1. Division of Pulmonary and Critical Care Medicine, Texas A&M University, TX, USA
2. Christus Spohn Hospital, Corpus Christi, TX, USA
3. Corpus Christi, TX, USA
4. The University of Texas Health Science Center at Houston, TX, USA
5. The University of Texas Medical Branch at Galveston, TX, USA
6. University General Hospital, Houston, TX, USA