Diffusion, Hypoxia and Hypoxemia, misc.

Question 1

What is tracheomalacia refer to in adults?

Answer 1

diffuse or segmental weakness of the trachea

Question 2

What blood gas value is roughly equivalent to the partial pressure of CO2 (PCO2) in the alveoli?

Answer 2

Arterial PCO2

Question 3

Bronchial thermoplasty (radiofrequency ablation) is aimed at reducing _______ in the airway.

Answer 3

Smooth muscle (hypertrophy)

Question 4

What is the target of Omalizumab?

Answer 4

IgE

Question 5

What is the normal mean pressure of the main pulmonary artery?

Answer 5

15 mmHg

Question 6

What are the normal systolic/diastolic pressures of the main pulm artery?

Answer 6

25/8

Question 7

Why does diffusion capacity increase by 2-3 times during exercise?

Answer 7

recruitment and distention of pulmonary capillaries

Question 8

What is the normal diffusing capacity for carbon monoxide (DLCO) at rest?

Answer 8

~25 mL/(min x mmHg)

Question 9

What are the 2 factors that affect the diffusion capacity of the lung? (may be summed to produce the “diffusion resistance”)

Answer 9

blood gas barrier and reaction of O2 w/ Hb

Question 10

ABG: What is the normal value for pH?

Answer 10

7.35-7.45

Question 11

ABG: What is the normal value for PCO2?

Answer 11

35-45

Question 12

ABG: What is the normal value for HCO3-?

Answer 12

22-27

Question 13

ABG: What is the normal value for PaO2?

Answer 13

80-100

Question 14

ABG: What is the normal value for SaO2?

Answer 14

> 95%

Question 15

What are th 3 causes of hypoxemic hypoxia?

Answer 15

(a) decreased PaO2 (low FiO2, low Pbar, hi PCO2)
(b) V/Q mismatch (pna, ht. fail., atelectasis)
(c) increased pulmonary mismatch (e.g. ARDS)

Question 16

What are the four types of non-hypoxemic hypoxia?

Answer 16

1. stagnant (circulatory)
2. anemic
3. histotoxic
4. oxygen affinity

Question 17

Under what circumstances are ABGs misleading and VBGs are more reliable indicators of tissue perfusion?

Answer 17

Impaired cardiac output, e.g. cardiac shock

Question 18

Why are ABGs unreliable when cardiac output is reduced?

Answer 18

Ventilation continues, so blood leaving the lungs is well perfused, but blood at the tissues may be very acidotic. (Does this only applying to central arterial lines?)

Question 19

Why shouldn’t bicarbonate be administered to acidotic pts with poor tissue perfusion?

Answer 19

Reaction of HCO3- with H+ produces more CO2.

Question 20

What are two causes of circulatory hypoxia?

Answer 20

(a) low cardiac output (e.g. cardiogenic shock)

b) non-pulmonary shunting (e.g. cirrhosis

Question 21

What is the classic example of histotoxic hypoxia?

Answer 21

cyanide poisoning

Question 22

What are two causes of oxygen affinity hypoxia?

Answer 22

(a) CO poisoning

(b) massive transfusion

Question 23

What is the antidote for CO poisoning?

Answer 23

O2 (100% or hyperbaric)

Question 24

What is the main reason for the leftward shift of the oxyhemoglobin dissociation curve in massive blood transfusion?

Answer 24

loss of 2,3-DPG in stored blood