Effects of inhaled nitric oxide in chronic obstructive pulmonary disease patients with hypercapnic respiratory failure and pulmonary hypertension

Therapy with inhaled nitric oxide (iNO) in patients with hypercapnic respiratory failure (RF) and pulmonary arterial hypertension (PAH) is currently of scientific interest. The aim of this study was to evaluate the effects of iNO therapy on COPD patients with hypercapnic RF and PAH during exacerbation of the disease. Methods. A randomized, prospective, controlled trial included 30 patients with COPD (age 65 (62; 75) years) with hypercapnic RF and pulmonary arterial hypertension (PAH) treated at the State Budgetary City Teaching Hospital “City Clinical Hospital named after D.D.Pletnev of Healthcare Moscow City Department” (2021). The inclusion criteria were: PaCO 2 ≥ 45 mm Hg and pulmonary artery systolic pressure PASP > 40 mm Hg as accessed by Doppler echocardiography. The patients were divided into two groups. Patients of the main group were administered iNO in the form of daily 90-minute sessons for two weeks using Tianoks device (Russian Federal Nuclear Center – All-Russian Research Institute of Experimental Physics, State Corporation “Rosatom”, Russia). Patients of the control group received treatment that corresponded to the severity of their COPD exacerbation according to the guidelines by Global Initiative for Chronic Obstructive Lung Disease (GOLD), 2020 – 2021. Hemodynamics and gas exchange, exercise tolerance, vascular stiffness, and obstructive disorders were assessed at baseline, on Days 7 and 14. Results. The main group demonstrated a decrease in PASP (38 (32; 43) mm Hg vs 47 (44; 54) mm Hg; p = 0.001), a decrease in stiffness index (SI) (7.03 m / s (5.3; 19.2) vs 12.2 m / s (5.7; 15.1); p = 0.01), decrease the pulmonary shunt fraction (Qs / Qt) (4.33% (3.7; 6.1) vs 9.12% (7.12; 11.3); p = 0.01), an increase in arterial vascular tone measured by reflective index (RI) (62.4% (51.2; 64.3) vs 58.5% (51.7; 63.8); p = 0.01), and increased exercise tolerance measured by 6-minute walking test (6MWT) (358.1 m (320.5; 368.2) vs 321.5 m (280.4; 329.1); p = 0.001) as compared to the control group. Conclusion. Our study indicates that iNO-therapy effectively reduces hypoxemia, endothelial dysfunction, improves hemodynamics, walking distance, and exercise tolerance during the exacerbation of COPD in patients with hypercapnic RF and PAH.