Objective To analyze the lung ultrasonographic findings of respiratory distress syndrome（NRDS）in premature infants

and to explore the clinical value of different lung ultrasonographic findings in the diagnosis of NRDS.Methods A total of 109 preterm infants with suspected NRDS were selected from our hospital.Before treatment with exogenous pulmonary surfactant

continuous positive airway pressure or conventional mechanical ventilation

lung ultrasound examination

blood gas analysis and chest X-ray examination were performed. According to the clinical diagnosis results as the standard

different diagnostic criteria were established according to different lung ultrasonic manifestations（pleural line thickened

"B line"sign or"AIS"sign in at least one lung field was standard A

pleural line thickened

"white lung"sign appeared

"A line"sign disappeared was standard B

pleural line thickened

"white lung"sign and"lung onsolidation"sign visible in any lung field was standard C）

and their diagnostic efficacy for NRDS in premature infants were analyzed.Results Among the 109 NRDS preterm infants

31 cases were diagnosed as NRDS and 78 cases were not diagnosed as NRDS.The diagnostic sensitivity and negative predictive values of standard A for NRDS were both 100%

and those of standard B were higher than those of standard C（70.96% vs. 38.71%

89.66% vs. 80.41%

both P<0.05）.Among the 31 NRDS cases

15 cases were severe NRDS and 16 cases were non-severe NRDS.The sensitivity

specificity

positive predictive value and negative predictive value of standard C for the diagnosis of severe NRDS were 73.33%

93.75%

91.66% and 78.94%

respectively

and the Kappa value and AUC were 0.676 and 0.835.Conclusion "White lung"sign is an important imaging feature of lung ultrasound in early diagnosis of NRDS in premature infants."White lung"sign combined with"Lung consolidation"sign can be initially diagnosed as severe NRDS in premature infants.