Respiratory Failure

Question 1

What type of respiratory defect causes patients to become hypercapnic?

Answer 1

Ventilatory Failure (you aren’t blowing off enough O2)

PaCO2 ~ 1/ventilation

Question 2

What is the #1 most common cause of hypoxia?

Answer 2

V/Q (ventilation/perfusion) mismatch

• V/Q mismatch is a problem because you’re wasting cardiac output on areas that aren’t being ventilated so the blood perfusing these areas doesn’t exchange any gas
• Meanwhile there is less blood perfusing the areas that actually need gas assume that cardiac output from the right side is constant.

Question 3

***What are the 5 causes of Hypoxemia?

Answer 3

Normal A-a gradient:

1. Anemia
2. Hypoventilation

Elevated A-a gradient:

3. R to L shunt
4. V/Q inequality
5. Diffusion Limitation

Question 4

What are some causes of Hypercapnic Respiratory Failure?

Answer 4

ANYTHING that suppresses breathing. 
• Central Hypoventilation (opiates) 
• Muscle (pump) failure (Muscular Dystrophy, Myopathies, Myasthenia gravis, ALS)
• Botulism
• Guillian Barre Syndrome
• Airway Obstruction

Question 5

What are some causes of left shift in Hbg?

• Is left shift an increased or decreased affinity for binding?

Answer 5

• Hypothermia
• Alkalosis
• Fetal Hbg
• Carbon Monoxide

=> Left Shift = increased affinity for binding

Question 6

Evaluation of someone with Respiratory Failure:
• Hx and Physical
• Vital Signs and Pulse Oximetry
• CXR 
• EKG
• ABG (arterial blood gas)
• CBC 
•Electrolytes 
• Sputum and blood cultures, UA 
• Helical CT (often 1st to check for PE)

Answer 6

Evaluation of someone with Respiratory Failure:
• Hx and Physical
• Vital Signs and Pulse Oximetry
• CXR 
• EKG
• ABG (arterial blood gas)
• CBC 
• Electrolytes 
• Sputum and blood cultures, UA 
• Helical CT (often 1st to check for PE)

Question 7

Would you use a pulmonary function test in someone with acute respiratory failue?

Answer 7

NO - this is a method to evaluate people with chronic respiratory failure

Question 8

What is the 1st thing you do to treat the patient when they come in with respiratory failure?
• how does this treatment also aid in Dx?

Answer 8

• PUT THEM ON SUPPLEMENTAL O2

* if it doesn’t correct then you know you’re dealing with a SHUNTING issue

Question 9

Differentiate the use of Albuterol, Ipratropium, and Formoterol in the treatment of COPDs?

Answer 9

Albuterol: treats asthma
Ipratropium: treats COPD
Formoterol: Rapid onset and LONG ACTING

Question 10

Why can’t corticosteroids eliminate all bronchospasm?

Answer 10

PENETRATION - if they can’t access the tissue then they can’t activate ß2 receptors

Question 11

What are some ques to determine if someone is tired as a result of respiratory failure?

Answer 11

• Increase Somnolence
• Decreasing RR
• Decreased Respiratory Excursions
• Borderline O2 sat. (may not see this if you’re giving the patient supplemental O2).

Question 12

What is the ABG likely to reveal in someone with respiratory failure?

Answer 12

Hypercapnia

Question 13

What do you do when the CO2 starts going up in a patient with respiratory failure?

Answer 13

put them on ASSISTED VENTILATION

Question 14

T or F: exhalation will be prolonged in patients with COPD.

Answer 14

True, this is why their FEV1/FVC is reduced

Question 15

T or F: PaO2 makes a large contribution to blood O2.

Answer 15

False, PaO2 is only a small fraction of blood O2

Question 16

What are 4 causes of increased CO2 retention after supplmental O2?

Answer 16

1. Blunting of Hypoxic Drive
2. Worsening of V/Q mismatch
3. Haldane Effect
4. Neuromuscular Fatigue

Question 17

Why does the V/Q mismatch become more significant on supplemental O2?

Answer 17

Worsening of V/Q mismatch:
• supplemental O2 abolishes hypoxic induced vasoconstriction of pulmonary vasculature

• Poorly ventilated areas of the lung start getting perfused
• These areas are not functional so you start perfusing areas that can’t exchange O2 and the V/Q mismatch gets worse

Question 18

What is the Haldane Effect?

Answer 18

1. In hypoxic individuals CO2 binds to Hbg
2. Supplemental O2 raises both PaO2 and SaO2
3. CO2 gets kicked off of Hbg and replaced with O2
4. CO2 has to go somewhere so it dissolves in the blood to raise the PCO2

Question 19

How should you manage a patient experiencing bronchospasm that is precipitating respiratory failure?

Answer 19

• Bronchodilators
• Hydration
• SYSTEMIC Corticosteroids
• Treat the precipitating cause

Question 20

What will be ABG look like for a patient who is getting tired as a result of respiratory failure?

Answer 20

They will become increasingly hypercapnic.

You should consider assisted breathing, mechanical ventilation, or intubation in these patients.