Thread by @SkylerLentz

Tips on the mechanically ventilated ARDS and sick hypoxemic patient.

Protect the lungs from the start! See the basics below.

#Tweetorial #foamcc #foamed

Based on prior work with @mattroginski @roo_atchinson

@UVM_EM

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What is the definition of ARDS?

The Berlin criteria: Acute onset within one-week, bilateral opacities on CXR not explained by cardiogenic pulmonary edema, pleural effusion etc. and a PaO2/FiO2 ratio of <300 mm Hg with PEEP 5 cm H2O.

jamanetwork.com/journals/jama/…

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More simply in the ED or acute setting I consider anyone with bilateral infiltrates + inflammation (sepsis, pneumonia, trauma etc) + hypoxemia to be at risk for ARDS and if intubated manage them with lung protective ventilation.
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ARDS, acute lung injury causes non-cardiogenic edema, atelectasis & alveolar-capillary damage that leads to less aerated lung and thus poor compliance, high plat pressure & hypoxemia.

On the CT cut below we see a smaller area of healthy lung units, some call this “baby lung”
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Low tidal volume is a mainstay of lung protective strategies.

Less aerated healthy lung to ventilate =give less tidal volume.

Too much tidal volume and you risk damaging the remaining healthy, compliant lung.

Start at 6 ml/kg IDEAL body weight based on height.

Measure!
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Next step is to check a plateau pressure to make sure the tidal volume + poor lung compliance is not generating a high and potentially injurious plateau pressure.

Perform an end inspiratory hold on the vent in a passive patient (or ask an RT to help).

Example too high!

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Plateau pressure approximates alveolar pressure. The alveoli are thought to be maximally distended at a pressure of ~ 30 cm H20

Keep < 30 cm H20 in almost all patients!

*The very obese/stiff chest wall may tolerate a higher plat pressure (Why? Read transpulmonary press)
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The plateau pressure roughly = tidal volume/compliance of the respiratory system

Decreasing the tidal volume decreases the plateau pressure!

If plateau still > 30 cm H2O at 6 ml/kg decrease the tidal volume by 1 ml/kg to as low as 4 ml/kg IBW
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The small tidal volume means you must increase the RR to maintain minute ventilation.

A pH of > 7.2-7.25 is probably ok and usually safer than increasing the tidal volume

Most patients with ARDS tolerate RR up to 30/min but watch for air trapping just in case (example below)
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Adequate PEEP is helpful in ARDS.

It prevents atelectrauma (dangerous opening and closing of the alveoli with each breath) and helps to maintain recruitment by keeping alveoli open and participating in gas exchange.

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@mattroginski @ResusPadawan

How to set PEEP in ARDS is controversial but a simple and effective way is the PEEP/FiO2 table.

Following either the high or low chart are both good options.

I tend to favor the high PEEP/FiO2 in the obese and lower PEEP in all others

ardsnet.org/files/ventilat…
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Gradually increase the PEEP/FiO2 to your target.

Go up slowly by about 2 every 15 minutes.

Watch for adverse effects of PEEP such as hemodynamic instability, a major jump in plateau or even worsening oxygenation by over-distending the healthy alveoli
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Turn down the O2!

Tolerate a lower PaO2 (55-80 mmHg) or saturation 88-95%

Hyperoxia is harmful to the injured lung.

Also replacing the alveoli with 100% oxygen can lead to resorption atelectasis because there is no more un-absorbed nitrogen to keep the alveoli open.
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If this strategy fails to oxygenate, ventilate or maintain safe plateau pressures in your patient, consider advanced ARDS therapies such as proning, neuromuscular blockade (unclear benefit with new trial) or V-V ECMO.

Call for help!

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Tips:
Lung protective strategies in anyone with hypoxemia + inflammation +bilateral infiltrates

-Tidal volume 6 ml/kg IBW or lower
-Plateau pressure < 30, lower tidal volume to lower plateau
-Adequate PEEP-use a PEEP table
-Tolerate lower PaO2 55-80 mm Hg or sats 88-95%
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These are the basics. It can get more complex and controversial.

Please add your tips below

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