Author(s): SPINELLO, L., SIMONELLI, C., SALVI, B., VITACCA, M., VENTURELLI, M., PANERONI, M., Institution: UNIVERSITY OF VERONA, Country: ITALY, Abstract-ID: 530

INTRODUCTION:
Patients with chronic obstructive pulmonary disease (COPD) and chronic respiratory failure (CRF) experience exaggerated neuromuscular fatigue (NMF). Reduced muscle oxygen availability leads to increased metabolite production, exacerbating peripheral component of NMF, while chronic hypoxemia leads to exacerbation of central components of NMF. Oxygen therapy can correct hypoxemia, enhance aerobic metabolism, and reduce ventilatory effort. However, its effects on NMF development in COPD remain unclear.
This cross-sectional study hypothesizes that NMF is sensitive to changes in the inspired oxygen fraction (FiO2). The aim was to evaluate whether different levels of FiO2 (%) influence NMF development in COPD patients with CRF.
METHODS:
Twenty patients (81% male, age 72±6 YRS, BMI 25±6, FEV1 34.5±10.9%, FEV1/FVC 39.6±9.3, RV 206.5±53.1%) completed three intermittent isometric quadriceps tests at 80% of the time to exhaustion at 30% of maximal voluntary contraction (MVC). Tests were performed under three different FiO2 conditions using a Venturi mask®: A) 21%, B) 31%, and C) 60%. NMF was assessed through changes in MVC, voluntary activation (VA), and quadriceps potentiated twitch force (Qtw,pot) following exercise. Oxygen saturation (SpO2) was monitored throughout.
RESULTS:
The mean test duration was 739.6±260.1 seconds. Changes in MVC were -27.6±9.5%, -24.4±7.8%, and -22.0±7.1% for conditions A, B, and C, respectively (P=0.023), with significant differences observed between A-B (P=0.043) and A-C (P=0.035). ΔQtw,pot showed changes of -31.1±14.3%, -31.3±16.7%, and -26.7±16.1% for conditions A, B, and C, respectively (P=0.019), with differences between A-C (P=0.023) and B-C (P=0.014). VA decreased similarly across conditions: A -3.9±4.1%, B -2.7±3.0%, and C -2.2±3.9% (P=0.211).
SpO2 remained stable during the tests but differed significantly between conditions: A) 88.7±4.2%, B) 95.8±2.7%, and C) 98.5±1.5% (P < 0.001).
CONCLUSION:
The progressive changes in the MVC suggest that the acute oxygen administration reduces neuromuscular fatigue development in COPD patients with CRF. Indeed, this result was primarly determined by greater responses on the peripheral component of NMF.