Written by: Emily Goins (NUEM ‘26) Edited by: August Grace (NUEM ‘24)
Expert Commentary by: Maren Leibowitz, MD
Acute respiratory distress syndrome (ARDS) is a condition that is characterized by poor oxygenation and ventilation as a result of diffuse alveolar and endothelial injury in the lungs. There are several etiologies including viral pneumonia, bacterial pneumonia, sepsis, trauma, and pancreatitis. A patient meets criteria for ARDS when they have the following: 1) acute onset, bilateral lung infiltrates on chest radiography or CT scan (suspected to be non-cardiac in origin) and 2) a ratio of arterial blood oxygen (PaO2) to fraction of oxygen in inspired air (FiO2) < 300. The mortality of ARDS is dependent on the severity of the disease; with 27% in mild disease, 32% in moderate disease, and 45% in severe disease (Diamond et. al., 2022).
What are the physiologic effects of proning?
Prone positioning, or having the patient lay face-down on the bed, has been used in the management of ARDS for several decades. The PROSEVA study is the most recent and famous randomized control trial. In this study, they found that prone positioning resulted in significant improvement in oxygenation, as well as a 50% decrease in mortality at 28 days (Guerin et. al., 2013). This maneuver improves oxygenation and gas exchange via three main mechanisms (Malhotra, 2022):
1. Reducing the anterior-posterior transpulmonary pressure difference
The transpulmonary pressure is defined as the difference between the pressure within the lungs and the pleural pressure. It is the distending force of the lungs, opposing the innate inward elastic recoil of the lung parenchyma (Neupane and Jamil, 2022). It is the reason why, even while at rest, there is still some air in your lungs and they are not completely collapsed.
In all patients, even those with healthy lungs, the anterior transpulmonary pressure is greater than the posterior transpulmonary pressure, leading to greater collapse of the posterior alveoli than the anterior alveoli. This is worsened with excess lung weight in ARDS, where edema pools in the dependent, or posterior, portion of the lung. This leads to hyperinflation of anterior alveoli and increased atelectasis in the posterior alveoli (Maley, 2020; Malhotra, 2022).
In prone positioning, pressures become more homogenous throughout the lung, leading to less hyperinflation of anterior alveoli and reduced atelectasis in posterior alveoli. The overall result is that prone ventilation recruits functional alveoli throughout the lung and thus improves both oxygenation and ventilation (Maley, 2020; Malhotra, 2022).
2. Decreased ventilation-perfusion mismatch
In ARDS, there is substantial ventilation-perfusion mismatch in the supine position, as blood flow is greatest in the dependent, or posterior, portions of the lung. This is the same area in which there is greater atelectasis, as noted above. Interestingly, perfusion is only minimally altered when a patient is changed from supine to prone positioning, as gravity does not have a significant effect on blood flow. However, because there is increased expansion of alveoli in the posterior portions of the lung, there is improvement in gas exchange due to decreased shunting, with improved ventilation in well-perfused areas of the lung (Guerin, 2020). Proning results in an increase in arterial oxygenation in as soon as 120 minutes (Pappert et. al., 1994).
3. Improved lung expansion
In supine position, the heart compresses the medial posterior lung against the posterior chest wall, and the diaphragm compresses the posterior and inferior portions of the lung. This is worsened in patients who are paralyzed for ventilation, as the loss of diaphragmatic and abdominal rectus tone leads to abdominal contents displacing the diaphragm superiorly (Malhotra, 2022). Proning makes the heart rest against the sternum, and the diaphragm is displaced inferiorly. This change in positioning of mediastinal structures allows for increased distention of the posterior lung (Koulouras et. al., 2016).
Should we prone non-intubated patients in the ED?
With the rise of ARDS during the COVID pandemic, there were many patients who had low oxygen saturations but were not in significant respiratory distress – patients we now commonly refer to as “happy hypoxemics.” As resources were scarce with a limited number of mechanical ventilators, many providers wondered if these same physiologic benefits would occur in patients who were not intubated. Prone positioning was evaluated as a method for increasing oxygenation in non-intubated patients, and preventing the need for mechanical ventilation. Caputo et. al. (2020) demonstrated that in a single-institution study with 50 patients, in addition to supplemental oxygen, proning was a valuable tool in improving oxygenation, increasing the mean SpO2 from 84% pre-proning to 94% five minutes after proning. Another study demonstrated that this transient increase extends beyond the initial proning period, to 30 minutes (Dubosh et. al., 2021). Proning in awake patients can usually be done by the patient themselves, and is free, without requiring the use of any additional personnel or resources (Caputo et. al., 2020). While a randomized control trial should be done to evaluate the effect of early proning in a controlled environment, these studies suggest that we should consider using this in our Emergency Department for patients who present with hypoxia and concern for mild to moderate ARDS without urgent need for intubation.
What are the contraindications to proning?
Absolute contraindications of prone positioning are severely increased intracranial pressure as positioning of the head in prone position can partially obstruct cerebral venous drainage, as well as unstable spinal fractures because the manipulation while repositioning a patient may lead to further injury (Guerin et. al., 2020). Hemodynamic instability and ongoing cardiac arrhythmias are a strong contraindication as chest access for cardiopulmonary resuscitation is limited (Koulouras et. al., 2016).
Relative contraindications are several, including difficulty with airway management, facial trauma, ventricular assist device, intra-aortic balloon pump, severe chest wall lesions or rib fractures, massive hemoptysis, unstable pelvic or long bone fractures, and open abdominal wounds. Patients with rheumatoid arthritis affecting the atlanto-occipital joint should not be proned until a neck collar has been placed (Guerin et. al., 2020; Koulouras et. al., 2016). In all of these situations, however, given the mortality benefit of prone positioning observed in the PROSEVA trial, it is important to discuss the benefits and risks of proning as a multi-disciplinary team.
Massive obesity should not be considered a contraindication, as these patients often benefit significantly (Guerin et. al., 2020). While these patients have decreased chest wall compliance and prone positioning decreases chest wall compliance, it is known that prone positioning does not affect total respiratory system compliance (Pelosi et. al., 2002). Prone positioning has also been shown to be beneficial in pregnant patients (Samanta et. al., 2013). While routine indications and contraindications apply to pregnant patients, additional caution should be taken with patients who are within 2 days after cesarean delivery, and careful positioning and padding should be used for patients over 24 weeks to offload the uterus and avoid obstruction of the inferior vena cava. In addition, figuring out a way to ensure continuous fetal monitoring is recommended beyond 24 weeks gestation (Tolcher et. al., 2020).
How should we prone patients who are intubated?
Based on the PROSEVA study, proning can occur after 12-24 hours of stabilizing the patient on supine ventilation, but before 36 hours. Patients should be considered for proning if they have a PaO2/FiO2 ratio of < 150, FiO2 setting of more than 60%, PEEP >5, and tidal volume of about 6 ml/kg of predicted body weight. Per the methods in the PROSEVA trial, patients should be proned for 16 consecutive hours/day until clinically improved, up to 28 days. With increased boarding time in the Emergency Department over the last several years, even intubated patients may be present long enough to prompt discussion with the intensive care specialists about proning in the department.
Steps and tips for prone positioning (adapted from Messerole et. al., 2002 for ED setting)
When possible, explain the indications and process of the maneuver to the patient and/or family.
Ensure that the patient does not have any contraindications to proning.
Review the recent chest x-ray to confirm positioning of the endotracheal tube.
Assemble all pads, pillows, and other types of supports that will be needed for appropriate positioning of the patient’s head and pressure points. Assemble 4-5 people who will be able to assist with the maneuver.
Prepare endotracheal suctioning equipment, as proning can lead to increased secretions.
Decide whether to log-roll the patient left or right.
Confirm that all tubes and lines connected to the patient are secured appropriately. Ensure all drainage bags and chest tube drains are on the opposite side of where you are rolling.
Place one or more people on both sides of the bed to be responsible for turning the patient, and a person at the head of the bed to be responsible for making sure devices such as the central line and endotracheal tube are not dislodged. It may also be helpful to have a respiratory therapist at bedside to assist with ventilator care if anything becomes dislodged or removed.
Increase FiO2 to 100%.
Pull the patient to the edge of the bed furthest from whichever lateral decubitus position will be used while turning.
Place a new bed sheet on the side of the bed that the patient will face when in this lateral decubitus position. Leave most of the sheet hanging.
Turn patient into lateral decubitus position.
Remove ECG leads and patches. Suction as needed.
Log-roll the patient into the prone position.
Reposition in the center of the bed using the new bed sheet.
Turn the patient’s face toward the ventilator to ensure that the airway is not kinked.
Support the face and shoulders appropriately, avoiding any contact of the supportive padding with the eyes.
Position arms in a comfortable position, avoiding any position that could cause a brachial plexus injury, and ensure they are well-supported to avoid pressure ulcers.
Auscultate the chest for bilateral breath sounds, and reassess tidal volume and minute ventilation.
Adjust all tubing and reassess connections.
Reattach EKG leads to back.
Tilt patient into reverse Trendelenburg. Slight, intermittent lateral repositioning (20-30 degrees) should also be used, changing sides at least every 2 hours.
Document thorough skin assessment every nursing shift, and inspect weight-bearing ventral surfaces.
Ventilation – Mortality benefits of prone positioning have primarily been observed in low-tidal volumes, which is defined as less than or equal to 8 ml/kg of predicted body weight (Beitler et. al., 2014). The PROSEVA trial used 6 mL/kg for tidal volume for increased lung protection. They also used a PEEP of 5, although the optimal PEEP setting is unknown. In general, providers should use standard recommended plateau pressure <30, and the standard PEEP-FiO2 table can be used to guide these settings (Guerin et. al., 2013; Mi et. al., 2022). After proning, you may be able to decrease ventilatory support.
Monitoring – Electrocardiographic leads are placed on the back. The need for endotracheal suctioning should be assessed with increased frequency after the patient is placed prone because large quantities of pulmonary secretions may drain into the tube due to gravity (Messerole et. al., 2002).
Sedation – In the PROSEVA trial, more patients required neuromuscular blockade in the prone position than in the supine position (Guerin et. al., 2013). Thus, if a patient is not paralyzed prior to proning, observe the patient for dyssynchrony with the ventilator to determine the need for this. As always, ensure that the patient has a RASS -4/-5 if considering neuromuscular blockade.
Expert Commentary
Thank you Dr. Goins and Dr. Grace for this great review on an important part of the care of our severe ARDS patients. While proning is a maneuver frequently used and seen in our intensive care units, the COVID-19 pandemic brought proning into our emergency departments, both in ventilated and non-ventilated patients (1) .Post-pandemic, boarding of critically ill patients in our emergency departments continues to be common and is likely to continue (2), and it is important to be familiar and comfortable with taking care of ARDS patients after their initial stabilization.
In my opinion there are three big takeaways on proning for severe ARDS:
Proning is not meant to “clear” the fluid filling the alveoli. If you were like me when I first learned about proning for ARDS, you may have thought that the position change moved the fluid out of the alveoli, allowing them to oxygenate better (similar to how I thought positive pressure ventilation pushes pulmonary edema out of the alveoli in the treatment heart failure exacerbations). It’s not true! And while proning may mobilize some secretions in the main bronchi, the main impact comes down to improved alveolar opening leading to improved ventilation-perfusion matching as the change in position affects aeration more than regional blood flow (3,4). The above post outlines the pathophysiologic changes of proning beautifully.
Timing matters. While we still don’t know the ideal timing of when and how long patients with severe ARDS should be proned, we do know that survival benefit has been shown in patients who are proned earlier in their course and for longer. This is primarily based on the results of the PROSEVA trial which randomized their patients within 36 hours of intubation but after 12-14 hours of vent optimization and had patients remain in the prone position for 16 hours daily (5).
Proning should not be viewed as a benign intervention. As always, everything we do in medicine has potential risks and adverse effects. While endotracheal tube dislodgment is the worst case scenario when it comes to risks of proning, vascular access issues and pressure injuries can also occur. Dependent edema of the face is common which can be distressing to families visiting their loved ones (4). Well defined protocols and experienced provider teams are essential to help minimize procedural risk and to ensure continued appropriate care during the proning process and while the patient is prone.
All in all, when done appropriately, proning is a great option and intervention to have in your toolkit for persistent hypoxemia in the patient with severe ARDS despite ventilator optimization. It should also be considered in your awake, non-intubated patients if you are rapidly uptitrating their oxygenation support and their hemodynamics and overall clinical trajectory allow them to do it safely.
Expert Commentary References
McGurk K, Riveros T, Johnson N, Dyer S. A primer on proning in the emergency department. J Am Coll Emerg Physicians Open. 2020 Jul 4;1(6):1703-1708.
Mohr NM, Wessman BT, Bassin B, Elie-Turenne MC, Ellender T, Emlet LL, Ginsberg Z, Gunnerson K, Jones KM, Kram B, Marcolini E, Rudy S. Boarding of Critically Ill Patients in the Emergency Department. Crit Care Med. 2020 Aug;48(8):1180-1187.
Guérin C, Albert RK, Beitler J, Gattinoni L, Jaber S, Marini JJ, Munshi L, Papazian L, Pesenti A, Vieillard-Baron A, Mancebo J. Prone position in ARDS patients: why, when, how and for whom. Intensive Care Med. 2020 Dec;46(12):2385-2396.
Scholten EL, Beitler JR, Prisk GK, Malhotra A. Treatment of ARDS With Prone Positioning. Chest. 2017 Jan;151(1):215-224.
Guérin C, Reignier J, Richard JC, Beuret P, Gacouin A, Boulain T, Mercier E, Badet M, Mercat A, Baudin O, Clavel M, Chatellier D, Jaber S, Rosselli S, Mancebo J, Sirodot M, Hilbert G, Bengler C, Richecoeur J, Gainnier M, Bayle F, Bourdin G, Leray V, Girard R, Baboi L, Ayzac L; PROSEVA Study Group. Prone positioning in severe acute respiratory distress syndrome. N Engl J Med. 2013 Jun 6;368(23):2159-68.
Blog Post References
Caputo, N.D., Strayer, R.J., Levitan, R. 2020. Early self-proning in awake, non-intubated patients in the emergency department: a single ED’s experience during the COVID-19 pandemic. Academic Emergency Medicine. 27(5): 375-378.
Diamond, M. Peniston, H.L., Sanghavi, D., Mahapatra, S. 2022. Acute respiratory distress syndrome. StatPearls.
Dubosh, N.M., Wong, M.L., Grossestreuer, A.V., Loo, Y.K., Sanchez, L.D., Chiu, D., Leventhal, E.L., Ilg, A., Donnino, M.W. 2021. American Journal of Emergency Medicine. 46: 640-645.
Guerin, C., Reignier, J., Richard J-C., Beuret, P. Prone positioning in severe acute respiratory distress syndrome. 2013. New England Journal of Medicine. 368:2159-2168.
Guerin, C., Albert, R.K., Beitler, J., Gattinoni, L., Jaber, S., Marini J.J., Munshi, L., Papazian, L., Psenti, A., Vieillard-Baron, A., Mancebo, J. 2020. Prone position in ARDS patients: why, when, how and for whom. Intensive Care Medicine. 46(12): 2385-2396.
Koulouras, V., Papathanakos, G., Papathanasiou, A., Nakos, G. Efficacy of prone positioning in acute respiratory distress syndrome patients: a pathophysiology-based review. World Journal of Critical Care Medicine. 5(2): 121-136.
Mi, L., Chi, Y., Yuan, S., He, H., Long, Y., Frerichs, I., Zhao, Z. 2022. Effect of prone positioning with individualized positive end-expiratory pressure in acute respiratory distress syndrome using electrical impedance tomography. Frontiers in Physiology.
Malhotra, A. 2022. Prone ventilation for adult patients with acute respiratory distress syndrome. UpToDate, Waltham, MA.
Messerole, E. Peine, P., Wittkopp, S., Marini, J.J., Albert, R.K. 2002. The pragmatics of prone positioning. American Journal of Respiratory and Critical Care Medicine. 165(10).
Pappert, D. Rossaint, R., Slama, K. Gruning, T., Falke, K.J. Influence of positioning on ventilation-perfusion relationships in severe adult respiratory distress syndrome. Chest. 10695):1511-1516.
Pelosi P, Brazzi L, Gattinoni L. Prone position in acute respiratory distress syndrome. European Respiratory Journal. 2002;20:1017–1028.
Samanta, S., Samanta, S., Wig, J., Baronia, A.K. 2014. How safe is the prone position in acute respiratory distress syndrome at late pregnancy. American Journal of Emergency Medicine. 32(6): 687.
Scaravilli V., Grasselli G., Castagna L. 2015. Prone positioning improves oxygenation in spontaneously breathing nonintubated patients with hypoxemic acute respiratory failure: a retrospective study. Journal of Critical Care. 30:1390–1394.
Tolcer, M.C., McKinney, J.R., Eppes, C.S., Muigai, D., Shamshirsaz, A., Guntupalli, K., Nates, J.L. Prone positioning for pregnant women with hypoxemia due to coronavirus disease 2019. Obstetrics & Gynecology. 136(2): 259-261.
Maren Leibowitz, MD
Critical Care Fellow
Mount Sinai Hospital
How To Cite This Post:
[Peer-Reviewed, Web Publication] Goins, E. Grace, A. (2025, 3/4/2025). Proning for ARDS. [NUEM Blog. Expert Commentary by Leibowitz, M]. Retrieved from http://www.nuemblog.com/blog/proning-for-ARDS
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