INTRODUCTION
Pneumonia is known as one of the most common serious infections in the pediatric population worldwide. Pneumonia-related mortality is rare in developed countries, but in developing countries, it is still one of the major causes of mortality in childhood ¹,². Most children can be treated as outpatients, although hospitalization rates may vary from 19% to 69% in emergency departments ³,⁴. Although the diagnosis is based on clinical parameters, there are no highly specific criteria for diagnosis. Chest X-ray (CXR) is not routinely recommended, while the World Health Organization recommends CXR in children who are clinically diagnosed with severe pneumonia at tertiary centers. The level is 90% for children with suspected pneumonia ⁵,⁶. The severity of the disease can be predicted using demographic characteristics, risk factors, and clinical parameters, but this may be difficult in an emergency department. Scoring systems have been adopted to quantify the severity of the disease and prognosis, but they were based on clinical findings that can vary according to the subjective assessment of the clinician ⁷. Biomarkers have been found to be useful in diagnosis, in differentiating bacterial or viral etiology, and in predicting severity or prognosis recently, but they are expensive when evaluated in combination to reflect various pathophysiological pathways ⁸,⁹. Therefore, it is crucial to develop an objective and useful parameter to demonstrate the severity of the disease and outcomes.
Point-of-care lung ultrasound (LUS) has increasingly been used in pediatric emergency settings recently. It is easy to perform, rapid, cost-effective, repeatable without limitations, and radiation-free. In a meta-analysis, LUS was found to be more sensitive and specific compared to CXR for diagnosing pneumonia in children ¹⁰. Another meta-analysis demonstrated that LUS had sensitivity of 96%, specificity of 93%, positive likelihood of 15.3, and negative likelihood of 0.06 when compared to CXR alone or in combination with clinical and laboratory findings and CXR ¹¹. Jones et al. also showed that the use of LUS reduced CXR levels over 38% and shortened the length of stay in the emergency department ¹². Lung ultrasound seems to be a highly promising tool for pneumonia diagnosis in pediatric emergency departments.
The diaphragm is the main respiratory muscle and diaphragmatic dysfunction may cause severe problems for respiration ¹³. Diaphragm ultrasound has been used to evaluate diaphragmatic fatigue after cardiac surgery or to predict extubation success from mechanic ventilators in adult and pediatric intensive care units recently ¹⁴¹⁶. However, there is no study providing information on the evaluation of DUS in children with the diagnosis of pneumonia. We hypothesized that DUS parameters could be a new useful tool to objectively score the severity of the disease and predict outcomes in previously healthy children with pneumonia in the emergency department.