Characteristics and Quality of Life of Patients with COPD with Different Degrees of Exercise-Induced Desaturation on Six-minute Walk Test.

Objective: To identify predictive factors for different exercise-induced desaturation (EID) severities and evaluate health-related quality of life six months later in chronic obstructive pulmonary disease (COPD) patients.

Methods: This retrospective study consecutively analyzed 116 COPD outpatients (male: 82.8% [96/116]; age: 63.48 ± 7.48 years; disease severity distribution: GOLD 1/2/3/4 = 55.8%/34.6%/7.7%/1.9%). Patients were categorized into three groups based on oxygen desaturation (SpO₂) during the six-minute walk test (6MWT): non-EID (n = 52), mild-EID (n = 42), and severe-EID (n = 22). EID was classified as follows: Mild EID: SpO₂ decrease ≥4% with nadir SpO₂ ≥90%. Severe EID: SpO₂ decrease ≥4% with nadir SpO₂ ≤90%. Non EID: SpO₂ decrease <4% with nadir SpO₂ ≥90%. A six-month follow-up was conducted via telephone to record adverse events and assess quality of life using the Chinese version of the EQ-5D questionnaire, which includes five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, along with the EQ-VAS scale.

Results: Significant differences were observed across the three groups in peripheral blood oxygen saturation (SpO₂, %), peak expiratory flow (PEF, L/s), PEF (%), forced expiratory volume in the first second (FEV1, L), FEV1 (%), 6MWT distance (6MWD, m), Borg dyspnea, and Borg fatigue scores. The optimal cutoff values for predicting EID severity was 54.45% for FEV1% (AUC=0.716), 450.5 m for 6MWD (AUC = 0.761), and 94.5% for resting SpO₂ (AUC = 0.737). Multivariate logistic regression analysis identified low FEV1%, reduced 6MWD, and low resting SpO₂ as risk factors for severe EID (FEV1%: p = 0.002; 6MWD: p = 0.008; SpO₂: p = 0.018. Severe EID patients had significantly lower EQ-5D index and EQ-VAS scores (EQ-5D index: p = 0.002; EQ-VAS: P = 0.005), particularly in mobility and usual activities dimensions (mobility: p = 0.001; usual activities: p = 0.038).

Conclusion: Low FEV1%, reduced 6MWD, and low resting SpO₂ are key risk factors for severe EID, provide practical thresholds for clinical management of EID in COPD patients.