1. Hospital de la Mujer y su Familia, Monterrey, Mexico.
2. Department of Acute and Continuing Care, The University of Texas Health Science Center at Houston, Houston, Texas.
3. Division of Pulmonary and Critical Care, The University of Texas Medical Branch at Galveston, Galveston, Texas.
4. Department of Critical Care Services, University General Hospital, Houston, Texas.
5. Department of Neurocritical Care Services, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.