Aim. To study the frequency of clinical and radiological signs of reperfusion pulmonary edema and compare them with the volume of endovascular intervention after balloon pulmonary angioplasty (BPA) in patients with chronic thromboembolic pulmonary hypertension (CTEPH).Materials and methods. The study included 50 patients with CTEPH, who underwent stage 1 PLA. To prevent severe reperfusion edema, the number of segmental arteries planned for angioplasty was taken into account, the Pulmonary Edema Predictive Scoring Index (PEPSI) was determined, and after the intervention, noninvasive ventilation was performed in the Continuous positive airway pressure (СPAP) mode for 24 hours. Clinical manifestations of reperfusion edema were assessed 1, 24, 48 and 72 hours after BPA. Radiological signs of edema were considered based on the results of multislice computed tomography (MSCT) or chest x-ray.Results. Angioplasty was performed on 97 segmental, 6 lobar pulmonary arteries, incl. by 45 (46,4%) – with occlusive lesions. The number of arteries undergoing angioplasty ranged from 1 to 7 in each patient, on average 1,9 ± 1,4, change in pulmonary flow grade (ΔPFG) – 4,3 ± 3,4, PEPSI 58,4 ± 51,0, which exceeded the recommended value of 35,5. During the 72-hour observation period, 28 (56%) patients had grade 1 edema, grade 2 reperfusion edema was observed in 15 (30%), grade 3 – in 5 (10%), grade 4 – in 2 (4%) patients. Patients with grade 2-4 edema had higher baseline mPAP (p = 0,015) and PEPSI (p = 0,046). All manifestations of reperfusion edema of 2-4 degrees were stopped due to the prolonged regimen of CPAP therapy for 3 ± 2 days. None of the patients reached grade 5 edema, and there were no deaths. Clinical manifestations of reperfusion injury were observed in 25 (50%) patients, their highest frequency was observed after 24 hoursConclusion. Balloon pulmonary angioplasty of the pulmonary arteries is a safe method for the treatment of inoperable patients with chronic thromboembolic pulmonary hypertension, provided that recommendations for the prevention of reperfusion pulmonary edema are observed. CPAP therapy can successfully prevent and stop the development of severe reperfusion injuries after BPA even when the risk index for reperfusion pulmonary edema is exceeded.