Objective:To evaluate the dynamic changes of pulmonary arterial pressure (PAP) and cardiac function in neonates with pulmonary or extra-pulmonary acute respiratory distress syndrome (ARDSp/ARDSexp).Methods:An observational study was conducted. A total of 128 neonates with ARDS admitted to neonatology department of the Affiliated Yancheng Hospital of Southeast University Medical College from January 2016 to December 2020 were enrolled, with 67 neonates in ARDSp group and 61 neonates in ARDSexp group. After starting mechanical ventilation, oxygenation index [OI, OI = mean airway pressure (Pmean)×fraction of inspired oxygen (FiO 2)/arterial partial pressure of oxygen (PaO 2)×100], PAP, cardiac function parameters [cardiac index (CI), left ventricular ejection fraction (LVEF), right ventricular Tei (RV-Tei)], and plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) were compared between the two groups; the incidence of pulmonary arterial hypertension [PAH, pulmonary artery systolic pressure (PASP) was more than 35 mmHg (1 mmHg = 0.133 kPa) or more than 2/3 of the systolic blood pressure of the body circulation] of neonates was recorded. The correlation between PAP and NT-proBNP was analyzed by Pearson correlation method. The dynamically changes in PAP and RV-Tei before and after using Milrinone in neonates with ARDSp and ARDSexp combined with moderate-severe PAH (PASP 50-69 mmHg was moderate, and PASP≥70 mmHg was severe) were observed. The duration of mechanical ventilation, total length of hospital stay and prognosis were recorded; Kaplan-Meier survival curve was drawn to analyze the 28-day survival of the two groups. Results:The occurrence rate of PAH in ARDSp group was significantly higher than that in ARDSexp group (97.01% vs. 70.49%, P < 0.01). OI, PAP, NT-proBNP and RV-Tei were also higher [OI: 17.61±6.12 vs. 11.04±5.35, PAP (mmHg): 64.27±9.54 vs. 53.61±6.47, NT-proBNP (ng/L): 23 126.32±1 485.14 vs. 18 624.24±1 647.15, RV-Tei: 0.61±0.22 vs. 0.52±0.19, all P < 0.05], but there was no significant difference in CI or LVEF between the two groups. Pearson correlation analysis showed that PAP was significantly positively correlated with NT-proBNP ( r = 0.918, P < 0.01). There were 97 ARDS neonates with moderate-severe PAH with 63 in ARDSp group and 34 in ARDSexp group. Both PAP and RV-Tei in the two group showed a decreasing trend with the prolongation of Milrinone treatment, the decrease was more significant in the ARDSexp group compared with ARDSp group, the difference was statistically significant at 72 hours of treatment [PAP (mmHg): 38.42±8.95 vs. 45.67±13.32, RV-Tei: 0.58±0.19 vs. 0.61±0.13, both P < 0.05]; there was no significant difference in PAP or RV-Tei before extubation between the two groups. The duration of mechanical ventilation and the total length of hospital stay in ARDSp group were significantly longer than those in ARDSexp group [duration of mechanical ventilation (days): 10.12±1.36 vs. 6.31±1.31, total length of hospital stay (days): 16.52±3.25 vs. 13.12±3.57, both P < 0.01]. Kaplan-Meier survival curve showed that neonate in ARDSp group had a significantly lower 28-day cumulative survival rate as compared with ARDSexp group (82.09% vs. 95.01%; Log-Rank test: χ2 = 5.062, P = 0.025). Conclusions:Both PAP and RV-Tei were significantly increased in neonates with ARDS, PAP in neonates with ARDSp were significantly higher than that in neonates with ARDSexp. Dynamic monitoring of PAP and RV-Tei can reflect the severity of ARDS in neonates, and targeted intervention of pulmonary surfactant combined with Milinone for improving oxygenation and reducing PAP is one of the effective methods for the treatment of PAH.