Dynamic changes of lung function in infant of different gestational ages

Abstract

To explore the dynamic changes of lung function in infants born at different gestational ages without respiratory complications. 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. 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). 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.