Respiratory Failure

Question 1

Define acute hypoxemic respiratory failure

Answer 1

PaO2 <60 or O2 sat <90%

Question 2

How do you calculate A-a gradient?

Answer 2

A-a gradient = PAO2 (calculated) - PaO2 (measured)

PAO2 = (760 - 47)(FIO2 .21) - .4/.8
Normal PAO2 on RA 100 mmHg

Question 3

What is normal A-a gradient?

Answer 3

<10 or (2.5 + .25(age))

Question 4

What does P:F ratio tell you?

Answer 4

how hypoxemic pt is

Question 5

What are 3 causes of increased A-a gradient

Answer 5

Low V/Q
Shunt
Diffusion abnormality

Question 6

What are 3 causes of normal A-a gradient resp failure

Answer 6

Hypoventilation
Low barometric pressure
Low FiO2 (inhalation injury)

Question 7

Complete these pO2-SaO2 pairs:

Normal: 95mmHg / ? %
Safe but borderline: 60mmHg / ? %
Mixed venous: 40mmHg / ? %

Answer 7

Normal: 95mmHg / 98 %
Safe but borderline: 60mmHg / 90 %
Mixed venous: 40mmHg / 75%

Question 8

Acidemia and fever shift the Hgb dissociation curve ________ (R or L)

Answer 8

shift RIGHT

Question 9

Alkalemia and hypothermia shift the Hgb dissociation curve ________ (R or L)

Answer 9

shift LEFT

Question 10

What is the alveolar gas equation?

Answer 10

PAO2 = (Patm – PH2O)FiO2 – PaCO2/R

Question 11

What are the Berlin criteria for ARDS? (4)

Answer 11

1. Timing within 1 week of known insult of new/worsening respiratory symptom
2. Bilateral (patchy, diffuse, or homogenous) opacities not fully explained by effusions, lung collapse, or nodules
3. Respiratory failure not fully explained by cardiac failure or fluid overload
4. P/F ratio <300 with PEEP 5 cm H2O
   Mild: 200-300
   Moderate: 100-200
   Severe: <100

Question 12

What are goal vent settings for ARDS patients?

Tidal volume
PaO2
PEEP
Plateau pressure
pH

Answer 12

Goal VT 6 cc/kg for IBW
Oxygenation goal: PaO2 55-80 (88-95%)
Use PEEP to achieve goals with lowest FiO2
Plateau pressure < 30 cm H2O
pH goal 7.30-7.45

Question 13

What are indications for non-invasive ventilation?

Answer 13

Pneumonia
Hypercapnic respiratory failure
NM disease
Pulmonary edema
COPD/asthma exacerbation
Must have a mental status