In short-term artificial lungs (used, for example, during heart surgery) blood oxygenation is accomplished by bubbling pure oxygen directly through the blood. However, the high surface energy at the gas–

liquid interface causes excessive damage to the blood and this method is not suitable for extended uses. To avoid this problem, the blood is separated from air by an oxygen-permeable membrane. In a particular design of such system, blood flows inside thin silicone rubber tubes and pure oxygen flows outside at 1 atm absolute pressure. The tubes have inside and outside diameters of 0.025 and 0.05 cm and the rate of oxygen transfer is 2.0 × 10⁻⁴

cm³ (STP)/min per linear cm of tube. The diffusivity of O2 in silicone rubber is 2.0 × 10⁻⁵ cm²/s, and the solubility is 6.0 × 10⁻² cm³ (STP)/(atm cm³ membrane). Determine the percentage by which the O2 partial pressure will be reduced at the blood–membrane interface.