EXAM #2: OXYGEN THERAPY

Question 1

Generally, what is happening at the flat upper portion of the oxyhemoglobin curve?

Answer 1

Loading of oxygen on Hb

Question 2

Generally, what is happening at the steep lower portion of the oxyhemoglobin curve?

Answer 2

Unloading of oxygen from Hb

Question 3

What causes a right shift of the oxyhemoglobin curve?

Answer 3

1) Increased temp.
2) Increased 2-3 BPG
3) Increased H+

*Decreased affinity

Question 4

What causes a left shift of the oxyhemoglobin shift?

Answer 4

1) Decreased temp.
2) Decreased 2- BPG
3) Decreased H+
4) CO

*Increased affinity

Question 5

What is hypoxia?

Answer 5

Oxygen delivery is inadequate to meet metabolic need

Question 6

What is hypoxemia?

Answer 6

Failure of respiratory system to oxygenate arterial blood

Question 7

How is hypoxemia defined in adults? What about neonates?

Answer 7

• PaCO2 less than 60 mmHg, or SpO2 less than 90%

* Less than 50 mmHg in neonates

Question 8

What is dysoxia?

Answer 8

Impaired ability for tissue to utilize oxygen

E.g. Cyanide poisoning

Question 9

What does V/Q greater than 1.0 mean?

Answer 9

Ventilation (V) exceeds perfusion (blood flow)

Question 10

What does V/Q less than 1.0 mean?

Answer 10

Inadequate ventilation compared to perfusion*

*This is what accounts for most hypoxemia

Question 11

How does gravity affect V/Q in the apcies and bases of the lungs?

Answer 11

• 3 in apices

- Less than 1 in bases

Question 12

What is the V/Q in the alveolar deadspace?

Answer 12

0

Question 13

What is an anatomic shunt?

Answer 13

Blood flow that does NOT participate in gas exchange

E.g. Right to left shunt in a congenital heart defect

Question 14

Does an anatomic shunt respond to oxygen therapy?

Answer 14

NO

Question 15

What is alveolar shunt?

Answer 15

Areas of poor ventilation in relation to perfusion

Question 16

What are the ominous signs of severe hypoxia?

Answer 16

1) Cyanosis
2) Bradycardia/ arrhythmia
3) Hypotension
4) Somnolence

Question 17

In regards to FiO2, how do oxygen percentage and partial pressure change with increased elevation?

Answer 17

• Percentage is ALWAYS 21%
• Partial pressure is proportional to atmospheric pressure

*Thus, increased elevation = decreased partial pressure of oxygen

Question 18

With exposure to 100% O2 for 0-12 hours, what are the physiologic responses?

Answer 18

• Tracheobronchitis

- Substernal chest pain

Question 19

With exposure to 100% O2 for 12-24 hours, what are the physiologic responses?

Answer 19

Decreased vital capacity

Question 20

With exposure to 100% O2 for 24-30 hours, what are the physiologic responses?

Answer 20

• Decreased lung compliance

- Increased A-a gradient

Question 21

With exposure to 100% O2 for 30-72 hours, what are the physiologic responses?

Answer 21

Decreased diffusion capacity

Question 22

What two organs are primarily affected by oxygen toxicity?

Answer 22

Lungs and CNS

Question 23

What causes the damage seen in oxygen toxicity?

Answer 23

Oxygen free radicals that induce an inflammatory reaction

Question 24

Describe the physiologic mechanism of oxygen-induced hypoventilation in a COPD patient.

Answer 24

• COPD= blunted CO2 response
• Respiratory drive is based on HYPOXIA
• High blood O2 suppresses ventilatory drive

Question 25

What is retinopathy of prematurity?

Answer 25

Blindness and retinal detachment associated with prematurity and oxygen toxicity

Question 26

What causes retinopathy or prematurity?

Answer 26

1) Excessive oxygen causes retinal vasoconstriction
2) New blood vessels form and increase in number
3) Hemorrhaging of new vessels causes scarring

Question 27

What is absorption atelectasis?

Answer 27

• Oxygen therapy replaces a large volume of nitrogen in the lung with oxygen
• Oxygen is then absorbed into the blood, reducing the volume of the alveoli
• Alveolar collapse results i.e. absorption atelectasis.

Question 28

What are the indications for hyperbaric oxygen therapy?

Answer 28

1) Air embolism
2) CO poisoning
3) Wound therapy

Question 29

If you use a simple oxygen mask, what flow rate is required as a minimum?

Answer 29

5 L/min

Question 30

What is the minimum flow rate for a rebreather mask?

Answer 30

8 L/min

*Note that this mask has 2x ports that block inhalation of room air vs. a partial that only has 1x

Question 31

When do you need to ensure that supplemental oxygen is humidified?

Answer 31

Anytime you’re bypassing the nose and mouth