Fig. 33:  This Figure shows the trial design of LOTT.^[22] LOTT was a randomized, controlled trial, but there was no placebo and it was not blinded.  In the end there were 14 core centers with multiple satellites.  There were about 45 centers overall who randomized patients after a screening visit to either supplemental oxygen or no supplemental oxygen.  The oxygen dose at rest and during sleep was prescribed at 2 L/min; the dose while ambulatory was individually prescribed at dosages sufficient to maintain oxygen saturation ≥ 90% for at least 2 minutes of walking. Participants with low blood oxygen levels at rest were instructed to use oxygen 24 hr/day; participants with normal resting blood oxygen levels but low/very low blood oxygen levels during exercise were instructed to use oxygen during physical activity and sleep.