ARDS and Prone Positioning: Why Do We Do It?

Picture of hospital bed

As a respiratory therapist, you are bound to come across your share of patients diagnosed with acute respiratory distress syndrome (ARDS). These patients usually suffered from something that caused a severe inflammatory response like aspiration pneumonia, trauma, or sepsis. ARDS becomes the diagnosis when the patient has an acute onset of bilateral chest infiltrates with low pO2 levels that are not explained by heart failure or fluid overload.  

ARDS looks a lot like pulmonary edema.  The patient’s alveoli are full of fluid, preventing oxygen from moving into the bloodstream and throughout the body. It leads to hypoxemic respiratory failure, extreme atelectasis and consolidation, and has a high mortality rate.  

In patients with severe ARDS there has been a shift in advised care, including placing these patients in prone position. There are several reasons why this posture is helpful. We all know that fluids are gravity-dependent, right? So, when a patient’s lungs are full of fluid, gravity will cause those fluids to settle in the dependent parts of the lungs – meaning the parts that are lowest in relation to gravity.  So, if the patient is standing up, the fluid would settle in the lower lobes. In the supine position, the fluid distributes itself throughout both lungs in virtually all lung fields but most significantly in the dorsal regions where the most perfusion takes place.   

It is not only the fluid buildup that makes ventilation and oxygenation of the ARDS patient in the supine position difficult.  Other factors that contribute are the pressure placed on the lungs by the weight of the heart and the abdominal organs compressing against lung tissue.  All of this leads to alveolar collapse and ventilating and oxygenating these patients becomes extremely difficult.

When a patient is placed in the prone position, the compression on the lungs is relieved and atelectasis decreases. Derecruited alveoli open back up, creating more areas within the lungs that are available for ventilation and oxygenation.  Also, prone positioning promotes pulmonary secretion drainage, further benefitting patients.  

Placing patients in the prone position during mechanical ventilation in the treatment of ARDS offers the patient a more even tidal volume distribution, improves lung volumes by reducing pressures placed by the heart and abdominal organs and overall prevents ventilator-induced lung injuries caused by overdistension when trying to overcome atelectasis in ARDS patients.


Report of the American-European Consensus conference on acute respiratory distress syndrome: definitions, mechanisms, relevant outcomes, and clinical trial coordination. Consensus Committee. Bernard GR, Artigas A, Brigham KL, Carlet J, Falke K, Hudson L, Lamy M, LeGall JR, Morris A, Spragg RJ Crit Care. 1994 Mar; 9(1):72-81

Beyond mortality: future clinical research in acute lung injury. Spragg RG, Bernard GR, Checkley W, Curtis JR, Gajic O, Guyatt G, Hall J, Israel E, Jain M, Needham DM, Randolph AG, Rubenfeld GD, Schoenfeld D, Thompson BT, Ware LB, Young D, Harabin ALAm J Respir Crit Care Med. 2010 May 15; 181(10):1121-7.

Prone position. Guérin C. Curr Opin Crit Care. 2014 Feb; 20(1):92-7

About Anne Wandycz BS, RRT-NPS-ACCS 7 Articles
Anne is a staff Respiratory Therapist at Children's Specialized Hospital, Toms River, NJ as well as an adjunct instructor in the Respiratory Care program at Brookdale Community College, Lincroft, NJ.