In VivoTesting of an Ambient Air Based, Portable, and Automated CO2Removal Controller for Artificial Lungs

Portable artificial lung (AL) systems are under development, but there are few technologies available that adjust the carbon dioxide (CO2) removal in response to changes in patient metabolic needs. Our work describes the second generation of a CO2-based portable servoregulation system that automatically adjusts CO2removal in ALs. Four adult sheep (68 ± 14.3 kg) were used to test the servoregulator. The servoregulator controlled air sweep flow through the lung to meet a target exhaust gas CO2(tEGCO2) level in normocapnic and hypercapnic (arterial partial pressure of CO2[PaCO2] >60 mm Hg) conditions at varying flow rates (0.5–1.5 L/min) and at tEGCO2levels of 10, 20, and 40 mm Hg. In hypercapnic sheep, average post-AL blood partial pressure of CO2(pCO2) values were 22.4 ± 3.6 mm Hg for tEGCO2of 10 mm Hg, 28.0 ± 4.1 mm Hg for tEGCO2of 20 mm Hg and 40.6 ± 4.8 mm Hg for tEGCO2of 40 mm Hg. The controller successfully and automatically adjusted the sweep gas flow to rapidly (<10 minutes) meet the tEGCO2level when challenged with changes in inlet blood flow or target EGCO2levels for all animals. These in vivodata demonstrate an important step toward portable ALs that can automatically modulate CO2removal and allow for substantial changes in patient activity or disease status in ambulatory applications.