients were admitted to the ICU, 24 (12.5%) of whom were diagnosed with respiratory failure and COPD. The mean length of ICU stay was 12.0 ± 11.1 days. Noninvasive ventilation was used in 10 of the 24 patients (41.66%) and failed in 5 of those 10. Invasive mechanical ventilation (IMV) was used in a total of 15 patients (62.5%). Overall ICU mortality and 28-day mortality were 20.83% and 33.33%, respectively. However, 18-month mortality was 62.5%. CONCLUSIONS: Respiratory failure associated with COPD was responsible for 12.5% of the ICU admissions. Orotracheal intubation and IMV were necessary in 62.5% of the cases. The ICU mortality rate was in accordance with that predicted by the APACHE II scores. However, late mortality was high.

Características de pacientes com DPOC internados em UTI de um hospital de referência para doenças respiratórias no Brasil / Characteristics of COPD patients admitted to the ICU of a referral hospital for respiratory diseases in Brazil

OBJETIVO: Relatar dados referentes às internações de pacientes com DPOC na UTI de um hospital de referência para doenças respiratórias, incluindo desfechos e avaliando seu atendimento. MÉTODOS: Estudo de uma série de pacientes internados por insuficiência respiratória e DPOC na UTI do Hospital Nereu Ramos, localizado na cidade de Florianópolis (SC) no período entre outubro de 2006 e outubro de 2007. Dados demográficos, causas da internação, tratamento farmacológico, suporte ventilatório, duração e complicações da internação, mortalidade em UTI e mortalidade em 28 dias foram obtidos através de consulta aos prontuários médicos. O índice Acute Physiology and Chronic Health Evaluation II (APACHE II) foi calculado. A mortalidade em 18 meses foi avaliada através de posterior contato telefônico. RESULTADOS: No período, foram internados 192 pacientes na UTI, 24 dos quais (12,5 por cento) com insuficiência respiratória e DPOC. O tempo médio de internação na UTI foi de 12,0 ± 11,1 dias. A ventilação não invasiva foi utilizada em 10 dos 24 pacientes (41,66 por cento) e falhou em 5/10. A ventilação mecânica invasiva (VMI) foi utilizada em 15 pacientes (62,5 por cento). As taxas de mortalidade na UTI e aquela em 28 dias foram de 20,83 por cento e 33,33 por cento, respectivamente. Entretanto, decorridos 18 meses, a mortalidade foi de 62,5 por cento. CONCLUSÕES: A insuficiência respiratória relacionada à DPOC foi responsável por 12,5 por cento das internações na UTI. Houve necessidade de intubação orotraqueal e utilização de VMI em 62,5 por cento dos pacientes. A mortalidade na UTI estava de acordo com a predita pelo índice APACHE II, mas a mortalidade tardia foi elevada.

OBJECTIVE: To report data regarding COPD patients admitted to the ICU of a referral hospital for respiratory diseases, including outcomes and treatment evaluation. METHODS: Study of a series of patients with respiratory failure and COPD admitted to the ICU of Nereu Ramos Hospital, located in the city of Florianópolis, Brazil, between October of 2006 and October of 2007. Data related to demographics, causes of hospitalization, pharmacological treatment, ventilatory support, length of hospital stay, in-hospital complications, ICU mortality, and 28-day mortality were obtained from the medical charts of the patients. Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were calculated. Mortality at 18 months was assessed by subsequent telephone calls. RESULTS: During the study period, 192 patients were admitted to the ICU, 24 (12.5 percent) of whom were diagnosed with respiratory failure and COPD. The mean length of ICU stay was 12.0 ± 11.1 days. Noninvasive ventilation was used in 10 of the 24 patients (41.66 percent) and failed in 5 of those 10. Invasive mechanical ventilation (IMV) was used in a total of 15 patients (62.5 percent). Overall ICU mortality and 28-day mortality were 20.83 percent and 33.33 percent, respectively. However, 18-month mortality was 62.5 percent. CONCLUSIONS: Respiratory failure associated with COPD was responsible for 12.5 percent of the ICU admissions. Orotracheal intubation and IMV were necessary in 62.5 percent of the cases. The ICU mortality rate was in accordance with that predicted by the APACHE II scores. However, late mortality was high.

Specification of supervisory control systems for ventricular assist devices

One of the most important recent improvements in cardiology is the use of ventricular assist devices (VADs) to help patients with severe heart diseases, especially when they are indicated to heart transplantation.TheInstitute Dante Pazzanese of Cardiology has been developing an implantable centrifugal blood pump that will beable to help a sick human heart to keep blood flow and pressure at physiological levels. This device will be used asa totally or partially implantable VAD. Therefore, an improvement on device performance is important for thebetterment of the level of interaction with patient’s behavior or conditions. But some failures may occur if the device’s pumping control does not follow the changes in patient’s behavior or conditions. The VAD control system must consider tolerance to faults and have a dynamic adaptation according to patient’s cardiovascular system changes, and also must attend to changes in patient conditions, behavior, or comportments. This work proposes anapplication of the mechatronic approach to this class of devices based on advanced techniques for control, instrumentation, and automation to define a method for developinga hierarchical supervisory control system that is able to perform VAD control dynamically, automatically, andsecurely. For this methodology, we used concepts based on Bayesian network for patients’ diagnoses, Petri nets to generate a VAD control algorithm, and Safety Instrumented Systems to ensure VAD system security. Applying theseconcepts, a VAD control system is being built for method effectiveness confirmation.

Implantable centrifugal blood pump with dual impellerand double pivot bearing system: electromechanical actuator, prototyping, and anatomical studies

An implantable centrifugal blood pump hasbeen developed with original features for a left ventricularassist device. This pump is part of a multicenter and internationalstudy with the objective to offer simple, affordable,and reliable devices to developing countries. Previous computationalfluid dynamics investigations and wear evaluationin bearing system were performed followed byprototyping and in vitro tests. In addition, previous bloodtests for assessment of normalized index of hemolysis showresults of 0.0054 2.46 ¥ 10-3 mg/100 L. An electromechanicalactuator was tested in order to define the bestmotor topology and controller configuration. Three differenttopologies of brushless direct current motor (BLDCM)were analyzed.An electronic driver was tested in differentsituations, and the BLDCM had its mechanical propertiestested in a dynamometer. Prior to evaluation of performanceduring in vivo animal studies, anatomical studieswere necessary to achieve the best configuration and cannulationfor left ventricular assistance. The results wereconsidered satisfactory, and the next step is to test theperformance of the device in vivo.