AMP 20: Oxygen Therapy

Question 1

What is the definition of hypoxemia?

Answer 1

PaO2 < 80 mm Hg

Question 2

List 5 causes for hypoxemia

Answer 2

• Hypoventilation
• ventilation/perfusion (V/Q) mismatch
• low inspired oxygen
• diffusion-barrier impairment
• right-to-left extrapulmonary blood shunting

Question 3

How close to the nose or mouth should flow-by oxygen be placed?

Answer 3

2-4 cm

Question 4

What FiO2 can be achieved with flow-by O2 supplementation at 2 L/min?

Answer 4

29.5 to 48% FiO2

Question 5

What FiO2 can be achieved with mask O2 supplementation?

Answer 5

50-60% at 8-12 L/min

Question 6

What FiO2 can be achieved with nasal cannula O2 supplementation?

Answer 6

FiO2 of 40-65% at a flow rate of 50-100 mL/kg/min

Question 7

What decreases the FiO2 in an animal with nasal cannula O2 supplementation?

Answer 7

open mouth breathing or panting

Question 8

What are contraindications for nasal insufflation catheters?

Answer 8

• nasal mass
• epistaxis
• nasal fracture
• rhinitis

Question 9

After how long can O2 supplementation at 100% FiO2 lead to oxygen toxicity?

Answer 9

>12 hours

Question 10

If the animal suffers from oxygen toxicity or is at high risk for oxygen toxicity, but decreasing or discontinuing supplemental O2 leads to persistent hypoxemia, what is the next step?

Answer 10

mechanical ventilation will be required to reduce FiO2 while hopefully maintaining adequate oxygenation

Question 11

How does airway obstruction lead to atalactasis

Answer 11

Eventually all gas diffuses into blood, leaving the alveoli empty ⇒ alveolar collapse

Question 12

Why does oxygen supplementation increase the risk for atalactasis/airway collapse

Answer 12

at some point all gas diffuses into blood = absorption atalactasis, but some gases take longer than others ⇒ nitrogen does not readily diffuse ⇒ absorption atalactasis takes long to develop

O2 supplementation ⇒ O2 replaces nitrogen ⇒ O2 more readily diffuses ⇒ fastened absorption atalactasis