Acute Effects of Oxygen Supplementation on Quadriceps Neuromuscular Fatigue in Patients With COPD and Chronic Respiratory Failure.

BACKGROUND

Patients with COPD and chronic respiratory failure (CRF) receiving long-term oxygen therapy experience exaggerated quadriceps neuromuscular fatigue (NMF). In this context, the effect of oxygen therapy on NMF remains unclear.

RESEARCH QUESTION: What is the impact of different Fio2 levels on neuromuscular fatigue during intermittent isometric quadriceps exercise in a population with COPD and CRF?

STUDY DESIGN AND

METHODS

Three intermittent isometric quadriceps tests, all at 80% of the time to exhaustion (TTE) at 30% of maximal voluntary contraction (MVC), were performed randomly in each patient with 3 different Fio2 measurements: 21%, 30%, and 60%. TTE was evaluated previously by breathing Fio2 at 21%. NMF was assessed through changes in MVC, twitch force quadriceps potentiated (Qtwpot), and voluntary activation (VA) after exercise (at peak, and at 30 seconds and 10 minutes after). Electromyography results were evaluated continuously.

RESULTS

We enrolled 20 patients (80.9% male; mean [SD] age, 71.80 [5.81] years; mean [SD] FEV1 to FVC ratio, 39.56 [9.32]; mean [SD] residual volume, 206.49% [53.14%]). Mean (SD) MVC changes were -27.60% (9.50%), -24.35% (7.80%), and -22.00% (7.13%) for the 21%, 30%, and 60% tests, respectively (P = .0341), with differences between the 21% and 30% Fio2 measurements (P = .032) and 21% and 60% tests (P = .032). Qtwpot showed mean (SD) changes of -31.10% (14.30%), -31.25% (16.70%), and -26.70% (16.10%) for the 21%, 30%, and 60% tests, respectively (P = .019), with differences between the 21% and 60% tests (P = .027) and the 30% and 60% tests (P = .014). VA decreased similarly across conditions (P = .211).

INTERPRETATION: Our results show that acute oxygen administration reduces quadriceps NMF in patients with COPD and CRF. These results highlight the role of oxygen availability in modulating NMF in this population. Future studies should investigate this effect during exercise training, as well as long-term consequences.

CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT05533957; URL: www.

CLINICALTRIALS: gov.