In this study, we compared the therapeutic efficacy of lung recruitment plus INSURE and INSURE alone for the preterm neonates with RDS. The results showed that compared to the control group, the lung recruitment group had a significantly lower proportion of preterm neonates requiring MV within 72 h after extubation (23% vs. 38%, P = 0.025) and pulmonary surfactant administration, as well as a shorter MV duration. Nevertheless, there were no significant differences in other secondary outcomes, 4 parameters of blood gas, and the incidence of complications between the two groups. Multivariate logistic regression analysis demonstrated that the control group had a 2.17-time higher risk of requiring MV than the lung recruitment group (AOR: 2.17, 95% CI: 1.13–4.18; P = 0.021). Compared with infants with a normotensive mother, infants with a hypertensive mother have a 2.41-time higher risk of requiring MV (AOR: 2.41, 95% CI: 1.15–5.05; P = 0.020).
Lista et al. conducted a clinical trial in which preterm infants with RDS treated with sustained lung inflation (25 cm H2O, sustained for 15 s) at birth and concluded that preterm infants with RDS received sustained lung inflation at birth may decrease the need for MV and did not induce adverse effects as compared with a historical control group [18]. Therefore, the condition of 25 cm H2O for 15 s was used in this study. Consistent with Lista et al.’s observation, our results suggested that lung recruitment can effectively reduce the need for MV but did not increase the adverse effects. In addition, both MV duration and the number of pulmonary surfactant administration were significantly reduced in the lung recruitment group as compared with the control group, which were in line with previous findings [11, 12, 18,19,20]. The lung recruitment technique might positively affect the clearance of lung fluid and allows a more even distribution of air throughout the lungs, thus facilitating the formation of FRC [21]. Therefore, the beneficial effects may be attributed to lung recruitment, subsequent FRC achievement and inflation-induced alveolar expansion.
BPD is a major complication of preterm birth [22] and has a complicated pathogenic mechanism. Immature lung development, acute lung injury, and abnormal repairment after injury are key points leading to BPD [23]. One of the most important pathogenic factors of BPD is ventilator-induced lung injury [24]. In this study, the incidence of BPD was lower in the lung recruitment group than in the control group (33% VS 40%), but the difference did not reach statistical significance. The incidence of different severe BPDs was also not significantly different between the two groups. This result suggested that lung recruitment did not increase the incidence of BPD. In this study, lung recruitment did not increase the incidences of adverse effects, including IVH, NEC, PDA, ROP, which is in agreement with previous studies [13, 14, 18, 25].
In this study, neonates of hypertensive mothers had a higher risk of the need for MV within 72 h after extubation than those of normotensive mothers. It has been shown that gestational hypertension can promote maternal production of soluble fms-like tyrosine kinase-1 (sFlt-1), an anti-angiogenic factor that can block vascular endothelial growth factor (VEGF) signaling [26, 27]. Since VEGF signaling is essential for the growth of pulmonary blood vessels and the production of surfactants, sFlt-1 may lead to increased incidence and severity of RDS in preterm neonates with hypertensive mothers. Lung recruitment seemed did not help these patients, and the underlying mechanism is needed to be further investigated.
In this study, two cases had pneumothorax in the lung recruitment group and three cases had pneumothorax in the control group, suggesting that lung recruitment did not increase the risk of pneumothorax. This result is consistent with previous reports [10, 14, 15, 25]. By contrast, Lista et al. have reported that patients with lung inflation treatment have a 4.57-time high risk of pneumothorax than the control patients [11]. The discrepancy might be attributed to different study subjects, and the effect of lung recruitment on pneumothorax should be further investigated.
In this study, no difference in mortality was found between the two groups. Two cases of death in the lung recruitment group because their parents gave up treatment rather than pneumothorax or other severe complications. This result suggested lung recruitment did not increase mortality. The comparison in the blood gas parameters between the two groups showed no significant difference, suggesting that lung recruitment did not impact the circulation and the rate of acidosis. This may be due to the comprehensive influence of ventilation improvement.
There are still some limitations to this study. First, the study was not a double-blind design. The staffs performing the study also cared for the infants later, which might affect the outcomes. We tried to minimize this bias by strictly following the trial protocol during the whole trial. In addition, this was a single-center trial and the sample size was still relatively small. In the future, a large multicenter trial should be conducted to validate the findings of this study.