B. J. Shuman, S. Yi, C. Finger, Spiration Inc., Redmond, WA
The dynamic and complex environment of the pulmonary system creates unique design and testing challenges for pulmonary devices compared to traditional cardiac arterial devices. Diseased segmental airways undergo significant asymmetric radial compression during breathing and may completely close during coughing. These conditions have dictated the design, manufacture and testing of the IBVTM Valve System, which acts as a one-way valve to restrict distal airflow into diseased sections of the lung while allowing the natural proximal fluid clearance mechanism to function. The valve utilizes a superelastic NiTi frame and a thin polyurethane membrane which, in combination, permits it to conform to the airway’s cyclic radial displacements. Manufacturing challenges include tight control of the Af temperature during shape setting, laser welding and surface treatments to give the valve acceptable fatigue life and corrosion resistance. Testing challenges include developing realistic airway models, establishment of acceptable boundary conditions for fatigue testing and corrosion testing.
Summary: The IBV Valve System is a unique device for the treament of chronic obstructive pulmonary disease (COPD), primarily emphysema. It has been developed over the last 5 years. It is currently undergoing clinical trials, prior to human use extensive animal testing was done in a variety of animal models. The valve is one of the first implantable devices to be used clinically at the segmental level of the pulmonary tree.
One of the critical elements of the valve's design is its NiTi frame. By using NiTi the valve is able to be compressed into a narrow catheter for clinical delivery and have sufficient compliance and fatigue resistance to function at the segmental level in the pulmonary tree. By continually improving the manufacturing processes, the valves have superior mechanical performance, durability and corrosion resistance.
By presenting at the SMST conference the team that designed the valve will be able to show how the its design developed in response to the challenges of the pulmonary environment. In particular, the differences and similarities between the pulmonary vs. the cardiac environment will be highlighted.
