The purpose of this study is to evaluate the influence of exercise capacity and safety of iNO at doses of 10 ppm or 40 ppm for 2 hours per day after continuous treatment for one week, which is of great significance for finding safe and effective methods for treating COPD.

Inclusion Criteria:

1. Age ≥ 40 years, ≤ 75 years;
2. Previous smoking history ≥ 10 pack-years, and had stopped smoking for one month before study entry;
3. Met the diagnosis criteria of moderate and severe COPD: a post-bronchodilator FEV1/FVC < 0.7, and 30%< FEV1 < 80% predicted;
4. Signed informed consent and performed all the study mandated procedures.

Exclusion Criteria:

1. Pregnant or lactating women;
2. Current or recent month user of nicotine-like substances (including nicotine patches, etc.);
3. A diagnosis of asthma or other non-COPD respiratory disease, in the opinion of the Investigator;
4. Lack of patency of nares upon physical examination;
5. Experienced during the last month an exacerbation requiring start of or increase in systemic oral corticosteroid therapy;
6. Left ventricular systolic dysfunction: left ventricular ejection fraction (LVEF) < 50%;
7. Clinically significant valvular heart disease, including aortic valvular disease (moderate or severe aortic stenosis or regurgitation) and/or mitral valve disease (moderate or severe mitral stenosis or regurgitation), or status post mitral valve replacement;
8. Use within 30 days of screening or current use of approved pulmonary hypertension medications such as sildenafil, bosentan or prostacyclines;
9. Use of investigational drugs or devices within 30 days prior to enrollment into the study;
10. Any underlying medical or psychiatric condition that, in the opinion of the Investigator, makes the subject an unsuitable candidate for the study.