Introduction. No data describes strength (S), effort tolerance (ET) and muscle fatigue (MF) in COPD with Chronic Respiratory Failure under Long Term Oxygen Therapy (COPD-LTOT) with different lung obstruction severity.

Aims To define S, ET and MF in COPD-LTOT patients categorized by pulmonary obstruction severity (POS) [FEV1 > 30 % < 50% = Higher FEV1 (HF) and FEV1< 30% = Lower FEV1 (LF)].

Methods Quadriceps Strength was assessed by Maximal Voluntary Contractions (MVC). Effort tolerance was assessed by 6-minute walking test (6MWT) and time to exhaustion (Tlim) at Constant Work Rate Cycling Test (CWRCT) set at 80% of Wmax, with rating of perceived exertion (RPE). MF was calculated as percent reduction in MVC after the CWRCT.

Results We included 47 patients (62% of males) (Table1). HF showed higher effort tolerance (?6MWT +56 m and ?Tlim +67 s), higher MF, lower peak RPE dyspnea (7.151.84 vs 8.110.58 p < 0,0141) with similar S.

Conclusions COPD-LTOT patients with more advanced POS had: more effort intolerance, equal rest strength more peak RPE dyspnea and less MF after the CWRCT than patient with less POS. Ventilatory limitations (Higher obstruction, hyperinflation and dyspnea) could be causes which doesn?t allow a longer exercise with higher MF.