Acute respiratory failure is one of the most challenging critical conditions due to a wide variety of differential diagnosis. Bedside lung ultrasound in emergency (BLUE) protocol allows accurate differentiation between the most common underlying causes of acute respiratory failure in up to 90% of the cases. The assessment of left atrial pressure affecting left ventricular filling is essential in critically ill patients guiding volume substitution, optimization of left ventricular function and prevention of pulmonary congestion, thus ensuing haemodynamic stability. A simple, non-invasive method of left atrial pressure evaluation is the echocardiographic assessment of interatrial septum shape and motion, which is affected by interatrial pressure gradient. Aiming to improve the accuracy of the BLUE protocol, we propose the simple, non-invasive echocardiographic assessment of interatrial septum shape and motion as an upgrade, providing additional information of the loading of left and right atrium thus distinguishing the most common causes of acute respiratory failure.

Key words: lung ultrasound, BLUE protocol, interatrial septum, echocardiography

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