Role of alveolar nitric oxide in gastroesophageal reflux-associated cough: prospective observational study.

Role of CaNO in GERCWhy was the study done? This study aimed to investigate the role of concentration of alveolar nitric oxide (CaNO) as a biomarker for peripheral airway inflammation in patients with gastroesophageal reflux-associated cough (GERC). The evaluation of airway inflammation in GERC has not been widely practiced in clinical settings, and the potential of CaNO as a biomarker remained unclear.What did the researchers do? The researchers conducted a prospective study involving patients diagnosed with GERC and compared the changes in CaNO levels between GERC patients and those with cough due to other causes. The study also identified potential factors contributing to elevated CaNO levels in GERC patients relative to the normal range. Additionally, CaNO level changes were evaluated in a subgroup of GERC patients with initially elevated CaNO levels (n = 26).What did the researchers find? The study found that CaNO levels were significantly increased in GERC patients. Using a reference value for normal CaNO, the GERC patients were divided into a high CaNO cohort and a normal CaNO cohort. More proximal reflux episodes and higher level of pepsin in sputum supernatant were observed in the high CaNO cohort. Moreover, CaNO demonstrated moderate predictive value for the therapeutic efficacy of intensified anti-reflux therapy in GERC patients. After several weeks of anti-reflux therapy, CaNO levels significantly decreased along with the resolution of cough. These findings further confirmed the predictive value of CaNO for anti-reflux therapy.What do the findings mean? The findings suggest that CaNO may have the potential to be used as a non-invasive biomarker for detecting peripheral airway inflammation in GERC patients. Increased CaNO may be associated with potential micro-aspiration. Furthermore, high CaNO may predict the need for intensified anti-reflux therapy.