Combined Lung and Diaphragmatic Ultrasound to Predict Respiratory Failure in Blunt Chest Trauma

The Additive Value of Diaphragmatic Ultrasound to Lung Ultrasound for Early Prediction of Hypoxemic Respiratory Failure Following Isolated Blunt Chest Trauma: A Prospective Cohort Study

Blunt chest trauma is a leading cause of emergency hospital visits and can result in severe breathing complications such as hypoxemic respiratory failure. While computed tomography (CT) scans provide detailed imaging of the chest, their routine use is limited by radiation exposure, high cost, and the inability to perform frequent bedside monitoring. Bedside lung ultrasound (LUS) is commonly used to detect structural injuries like lung contusions or collapsed lungs, but it cannot assess how well the breathing muscles are working. Because acute respiratory failure after chest trauma involves both lung tissue damage and impaired breathing muscle mechanics, combining lung ultrasound with diaphragmatic ultrasound may improve early risk assessment.

The primary purpose of this prospective cohort study is to determine whether combining point-of-care lung ultrasound with diaphragmatic ultrasound provides better early prediction of hypoxemic respiratory failure than lung ultrasound alone in adult patients with isolated blunt chest trauma.

Participants will undergo bedside lung ultrasound, diaphragmatic ultrasound, and arterial blood gas testing at four standardized time points: upon hospital admission (baseline), and at 6, 12, and 24 hours after admission. The lung ultrasound examination assesses the degree of lung tissue injury using a standardized 12-zone Lung Ultrasound Score (LUS). Diaphragmatic ultrasound measures muscle movement (diaphragmatic excursion) and contraction strength (diaphragm thickening fraction). Arterial blood gas results will be used to track oxygenation via the PaO2/FiO2 ratio, with a ratio of 300 mmHg or lower defining hypoxemic respiratory failure. All participants will also receive a standard-of-care chest CT scan as a reference comparison.

The study aims to evaluate whether this non-invasive, radiation-free bedside approach helps emergency physicians identify high-risk patients earlier, guiding timely respiratory support and intensive care triage while minimizing the need for repeated CT scans.

Inclusion Criteria:

• Age 18 years or older
• Presentation to the trauma unit within 24 hours of injury
• Diagnosed with isolated blunt chest trauma
• Willingness to participate with written informed consent provided by the patient or legally authorized representative

Exclusion Criteria:

• Penetrating chest trauma
• Immediate endotracheal intubation before baseline ultrasound assessment
• Massive hemothorax or tension pneumothorax requiring immediate emergency intervention prior to ultrasound evaluation
• Inadequate ultrasound acoustic window due to extensive subcutaneous emphysema or severe obesity
• Known preexisting chronic pulmonary disease (e.g., chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, bronchial asthma)
• Known preexisting cardiac disease (e.g., ischemic heart disease, rheumatic heart disease)
• Known neuromuscular disorders affecting respiratory muscles
• Previous thoracic surgery affecting diaphragmatic excursion or documented diaphragmatic paralysis
• Pregnancy
• Refusal to provide informed consent or withdrawal from the study