1. Division of Cardiovascular Disease and
2. Department of Anesthesia, Critical Care and Pain Medicine,
3. Harvard Medical School, Boston, Massachusetts; and
4. School of Nursing, University of Alabama at Birmingham, Birmingham, Alabama;
5. Anesthesia Critical Care Center for Research, and
6. Respiratory Care Services, Massachusetts General Hospital, Boston, Massachusetts;
7. Section of Cardiology, Birmingham Veterans Affairs Medical Center, Birmingham, Alabama