Tissue Hypoxia

Question 1

Define hypoxia.

Answer 1

Inadequate oxygenation of tissue

Question 2

What does pulse oximetry measure?

Answer 2

SaO2

Question 3

Contrast the SaO2 levels detected by a pulse oximeter and a co-oximeter.

Answer 3

Pulse oximeter- falsely elevated SaO2 if dyshemoglobins are present
Co-oximeter- accurately measures SaO2 if dyshemoglobins are present

Question 4

What are the clinical findings of tissue hypoxia?

Answer 4

Cyanosis
Confusion
Cognitive impairment
Lethargy

Question 5

Detail the normal diffusion of oxygen from the atmosphere to the RBC.

Answer 5

Oxygen diffuses down a gradient from the atmosphere, to the alveoli, to plasma, into RBC where it attaches to heme groups

Question 6

Define oxygen content.

Answer 6

A measure of the total amount of O2 carried in blood.

O2 content= Hb*SaO2+PaO2

Question 7

What state must iron be in to carry oxygen?

Answer 7

2+ (ferrous)

Question 8

Define oxygen saturation.

Answer 8

The oxygen in the RBC attached to heme groups

Question 9

If the partial pressure of arterial oxygen decreases, what must happen to the oxygen saturation?

Answer 9

Decreases

Question 10

Define ischemia.

Answer 10

Decreased arterial blood flow

Question 11

What is the most common cause of ischemia?

Answer 11

Thrombus

Question 12

Define hypoxemia.

Answer 12

Decrease in partial pressure of oxygen

Question 13

When a person has respiratory acidosis, what has to happen to the PaO2?

Answer 13

Goes down- hypoxemia

Question 14

What is the sum of the partial pressures of O2, CO2, and N in the alveoli at sea level?

Answer 14

760 mmHg

Question 15

In addition to respiratory acidosis, what are other causes of hypoxemia?

Answer 15

Decreased inspired PO2
Ventilation defect
Perfusion defect
Diffusion defect
Cyanotic congenital heart disease

Question 16

Define ventilation defect.

Answer 16

Lung is perfused but not ventilated

Question 17

Define perfusion defect.

Answer 17

Lung is ventilated but not perfused

Question 18

Define diffusion defect.

Answer 18

Decreased diffusion of oxygen through the alveolar-capillary interface

Question 19

What causes intrapulmonary shunting?

Answer 19

Ventilation defects

Question 20

What causes increased dead space?

Answer 20

Perfusion defects

Question 21

What are the causes of tissue hypoxia?

Answer 21

Ischemia
Hypoxemia
Hb abnormalities

Question 22

Respiratory distress syndrome (hyaline membrane disease) is an example of what type of V/Q defect?

Answer 22

Ventilation defect- lack of surfactant causes atelectasis

Question 23

A patient has hypoxemia and is given 100% oxygen. After 20 minutes, the PaO2 is checked and has not increased. What type of V/Q defect is present?

Answer 23

Shunt

Question 24

What is the most common perfusion defect?

Answer 24

PE

Question 25

What is the leading cause of death due to poisoning?

Answer 25

Carbon monoxide poisoning

Question 26

How do you treat carbon monoxide poisoning?

Answer 26

100% O2

Question 27

Do you see cyanosis in a patient with CO poisoning?

Answer 27

No- cherry red pigment

Question 28

Patients who are victims of a house fire are at risk of poisoning from what 2 compounds?

Answer 28

CO | Cyanide

Question 29

What is methemoglobin?

Answer 29

Iron is Fe 3+ (ferric)

Question 30

What color is the blood from a person with methemoglobinemia?

Answer 30

Brown

Question 31

What molecule reduces ferrous iron to ferric iron in Hb?

Answer 31

NADPH-methemoglobin reductase

Question 32

What is the treatment for methemoglobinemia?

Answer 32

IV methylene blue | Vitamin C- reducing agent

Question 33

What drug classes can produce methemoglobinemia?

Answer 33

Sulfa drugs | Nitro drugs

Question 34

Regarding the OBC, is a R shift or L shift better?

Answer 34

Right shift- increased release of oxygen

Question 35

What produces a left shift in the OBC?

Answer 35

``` Alkalosis Decreased 2,3-BPG Decreased temperature Increased HbF CO poisoning MetHb ```

Question 36

What produces a right shift in the OBC?

Answer 36

Acidosis Increased 2,3-BPG Increased temperature Altitude

Question 37

Why does 2,3-BPG cause a right shift in the OBC?

Answer 37

2,3-BPG stabilizes taut form of Hb, this decreases the affinity of Hb for oxygen causing oxygen to move from Hb into plasma and into tissue by diffusion

Question 38

Enzyme inhibition at any level of oxidative phosphorylation decreases ATP synthesis and shuts down the ETC. This is easily remembered as the 3 C's, what are these?

Answer 38

Cytochrome oxidase CO Cyandie

Question 39

Define uncoupling of oxidative phosphorylation.

Answer 39

Protons from the intermembranous space move through the innermitochondiral membrane into the mitochondtrial matrix and bypass ATP synthase

Question 40

Salicylic acid is a metabolite of what drug?

Answer 40

Aspirin- acetylsalicylic acid

Question 41

With any cause of hypoxia there is cellular swelling, why?

Answer 41

Decreased oxygen results in decreased ATP synthesis, this limits the Na-K ATPase leading to influx of Na and cellular swelling

Question 42

Why does calcium lead to irreversible cellular damage?

Answer 42

Activates enzymes