1 UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL, USA.
2 UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL, USA; Birmingham VA Medical Center, Birmingham, AL 35294, USA.
3 UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL, USA; Birmingham VA Medical Center, Birmingham, AL 35294, USA. Electronic address: [email protected].