Ventilator Management on VV ECMO

 

In VV modality, infusion blood from the circuit mixes with systemic venous return blood. At typical blood flow, the ratio of infusion blood to deoxygenated right atrial blood is usually around 3:1. This results in PCO2 41, PO2 40, sat 80%, content 17ccO2/dL in the pulmonary artery. If there is no native lung function, this will be the composition of gases in the arterial blood.

It is important to realize that systemic arterial saturation around 80% is typical during VV support. As long as the hematocrit is over 40% and cardiac function is good, systemic oxygen delivery will be adequate at this level of hypoxemia. It is not recommended to increase vent settings from rest settings because of hypoxemia. Any native lung function will increase oxygenation over 80% saturation.

Patients are on high FiO2 and ventilator settings during cannulation. The goal of ventilator management on ECLS is to initiate Lung Protective Ventilation as soon as possible.

Lung Protective Ventilation
*also known as vent rest settings - determined as the gold standard by ELSO based on the outcomes from the EOLIO and CESAR trials

  • Plateau pressure less than or equal to 25cm H2O

  • Respiratory rate 4-10 breaths per minute

  • Positive end-expiratory pressure 10-15cm H20

  • Driving pressure <15cm H2O

  • FiO2 <50% to maintain saturations greater than or equal to 85%

    *Ventilator dyssynchrony in setting of a high respiratory drive may lead to secondary lung injury and should be avoided.

After 24-48 hours: 
Stable hemodynamics off of pressors, fluid balance underway, sepsis pharmacotherapy underway, moderate to minimal sedation. Lung protective ventilation.

After 48 hours:
Minimal to no sedation. PCV as above or CPAP20 plus spontaneous breathing. Trach or extubate within 3-5 days.

 

Recruiting Trials

Do not complete any recruiting trials until significant aeration on CXR and > 4 cckg/ min tidal volume. After aeration is established, conduct a Cilley test. 

Cilley Test:
Increase FiO2 to 1.0 with no other changes 
A positive test is rapid increase to SaO2 100%

If the Cilley test is positive, start recruitment. 

Recruitment strategies:

  • CPAP with spontaneous breathing at 25cm H2O
    or 

  • PSV at 25/10

  • Rate 5

  • I:E 3:1

  • 10 min/hr


Return to rest settings.
Readjust blood and sweep flow if recruitment is successful.
Repeat at intervals.
Expect decreasing ECLS support as native lung function improves.

 

CESAR Trial


EOLIA


ELSO Guideline


 

Reference: ELSO - Guidelines for Adult Respiratory Failure, 2017