Background and aims: The use of fractional exhaled nitric oxide (FeNO) has been suggested as a quantitative marker for pulmonary arterial hypertension (PAH) in humans. To further characterize FeNO in PAH we investigated this marker in a rodent model. As there is no standardized technique for FeNO measurement in animals, we intended to reduce measuring errors and confounders of an existing published method by mathematical modification and tested its applicability in an NO-regulating therapy concept of PAH. Methods: Thirty-three male Sprague-Dawley rats underwent unilateral pneumonectomy and monocrotaline (P/MCT) injection and were observed for 49 days. A telemetric catheter was introduced into the left pulmonary artery to continuously record mean pulmonary arterial pressure (mPAP) and FeNO was assessed. After 35 days, animals were randomised to receive either oral L-arginine (300mg/kg) in combination with tetrahydrobiopterin (20mg/kg) therapy (n=12) or vehicle (n=11) daily over a period of 14 days. Results: Mean PAP at baseline was 17.19±9.62mmHg, which increased to 53.1±10.63mmHg 28 days after monocrotaline exposure (p<0.001). Using the modified technique there was an inverse correlation between exhaled NO and pulmonary pressures before (r=-0.366, p=0.043) and after MCT (r=-0.363, p=0.038) as well as after therapy administration (r=-0.657, p=0.02). Conclusion: Our modified technique proved robust in a rodent model, since valid and reproducible data were gained and showed an inverse correlation between exhaled NO and mPAP, while the existing method did not.