Inginerie biomedicala - ub
Transcript of Inginerie biomedicala - ub
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Inginerie biomedicala
Curs nr
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Dispozitive cardiovasculare
• Introducere
• Valve cardiace – Mecanice
– Bioprosthetice
• Pacemaker
• Grefe vasculare
• Rinichi artificiali
• Dispozitiv de suport circulator
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Introducere
• Afectiunile cardiovasculare sunt una din principalele cauze de deces.
• Multe cercetari s-au orinetat catre tehnologii avansate pentru dispozitive cardiovasculare care sa inlocuiasca functiuni pierdute
• In cadrul acestui curs vor fi abordate – Valve cardiace – Stenturi – Pacemaker – Defibrilatoare implantabile – Hemoanalizoare – Catetere – Dispozitive de suport pentru circulatie – Oxigeneratoare pentru sange
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Valve artificiale
• Studiu de piata – Anual se fac peste 350000 de implanturi de valve din care peste
50% sunt mecanice artificiale
• Istoric – Proiectarea valvelor cardiace artificiale dateaza inca din 1950
existand mai mult de 80 de variante constructive
• Exista doua tipuri generale de inlocuiri de valve – Mecanice – Biologice
• Valvele mecanice sunt de trei tipuri – Caged-ball – Single-tilting-disc – bileaflet
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Clasificare
• Valve preluate de la acelasi pacient
– Homograft biologic valves obtinute din valve aortice umane
– Autograft- valve pulmonare mutate chirurgical in locatie aortica
• Prelevate de la animale
– Heterograft bioprosthetic valves obtinute din tesut pericardial de la porcine sau bovine asezate pe o structura suport
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Valve mecanice
• Caged-ball mechanical valve folosesc o sfera din polimer constransa intr-o cusca metalica
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• Single disc valves au un disc central care ocluzeaza un inel
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• Bileaflet valves
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Conditii impuse
• Considerente structurale – Oboseala si integritatea dispozitivului – Profilul valvei – Rotabilitatea – Interferenta de ocluziune
• Uzura asociata solicitarilor de milioane de mii de ori la inchidere si deschidere au impus folosirea unor oteluri durabile si a unui inel polimeric rezistent
• Rotabilitatea sugereaza un optim al orientarii care sa minimizeze turbulenta si existenta semnalelor microembolice existente in vivo
• Ocluziunea –alegerea acelor solutii care impiedica realizarea inchiderii complete (tesuturi adiacente, resturi de valve remanente sau material chirurgical )
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Conditii impuse
• Factor hemodinamic – Gradientul de presiune transvalvular – Durata de deschidere a valvei – Fractia regurgitanta dinamica – Rata statica de curgere
• Gradientul de presiune transvalvular este o functie de regimul de curgere (laminar sau turbulent) si de suprafata efectiva a orificiului
• masa elementului ocluziv si mecanismul de actionare joaca un rol important in durata de deschidere a valvei si in fractia regurgitanta dinamica
• Se are in vedere minimizarea depunerilor trombotice
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Heterograft bioprosthetic valves
De la porcine De la bovine
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Tendinte
• Cu implantare percutanata –
• minimum invaziv la implantare
• In pozitie aortica in valva nativa
• utilizarea de substante sintetice sau ţesut decelurizat semănat cu celule
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Stenturi , terapii vasculare percutanate
• Stent = orice material folosit pentru a mentine in pozitie un tesut (Taber Cyclopedic Medical Dictionary)
• Percutaneous transluminal coronary angioplasty (PTCA) - balloon angioplasty
• Sunt folosite la tratarea afectiunilo aortei si a oricarei interventii vasculare
• in medie 2 milioane de interventiipe an si in medie peste 70000 de implanturi pe an
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Designul stenturilor vasculare
• Cerinte – Radioopacitate mare pentru vizualizare in
fluoroscopie
– Flexibilitate mare pentru a putea fi transportat pe artere
– Dimensiune mica pentru usurinta la transport
– Rezistenta la cantrareactia arteriala (spasm)
– Biocompatibilitate pe termen lung (pentru evitarea complicatiilor
– Durabilitate si rezistenta la coroziune
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Variante • Se impart in doua categorii dupa metoda de
expandare
– Stent cu balon de expandare
– Stent cu autoexpandare
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Flexibilitatea stentului
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Pacemaker si defibrilatoare implantabile
• Se compun din doua componente implantabile si o componenta externa – Generatorul
– Firele de conectare
– Programator
• Cerinte – Nivel de complicatii redus
– Dimensiune mica
– Durabilitate
– Longevitate
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Generatorul
• Generatorul si bateria trebuie sa stea aprox 5-9 ani in organism
• Mici
• Plate
• 20-30g
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Conductor electric
• Se compune din
– Conectori
– Conductori
– Izolatori
– Electrozi
– Mecanisme de fixare
• Trebuie sa aiba diametru mic, sa fie flexibili, durabili, sa aiba caracteristici favorabile de consum, fixare buna pentru a preveni migrarea, biocompatibilitate buna
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Programatorul
• Permite medicului sa sa faca setarile necesare
• Foloseste unde de radiofrecvanta sau campuri magnerice
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Grefe vasculare artificiale
• Grefele vasculare artificiale sau proteze se clasifica dupa origine: biologica sau sintetica
• Grefele biologice pot fi
– Xenograft- de la alte specii si
– Autograft – de la pacient
• Abordarea va fi facuta pentru cele sintetice
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Grefe vasculare sintetice
• Sa mimeze e native • Plasare chirurgicala usoara • Complexitatea manufacturarii si cost minim • Caracteristici biologice
– Biocompatibile – Rezistente la infectii – Antitrombotice – Durabile
• Caracteristici de implantare – Tipodimensiuni diferite – Sterilizare usoara – Saturabilitate buna – Flexibile la manipulare – Fara scurgeri de sange
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Grefele comerciale polimerice • Sunt cu forma textila si nontextila • Cele textile sunt din tereftalat de
polietilena tesut sau tricotat • Cele netesute sunt fabricate in
general din politetrafluoretilena expandata
• se mai folosesc materiale ca • Nailon sau poliamide • Politetrafloretilena neexpandata • Poliacrilonitril • Poliuretrani (cel mai folosit)
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Rinichi artificial
• Trei procedee fizice determina indepartarea toxinelor prin dispozitive bazate pe membrane – Convectie- indepartarea toxinelor prin membrane
semipermeabile
– Difuzie- afecteaza moleculele mici cu coeficient mare de difuzie
– Adsorbtie
• Convectia si difuzia sunt procese predominant fizice
• Adsorbtia este controlata prin forte electrostatice van der Waals
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Tendinte
• Materiale noi biocompatibile pentru zona hemodinamica (Ex indep. Toxinelor fara indepartarea proteinelor benefice)
• Tumlin et al., 2008 rinichiul artificial a trecut de faza II a testelor clinice
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Dispozitive de suport circulator
• intra-aortic balloon pump (IABP) 1968 prima aplicatie
• Consta dintr-o pompa externa care monitorizeaza variabilele fiziologice ale pacientului care ofera un volum de gaz printr-uncateter montat in aorta pacientului
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