Exercise oxygen flow titration methods in COPD patients with respiratory failure

Abstract

We compare the adequacy of several titration procedures of oxygen flow in maintaining SpO(2) > 90% during the activities of daily life in patients with very severe COPD. Thirty-one very severe COPD patients undergoing oxygen-therapy were recruited. Three titration methods were randomly performed: (1) 6-min walking tests; (2) cycle-ergometer constant work-rate tests at a load equivalent to 12 ml/min/kg of oxygen uptake; (3) one single constant work-rate test at 40 W 12-h pulse-oximeter monitoring was performed on four consecutive days with the following oxygen flow during exercise: 1 l·min(-1) above the resting prescription (NOTT guidelines) and those established by the titration procedures. The time spent SpO(2) < 90% was higher for the titration based on NOTT and walking tests than for the oxygen flow established by the constant work-rate tests at 12 ml O(2)/min/kg (22.1 ± 18.7, 20.8 ± 19.5 and 6.7 ± 12.7%, respectively). As for the oxygen uptake-based titration, the simplified procedure (a single exercise test at 40 w) generates longer times spent SpO(2) < 90% and SpO(2) < 85%, although it maintains a SpO(2) > 90% for more 90% of the time. In COPD patients, exercise oxygen flow titrations by NOTT guidelines or walking tests do not allow a suitable oxygenation during the activities of daily life. Two more adequate alternative methods, based on constant work-rate tests, are proposed.