Respiratory diseases are a leading contributor to respiratory failure and death in neonatal inpatient wards (1). There are many causes of respiratory distress in neonates, the most being respiratory distress syndrome (RDS), pneumonia, transient tachypnea of the newborn (wet lung), persistent pulmonary hypertension of the newborn (PPHN), asphyxia, and early-onset sepsis, among others (2). When severe respiratory distress occurs clinically, mechanical assisted ventilation may be required. In developed countries, the use of mechanical ventilation for very preterm infants (<28 weeks) is 80%–90% (3). About 30%–50% of neonates in NICUs in developed countries require mechanical ventilation (4). In developing countries, the proportion of neonates requiting mechanical ventilation is about 10%–20%, but the mortality rate of respiratory failure is as high as 30%–50% (5). The mechanical ventilation rate of very low birth weight infants (<1,500 g) is about 60%–80%. The proportion of mechanical ventilation in full-term infants is about 2%–5% (6, 7). Early identification of severe respiratory failure, improving awareness of the need for mechanical ventilation, and reducing its overall use have become critical areas of clinical focus.

The influencing factors for mechanical ventilation include prematurity, perinatal asphyxia, infection, and maternal pregnancy diseases (8). Currently, identifying key indicators for mechanical ventilation, such as increased respiratory distress (RD), increased fractional inhaled oxygen (FiO₂), and abnormal gas exchange, has limitations. To illustrate, increases in FiO2 and respiratory severity scores [e.g., Silverman Anderson score (SAS)] often occur only after changes in pulmonary ventilation (9). In addition, arterial blood gas analysis is performed only infrequently because of its invasive nature, whereas capillary samples, frequently used, are cornerstones of decision-making in many NICUs. No reliable indicators currently exist to determine or predict the need for mechanical ventilation (10), underscoring the need for an early-stage screening tool to identify infants requiring invasive ventilation.

The neonatal Lung Ultrasound Score (LUS) is a noninvasive bedside-ultrasound tool that evaluates neonatal pulmonary lesions by quantifying several characteristic signs. The absence of A-lines indicates a loss of normal aeration. Coalescent B-lines suggest pulmonary edema, whether cardiogenic or associated with acute respiratory distress syndrome (ARDS) (11, 12). Lung consolidation indicates alveolar filling (pneumonia, atelectasis). Regional score differences reflect ventilation/perfusion imbalance (13). Pleural effusion can exacerbate atelectasis, further compromising ventilation. The LUS score is typically calculated by dividing the lungs into multiple anatomical regions, each scored from 0 to 3 based on ultrasound findings. A higher total score indicates more severe lung involvement. Its advantages include real-time imaging, absence of radiation and reproducibility, making it especially suitable for dynamic evaluation of critically ill neonates in the neonatal intensive care unit (NICU). LUS quantifies lung ventilation status and severity of lesions by analyzing ultrasound image characteristics of different areas of the lung to provide basis for clinical intervention (14). Evidence from previous studies indicates that pulmonary ultrasound (LU) enables detection of pulmonary ventilation changes before subsequent elevation of RD and FiO₂ (15). Pulmonary ultrasound offers significant advantages in neonatal intensive care due to its non-radiation, high observer correlation and short learning curve. The classical method of lung region partitioning divides the lungs into 12 regions (6 per side). The anterior chest is divided into upper and lower regions by the intermammillary line. The lateral thorax (from the anterior to posterior axillary lines) is also divided into upper and lower regions. The posterior thorax is similarly separated into upper and lower regions. In some studies, a simplified method is used, dividing each lung into 3 zones (anterior, lateral, posterior), for a total of 6 zones, which is suitable for rapid assessment. Each region is scored based on its ultrasound findings (0–3 points), and the regional scores are summed. The total LUS ranges from 0 to 36 points (12-zone method) or 0–18 points (6-zone method). Vc, et al. showed that a low LUS value can exclude the need for mechanical ventilation (16).

The previous Meta was published by Abdul Razak et al. in 2019 and included literature up to October 2018. Since then, nearly 100 new studies have been published. At present, there are still many controversies in the research, and so far, there is no definitive conclusion on whether LUS can be used to accurately predict mechanical ventilation in newborns and infants. Therefore, our study incorporates the most recently published findings and aims to summarize the existing clinical evidence through a systematic review and meta-analysis.

This systematic review and meta-analysis was conducted in accordance with the PRISMA 2020 statement and registered in the PROSPERO database (CRD420251029542).

As a non-invasive imaging evaluation tool, LUS can quantitatively grade the degree of lung lesions by systematically analyzing the characteristic ultrasound signs of the lungs (such as coalescent B lines, lung consolidation and pleural abnormalities) (26). The scoring system divides the bilateral chest into 12 standard areas and assigns a score ranging from 0 to 3 points according to the severity of abnormal signs in each area. The cumulative total score is positively correlated with the severity of lung lesions. Studies have shown that when the total LUS score exceeds a critical value, it often indicates that patients need mechanical ventilation support (27). In the field of critical care medicine, LUS has become an important auxiliary too for evaluating and managing patients requiring mechanical ventilation. The study by Pathak, et al. showed that LUS score correlates with different types of respiratory support and increases with the level of support (22). LUS scores have also been associated with clinical outcomes such as death, extubation failure, and recovery (28). In addition, this scoring system has important predictive value for clinical prognosis: a high LUS score is not only significantly correlated with mortality and the risk ofextubation failure in mechanically ventilated patients, but can also serve as an objective indicator to evaluate pulmonary inflammation resolution and to guide timing of weaning (29). These findings highlight the guiding role of LUS in individualized treatment decisions for critically ill patients.

In this meta-analysis, we found that higher LUS scores were correlated with an increased risk of mechanical ventilation in neonates and infants (OR: 1.18, 95% CI: 1.06–1.30). Neonates and infants requiring mechanical ventilation had significantly higher LUS scores than those who did not (SMD: 2.48, 95% CI: 1.66–3.29). Additionally, sensitivity analysis and Egger's test revealed no significant instability or publication bias among the included studies, further supporting the reliability of LUS in predicting the need for mechanical ventilation. The combined AUC value of LUS in predicting mechanical ventilation was 0.82 (95%CI: 0.79%–0.85%), indicating good diagnostic accuracy. Among the included studies, six used the 0–18 scoring system for pulmonary ultrasound, three used the 0–36 scale. Only four studies in the original literature reported LUS thresholds for mechanical ventilation with heterogeneous scoring methods, precluding determination of an optimal LUS cut-off for predicting mechanical ventilation. Current consensus recommends two LUS protocols for neonates and infants <1 year: (A) simplified (three regions per hemithorax-two anterior and one lateral-during the first 24–48 h) and (B) extended (five regions per hemithorax-similar to adults but with one lateral region-after 24–48 h) (30). Three included studies employed bilateral partitioning, a technique that complicates clinical application.

The previous meta-analysis by Razak et al. (31) included studies published prior to October 2018. It assessed the accuracy of LUS in predicting the need for surfactant therapy and mechanical ventilation in neonates with respiratory diseases receiving NCPAP support. Six studies were included: three used LUS scores, two utilized type 1 lung profiles, and one applied high-risk LUS assessment criteria. Their findings suggested that LUS could accurately determine whether neonates with respiratory distress on NCPAP required surfactant therapy or mechanical ventilation. In contrast, the present meta-analysis incorporates nine recent high-quality clinical studies, all of which used LUS scores. Through a combined analysis of multivariate categorical variables and diagnostic data, we found that a higher LUS score was positively associated with the need for mechanical ventilation, regardless of gestational age, including in young infants. Funnel plots and Deeks’ test indicated no publication bias among the included studies, further supporting the predictive value of LUS for mechanical ventilation in neonatal and infant populations.

The LUS score, derived from lung ultrasound, evaluates pulmonary lesions by quantifying several characteristic signs. As such, the LUS score can effectively predict the need for mechanical ventilation by reflecting the severity of pulmonary lesions and overall respiratory status and prognosis in children (32, 33). This study further confirmed the predictive value of high LUS scores for mechanical ventilation and suggests several underlying pathophysiological mechanisms: First, the vicious cycle of oxygenation dysfunction. A high LUS score directly reflects the extent of alveolar-interstitial edema and lung tissue consolidation by quantifying B-line density and the size of consolidated areas (26). Consolidated regions lose their capacity for gas exchange due to alveolar collapse and exudative filling. Coalescent B lines indicate interstitial edema, which thickens the alveolar-capillary barrier, exacerbating V/Q mismatch and leading to refractory hypoxemia (34). In such cases, it is difficult to correct hypoxia with conventional oxygen therapy, and positive end-expiratory pressure (PEEP) should be implemented through mechanical ventilation to reinflate and collapse alveolus, reduce intra-pulmonary shunt, and improve oxygenation efficiency through precise regulation of FiO₂ (35). Second, deterioration in respiratory mechanics and increased energy expenditure. Lung consolidation, resembling liver tissue (“hepatization”) due to organizing inflammatory exudate, markedly reduces lung compliance (36). In order to maintain the same tidal volume, the respiratory muscle of the child needs to overcome higher elastic resistance to do work, and the energy consumption increases. The high proportion of fatigue-prone type II fibers in children's diaphragm fibers makes them more prone to respiratory muscle fatigue (37). When the shallow respiratory index (RSBI) is >105 times/min/L or the maximum inspiratory pressure (MIP) is <30 cmH₂O, it indicates that the respiratory pump function is about to be decompensated, and mechanical ventilation can reduce oxygen consumption by partially or completely replacing spontaneous respiration, thereby preventing multi-organ failure (38). In addition, pulmonary ultrasound offers time-series early warning capability through dynamic monitoring, and LUS provides greater bedside accessibility and superior sensitivity for detecting parenchymal changes compared to chest x-ray (15). By establishing a LUS score trend model, it was found that an increase of ≥3 points within 24 h was associated with a 4.2-fold increase in the risk of intubation within 48 h (39). Typical warning signs include: progression from focal to coalescent on line B (40), dynamic air bronchogram within consolidation areas (indicating mechanization of exudation), and increased pleural effusion volume with disappearance of pulmonary slip sign. This real-time visual monitoring allows clinicians to implement lung-protective ventilation strategies before deterioration in blood gas analysis occurs (41).

This study has several limitations that may impact the conclusions and suggest directions for future improvement: (1) Limited number of included studies and the risk of potential selection bias: insufficient sample size may lead to reduced statistical efficiency and affect the robustness of the results. (2) Limited geographical representation and external validity: Most of the included studies were conducted in Asia and Europe, which may introduce confounding factors such as genetic differences, environmental exposures, and variations in clinical practice. This regional concentration limits the generalizability of the results to other populations. (3) Indicator heterogeneity affecting evidence quality: Significant heterogeneity was observed in key metrics, primarily due to variations in measurement tools, inconsistent follow-up periods, and differing definitions of clinical interventions. (4) Limited original data and inaccessible patient-level records preclude calculation of a precise cut-off, standardized LUS protocols and larger prospective studies are required to validate these findings (30).

The meta-analysis of multivariate categorical variables indicated that higher LUS scores were associated with an increased risk of mechanical ventilation in children. The combined diagnostic meta-analysis further demonstrated that LUS scores have high accuracy in predicting the need for mechanical ventilation. However, given the substantial heterogeneity among individual indicators and the presence of regional selection bias, there is a clear need to standardize primary endpoint assessment tools. Future efforts should focus on establishing an international, multicenter research platform and conducting large-scale prospective studies that include diverse populations, especially from underrepresented regions.