[1] Wake Forest Univ, Baptist Med Ctr, Dept Internal Med, Sect Pulm Crit Care, Winston Salem, NC 27157 USA
[2] Wake Forest Univ, Baptist Med Ctr, Dept Publ Hlth Sci, Winston Salem, NC 27157 USA
[3] Wake Forest Univ, Baptist Med Ctr, Dept Neurosurg, Winston Salem, NC 27157 USA
[4] Wake Forest Univ, Baptist Med Ctr, Dept Anesthesiol, Winston Salem, NC 27157 USA
[5] Vanderbilt Univ, Sch Med, Div Allergy Pulm & Crit Care Med, Nashville, TN 37212 USA
[6] Johns Hopkins Univ, Sch Med, Div Pulm & Crit Care Med, Baltimore, MD USA