1. Division of PulmonaryCritical Care, and Sleep MedicineUniversity of Texas Medical BranchGalvestonTXUSA
2. Division of PulmonaryCritical Care, and Sleep MedicineUniversity of Florida College of MedicineJacksonvilleFLUSA
3. Division of Pulmonary and Critical Care MedicineUniversity of Virginia School of MedicineCharlottesvilleVAUSA
4. Office of BiostatisticsDepartment of Preventive Medicine and Community HealthUniversity of Texas Medical BranchGalvestonTXUSA