ABSTRACT
Background: An uncertain proportion of COVID-19 survivors may present persisting symptoms,referred to the term "Long COVID". The prevalence of exercise-induced oxygen desaturation (EID) in patients with Long COVID is still uncertain, ranging between 22% and 50%;moreover, the relationship of EID with exertional dyspnea and baseline Pulmonary Function Tests (PFTs) remains unclear. Aim(s): The study was designed to investigate the prevalence of EID in patients with "Long COVID" and assess its relationship to exertional dyspnea and PFTs. Method(s): A prospective cohort study was conducted including 194 consecutive "Long COVID" patients (M/F:132/62;age: 62.8+/-12.8 yrs) discharged from 2 university hospitals in North-Eastern Italy. At 6 month follow-up visit, patients underwent 6-min walking test (6MWT) and PFTs, including spirometry and diffusing capacity (DLco). The level of dyspnea was assessed by mMRC dyspnea scale. Result(s): Thirty-three (17%) patients showed early EID (SaO2 drop: 3.4 +/- 2.5;p<0.001) with a synchronous positive chronotropic response. Compared to non-desaturators, desaturators showed significantly reduced 6-min walk distance (420 [355-525] vs 500 [443.5-581] m;p=0.002) and DLco (70.6+/-24.7%pred vs 85.7+/-16.9%pred;p<0.001). The level of dyspnea didn't significantly differ between desaturators and non desaturators (mMRC dyspnea score: 1 [1-2] vs 1 [1-1];p=0.184). Conclusion(s): A significant proportion of survivors with "Long COVID" shows persistent oxygen desaturation during exercise which seems to be unrelated to the degree of dyspnea. 6MWT should be regularly performed after discharge from hospital to understand the extent and severity of EID and whether it may be associated with worse prognosis.