Diagnostic & predictive utility of lung ultrasound in preterm neonates with respiratory distress syndrome

Introduction

Respiratory distress syndrome (RDS) is a common cause of admission of neonates in NICU. It is  seen in 29% of late preterms and even higher for infants born before 34 weeks  gestation(1). It is a progressive disease occurring due to surfactant deficiency presenting as respiratory distress since birth(2). The incidence of RDS is inversely proportional to gestational age. The current modality of diagnosis of RDS is by signs of respiratory distress, arterial blood gas and chest x-ray  suggestive of low lung volume, reticulonodular pattern/ground glass appearance with or without air bronchograms in a preterm baby(3). Chest x-ray is being used extensively for both diagnosis and to see the response of ongoing treatment leading to considerable amount of radiation exposure in preterm neonates. Neonatal lung ultrasound being  free of ionizing radiation ,non invasive and a bedside tool has become a field of intense upcoming clinical research with relevant implications(4) . Lung ultrasound score (LUS) has been proposed to guide surfactant treatment , monitor progress and predict failure of non invasive ventilation in RDS(5).Surfactant replacement therapy is a crucial part of treatment of RDS and current guidelines  are based on its administration after failure of continuous positive airway pressure(CPAP) trial(6).  As there are no currently available techniques to accurately diagnosis the degree of surfactant deficiency, delay in surfactant therapy can lead to poor outcomes. LUS will be used here to study predictability of surfactant requirement at the time of admission itself to prevent unnecessary delays. LUS is proposed to identify patients at risk in the initial phase of the pathological process and enable targeted therapies when they may be more effective. Many LUS scoring systems have proven their application in critical adult pulmonary diseases(7),  and this study will try to extrapolate the diagnostic and prognostic  benefits in neonatal RDS.

Research question

Can lung ultrasound be used for early diagnosis, prediction of surfactant need and clinical course in neonates with respiratory distress syndrome?

Our Hypothesis

Our hypothesis is that lung ultrasound can be used to diagnose RDS in order to replace chest xray as well as guide the use of surfactant therapy.

PICOT

P: Preterm neonates with respiratory distress syndrome (RDS) admitted in NICU

I: lung ultrasound

C: chest x-ray

O: diagnostic accuracy of lung ultrasound for RDS and utility of LUS for prediction of surfactant therapy

T: till recruitment

AIMS AND OBJECTIVES

Aim: To study the utility of lung ultrasound as an early diagnostic tool for respiratory distress syndrome as well as prediction of the need for surfactant therapy and in preterm neonates .

Objectives :

Primary

To determine the accuracy of ultrasound for diagnosis of RDS as compared to chest x-ray.

To know the correlation of lung ultrasound score (LUS) with CPAP failure leading to surfactant administration.

Secondary

To know the correlation of post surfactant LUS with need for retreatment with surfactant

To know the correlation of LUS with oxygenation indices (Spo2/Fio2 ratio and PaCO2)

To know the correlation of LUS with duration of ventilation (invasive and noninvasive) and predictability of invasive ventilation.

To know the correlation of LUS with duration of hospital stay and final outcome.

MATERIALS AND METHODS

Study Settings

This study will be conducted in the level 3 NICU, Department of Neonatology, in Jawaharlal Nehru Medical College & AVBR Hospital, Sawangi, meghe, Wardhaâ€.

Selection Criteria

Inclusion criteria

All preterm neonates with gestational age  < 37 weeks with  respiratory distress admitted in NICU within 24 hour of life

Exclusion Criteria

·    Neonates who received surfactant in delivery room or in referral hospital.

·    Neonates with chromosomal anomalies or complex congenital malformations.

·    Neonates with congenital lung malformations diagnosed antenatally.

·     Parents denying consent for participation in the study.

Study Design:  cross sectional analytical study

Methodology: A detailed information sheet will be given to the parents of the newborn in whom the application of lung ultrasound in the ongoing current treatment plan will be explained in their local language and a written consent will be taken for the same.

Neonates fulfilling the inclusion criteria of gestational age and postnatal age with respiratory distress will be labeled as respiratory distress syndrome according to European consensus guidelines of RDS as stated below.(8)

The clinical features would include early respiratory distress comprising of cyanosis on room air, grunting, retractions, tachypnea and the diagnosis can be confirmed on chest X-ray with a classical ‘ground glass’ appearance, reticulonodular pattern and air bronchograms.(8)

Lung ultrasound will be performed by the investigator on admission i.e day 1; lung ultrasound score will be calculated as well. The management of disease i.e surfactant administration or CPAP will be according to standard European consensus guidelines on RDS management 2019(6). Lung ultrasound score will not be used to guide any of the clinical decisions.

 Lung ultrasound protocol:

Ultrasound variables used in this study are as follows:

1)    A-lines: they are seen as reverberation artifacts originating from the pleural line. They look like a series of  horizontal, parallel and equidistant lines beyond the pleural line(9,10).

2)    B-lines: they are seen as vertical lines which project from the pleural line to the edge of the screen formed by the alveolar gas–liquid interface. These lines move synchronously with respiration(9,10).

3)    White out lungs: defined as the presence of compact B-lines in six areas without horizontal reverberation. It depicts alveolar edema (11,12).

4)    Lung consolidation: its visualized as areas of hepatization (tissue pattern) with the presence of air or fluid bronchograms(11,12)

    Diagnosis of RDS on lung ultrasound will be studied with the following variables:

Major criteria

Minor criteria

|lung consolidation(9,11)

abnormal pleural line (thickness of >0.5mm or blurred)(9,11)

|bilateral white lung(9,11)

disappearance of A lines(9,11)

 Provisional diagnosis of RDS will be done if 2 major or 1 major and 1 minor criteria are fulfilled.

Each lung will be divided into 3 regions (upper anterior, lower anterior, and lateral) and a score from 0 to 3 for each area will be assigned according to the table below (12).

 

Score

Ultrasound finding

|0

Presence of only A lines

|1

Presence of >3 well spaced B lines

|2

Presence of crowded/coalescent B lines with or without consolidations limited to subpleural space

|3

Extended consolidations

The sum of all the 6 areas will be taken as total LUS score ranging from 0-18.

The detailed demographic, clinical and radiological findings will be entered in a pre-validated proforma. The lung ultrasounds findings will be confirmed by a trained radiologist who will be blinded to the clinical case details.