Predicted oxygenation efficacy of a thoracic artificial lung.

A thoracic artificial lung (TAL) provides respiratory support for lung disease. How well a TAL improves blood oxygenation for a specific pathology depends on how the TAL is attached to the pulmonary circulation: in series with the natural lungs (NLs), in parallel, or in a hybrid series/parallel combination. A computational model, including hemodynamic and O(2) and CO(2) exchange components, predicts TAL effects on blood flow rates and gas transport in pulmonary disease states modeled by elevated pulmonary vascular resistance (PVR) or reduced oxygen diffusivity in the NLs.

Microchannel technologies for artificial lungs: (3) open rectangular channels.

Lithographic techniques were used to develop patterned silicone rubber membranes that provide 15 microm high microchannels for artificial lungs. Two types of devices were fabricated as a proof-of-concept: one has a series of parallel, straight, open rectangular channels that are each 300 microm wide, separated by 200-microm walls, and 3-mm long and the other is a wide rectangular channel with support posts, also 3- mm long. Experiments with 30% hematocrit, venous, bovine blood showed average oxygen fluxes ranging from 11 x 10(-7) moles/(min x cm(2)) at a residence time of 0.

Microchannel technologies for artificial lungs: (2) screen-filled wide rectangular channels.

Artificial lungs with blood-side channels on a 10-40 microm scale would be characterized, similar to the natural lungs, by tens of thousands to hundreds of millions parallel blood channels, short blood paths, low pressure drops, and low blood primes. A major challenge for developing such devices is the requirement that the multitude of channels must be uniform from channel to channel and along each channel. One possible strategy for developing microchannel artificial lungs is to fill broad rectangular channels with micro scale screens that can provide uniform support and stability.

Microchannel technologies for artificial lungs: (1) theory.

The feasibility of developing micro channel artificial lungs is calculated for eight possible strategies: 12 and 25 microm circular channels imbedded in gas-permeable sheets, 12 and 25 microm high open rectangular channels with gas-permeable walls, 12 and 25 microm high broad open channels with support posts and gas-permeable walls, and two 40 microm high screen-filled rectangular channels with gas-permeable walls. Each strategy is considered by imposing a pressure drop maximum of 10 mm Hg and limiting the possibility of shear-induced blood trauma. The pressure drop limit determines the acceptable channel length and required size to oxygenate 4 L/min of venous blood.

Pulmonic valve function during thoracic artificial lung attachment.

Pulmonic valve incompetence has been observed during implantation of total artificial lungs (TAL) and may contribute to right ventricular dysfunction in certain attachment modes. The roles of pulmonary system resistance and inertia on valve function were examined retrospectively using data from attachments of a prototype TAL in six pigs. The TAL was attached in parallel and in series with the natural lungs and a hybrid of parallel and series.