1. Division of Thoracic Surgery, Department of Cardiothoracic SurgeryStanford University School of MedicineStanfordCaliforniaUSA
2. Veterans Affairs Palo Alto Healthcare SystemPalo AltoCaliforniaUSA
3. Department of SurgeryUniversity of Pennsylvania School of MedicinePhiladelphiaPennsylvaniaUSA
4. Philadelphia Veterans Affairs Medical CenterPhiladelphiaPennsylvaniaUSA
5. Critical Care DivisionRoyal Victoria Hospital, McGill UniversityMontrealQuebecCanada
6. Respiratory DivisionRoyal Victoria Hospital, McGill UniversityMontrealQuebecCanada