Evaluation of lung inflammation using Exhaled breath condensate in patients with post-COVID syndrome.

Abstract

<b>Introduction:</b> The term “post-COVID syndrome” encompasses a wide range of clinical conditions following SARS-COV2 infection. Whether post-COVID syndrome can be associated with a prolonged inflammatory and immune response is still unknown. Exhaled Breath Condensate (EBC) pH has been recognized as a robust marker of lung inflammation in various diseases (Kharitonov et al. Chest 2006; 130(5):1541-46). However, evidences on the role of EBC pH in diagnosing lung inflammation in post-COVID syndrome are still lacking. <b>Aims and objectives:</b> We aimed to investigate EBC pH in patients suffering from post-COVID syndrome. <b>Methods:</b> We enrolled 10 patients hospitalized with acute respiratory failure and COVID-19 pneumonia. We performed a complete follow up after 3 months (T1) and 6 months (T2) from discharge. Each visit included routine blood tests, arterial blood gas analysis, 6 minute walking test and body plethysmography. Finally, bronchial and alveolar EBC pH were collected at the end of each visit. <b>Results:</b> Alveolar EBC pH was significantly lower at T1 compared with T2 samples (p= 0.0007). Moreover, in T1 analysis, we found a less acid pH in bronchial EBC compared to the alveolar one (p=0.003). Alveolar and bronchial EBC did not differ at T2, as well as bronchial EBC from T1 to T2. Serum inflammatory biomarkers did not differ from T1 to T2 analysis. Finally, alveolar EBC was directly correlated with Neutrophil-Lymphocyte ratio (R=0.71, p=0.02). <b>Conclusions:</b> Alveolar EBC pH is a useful non-invasive tool to characterize and monitor lung inflammation in patients with post-COVID syndrome. Furthermore, no other serum biomarker seems to be sensitive enough to identify residual phlogosis after COVID-19 disease.