“Previously reported data concerning the effect of LVRS on arterial oxygenation and oxygen use have been conflicting,” Dr. Joshua O. Benditt from University of Washington School of Medicine, Seattle, and colleagues point out in the August 15 issue of the American Journal of Respiratory and Critical Care Medicine.
They analyzed data from 1078 patients enrolled in the National Emphysema Treatment Trial (NETT) – a large multicenter, randomized clinical trial of maximal medical therapy compared with LVRS for severe emphysema.
During the trial, investigators collected arterial blood gas data, performed a standardized oxygen titration test and asked patients about supplemental oxygen use at baseline and at different time points after LVRS or medical therapy in patients with severe COPD.
“LVRS as performed in the NETT results in an improvement in oxygenation that is small but significant,” Dr. Benditt told Reuters Health. There was a significant increase in arterial oxygenation (PaO2) and a decrease in arterial CO2 (PaCO2) “at all measured time points after LVRS,” he and colleagues note in their report.
Although the treatment groups were nearly identical at baseline, significantly larger percentages of medical patients had insufficient arterial blood oxygenation, with a PaO2 of 55 mm Hg or less, at each follow-up visit, compared with LVRS patients (22% vs 10% at 6 months; 22% vs 14% at 12 months; and 25% vs 15% at 24 months.
Significantly more LVRS patients than medical patients had a PaO2 at 24 months that was improved or stable compared with baseline (65% vs 39%; p < 0.001). Twenty-four months after randomization, 53% of LVRS patients with PaO2 of 55 mm Hg or less at baseline showed an increase to a PaO2 of greater than 55 mm Hg compared with only 17% in the medical group.
And while fewer medical patients required oxygen for treadmill walking at baseline compared with surgical patients (46% vs 53%), more medical patients required oxygen for treadmill walking at 6 months (49% vs 33%), 12 months (50% vs 36%), and 24 months (52% vs 42%).
“No factor predicting a shift from needing oxygen preoperatively to not needing oxygen postoperatively could be identified,” Dr. Benditt noted. As would be expected, baseline oxygenation status was the best predictor of postoperative oxygenation.
Am J Respir Crit Care Med 2008;178:339-345.