Prone Position

last updated: April 15, 2020

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General

ARDS is characterized by infiltrates that accumulate in the

dependent alveoli.

• PROSEVA (Proning in Severe ARDS) trial (1)

  • 16 hours of prone position​

  • 28 day mortality 16% vs. 32.8% prone vs. supine

  • 90 day mortality 23.6% vs. 41% prone vs. supine

  • supine group was sicker with a slightly higher SOFA score, on more pressors and neuromuscular blockers

  • PROSEVA staff was highly trained and experienced in prone positioning 

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Physiology

In the supine position, there are fewer alveoli available anteriorly

compared to posteriorly (2).  Because of gravity, these infiltrates

accumulate and compromise the posterior alveoli when in the supine

position. 

• apex picture from prone video

• supine: posterior alveoli get more compressed due to:

  • gravity​

  • shape of the chest wall

  • heart/diaphragm act under gravity to compress the posterior alveoli

• the anterior lung parenchyma is more conical than the posterior lung parenchyma. The anterior alveoli thus have a greater volume of intra-thoracic cavity available to expand and are thus more distended than the posterior alveoli

• more alveoli recruitment occurs in the prone position than in the supine position because the posterior lung parenchyma is no longer under the influence of gravity, the heart and diaphragm

• PP reduces difference between dorsal and ventral transpulmonary pressure

• ventilation becomes more homogeneous

• decreases alveolar overinflation and dorsal alveolar collapse

• blood flow is upward

• "sponge-lung" model

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How its done

• Mepilex over bony places

• 16 hours

• where are staff positioned?

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Complications

• transient desaturation

• transient hypotension

• accidental extubation

• catheter displacement 

• pressure ulcers

• vomiting

• excessive sedation needed

• compression of nerves

• compression of retinal vessels

• facial edema 

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References

1. Guérin et al. Prone positioning in severe acute respiratory distress syndrome. N Engl J Med 2013

2. Mackenzie CF. Anatomy, physiology, and pathology of the prone position and postural drainage. Crit Care Med 2001

3. ​https://www.wjgnet.com/2220-3141/full/v5/i2/121.htm