Arterial Blood Gases–O2 Carriage/CO2 Carriage

Question 1

There is about 26.4 mM of carbon dioxide in the blood. Of that, roughly ____ is in the form of HCO3-; the rest is split evenly as CO2 and carbamino proteins.

Answer 1

24 mM

Question 2

Describe the Bohr effect.

Answer 2

CO2 binding to hemoglobin decreases the oxygen affinity of hemoglobin

Question 3

What is the Haldane effect?

Answer 3

Oxygen binding decreases the CO2 affinity of hemoglobin

Question 4

What factors decrease the oxygen affinity of hemoglobin?

Answer 4

Increased temperature, decreased pH, and increased CO2 concentration

Question 5

What is D(O2)?

Answer 5

The delivery of oxygen to a tissue in one minute. It is given by the following formula: flow x C(a[O2]).

Question 6

C(a[O2]) = _____________.

Answer 6

SaO2 x [Hb] x 1.39 ml O2/gm Hb + 0.003 x Pa(O2)

Question 7

Define hypoxia.

Answer 7

Low O2 at tissues (P[O2]

Question 8

What pathophysiologies can lead to hypoxia?

Answer 8

Low cardiac output; low arterial oxygen saturation (a syndrome called hypoxemia); or failure to deliver oxygen to the tissues (such as from anemia or carbon monoxide poisoning)

Question 9

What five things can cause hypoxemia?

Answer 9

Decreased P(I[O2]); decreased P(A[O2]); diffusion problems; shunts; and V/Q mismatches

Question 10

At high altitude, arterial CO2 _______, due to _________.

Answer 10

decreases; increased respiratory rate

Question 11

What is the conversion between mM of CO2 and Torr?

Answer 11

0.03 mM/Torr

Question 12

How does V(O2) differ from D(O2)?

Answer 12

D(O2) represents the amount of oxygen delivered to the tissues in one minute, while V(O2) represents the amount of oxygen consumed in one minute.

Question 13

V(O2), which is the amount of blood consumed by the tissues in one minute, is given by ___________.

Answer 13

Q x ∆C(O2)

Also written Q x (Ca[O2] - Cv[O2])

Question 14

Hypoxemia is defined as _______ in Denver and ________ at sea level.

Answer 14

Pa(O2)

Question 15

What are some ramifications of carbon monoxide poisoning?

Answer 15

CO (1) decreases the Sa(O2); (2) increases O2 affinity, which decreases O2-offloading; and (3) binds tightly and won’t release

Question 16

The A-a gradient is _________.

Answer 16

P(A[O2]) - P(a[O2])

Question 17

The normal A-a gradient is _________.

Answer 17

5-10 Torr

Question 18

What three hypoxemic conditions lead to increased A-a gradient?

Answer 18

V/Q mismatch, interstitial lung diseases, and consolidation pneumonias

Question 19

Those at high altitude produce more _______.

Answer 19

2,3-BPG (to decrease the oxygen affinity of hemoglobin and thus increase delivery)

Question 20

Ca(O2) is typically ______.

Answer 20

20.7 ml O2 / 100 ml blood

Question 21

Pulse-oximeters only give _________. To get an Pa(O2), you must get _________.

Answer 21

Sa(O2); an arterial blood gas

Question 22

Diseases such as __________ respond to 100% oxygen, while ______ do not.

Answer 22

asthma, bronchitis, and emphysema; diffusion disorders