Respiratory Failure

Question 1

How do we classify ARDS?

Answer 1

Acute- post trauma or infection
Chronic- COPD, CF, lobectomy
Acute on chronic- infective exacerbation

Question 2

How do we quantify ventilation?

Answer 2

Minute ventilation (gas leaving the lung): tidal vol L x breaths per minute
Alveolar ventilation (gas leaving the alveoli): (tidal vol L - dead space L) x respiratory rate (breaths per minute)

Question 3

Where in the lung is ventilation and perfusion most effective?
What do each of these mean?
Why is ventilation and perfusion most effective at this place of the lung?

Answer 3

Ventilation- amount of air going into the alveoli
Perfusion- amount of blood going into alveolar capillaries
At the base of the lung
due to gravity and alveoli being more compliant and less resistance

Question 4

How do we classify respiratory failure?
What are they each due to?

Answer 4

T1-hypoxia - due to alveolar flooding (Low PaO2): increased QS shunt
T2-hypercapnia - dead space ventilation (High paCo2): decreased alveolar minute ventilation
T3-perioperative - lower FRC due to increased atelectasis (inward recoils of the lung) (high PaCO2 or low PO2)
T4-shock (people on ventilators): RV increased preload and after load

Question 5

What is ARDS?
What are the 5 causes of ARDS?

Answer 5

Acute respiratory distress syndrome, fluid build up in lungs preventing oxygen entering the bloodstream
Infection
Trauma
Pancreatitis
Burns
Drug toxicity

Question 6

What is the séquelle of ARDS?

Answer 6

Poor gas exchange
Hypercapnoea
More prone to infection

Question 7

What scoring systems can we use for lung failure?

Answer 7

Murray score
Scoring system to see how bad your oxygenation is
Add all numbers and divide by 4
Anything 3 or over start ECMO
New one = Berlin definition

Question 8

How is ARDS managed?

Answer 8

Treat underlying disease
Bronchodilators
AB
Steroids
Oxygen
Ventilator
Fluids
Renal support

Question 9

How do we calculate lung elastance and compliance?
What do elastance and pressure tell us about the lung?

Answer 9

Elastance = change in pressure/ change in volume EPV
Compliance = change in volume /change in pressure
Elastance - tendency to recoil to original shape
Compliance- tendency to distort under pressure

Question 10

What is an ECMO?
How does it differ from heart lung bypass?

Answer 10

Extracorporeal membrane oxygenation
More long term use than a bypass, drains blood from IVC into artificial membrane and then back into right atrium