Prone positioning has been proposed as a potential option for treatment of acute lung injury and acute respiratory distress syndrome (ARDS). ARDS is a complex condition affecting critically ill patients, resulting from direct or indirect lung injury. Lung injuries can cause pulmonary congestion, reduced aerated lung volumes and decreased pulmonary compliance, ultimately resulting in severe hypoxemia that is often refractory to conventional treatments. ARDS is associated with increased mortality and morbidity rates, as well as increased costs of care. Despite many experimental trials, mortality rates from ARDS remain unacceptably high, ranging from 35% to 45%, depending on the center.(1) While understanding of the pathophysiology related to ARDS has become more clear, there has been little progress in the development of effective treatments.
To date, the only proven, widely accepted treatment option for ARDS is protective lung ventilation using a low tidal volume strategy. Data from the National Heart, Lung, and Blood Institute’s ARDS Network (ARDSNet) trial support the use of lower tidal volume ventilation, as it results in a lower mortality rate than traditional tidal volumes (31% vs. 39.8%, p=0.007).(2) Even with this statistically significant decrease in mortality rates, widespread use of this therapy remains elusive.
Many other proposed ventilator and treatment strategies have been employed or studied in the treatment of ARDS, such as high-frequency oscillatory ventilation (HFOV), extracorporeal membrane oxygenation (ECMO) methods, high positive end-expiratory pressure, airway pressure release ventilation, nitric oxide, steroids, recruitment maneuvers and prone positioning. A review of HFOV and ECMO finds that both are effective therapies, depending on the patient’s condition. HFOV is a therapy with promising prospects, shown to improve survival rates with little risk for causing harm.(3) A recent meta-analysis on HFOV found demonstrated decreased mortality rates, but substantial heterogeneity among trials for physiological, but not clinical, outcomes. An upcoming large, multicenter trial is expected to provide more data to help clinicians who use or are considering this technique for patients with ARDS.(3) ECMO also has gained surprising interest recently. A meta-analysis of the randomized controlled trials revealed significant heterogeneity in the risk of mortality. The most recent trial found a reduction in mortality and severe disability rates at six months among patients in whom ECMO was considered. Although there is insufficient evidence to provide a recommendation for ECMO use among those with respiratory failure, clinicians should consider it in the context of other rescue therapies for acute respiratory failure.(4)
Prone positioning is another potential therapy for treatment of ARDS and is the focus of this article. This therapy typically is used in the context of a rescue therapy; however, greater improvements may be seen when used earlier in the course of ARDS. Prone positioning should be viewed as an adjunctive therapy to be used in combination with other accepted therapies in the treatment of critically ill patients. Widely known to improve oxygenation in the majority of patients with ARDS and shown to aid in alveolar recruitment, it has sporadic use among clinicians depending on the setting, as controversy over its use in clinical practice continues. A recent meta-analysis by Sud et al showed a decrease in mortality rates when this therapy was used among patients with severe hypoxemia, which was defined as a Pao2/Fio2 ratio <100 mm Hg; the use of prone positioning showed a 16% decrease in the relative risk of death.(5)
Meta-analyses of prone positioning for patients with ARDS reflect two major points: 1) the therapy seems to improve systemic oxygenation, especially in hypoxemic patients, and 2) in severe ARDS patients, when lung heterogeneity is the greatest, it appears to provide about a 10% survival benefit.(6)
Prone therapy appears to be most beneficial if employed early in the course of ARDS when alveolar recruitment is still possible, though it often is not implemented early enough in the disease process to promote the best possible patient outcome. Extended prone position ventilation, most beneficial when administered 18 to 20 hours daily, is safe and effective in ARDS patients when performed by trained staff within an established protocol. Extended prone positioning is emerging as an effective therapy for patients with ARDS and severe hypoxemia.(7)
Even with evidence supporting the use of prone therapy, its use is still sporadic within the medical community. Some believe that placing patients in the prone position is too difficult to achieve; however, with education and experience, it is easier than often perceived. Nurses experienced in its use are able to provide safe therapy with minimal complications. Team members should understand the goals of therapy and collaborate to identify eligible patients. There are different methods used to place a patient into the prone position, and each facility should have established protocols and procedures. Depending on the modality used, several staff members may be needed to complete the procedure.
Manual Versus Automated Prone Positioning
The advantage of manual prone positioning is its cost effectiveness, as it can be achieved with a sheet or assistive devices. However, it is more difficult to accomplish and requires additional nursing resources. Depending on a patient’s weight, it can take six to eight staff members to accomplish safely. Also, emergency treatment may be delayed if the patient has to be returned to the supine position before cardiopulmonary resuscitation.
Automated prone positioning can be achieved with one nurse, and therapy can be individualized based on a patient’s needs and responses. Rental fees make it more costly, but once the patient is properly positioned within the device, he or she can be turned from supine to prone and back with minimal effort.
Research literature cites many complications, but most of these are associated with manual positioning. In those patients with severe hypoxia, the benefits of prone positioning often outweigh the potential risks. The risk of developing pressure ulcers is ever-present, as the patient is immobile and pressure on bony prominences may be prolonged. Nurses should be aware of the potential complications in all patient populations to anticipate and prevent these occurrences. Regardless of the method used to position patients, several key care elements should be instituted to ensure patient safety.
Line securement. All devices, lines and tubing must be positioned either at the head or foot of the bed to help prevent inadvertent dislodgement during the turning procedure. If automated positioning is utilized, it is important to use the tube management system to support lines and tubing.
Eye care. Eye protocols using lubricant and/or artificial tears should be utilized to reduce the risk of corneal abrasions associated with prone positioning. Continuous and prolonged prone time should be avoided because of the potential for intra-ocular pressure and associated complications.
Skin Care. Because of the potential breakdowns caused by pressure areas or devices, caregivers should assess all areas frequently, with special focus on pressure areas. Pressure will be placed on different structures in the prone position than in the supine, specifically on the chest, cheeks, forehead and sides. Skin moisturizing and a barrier for areas that share moisture are important, and hydrocolloid or foam dressings should be placed prophylactically on known pressure areas (e.g., sides of chest, hips, top of shoulders) to prevent shear, friction and pressure. Use of heel lift devices, such as waffle boots, also may be beneficial. If red areas are noted during skin assessment, repositioning can relieve pressure.
Management of edema. Patients in the prone position will often experience dependent edema of the face (eyes, lips and tongue). Ice packs placed on the patient’s face when in the supine position have been found to be beneficial on these areas. If the patient’s tongue becomes edematous to the point of teeth cutting into the tongue, use of a dental mouth prop can prevent injury. The edema can be very disturbing for the patient’s family to view, so it is important to prepare them for the edema and assure it is only temporary.
Nutrition. Enteral feeding is possible and preferred with prone positioning. To avoid complications associated with enteral feeding, post-pyloric feedings or pro-motility agents are recommended to prevent aspiration.(8)
Mortality rates with ARDS remain high even with protective lung ventilation. Further experimental trials for ARDS treatment are required to determine the best course of therapy. Prone positioning has been shown to improve oxygenation and decrease mortality in patients with severe refractory hypoxemia. The therapy should be instituted early in the course of ARDS with the goal of 18 to 20 hours daily and should be used as an adjunctive therapy in the treatment and support of patients. Healthcare professionals who are knowledgeable on proper techniques and protocols for prone positioning can implement the therapy in a safe and effective manner.
1. Phua J, Badia JR, Adhikari NKJ, et al. Has mortality from acute respiratory distress syndrome decreased over time? Am J Respir Crit Care Med. 2009; 179:220-227.
2. The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000; 342:1301-1308.
3. Sud S, Sud M, Friedrich JO, et al. High frequency oscillation in patients with acute lung injury and acute respiratory distress syndrome (ARDS): systematic review and meta-analysis. BMJ. 2010; 340:c2327.
4. Mitchell MD, Mikkelsen ME, Umscheid CA, et al. A systematic review to inform institutional decisions about the use of extracorporeal membrane oxygenation during the H1N1influenza pandemic. Crit Care Med. 2010; 38:1398-1404.
5. Sud S, Friedrich JO, Taccone P, Polli F, Adhikari NKJ, Latini R. Prone ventilation reduces mortality in patients with acute respiratory failure and severe hypoxemia: systematic review and meta-analysis. Intensive Care Med. 2010; 36:585-599.
6. Gattinoni L, Pietro Caironi P. Prone positioning, beyond physiology. Anesthesiology. 2010; 113:1262-1264.
7. Romero CM, Cornejo RA, Galvez LR, et al. Extended prone position ventilation in severe acute respiratory distress syndrome: a pilot feasibility study. J Crit Care. 2009; 24:81–88.
8. Reignier J, Thenoz-Jost N, Fiancette M, et al. Early enteral nutrition in mechanically ventilated patients in the prone position. Crit Care Med. 2004; 32:94-99.
The author was a part of the Speakers Bureau for topics on ARDS, prone positioning and use of KCI-RotoProne.