In-Parallel Attachment of a Low-Resistance Compliant Thoracic Artificial Lung Under Rest and Simulated Exercise

Abstract

Background Previous thoracic artificial lungs (TALs) had blood flow impedances greater than the natural lungs, which could cause abnormal pulmonary hemodynamics. New, compliant TALs (cTALs), however, have an impedance lower than the natural lung. Methods In this study, a new cTAL design was attached between the pulmonary artery and left atrium in five sheep (60.2 ± 1.9 kg). A distal pulmonary artery band was placed to control the percentage of cardiac output routed to the cTAL. Rest and exercise conditions were simulated using a continuous dobutamine infusion of 0 and 5 mcg/kg/min, respectively. At each dose, a hemodynamic data set was acquired at baseline (no flow to the cTAL) and 60, 75, and 90% of CO shunted to the cTAL. Results Device resistance did not vary with blood flow rate, averaging 0.51 ± 0.03 mmHg/(L/min). Under all conditions, cardiac output was not significantly different from baseline. Pulmonary system impedance only increased above baseline with 5 mcg/kg/min of dobutamine and 90% of cardiac output diverted to the cTAL. Conclusion Results indicate minimal changes in pulmonary hemodynamics during pulmonary artery – left atrium cTAL attachment for high device flows under rest and exercise conditions.

Fourteen Day In Vivo Testing of a Compliant Thoracic Artificial Lung

“…18,19 Overall, the cTAL demonstrated its capability to be used for at least two weeks without anti-coagulant coatings, and likely longer with more sophisticated biomaterials approaches. The device maintained a low, constant resistance.…”

“…Left thoracotomy, instrumentation, graft attachment, and closure proceeded according to previous methods. 18,19 Blood inflow and outflow graft-conduits with a combined prime volume of 116 mL were fabricated by bonding vascular grafts (Maquet Getinge, Wayne, NJ, or Terumo Cardiovascular, Ann Arbor, MI) to PVC tubing using previous methods. 20 These were attached to the PA and LA for cTAL connection.…”

“…17 This design maximizes spatial and temporal blood flow uniformity in an effort to reduce blood flow resistance, improve gas exchange efficiency, and limit device thrombosis. 17 The cTAL’s rated flow exceeds 7 L/min, and its 0.5 mmHg/(L/min) resistance 17,18 was able to unload the right ventricle in an animal model of PH using a PA-LA attachment. 18 The present 14 day study examines whether the cTAL can maintain the gas exchange and resistance characteristics demonstrated during acute in vitro and in vivo studies, while maintaining normal animal physiology.…”

Artificial lungs––Where are we going with the lung replacement therapy?

“…Currently, there are two predominant modes of placement: series and parallel 27,48,54 . The parallel configuration is likely to be used in patients with pulmonary hypertension as the least stressful method for the right ventricle 27,48,63 . For this configuration, the blood inlet to the artificial lung is anastomosed surgically to the pulmonary artery, and the blood outlet to the left atrium provides complete bypass of the native lungs 27,48 .…”

“…The compliant thoracic artificial lung (cTAL) has been studied in acute experiments in vivo and in vitro 80 for the development of the Biolung (Michigan Critical Care Consultants [MC3], Ann Arbor, MI, USA) 63 . The devices are being developed to serve as a long‐term bridge to lung transplant for patients with end‐stage lung disease and have always featured excellent gas exchange 63 .…”