Cardiopulmonary exercise testing and ventilatory efficiency in long COVID-19: 15 months follow-up

Abstract

Long COVID-19 is defined as persistency of symptoms, such as exertional dyspnea, twelve weeks after recovery from SARS-CoV-2 infection; its pathophysiology still needs to be fully understood. We investigated exercise tolerance and ventilatory efficiency using cardiopulmonary exercise testing (CPET) in patients with long COVID-19. <b>Methods.</b> One hundred patients admitted&nbsp;to our hospital from March to August 2020 for a moderate to critical COVID-19 were enrolled in our long COVID-19 program. Medical history, physical examination and chest HRCT were obtained at hospitalization (T₀), at 3 (T₃) and 15 months (T₁₅). All HRCTs were revised using a semi-quantitative CT severity score (Pan, F. et al. Radiology 2020; 295(3):715–721). Pulmonary function tests (PFTs) were obtained at T₃ and T₁₅. CPET was performed at T₁₅ in twenty patients (10 male/10 female; mean age 62 years) with residual respiratory symptoms (e.g., exertional dyspnea) and/or an impairment in PFTs, D_LCO and/or K_CO. <b>Results.</b> At CPET, peak oxygen uptake (VO₂-peak) and ventilatory efficiency (V_E/VCO₂ slope) were 95.9±18.4 SD %pred and 31.4±3.9 SD, respectively. Of notice, significant correlations between VE/V’CO₂ slope and CT score (T₀) (r=0.403; p=0.039), CT score (T₃) (r=0.453; p=0.022) and D_LCO&nbsp;(T₃) (r=-0.465; p=0.019) were observed. <b>Conclusions.</b> At fifteen-months from COVID-19 pneumonia, a significant number of subjects (20%) still complains of exertional dyspnea. At CPET this may be explained by reduced ventilatory efficiency (i.e., increase in V_E/VCO₂), possibly related to the degree of lung parenchymal involvement in the COVID-19 acute phase, likely reflecting a damage in the interstitial/pulmonary capillary structure.