Pulmonic valve function during thoracic artificial lung attachment

Abstract

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. These conditions lead to varying conditions of resistance and inertia in each animal. The periods of ejection (TE), regurgitation (TR), and sealed valve (TSV), and the regurgitant fraction (Fr) were determined at each condition. The relationships between these variables and the effective pulmonary system resistance (R) and the calculated inertial pressure drop during flow deceleration (DeltaPI) were determined. A large R created pulmonic valve incompetence and increased regurgitation, as evidenced by a decreased TSV. A highly negative DeltaPI decreased regurgitation by increasing TE. When R <5 mm Hg/(L/min), Fr remained at baseline levels, regardless of other conditions. When R >5 mm Hg/(L/min), the relationship between Fr, R, and DeltaPI was found to be Fr = 0.014R + 0.011DeltaPI + 0.15 (R = 0.82). Thus, pulmonary system resistance should be maintained <5 mm Hg/(L/min) to avoid pulmonic valve incompetence. High device inertance reduced regurgitation but also lead to increased pulmonary system impedances and ventricular work. The design and implementation of a TAL, thus, should focus on having a small effective pulmonary system resistance.