Prone-Positioning Therapy in ARDS
Section snippets
Physiologic effects of prone position in ARDS
When the ARDS patient is prone, the mass of the dorsal lung, which reinflates (ie, dorsal becomes the nondependent lung regions), is greater than the potential mass of the ventral (now dependent) lung regions, which may collapse (Fig. 1).3 When lung perfusion is substantially unmodified, the overall ventilation/perfusion (V/Q) matching improves as new pulmonary units are recruited for more effective gas exchange.
This mechanism is probably the primary one for the improvement in oxygenation in
Prone position in ARDS: evidence for efficacy
Changes in patient positioning can have a dramatic effect on oxygenation and ventilation in severe ARDS. Changing the patient position to prone or a steep lateral decubitus position can improve the distribution of perfusion to ventilated lung regions, decreasing intrapulmonary shunt and improving oxygenation.7 The use of intermittent prone positioning has been documented to significantly improve oxygenation in 60% to 70% of acute lung injury (ALI) and ARDS patients.1, 8
The Prone-Supine I Study9
Updated meta-analyses of randomized trials in severe ARDS
In patients with ALI or ARDS, more recent randomized controlled trials (RCTs) showed a consistent trend of mortality reduction with prone ventilation. An updated meta-analysis included 2 subgroups of studies: those that included all ALI or hypoxemic patients, and those that restricted inclusion to only ARDS patients. In the overall meta-analysis that included 7 RCTs with 1675 adult patients (862 in prone position), prone position was not associated with a mortality reduction (OR 0.91, 95% CI
Extended prone position ventilation
Extended prone position ventilation (extended PPV) in severe ARDS has been confirmed in a recent pilot feasibility study. Extended PPV was defined as PPV for 48 hours or until the oxygenation index was 10 or less. A prospective interventional study25 in 15 patients confirmed that there was a statistically significant improvement in oxygenation (PaO2/FiO2 92 ± 12 vs 227 ± 43, P<.0001) and oxygenation index (22 ± 5 vs 8 ± 2, P<.0001), reduction of PaCO2 (54 ± 9 vs 39 ± 4, P<.0001) and plateau
Complications associated with prone position
Prone positioning has associated risks to both the patient and the health care worker. One hindrance to use of the prone position in ARDS patients has been the difficulty of safely moving a patient with severe hypoxemia due to ARDS. Complications can arise in the process and include unplanned extubation, lines being pulled, and tubes becoming kinked. In addition, proning obese patients can be labor intensive and can result in staff injuries. However, the technique can be performed safely by
Methods for prone positioning
Several methods for prone positioning have been developed. The authors use a simple, manual 3-step procedure (Figs. 6 and 7) that takes 4 staff members (2 on each side of the bed) to manage all lines and tubes. First, patients are moved to the edge of the bed with a full sheet. This sheet is then wrapped around the patient’s arm that is located toward the middle of the bed. A second flat sheet is tucked under the covered arm and then the patient is rolled further as far as possible to the side
Summary
In the authors’ experience, the use of the prone position is an effective strategy for the treatment of severe hypoxemia in patient with ARDS. To establish the prone position, the authors favor a simple technique that uses 4 staff members and a regular ICU bed with no specialized equipment. More recent studies document the benefit of extended prone position therapy (>20 hours per day) in ARDS. A recent review of all published meta-analyses on the efficacy of prone position in ALI and ARDS
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Conflicts of Interest: None.