Hypoxemia

Question 1

Hypoxemia

Answer 1

decreased oxygenation of blood, this issue highlights a problem with getting oxygen from the environment, into the blood and can cause hypoxia

Question 2

Hypoxia

Answer 2

decreased oxygenation of tissue, this issue can still allow for oxygenated blood but there might be an issue getting that oxygenated blood to the tissue

Question 3

Five major causes of hypoxemia ( ↓ PaO2)

Answer 3

1) Low PiO2
2) Hypoventilation
3) Diffusion impairment
4) Low Ventilation/Perfusion mismatch
5) Right-to-Left shunt

Question 4

Which of the gases has the highest concentration in atmospheric air?

Answer 4

Nitrogen

Question 5

True/False; Air in the alveoli is saturated with water vapor

Answer 5

True

Question 6

What would cause direct changes to FiO2

Answer 6

Supplemental O2 could ↑ FiO2

A problem with O2 source (gas anesthesia) or if patient in closed atmosphere would cause a ↓ in FiO2

Question 7

Nitrogen is what type of gas?

Answer 7

“inert” meaning it does not biologically interact so N2 doesn’t typically diffuse across the alveolar septa

Question 8

What role does nitrogen play in the respiratory system?

Answer 8

Prevents atelectasis as it helps maintain the structure of alveoli and without it the alveoli will collapse!

• 100% O2 → N2 washout → alveolar collapse

Question 9

What are the determinants of PiO2?

Answer 9

• FiO2
• Patm
• PH2O

Question 10

PiO2 calculation formula

Answer 10

PiO2 = (Patm - PH2O) x FiO2

Question 11

What can cause a change in PiO2?

Answer 11

Supplemental O2 could ↑

A problem with O2 source (gas anesthesia) or if patient in closed atmosphere would cause a ↓

When Patm is ↓(such as in higher altitudes)
When Patm is ↑( such as underwater)

Question 12

Why is PAO2 lower than PiO2 under normal conditions?

Answer 12

b/c alveolar is constantly being consumed while alveolus is constantly gaining CO2

Question 13

Alveolar gas equation

Answer 13

PAO2 = PiO2 – O2 consumed AKA
Respiratory quotient (RQ) = CO2 produced/O2 consumed

Question 14

O2 consumption formula

Answer 14

O2 consumed = CO2 produced/RQ

Question 15

PaO2 is determined by

Answer 15

PAO2 and the opportunity for alveolar O2 to diffuse into the pulmonary circulation

Question 16

Bicarbonate buffer system

Answer 16

CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-

Question 17

CA is above the arrows here; CO2 + H2O ↔ H2CO3, what does it represent?

Answer 17

CA = carbonic anhydrase

Question 18

What does FiO2 represent?

Answer 18

The fraction of oxygen in inspired air(meaning it’s the % of air inhaled that is oxygen)

Question 19

What does PiO2 represent?

Answer 19

The major determinate of partial pressure of oxygen in inspired air

Question 20

What does PAO2 represent?

Answer 20

The partial pressure of oxygen in the alveoli

Question 21

What does PaO2 represent?

Answer 21

Partial pressure of oxygen in systemic arterial blood

Question 22

Mechanisms of normal oxygenation

Answer 22

1) Adequate PiO2
2) Ventilation
3) Diffusion of gas across alveolar septa
4) Matching the distribution of ventilation and perfusion