[Characteristics of lung function in preterm infants with varying degrees of bronchopulmonary dysplasia].

OBJECTIVE: To explore the characteristics of lung function in preterm infants with varying degrees of bronchopulmonary dysplasia(BPD). METHODS: There were 407 infants (278 males and 129 females) were recruited from Shenzhen Children' Hospital between January 2011 and October 2012.Among them 188 term infants (term group)and 113 preterm infants (non-BPD preterm group) were selected as controls. A total of 106 BPD infants from the observation group were divided into mild(n = 48), moderate (n = 42) and severe(n = 16) sub-groups according to the definition of BPD. Infants with diseases interfering with lung function, such as congenital heart disease, congenital diaphragmatic hernia, or thoracic wall deformities, were excluded. Lung function was tested at a postmenstrual age (PMA) of 44 weeks.q test, Dunnett C test and Spearman analysis were used for statistical analysis. RESULTS: The age range was 17-116 d, test weight range 1.83-7.00 kg and test height range 40.0-64.0 cm.In non-BPD preterm group, the respiratory rate (RR) was higher than that in term group ((50 ± 13) vs (44 ± 10) times/min,P < 0.01) ,while the tidal volume(TV), ratio of time to peak tidal expiratory time and expiratory time (Tpef/Te) and peak expiratory flow(TPEF) were all less than those in term group ((25 ± 9) vs (29 ± 7)ml,29% ± 9% vs 33% ± 8%, (59 ± 23) vs (65 ± 25)ml/s,all P < 0.05) .Neither functional residual capacity(FRC) nor lung clearance index (LCI) had significant statistical difference between two groups ((20 ± 5) vs (19 ± 5)ml/kg, 8.4 ± 2.8 vs 8.7 ± 3.4, all P > 0.05)) . In moderate and severe BPD groups, RR ((57 ± 9), (58 ± 10) times/min) were both higher than that in non-BPD group(both P < 0.05) while RR in mild group ((53 ± 13)times/min)had no statistical significant difference with non-BPD group (P > 0.05). The values of TV and LCI in mild, moderate and severe BPD groups have no statistical significance with non-BPD group (all P > 0.05). Except for mild BPD group(24% ± 13%, (18 ± 5)ml/kg), Tpef/Te and FRC in both moderate and severe groups (20% ± 9% and 18% ± 5%, (15 ± 3)and (15 ± 4)ml/kg)were less than those in non-BPD group(all P < 0.05). Only in severe BPD group ((85 ± 11)ml/s), TPEF was higher than that in non-BPD group(P < 0.05). Correlation analysis showed that, except for LCI, all of these parameters were significantly associated with the degree of BPD(all P < 0.05). CONCLUSIONS: For BPD and non-BPD preterm infants, there are various changes in respiratory rhythm, lung volume, ventilation inhomogeneity, ventilatory efficiency and small airway resistance. The increases of pulmonary elastic recoil and degree of major airway constriction are obvious in moderate and severe BPD infants.

[Dynamic changes of lung function in infant of different gestational ages].

OBJECTIVE: To explore the dynamic changes of lung function in infants born at different gestational ages without respiratory complications. METHODS: A total of 110 cases of hospitalized neonatal patients were retrospectively recruited and analyzed at Shenzhen Children's Hospital from July 2010 to August 2012. By gestational age they were divided into 3 groups of full term (37-40 weeks, n = 55, 29 males and 26 females) with an average birth weight (3.1 ± 0.3) kg, late preterm group (34- < 37 weeks, n = 30, 18 males and 12 females) with an average birth weight (2.1 ± 0.3) kg and early preterm (<34 weeks, n = 25, 16 males and 9 females )with an average birth weight (1.4 ± 0.3) kg. At Days 1, 14 and 28, lung function parameters of functional residual capacity (FRC) and lung clear index (LCI) were measured by multiple breath washouts with an ultrasonic flow meter and tidal breathing. One-way ANOVA was used for each index. RESULTS: Tidal expiratory flow 75% remaining tidal volume (TEF75), tidal expiratory flow 50% remaining tidal volume (TEF50) and tidal expiratory flow 25% remaining tidal volume (TEF25) gradually increased at Days 1, 14 and 28 in 3 groups. However respiratory rate (RR) gradually decreased. Compared with full term and late preterm, the early preterm infants had lower TEF75, TEF50 and TEF25, lower the ratios of time to peak expiratory flow and expiratory time (TPTEF/TE), lower ratios of volume to peak expiratory flow and expiratory volume (VPEF/VE) ((71 ± 21) and (66 ± 16) vs (55 ± 19)ml/s, (70 ± 20) and (62 ± 17) vs (51 ± 16)ml/s, (54 ± 17) and (51 ± 13) vs (38 ± 10)ml/s, 37% ± 8% and 34% ± 9% vs 29% ± 6%, 38% ± 6% and 33% ± 8% vs 28% ± 7%, F = 5.82, 8.74, 11.30, 7.72, 16.40, all P < 0.01), higher RR and LCI at Day 28((49 ± 6) and (51 ± 8) vs (56 ± 7)/min, 8.6 ± 2.7 and 8.9 ± 2.2 vs 10.8 ± 2.0,F = 10.09, 7.15, both P < 0.05). At a matched post-menstrual age of 40 weeks, compared with full term and late preterm, the early preterm group had lower TEF50, TEF25, TPTEF/TE, VPEF/VE ((65 ± 21) and (62 ± 12) vs (50 ± 17)ml/s,(51 ± 13) and (47 ± 10) vs (39 ± 10)ml/s, 36% ± 8% and 31% ± 7% vs 30% ± 6%, 37% ± 10% and 32% ± 8% vs 29% ± 6%,F = 4.41, 8.23, 9.08, 7.35, all P < 0.05). CONCLUSIONS: Lung function improves with the elongation of days. The parameters of lung function in early infants are worse than those in full and late-preterm counterparts. At a corrected gestational age of 40 weeks, early preterm infants fail to achieve catch-up growth in lung function. Dynamic monitoring of lung function in preterm infants of different gestational ages is of vital importance for gauging respiratory maturity and assessing lung development especially for preterm infants.