发达国家早产儿出生率为5%～9%,其中美国出生率略高为12%。流行病学研究表明早产儿出生率在近10～20年逐渐升高。自20世纪90年代以来早产儿病死率未见明显升高,但其晚期并发症的发生率有所增高[1]因而早产儿综合管理的进展对早产儿晚期并发症的预防和治疗有重要意义。慢性呼吸系统疾病是早产儿常见的晚期并发症之一,在不同年龄阶段有不同表现。婴幼儿 The birth rate of premature children in developed countries is 5% ~ 9%, of which the U.S. birth rate is slightly higher at 12%. Epidemiological studies have shown that the birth rate of premature children gradually increased in the past 10 to 20 years. There has been no significant increase in the mortality rate of preterm infants since the 1990s, but the incidence of late complications has been increased [1]. Therefore, the progress of comprehensive management of preterm infants is of great importance for the prevention and treatment of late complications in preterm infants . Chronic respiratory disease is one of the most common late complications in preterm infants and manifests itself at different ages. Infants and young children