In 2000, Zieliński noted no controlled trials assessed LTOT in patients without COPD comparable to the Nocturnal Oxygen Therapy Trial or the British Medical Research Trial, two acknowledged 1980s trials still used to model life-saving COPD oxygen therapy. He catalogued COPD/non-COPD LTOT use in seven different countries finding variations from 39%/61% in Japan to 93.4%/6.6% in the Czech Republic. In the United States, where about 80% of LTOT users are Medicare recipients, rates were 76%/24% COPD/non-COPD. The non-COPD pulmonary conditions associated with LTOT were tuberculous sequelae, interstitial pulmonary fibrosis, pneumoconiosis, kyphoscoliosis, bronchiectasis, and cystic fibrosis; in children, these were restrictive lung disease conditions associated with neuromuscular disease and bronchopulmonary dysplasia. Although these conditions share oxygen use with COPD, none evince the total COPD pathophysiologic spectrum. Cystic fibrosis, OSA, and pulmonary hypertension associated with COPD and congestive heart failure constitute other LTOT populations.