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of the patient’s gas exchange requirements. Provides respiratory support with-
out hemodynamic support.
Functional oxygen saturation (SpO 2 ) and CO 2 are monitored continuously to
maintain values of 50%–80% and 35–45 mm Hg, respectively.
Complications include infections and sepsis, bleeding, DIC, intracranial bleed-
ing, air emboli, renal failure, pressure ulcers, and heparin-induced thrombocytope-
nia. Nursing care focuses on maintenance of the ECMO system and prevention of
complications.
Venoarterial (VA) ECMO
Blood from a large central vein is circulated through a membrane oxygenator
and returned to the arterial system. VA ECMO provides both respiratory and
hemodynamic support.
. .
Ventilation/Perfusion (V/Q) Mismatch
Both lung capillary perfusion and alveolar ventilation affected by body position
and gravity.
· ·
Perfusion and ventilation adequate and adequate gas exchange → V/Q
· ·
match exists. Normal V/Q ratio 4:5 = 0.8. If ventilation or lung capillary perfu-
· ·
· ·
sion, or both, is not adequate → V/Q mismatch. There are several types of V/Q
imbalances:
Shunting or physiological shunt (anatomical shunt; or right-to-left shunt) is
defined as the flow of blood from the right side of the heart → lungs → left side
of the heart without taking part in alveolar and capillary diffusion → pulmonary
blood perfuses completely unventilated alveoli.
■ Occurs in severe ARDS, pneumonia, tumor, mucous plug, and pulmonary edema.
· ·
■ A low V/Q ratio exists when capillary perfusion adequate but gas exchange
ineffective in the alveoli. Therefore, perfusion exceeds ventilation.
· ·
■ Dead-space V/Q mismatch occurs when alveoli ventilation normal but
inadequate or absent perfusion, so that adequate gas exchange is unable
to occur.
■ Results from pulmonary embolism, pulmonary infarction, or cardiogenic shock.
· ·
■ A high V/Q ratio exists when ventilation is normal but perfusion inadequate.
· ·
Therefore, a high V/Q ratio exists.
■ An absolute shunt (true shunt, silent unit) occurs with combination of
· ·
shunting and dead-space V/Q.
· ·
■ Little to no perfusion and ventilation are present. This V/Q mismatch is
generally refractory to oxygen therapy.
■ It is primarily caused by pneumothorax and severe ARDS.
Diagnostic Tests
· ·
■ V/Q scan
■ ABGs
RESP