Three of the four patients who experienced an increase in PaOa to levels above 55 mm Hg after six months demonstrated arterial oxygen desaturation to less than 85 percent when walking a mean of300 m at 0 percent grade. The fourth patient was unable to walk beyond 246 m and experienced a maximum reduction in Sa02 to 88 percent. The group of patients receiving TT02 therapy experienced a significant reduction in alveolar-arterial oxygen gradient (PtA-aJOj) (p=0.034 by the paired t test) during the study. The therapeutic regimen for management of COPD was unchanged during the study period, and all patients remained under the care of their referring physicians.
Review of the study by Weitzenblum et al disclosed that following observation for at least one year and monthly ABG measurements for three months before oxygen therapy was begun, three (25 percent) of 12 patients with arterial Po2 less than 55 mm Hg at the onset of oxygen therapy did not qualify for therapy at the end of one year. The mean reduction in pulmonary artery pressure (Ppa) was —4.1 mm Hg in patients in group A and was —1.80 in group B. These Ppa differences did not reach statistical significance for the two groups using the Mann-Whitney test for two groups (p<0.20); however, the authors did report a significant reduction in Ppa for all subjects.