Five-day Wearable Respiratory Support With a Novel Ambulatory Pulmonary Assist System in an Awake Ovine Model.

ABSTRACT

BACKGROUND: The pulmonary assist system (PAS) is a wearable respiratory support system that is currently under development for patients with chronic lung disease as a bridge to lung transplantation or as destination therapy. This study evaluates the long-term performance and biocompatibility of the PAS in a 5-d awake, ovine model. METHODS: The PAS was attached to normal sheep in venovenous configuration. Components of the PAS included a 0.9 m2 surface area oxygenator and a lightweight, battery-powered axial flow pump. The system was also tested using the Abbott PediMag as the control pump. Each sheep was supported on the PAS for 5 d with 2 L/min blood flow and 4 L/min sweep gas. Activated clotting times of 200-240 s were maintained using intravenous heparin. Pump performance, oxygen transfer, oxygenator resistance, and hematologic parameters were measured throughout the support. RESULTS: The PAS, either using the axial flow pump or PediMag (n = 4 each), was well tolerated by the sheep without signs of device-related organ damage or hemolysis. All the studies achieved the full, 5-d study duration. The oxygenator resistance remained consistent without significant clot formation in all experiments with an average resistance of 2.55 ±â€…0.10 mm Hg/(L/min). The system achieved an average oxygen transfer rate of 116.4 ±â€…5.5 mL/min, with an average Hb concentration of 9.2 ±â€…0.6 g/dL. White blood cell, platelet, and hematocrit levels also remained stable and within normal limits throughout the study period. CONCLUSIONS: The PAS provided 5 d of uncomplicated ambulatory respiratory support with minimal clot formation, stable gas exchange, blood flow resistance, and hematologic parameters.