Exercise related desaturation in patients with COPD is a reproducible phenomenon and important phenotypic marker

Exercise related desaturation is frequently observed in patients with moderate and severe COPD. It is an important marker of deterioration and unfavorable prognosis of the disease. Aim: To assess the reproducibility with time of exercise related desaturation (6MWT) in patients with COPD, who have been followed-up for more than 3 years. Patients and Methods: 90 male patients with COPD (age 65.1±9.4; BMI 25.6±5.3; smoking pack/years. 38.1±20.1; FEV1% = 46,1% ± 14,9%; МRС = 2,2 ± 0,8; САТ = 20,5 ± 6,8) performed field exercise test (6MWT = 492 ± 87 m). Oxygen saturation was monitored during exercise test and desaturation was defined as decrease of SpO2 by ≥4% and ≤88% for at least 3 min. Based on the decrease in SpO2 during exercise test the patients were divided into two groups – without desaturation (A, n=46) and with desaturation (B, n=44). The patients were followed-up for a period of 40,9±22,3 months. The data was managed by κ statistics. Results: 85 of the patients did not exhibit any change in exercise related desaturation (6MWT) during the follow-up. Three of the patients without desaturation during the initial 6MWT developed desaturation in the subsequent 6MWT and two of the patients with desaturation during the initial 6MWT did not reveal any signs of desaturation in the final 6MWT. The reproducibility of 6MWT with regard the manifestation of exercise related desaturation was very high (κ = 0,889). Conclusion: Exercise related desaturation is sustainable and reproducible with time. This phenomenon characterizes the initial pathophysiological mechanism of COPD and could be a trait of a separate phenotype of COPD with a worse prognosis.