Oxygen Transport

Question 1

In what mechanism is O2 transported from the alveoli to the capillaries?

Answer 1

Diffusion

Question 2

Increase O2 tension in the lung results in

Answer 2

Increase O2 delivery to the blood

Question 3

What is the formula for O2 content?

Answer 3

CaO2 = ([0.003 ml O2\dl blood/mmHg]PO2) + SaO2Hb*1.31 ml/dl blood)

Question 4

What is the most efficient way of increasing O2 content?

Answer 4

By Increasing Hemoglobin Bound O2 (SaO2Hb1.31 ml/dl blood).

Question 5

What is the O2 content if we have 85% Saturation of Hb?

Answer 5

0.3ml O2 + 16.7 ml O2 = 17.0 ml O2

Question 6

What is mixed Venous Oxygen?

Answer 6

The amount of O2 returning to the right side of the heart

Question 7

What is normal mixed Venous Sat?

Answer 7

65-75%

Question 8

What is normal mixed venous oxygen (dissolved)?

Answer 8

35-45 mmHg

Question 9

What is normal body O2 extraction of Hb?

Answer 9

25-35%

Question 10

Factors affecting mixed venous oxygen:

Answer 10

O2 sat
Concentration of Hb
O2 consumption
CO

Question 11

What is body’s O2 extraction formula?

Answer 11

CaO2 – CvO2 (CvO2 uses the same formula as CaO2 except the values are mixed venous blood for dissolved and sat Hb)

Question 12

Name a few factors that could increase O2 extraction:

Answer 12

febrile, sepses, high metabolic activity

Question 13

What is the formula for O2 delivery:

Answer 13

DO2 = CaO2*CO; by increasing CO, body compensate for decrease O2.

Question 14

O2 delivery depends on:

Answer 14

CO, Hb con, PaO2

Question 15

True or False: Delivery and consumption of O2 are independent at low level.

Answer 15

True (why)

Question 16

what is the normal value for C.O and O2 consumption:

Answer 16

5000 ml/min and 250 ml/min respectively

Question 17

Normal O2 stores is:

Answer 17

1500ml O2

Question 18

True of False: High Hb bound of O2 when low PAO2.

Answer 18

False

Question 19

Name factors that could result in right shift in O2 dissociation curve:

Answer 19

Inc 2,3-DBG, inc CO2, Low pH, high Temperature

Question 20

PaO2 of 60 mmHg =

Answer 20

90% Sat

Question 21

PaO2 of 35-45 mmHg (mixed venous sat)

Answer 21

65-75% sat

Question 22

What does it mean when O2 dissociative curve shifts to the right?

Answer 22

O2 is less bound in hemi ( hemi change its configuration); thus facilitating unloading of O2 to the tissue.

Question 23

What is 2-3 DGP?

Answer 23

It is part of hemi grourp that allows O2 to be unbound from the blood to the tissue

Question 24

What is Cardiac related Hypoxia?

Answer 24

Low perfusion of the tissue as a result of decrease in CO.

Question 25

What Hemic Hypoxia?

Answer 25

If Hbg is deranged of dysfunction (sickle cell), O2 caring capacity is affected; thus results in hypoxia.

Question 26

Body demand-based hypoxia:

Answer 26

Hypoxia as a result of high 02 body extraction (like in MH cases).

Question 27

Histotoxic Hypoxia:

Answer 27

A condition when a tissue can not utilizes O2. For example cyanide poisoning disrupted electron-transport to O2 in mitochondria as O2 is the final electron carrier.

Question 28

Name three ways of CO2 transport system:

Answer 28

Bicarbonate
Carbamino compound
Dissolved in plasma

Question 29

What is the chemical equation of CO2-Bicarbonate transport system?

Answer 29

H20+ CO2↔H2CO3↔H ions + HCO3; Bicarb serve as buffering for Acid-Base balance (Cl ion is pumped in the tissue and replacing bicarb: Hamburger shift)

Question 30

What is Carbamino compound (Haldane effect)?

Answer 30

CO2 react with amino group on protein and forming deoxygenated hemoglobin which has 3.5 times affinity for CO2.

Question 31

How our body control breathing?

Answer 31

Through: Respiratory Rhythm Generator, chemoreceptors, Arterial PO2, lung and airway receptors, and Vegal pulmonary stretch receptors.

Question 32

What are the two respiratory rhythm generators?

Answer 32

Ventral respiratory group (VRG) and Dorsal respiratory group (DRG)

Question 33

Which of the two respiratory rhythm generator controls expiration?

Answer 33

VRG

Question 34

What effects narcotic drugs have on VRG and DRG?

Answer 34

It might damage or affect the function these group and could blunt respiratory function

Question 35

True or False: Chemoreceptors alert VRG and DRG.

Answer 35

True

Question 36

What are the extubation criteria?

Answer 36

•	Vt > 5 cc/kg
•	Vital capacity > 10 cc/kg
•	Adequate Motor Strength 
•	NIF < -25 mmHg
•	Respiratory Rate < 30/minute 
•	TV/RR > 10
•	RSBI < 105   RSBI (rapid shallow breathing index = Respirator rate/ Vt)
Seriously, have you seen anyone following all this criteria before extubating a pt?

Question 37

State which of the following situations would be expected to lower PaO2.

a) anemia.
b) carbon monoxide toxicity.
c) an abnormal hemoglobin that holds oxygen with half the affinity of normal hemoglobin.
d) an abnormal hemoglobin that holds oxygen with twice the affinity of normal hemoglobin.
e) lung disease with intra-pulmonary shunting.

Answer 37

e, lung Dz with intra-pumonary shunting, because it affects V/Q mismatch.

Question 38

At 10 a.m. a patient has a PaO2 of 85 mm Hg, an SaO2 of 98%, and a hemoglobin of 14 gm/dl. At 10:05 a.m. she suffers a severe hemolytic reaction that suddenly leaves her with a hemoglobin of only 7 gm/dl. Assuming no lung disease occurs from the hemolytic reaction, what will be her new PaO2, SaO2, and CaO2?

a) PaO2 unchanged, SaO2 unchanged, CaO2 unchanged
b) PaO2 unchanged, SaO2 unchanged, CaO2 reduced
c) PaO2 reduced, SaO2 unchanged, CaO2 reduced
d) PaO2 reduced, SaO2 reduced, CaO2 reduced

Answer 38

B, SaO2 is mainly determined by PaO2.