|Year : 2020 | Volume
| Issue : 4 | Page : 272-275
Lung ultrasound and neonatal respiratory distress syndrome
Irmina Sefic Pasic1, Sabina Terzic2, Jovana Nisandzic2, Danka Pokrajac2
1 Department of Pediatric Radiology, Radiology Clinic, Clinical Center University of Sarajevo, Sarajevo, Bosnia and Herzegovina
2 Pediatric Clinic, Clinical Center University of Sarajevo, Sarajevo, Bosnia and Herzegovina
|Date of Submission||10-May-2020|
|Date of Decision||10-Jul-2020|
|Date of Acceptance||09-Aug-2020|
|Date of Web Publication||01-Oct-2020|
Dr. Irmina Sefic Pasic
Bolnicka 25, 71000 Sarajevo
Bosnia and Herzegovina
Source of Support: None, Conflict of Interest: None
Background: Respiratory distress syndrome (RDS) in premature neonates has high morbidity, and it is encountered as one of the most common pathological conditions in these patients. This prospective study included 51 patients with a mean gestational age of 31 gestational weeks, hospitalized in the neonatal intensive care unit (NICU) in a tertiary-level university hospital. Aims and Objectives: The aim of our study is a comparison between lung ultrasound (US) and chest radiography in diagnosing RDS in premature neonates. Materials and Methods: US findings were classified into three profile scales and X-ray findings into a four-grade radiographic scale. Results: The results show a good concordance between chest radiography and lung US with kappa, sensitivity, and negative predictive value results in favor of US. Most of the patients had US-profile 1, which corresponds to X-ray profiles 3 and 4. US finding included the presence of confluent B lines, “white lungs,” subpleural consolidations, and thick pleura, but also A-lines, mostly found in a resolution of the disease and mild cases. Conclusion: Lung US still is not a routine procedure despite its wide use in NICUs, and as non-harmful, repeatable method, it can be used as a complementary modality to a chest X-ray. By introducing lung US as a standard method of examination in day-to-day work, it would be possible to reduce the use of X-ray studies in premature neonates.
Keywords: Lung ultrasound, neonates, respiratory distress
|How to cite this article:|
Pasic IS, Terzic S, Nisandzic J, Pokrajac D. Lung ultrasound and neonatal respiratory distress syndrome. J Clin Neonatol 2020;9:272-5
| Introduction|| |
Respiratory distress syndrome (RDS) is one of the most common pathological conditions encountered in premature babies at neonatal intensive care units (NICUs). Due to insufficient production of surfactant in the fetus before 34 gestational weeks with immature lungs, the incidence of respiratory distress is higher in younger fetuses. There is an inverse proportion in gestational age (GA) and birth weight, and the most severe cases are premature with low birth weight and low GA.
The diagnosis of respiratory distress is based on clinical signs, arterial blood analysis, and chest X-ray (CXR).
Blood gas analysis includes hypoxemia, hypercarbia, and metabolic acidosis.
Lung ultrasound (US), although widely used in NICU departments, still has not been included in the algorithms of RDS patient's management, considering that this method does not involve ionizing radiation.
Children and especially premature babies are at a higher risk of the harmful effects of ionizing radiation because of their age and intensive growth process., Undoubtedly, CXR has its advantages, but it should be our intention to decrease the use of methods with ionizing radiation with nonharmful methods such as US, where possible.
In our study, we compared X-ray and lung US in the diagnosis of RDS in neonates.
| Methods|| |
This prospective cohort study included 51 preterm infants (≤35 weeks GA) in 1-year period that had positive clinical and laboratory signs of impaired respiratory function, suspected for RDS with a comparison between CXR and lung US. Patients were hospitalized in the neonatal intensive care department of a tertiary-level university hospital, and approval from the ethical committee was obtained for the study.
All US examinations were performed with high-frequency linear-array probes of 7, 5, and 10 MHz. Examinations were done in the supine and oblique positions of patients, with transverse and sagittal planes in the defined anatomical areas (anterior – between the sternum and anterior axillary line; lateral – between the anterior and posterior axillary lines; and posterior – between posterior axillary line and spine). Midaxillary, midclavicular, and paraspinal lines are imaginary vertical lines that go through the middle of axilla, clavicula, and scapula and are used as anatomical marks during the examination of the lung area.
Chest radiography was performed in the supine position using a single X-ray unit, GE TMX+ (General Electric, Boston, MA, USA) and Agfa CR30-X computed radiography (CR) imaging system (Agfa-Gevaert, Mortsel, Belgium). Exposure was done in anteroposterior projection with tube potential of 53 kV and tube loading of 3.2 mA, focus–skin distance of 87.7 cm, and CR detector size of 18 cm × 24 cm.
Interpretation of US and radiographic examinations was done by two pediatric radiologists with 10 and 6 years of clinical experience. The radiologists were aware of the clinical status and laboratory tests of patients during the US examination, but blinded for patient's chest radiography, which was later interpreted by another radiologist (blinded for US findings).
Interpretation of CXR was based on the analysis of a four-grade radiographic scale [Table 1].
The ultrasound examination include evaluation of pleural line, lung sliding, presence of A-lines and B-lines, interstitial syndrome/white lung, and subpleural lung consolidation.
US findings were classified into three profiles [Table 2].
Clinical staging, known as CRIB score (Clinical Risk Index for Babies), is correlated with a four-grade radiographic scale of a CXR.
| Results|| |
The present study included 51 pre-US term newborns, out of which 26 (50.9%) were female and 25 were male (49.1%). The median GA was 31 weeks, and the Median birth weight was 1790 g (1570-2160 g).
[Table 3] shows the results of X-ray and US classification grades, and these grades were in inverse proportion. Most of the patients had US-profile 1, which corresponds to X-ray profiles 3 and 4.
|Table 3: Ultrasound and X-ray profiles for respiratory distress syndrome|
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US findings showed irregularities of pleural line, presence of confluent B lines, and subpleural consolidations, while none of the patients had pleural effusion [Figure 1] and [Figure 2].
Prevalence of A-lines we founded in patients during the disease resolution [Figure 3].
US examination has been repeated consequently 3 days in a row, but for statistical analysis only initial US was compared to an initial CXR.
Results in [Table 4] show that US and X-ray have more or less similar results where accuracies are identical; parameters such as kappa, sensitivity, and negative predictive value are in favor of US, whereas others for the X-ray. An excellent indicator is also area under the curve where the results show that US is fair, whereas the X-ray is a weak diagnostic tool. The summary of all statistical parameters as box plots is shown in [Figure 1].
None of our patients had pleural effusion or significant consolidation, besides previously mentioned subpleural consolidations. All US findings are shown in [Table 5].
|Table 5: Ultrasound findings in patients with respiratory distress syndrome|
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| Discussion|| |
Lung US has been used in clinical settings for a long time, initially promoted in literature and articles published by various authors, mostly by Lichtenstein et al.,, The interpretation of US findings is based on the analysis of artifacts. The pathophysiology of RDS is well known and results in impaired lung function due to insufficient amount of surfactant and presence of fluid in alveolar and interstitial space.,
The fluid inside the lungs, on US, is presented as B lines, more or less confluent. The distance between B lines can be <3 mm, or, respectively, 7 mm, depending on fluid localization inside alveolar or in interstitial space. B lines erase physiological A-lines. In our cohort, we also found a thick pleural line, >3 mm, which is considered normal. In addition, subpleural consolidations were present, more frequently in severe patients who spent more days on continuous positive airway pressure (CPAP) or which required mechanical ventilation.
Classification of imaging findings was into 3-profile US scheme and 4-grade radiographic scale.,
The present study results showed that US is a sensitive method, compared to X-ray, with accuracy similar to CXR, which is considered a standard way of diagnosing RDS in neonates. These results are similar to those of other studies, that were conducted among premature babies with RDS.,,, Interobserver agreement (0.48) was interpreted as a moderate result. Because we performed an US examination 3 days in a row, we could evaluate patient condition on each day and follow the evolution of the disease. Considering timely information on patient condition and worsening of the US picture could alert clinicians and bring forth adjustment of treatment.
Subpleural consolidations were found dominantly in posterior parts of the lungs and mostly in patients who spent more days on CPAP or mechanical ventilation. Considering that the cohort of our patient is too small for results with a high power of significance, we can suggest that these findings should be further evaluated in a larger group of patients with RDS.
The limitation of our study can be relatively high GA for premature neonates, the mean GA of 31 weeks, and a limited number of 51 patients.
Similar results between X-ray and US, especially considering accuracy, in our study suggest that these two methods can be used simultaneously, taking into account that US is often more available to a clinician than an X-ray. Inevitably, all radiological findings should be interpreted together with the clinical status of patient and laboratory data.
| Conclusion|| |
Lung US still is not a routine procedure despite its wide use in NICUs.
US is a sensitive, nonharmful, bedside, repeatable tool, and it should be used complementary to X-ray in diagnosing patients with RDS In addition, in follow-up and monitoring of these patients, US can be used more extensively, considering that one of our goals is to decrease the number of ionizing radiation in premature neonates, knowing that this population is most vulnerable to its potential and long-term harmful effects.
By introducing lung US as a standard method of examination in day-to-day work, it would be possible to reduce the use of X-ray studies in premature neonates.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]