We greatly appreciate the readers for their valuable suggestions pertaining to lung ultrasound. As mentioned in the letter, it is a fact that lung ultrasound is a rapidly expanding topic with frequent new addition of research publications.

As far as pneumothorax is concerned we are aware of recent publications, which showed neonatal lung ultrasound to be more sensitive than chest X-ray, transillumination and clinical evaluation [1]. All these studies were published recently, after we had reviewed the literature.

We agree that transient tachpnea of newborn (TTN) part in our review is not very comprehensive because of the numerous topics we were covering under one heading. Double lung point has a very high specificity and sensitivity in diagnosing TTN as per the two prominent studies by the same group of authors [2,3]. Liu, et al. [4] in his earlier study in 2014 showed that double lung point has a sensitivity and specificity of 76.7% and 100%, respectively in the diagnosis of TTN. In his recent publication [5], sensitivity and specificity of double lung point in diagnosis of TTN was 45.6% and 94.8%, respectively. Liu, et al. [4,5] have not elaborated on the duration of mechanical ventilation, surfactant need, gestation of infants and its relation with ultrasound finding. The authors have also not mentioned about the timing and number of ultrasounds, and the interpreter was not blinded to the clinical diagnosis. TTN is often a diagnosis of exclusion. Copetti, et al. [2,3] in their studies had fewer infants with probably less severe TTN, which resolved within 72 hours. We attribute this discrepancy in ultrasound finding in studies by two different groups to the different definitions of TTN. However from the available studies, it appears that severe TTN may have an ultrasound picture close to the ultrasound picture of respiratory distress syndrome. Ultrasound diagnosis of TTN and its differentiation from respiratory distress syndrome is of operational importance so that infants with mechanical ventilation need may be transferred to a tertiary-care center with available facilities. Hence, we still believe double lung point has its relevance in the diagnosis of TTN.

1. Raimondi F, Fanjul JR, Aversa S, Chirico G, Yousef N, Luca DD, et al. Lung ultrasound for diagnosing pneumothorax in the critically ill neonate. J Pediatr 2016;175:74-8.

2. Vergine M, Copetti R, Brusa G, Cattarossi L. Lung Ultrasound Accuracy in Respiratory Distress Syndrome and Transient Tachypnea of the Newborn. Neonatology 2014; 106:87-93.

3. Copetti R, Cattarossi L. The ‘double lung point’: an ultrasound sign diagnostic of transient tachypnea of the newborn. Neonatology 2007;91:203-9.

4. Liu J, Wang Y, Fu W, Yang CS, Huang JJ. Diagnosis of neonatal transient tachypnea and its differentiation from respiratory distress syndrome using lung ultrasound. Medicine (Baltimore). 2014;93:e197.

5. Liu J, Chen XX, Li XW, Chen SW, Wang Y, Fu W. Lung Ultrasonography to Diagnose Transient Tachypnea of the Newborn. Chest. 2016;149:1269-75.