MICROCHANNEL TECHNOLOGIES FOR ARTIFICIAL LUNGS

Abstract

Blood-side passages in natural lungs are short and small, facilitating efficient blood-gas transfer and low-pressure drop. The blood-side passages in current artificial lungs, however, are often 150 to 250 microns in size, requiring transverse blood side mixing and often relatively long path lengths and large pressure drops. A variety of techniques are being explored to develop a technology for blood-side passages in the 10 to 45 micron range for artificial lungs, including wafers with about 250,000 circular microchannels per cm2, silicone membranes with imprinted support posts, and supported rectangular microchannels with flat, thin (25 to 300 microns) silicone rubber membranes on one side. The latter has been examined in experiments with bovine blood to evaluate gas transfer efficiency and the relative contributions of membrane resistance and blood-side resistance. The dependence of oxygen exchange efficiency on microchannel dimension, configuration and membrane thickness were examined. For a small prototype device with a channel height of 40 microns, a blood path length of 3 mm, a gas exchange area of about 37 cm2, a blood flow rate of 3.2 ml/min, the hemoglobin saturation increased from 65 to 96% in blood with a 30% hematocrit and the pressure drop was less than one cm of water. Scaling up, a device that could similarly arterialize 4 L/min would require a gas-exchange blood volume of less than 150 mL.