Pulmonary ultrasonography in the follow-up of respiratory distress syndrome on preterm newborns. Reduction of X-ray exposure

Current Trends in the Imaging Diagnosis of Neonatal Respiratory Distress Syndrome (NRDS): Chest X-ray Versus Lung Ultrasound

Neonatal respiratory distress syndrome (NRDS) is a major cause of morbidity and mortality in newborns, particularly in neonatal intensive care units (NICUs). Until recently, its diagnosis had been based on clinical signs, arterial blood gas analysis, and chest X-ray (CXR). However, the frequent use of CXR exposes newborns to ionizing radiation, which can have long-term negative effects, including an increased risk of cancer, especially among premature infants. Lung ultrasound (LUS) has been proposed as a promising alternative for diagnosing NRDS due to its many advantages: no exposure to radiation, the ability to be performed at the bedside, repeatability, and ease of use. This review compared the diagnostic accuracy of LUS with the reference standard, CXR, in evaluating NRDS in newborns admitted to the NICU. Studies have shown that LUS can identify specific signs of NRDS, such as bilateral "white lung," pleural line abnormalities, and lung consolidations. The method has high sensitivity and specificity for diagnosing this condition and offers several advantages over other diagnostic methods; it does not involve ionizing radiation, thereby eliminating the risk of radiation exposure; it is cost-effective, easy to use, and can be performed at the patient's bedside, making it a viable alternative to CXR for reducing ionizing radiation exposure. Additionally, LUS can be used to monitor the progression of respiratory diseases and guide clinical management, especially in determining the optimal timing for surfactant administration in newborns with respiratory distress syndrome (RDS). We conclude that LUS is an effective and non-invasive alternative method for diagnosing and managing NRDS, with the potential to improve the safety and quality of care in the NICU, where rapid and safe diagnostic tools are essential for managing the health of newborns.

Radiation exposure and estimated risk of radiation-induced cancer from thoracic and abdominal radiographs in 1307 neonates

OBJECTIVE

This study examined radiation exposure and the possible risk of radiation-induced cancer in a large sample of newborn and premature patients.

MATERIAL AND METHODS

In this retrospective study, we included all hospitalised neonates treated at our university hospital who received at least one X-ray examination from 1 January 2013 to 31 December 2018. We evaluated the dose area product (DAP), effective dose (ED), and estimated risk. The International Commission on Radiological Protection Publication 60 defines values (2.8-13 × 10-2 Sv-1) to calculate the estimated risk in relation to the ED.

RESULTS

Of the 3843 patients (aged 241.1 ± 35.45 days) treated in the neonatal care unit, 1307 (34%) received at least one X-ray. The mean number of X-ray examinations per patient was 3.19 and correlated negatively with birth weight. The mean cumulative DAP was 5.9 mGy*cm2, and the cumulative ED was 23.7 µSv per hospital stay. Patients with a birth weight of < 1000 g showed the highest cumulative ED and DAP (p < 0.001). Patients with a birth weight of < 2500 g had the highest ED and DAP per image (p < 0.001). The highest radiation exposure (ED/DAP) occurred for thoracic/abdominal examinations, especially for neonates < 500 g (p < 0.001).

CONCLUSION

There is a strong correlation between immaturity, the number of X-ray examinations, and radiation exposure. The total exposure was minimal, and the number of X-rays per patient has been decreasing in recent years.

CLINICAL RELEVANCE

Possible risks to newborns and premature infants caused by ionising X-rays are often the subject of scientific and clinical discussion. Nevertheless, conventional X-ray imaging remains a frequently used tool, and total exposure remains at a very low level.

KEY POINTS

The number of X-rays per patient has been decreasing in a large university hospital. Half of all patients received only one X-ray; most had a birth weight over 1500 g. This radiation risk can be classified as 'minimal' for patients with a birth weight of < 500 g and as 'negligible' for others.

The Associations Between Lung Ultrasonography Scores in the First Day of Life and Clinical Outcomes

OBJECTIVES

To investigate the role of lung ultrasonography (LU) in predicting noninvasive ventilation (NIV) failure and the relationship between lung ultrasonography scores (LUS) with clinical outcomes in neonatal respiratory failure (NRF).

METHODS

A prospective, cross-sectional study was conducted in newborns with NRF who needed NIV and were evaluated by LU. The first LUS (LUS1) was calculated at 2-6 hours and the second (LUS2) at 12-24 hours of life. The patients were divided into NIV failure and NIV non-failure groups. The relationship between LUS and clinical outcomes was evaluated.

RESULTS

Among 157 neonates, the median (interquartile range) of gestational week and birth weight were 37 weeks (34-39), and 2890 grams (2045-3435), respectively. The reasons for NRF were transient tachypnea of the newborn (n = 92, 58.6%), congenital pneumonia (n = 58, 36.9%), and respiratory distress syndrome (n = 7, 4.5%). The rate of NIV failure was 17.8% (n = 28). Both LUS1 and LUS2 were significantly higher in neonates with NIV failure compared to neonates with NIV non-failure (P = .001). A cutoff value of LUS1 ≥ 4 predicted NIV failure with 96% sensitivity and 63% specificity. There were positive correlations between LUS and PEEP values, IMV and total MV days, carbon dioxide values, length of hospital stay, and antibiotic days (ρ_LUS1 , P = .843, <.001; .474, <.001; .444, <.001; .258, .001; .212, .008; .270, <.001, respectively).

CONCLUSIONS

Lung ultrasound scores were higher in neonates with NIV failure than with NIV non-failure group, and strongly correlated with end-expiratory pressure values. Lung ultrasound scores were found to be related with some of the clinical outcomes of the NRF, and this suggested that LUS could provide information about the prognosis of NRF.

The Role of Lung Ultrasound as an Early Diagnostic Tool for Need of Surfactant Therapy in Preterm Infants with Respiratory Distress Syndrome

OBJECTIVE

This study aimed to determine the accuracy of neonatal lung ultrasound (LUS) in predicting the need for surfactant therapy compared with chest X-ray (CXR) in preterm infants.

STUDY DESIGN

A prospective double-blind study was conducted in infants with a gestational age <34 weeks with respiratory distress syndrome (RDS) by evaluation with LUS and CXR on admission.

RESULTS

Among 45 preterm infants, the median (interquartile range [IQR]) LUS score was 4 (2-8) in the mild RDS group, whereas it was 10 (IQR: 9-12) in the severe RDS group (p < 0.01). The LUS score showed a significant correlation with the need for total surfactant doses (ρ = 0.855; 95% confidence interval [CI]: 0.801-0.902; p < 0.001). A cut-off LUS score of four predicted the need for surfactant with 96% sensitivity and 100% specificity (area under the curve [AUC]: 1.00; 95% CI: 0.97-1.00; p < 0.01). LUS scores predicted continuous positive airway pressure (CPAP) failure accurately (AUC: 0.804; 95% CI: 0.673-0.935; p = 0.001). A significant correlation was observed between LUS scores and positive end-expiratory pressure levels (ρ = 0.782; p < 0.001). During the study period, the CXR number per infant with RDS decreased significantly when compared with preceding months (p < 0.001). The LUS score in the first day of life did not predict the development of bronchopulmonary dysplasia (AUC: 0.274; 95% CI: 0.053-0.495; p = 0.065).

CONCLUSION

The LUS score in preterm infants accurately predicts the severity of RDS, the need for surfactant and CPAP failure. The routine use of LUS can decrease the frequency of CXRs in the neonatal intensive care units.

KEY POINTS

· LUS is a nonhazardous bedside technique.. · LUS predicts the need for surfactant in preterm infants.. · LUS predicts the severity of RDS better than CXR..

Utility of lung ultrasound scanning in neonatology

The utility of point-of-care lung ultrasound in neonatology is rapidly expanding. This review summarises current evidence of a diagnostic, procedural and observational tool valuable in the management of newborns requiring intensive care. Approaching a patient, probe in-hand with focused clinical question is essential, and barriers to implication together with important research questions are explored.

Lung Ultrasound for the Differential Diagnosis of Respiratory Distress in Neonates

BACKGROUND

Respiratory distress (RD) is the most common neonatal illness. Lung ultrasound (LUS) is a technique previously tested in neonatal studies on RD, but literature regarding its routine clinical applicability is still lacking.

OBJECTIVE

To assess the concordance between LUS performed by neonatologists with different training levels and chest X-ray (CXR) for the diagnosis of RD in newborns during the first 24 h of life.

METHODS

We enrolled newborns with RD during the first 24 h of life. Patients underwent LUS and CXR. LUS and CXR diagnosis were compared to evaluate concordance. Twenty percent of patients received two LUS (one from an experienced and one from a novice sonographer) to calculate the interobserver agreement. The difference in time needed to reach a diagnosis with LUS and CXR, and from novice and expert operators, was measured.

RESULTS

We studied 124 patients; 134 diagnoses were reported. The concordance between LUS and CXR diagnosis was 91% (95% CI 86-96%) with a κ statistic of 0.88 (95% CI 0.81-0.94). The median time to diagnosis was shorter for LUS (9.5 min, IQR 5-15) than for CXR (50 min, IQR 33-64) (p < 0.0001). In 25/124 patients, LUS was performed by both novice and experienced sonographers with complete concordance. The median time to diagnosis was shorter for expert (9 min, IQR 5-15) than novice operators (15 min, IQR 10-20) (p < 0.0002).

CONCLUSION

LUS and CXR have a high concordance in the differential diagnosis of neonatal RD in the first 24 h of life. LUS has a shorter operation time than CXR.

Lung ultrasound immediately after birth to describe normal neonatal transition: an observational study

OBJECTIVE

Lung ultrasound (LUS) has shown promise as a diagnostic tool for the evaluation of the newborn with respiratory distress. No study has described LUS during 'normal' transition. Our goal was to characterise the appearance of serial LUS in healthy newborns from the first minutes after birth until airway liquid clearance is achieved.

STUDY DESIGN

Prospective observational study.

SETTING

Single-centre tertiary perinatal centre in Australia.

PATIENTS

Of 115 infants born at ≥35 weeks gestational age, mean (SD) gestational age of 38^6/7 weeks±11 days, mean birth weight of 3380±555 g, 51 were delivered vaginally, 14 via caesarean section (CS) after labour and 50 infants via elective CS.

INTERVENTIONS

We obtained serial LUS videos via the right and left axillae at 1-10 min, 11-20 min and 1, 2, 4 and 24 hours after birth.

MAIN OUTCOME MEASURES

LUS videos were graded for aeration and liquid clearance according to a previously validated system.

RESULTS

We analysed 1168 LUS video recordings. As assessed by LUS, lung aeration and airway liquid clearance occurred quickly. All infants had an established pleural line at the first examination (median=2 (1-4) min). Only 14% of infants had substantial liquid retention at 10 min after birth. 49%, 78% and 100% of infants had completed airway liquid clearance at 2, 4 and 24 hours, respectively.

CONCLUSIONS

In healthy transitioning newborn infants, lung aeration and partial liquid clearance are achieved on the first minutes after birth with complete liquid clearance typically achieved within the first 4 hours of birth.

TRIAL REGISTRATION NUMBER

ANZCT 12615000380594.

Excess Radiation to Newborns Hospitalized in the Intensive Care Unit

Newborns in intensive care units are generally subjected to a great number of X-rays procedures and to the risk of radiation-induced damage. This study evaluated a possible excess radiation by excess of radiographs, excess of dose per radiograph or under-collimation of the X-ray beam. The mean of X-rays per newborn was 12 (1-65) during a mean hospitalization of 29 d (1-226 d). The mean frequency was 0.8 X-ray exposures per newborn. About 13% of X-rays were performed without a well-defined clinical motivation. The mean entrance surface dose of 72 μGy was higher than in most of comparative studies. Under-collimation caused non-thoracic structures to appear frequently on chest radiographs. This study indicates a possible reduction in X-rays exposures by applying the justification principle for each X-ray procedure, recommends a multiprofessional work in the attempt to dose optimization, and shows need of correctly use of collimation system to avoid irradiation of non-thoracic structures.

Lung ultrasound during the initiation of breathing in healthy term and late preterm infants immediately after birth, a prospective, observational study

INTRODUCTION

Lung ultrasound (LUS) has shown promise for evaluation of newborns with respiratory distress. However, no study has described the appearance of LUS during the initiation of breathing. We used LUS to describe the appearance of the lungs in healthy infants immediately after birth, starting with the infant's first breath, through the first 20min after birth.

METHODS

This was a single-center observational study enrolling neonates born at ≥35 weeks. We obtained LUS video recordings with the initiation of breathing. Recordings that captured one of the 1st four breaths after birth were included. We also obtained recordings at 1-10 and 11-20min after birth. Recordings were graded using a modified version of a previously published system, with additional grades to describe the appearance of the lungs prior to establishment of the pleural line.

RESULTS

We studied 63 infants, mean gestational age=39^1/7±2 days, mean weight=3473g±422, 33 infants were delivered vaginally and 30 via cesarean section. We captured the first breath after birth in 28 infants and within the first four breaths from the remaining 35 infants. The pleural line was established by a median of 4 breaths (3-6). At the 1-10min examination, all infants had an established pleural line and 89% demonstrated substantial liquid clearance. At the 11-20min examination, all infants had substantial liquid clearance.

CONCLUSION

Establishment of the pleural line, indicating lung aeration and substantial liquid clearance is achieved with the first few breaths after birth in term and near term infants.

Neonatal respiratory distress syndrome: Chest X-ray or lung ultrasound? A systematic review

BACKGROUND AND AIM

Neonatal respiratory distress syndrome is a leading cause of morbidity in preterm new-born babies (<37 weeks gestation age). The current diagnostic reference standard includes clinical testing and chest radiography with associated exposure to ionising radiation. The aim of this review was to compare the diagnostic accuracy of lung ultrasound against the reference standard in symptomatic neonates of ≤42 weeks gestation age.

METHODS

A systematic search of literature published between 1990 and 2016 identified 803 potentially relevant studies. Six studies met the review inclusion criteria and were retrieved for analysis. Quality assessment was performed before data extraction and meta-analysis.

RESULTS

Four prospective cohort studies and two case control studies included 480 neonates. All studies were of moderate methodological quality although heterogeneity was evident across the studies. The pooled sensitivity and specificity of lung ultrasound were 97% (95% confidence interval [CI] 94-99%) and 91% (CI: 86-95%) respectively. False positive diagnoses were made in 16 cases due to pneumonia (n = 8), transient tachypnoea (n = 3), pneumothorax (n = 1) and meconium aspiration syndrome (n = 1); the diagnoses of the remaining three false positive results were not specified. False negatives diagnoses occurred in nine cases, only two were specified as air-leak syndromes.

CONCLUSIONS

Lung ultrasound was highly sensitive for the detection of neonatal respiratory distress syndrome although there is potential to miss co-morbid air-leak syndromes. Further research into lung ultrasound diagnostic accuracy for neonatal air-leak syndrome and economic modelling for service integration is required before lung ultrasound can replace chest radiography as the imaging component of the reference standard.

Lung Ultrasound in Early Diagnosis of Neonatal Ventilator Associated Pneumonia before Any Radiographic or Laboratory Changes

Neonatal pneumonia is reported to be the primary cause of neonatal respiratory failure and one of the common causes of neonatal hospitalization and death in developing countries. Chest X-ray was considered the gold standard for diagnosis of neonatal pneumonia. Lung ultrasonography has been described as a valuable noninvasive tool for the diagnosis of many neonatal pulmonary diseases. We report a case of ventilation associated neonatal pneumonia with very early diagnosis using lung ultrasound before any significant radiographic changes in chest X-ray or laboratory findings suggestive of infection.

Lung ultrasound accurately detects pneumothorax in a preterm newborn lamb model

AIM

Pneumothorax is a common emergency affecting extremely preterm. In adult studies, lung ultrasound has performed better than chest x-ray in the diagnosis of pneumothorax. The purpose of this study was to determine the efficacy of lung ultrasound (LUS) examination to detect pneumothorax using a preterm animal model.

METHODS

This was a prospective, observational study using newborn Border-Leicester lambs at gestational age = 126 days (equivalent to gestational age = 26 weeks in humans) receiving mechanical ventilation from birth to 2 h of life. At the conclusion of the experiment, LUS was performed, the lambs were then euthanised and a post-mortem exam was immediately performed. We used previously published ultrasound techniques to identify pneumothorax. Test characteristics of LUS to detect pneumothorax were calculated, using the post-mortem exam as the 'gold standard' test.

RESULTS

Nine lambs (18 lungs) were examined. Four lambs had a unilateral pneumothorax, all of which were identified by LUS with no false positives.

CONCLUSIONS

This was the first study to use post-mortem findings to test the efficacy of LUS to detect pneumothorax in a newborn animal model. Lung ultrasound accurately detected pneumothorax, verified by post-mortem exam, in premature, newborn lambs.