[1] Northwestern Univ, Pulm Hypertens Program, Div Pulm & Crit Care Med, Chicago, IL 60611 USA
[2] Northwestern Univ, Asthma COPD Program, Div Pulm & Crit Care Med, Chicago, IL 60611 USA
[3] Inova Fairfax Hosp, Adv Lung Dis Program, Falls Church, VA 22042 USA
[4] Univ Pittsburgh, Dept Pulm Allergy & Crit Care Med, Vasc Med Inst, Pittsburgh, PA 15213 USA
[5] Univ Chicago, Sect Pulm & Crit Care Med, Chicago, IL 60637 USA
[6] James A Haley Vet Hosp, Ctr Excellence Maximizing Rehabil Outcomes, Tampa, FL 33612 USA