Lung ultrasound to evaluate lung recruitment in neonates with respiratory distress (RELUS study)

Lung ultrasound (LUS) is a bedside tool useful to diagnose neonatal respiratory disease and to guide surfactant therapy. LUS scores have emerged as useful tool for newborn respiratory distress but is unknown if respiratory support settings may influence it. The aim of the study was to evaluate the feasibility of LUS scores evaluating lung recruitment in term newborns with respiratory distress when noninvasive respiratory it is increased.

Prospective study in a tertiary neonatal intensive care unit. Inclusion criteria were term neonates with respiratory distress requiring noninvasive respiratory support with nasal continuous positive airway pressure (nCPAP) within first 6 h of life with an LUS score higher than 8 were enrolled. LUS was performed three times. First LUS (LUS-1) was done in patients in nCPAP (Fabian Device) (Acutronic) (pressure of 6 cmH₂ O). Afterwards patients were placed in duo positive airway pressure (12/6 cmH₂ O), a second LUS (LUS-2) was performed immediately and a third (LUS-3) was done 2 h later on the same respiratory support. The primary outcome was to compare LUS scores in the different timelines. Second outcomes were to evaluate the level of respiratory distress and oxygenation were evaluated with SpO₂ /fraction of inspired oxygen (FiO₂ ) ratio (S/F ratio), FiO₂  ratio, respiratory rate, and blood gas analysis which were analyzed during the LUS-1 and the LUS-3. To evaluate newborn discomfort, patients were evaluated with Crying Requires oxygen Increased vital signs Expression Sleep (CRIES) scale.

Forty neonates were enrolled. Fifty percent were female (n = 20), median gestational age was 38 + 4 (interquartile range [IQR]: 37 + 5-39 + 4) with a median weight of 3155 g (IQR: 2637-3532). Duration of non invasive ventilation support was 72 h (IQR: 54-96). None of the patients required surfactant therapy or mechanical ventilation. LUS scores were no different between LUS-1 9 (IQR: 8.3-10) and LUS-2 9 (IQR: 8.3-10) (p = 0.675) but there were differences between LUS-1 and LUS-3 7 (IQR: 6.3-8.5) (p = 0.036). There was an improvement in the oxygen parameters, respiratory rate, and CO₂ between LUS-1 and LUS-3 (p < 0.001). There were no changes in the CRIES scale.

There is an improvement in clinical and laboratory parameters after the increasing of respiratory support in newborns with noninvasive ventilation. We observe a correlation with an improvement in the assessment of lung aeration were evaluated with LUS score.