OnlineMedEd: Pulmonology - "ARDS"

Question 1

ARDS primarily affects which gas, O2 or CO2?

Answer 1

O2

Recall that oxygen is diffusion-limited. ARDS is characterized by hyaline membranes that increase the diffusion distance. CO2 is perfusion-limited, and thus is not affected.

Question 2

ARDS can be described as ______________.

Answer 2

a non-cardiogenic pulmonary edema

Question 3

Define TRALI.

Answer 3

Transfusion-related acute lung injury

Question 4

ARDS can be caused by what etiologies?

Answer 4

• Septic shock
• TRALI
• Near-drowning incident
• Pancreatitis
• Diabetic emergencies

Question 5

Tests might ask you to differentiate between pulmonary edema from CHF and ARDS (aka, non-cardiogenic pulmonary edema). What evaluations can they use to do this?

Answer 5

• Post-capillary wedge pressure: will be elevated in CHF but normal or even decreased in ARDS
• LV function: decreased in CHF but normal or increased in ARDS

Note: you should not do either a Swan-Ganz catheter or an echo to diagnose ARDS in real life. This is an exam factoid.

Question 6

Describe the treatment for ARDS.

Answer 6

•Intubation:
- CO2: decrease tidal volume (to avoid stress on the lung) and increase RR
- O2: PEEP (to keep the alveoli open) and increased FiO2 (to reduce hypoxemia)
• Treat the underlying cause of ARDS
•Can try diuresis to limit fluid exudation

Question 7

How does PEEP work?

Answer 7

One of the main problems in ARDS is that exudate pushes against alveoli; this shrinks the alveoli –derecruiting them and increasing the diffusion area. Adding PEEP helps push against the exudate pressure, keeping the alveoli open and shrinking the diffusion barrier.