9. A disease or condition which in the opinion of investigator may put the patient at risk because of participation in this trial or limit the patient's ability to participate in this trial. Patients will be excluded if they require greater than 12L/min oxygen, are not ambulatory or require use of a walker or cane during the 6 Minute Titration Walk Test. Patients who cannot complete the 6 Minute Titration Walk Test are excluded from participation.