Prone Positioning

Efficacy outside the setting of COVID-19

Studies of prone positioning in patients with ARDS have shown improvement in oxygenation for up to 70% of patients, and this improvement can persist for hours after the patient has resumed a supine position.[1][2] Clinical guidelines for management of ARDS recommend prone positioning for at least 12 hours per day in these patients.[3]

Physiology

The physiologic basis for improved oxygenation from prone positioning is via several mechanisms (See Figure 1):[2]

• Reducing the difference in trans-pulmonary pressure -- by decreasing the amount of lung tissue in a dependent position, a larger lung volume can be recruited, and less lung is at risk of overdistention (reducing the risk of ventilator-associated lung injury);
• Reducing compression of the lung by the heart and diaphragm; and
• Increasing perfusion of lung tissue;

Figure PTP= transpulmonary pressure. (UpToDate)

COVID-19 patients who are intubated

There is currently limited published data about the use of prone positioning in COVID-19 patients, yet national and international guidelines typically recommend prone positioning for moderate to severe ARDS and/or refractory hypoxemia:

The American Thoracic Society led an International Task force,[4] concluded

• “For patients with refractory hypoxemia due to progressive COVID‐19 pneumonia (i.e., ARDS), we suggest prone ventilation.”
  • Refractory hypoxemia refers to an SpO2 consistently less than 90% despite maximal ventilator interventions to increase the SpO2.
  • The task force argues that the benefits of trying prone positioning (proven efficacy in ARDS, low risk and low cost) outweighs the risk (staffing, risk of infection), and even though ARDS from COVID-19 does not behave the same as typical ARDS.[4][5]

The Surviving Sepsis Campaign (Society of Critical Care Medicine and the European Society of Intensive Care Medicine) recommends[6]:

• “For mechanically ventilated adults with COVID-19 and moderate to severe ARDS, we suggest prone ventilation for 12 to 16 hours, over no prone ventilation (weak recommendation, low quality evidence)”

The World Health Organization Covid-19 guidelines state[7]:

• “In adult patients with severe ARDS, prone ventilation for 12–16 hours per day is recommended.”

In addition, other society guidelines in the UK8 and Germany[8] also recommend use of prone positioning for treatment of ARDS.

Prone positioning in the non-intubated patient

Although we have seen reports of PP being used successfully to avoid the need for intubation,[8] we were unable to find any published guidelines about the mild-moderate ARDS, non-intubated patient. Even so, some hospitals are choosing to use prone positioning in this setting,[9] and there is a physiologic argument to support its use (as outlined above under Physiology), even with use of non-invasive ventilatory support.

Update: a new study (see “additional resources” below) of 50 patients in the Emergency Room found that self-proning (plus supplemental oxygen) increased O2 sat higher than oxygen therapy alone. Treatment was given serially (first oxygen, then proning); there was no control group. 24% of patients required intubation within 24 hours of arrival in the ED. Nevertheless, it was a well tolerated and effective maneuver.

There are clinical trials in process that are evaluating the efficacy of prone positioning on hospitalized but non-intubated COVID-19 patients, such as this trial for patients on high-flow nasal cannula.[10]

Can prone positioning be used as a rescue maneuver?

While again there is no published data, we did see reports that some providers are concerned that prone positioning as a rescue maneuver puts the patient at risk of exertion-related hypoxemia, worsening their clinicial status, while simultaneously putting them in a position where intubation is difficult.

Gaps in knowledge

As above, clinical trials will help demonstrate whether prone positioning is effective in treating non-intubated patients, as well as more severe COVID-related ARDS.