Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, College of Medicine, University of Kentucky, 740 South Limestone, L543, Lexington, KY, 40536-0284, USA. Department of Biostatistics, College of Public Health, University of Kentucky, 725 Rose Street, Lexington, KY, MDS 205B40536-0082, USA. Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, College of Medicine, University of Kentucky, 740 South Limestone, L543, Lexington, KY, 40536-0284, USA. lacall2@email.uky.edu.