Ch.8 Oxygen Equilibrium & Transport

**what are the 2 forms of O2 being carried into the blood?

1. dissolved O2 in blood plasma 

2. chemically bound to Hb that is encased in erythrocytes or RBCs

**how is O2 carried in the blood by blood plasma? (tension)

•O2 dissolves into the liquid part (PO2 & dissolved O2 have linear relationship)

**how much O2 is dissolved in blood plasma?

•0.003 mL O2 will dissolve in 100mL of blood for 1 torr of PO2

→ at PO2= 1mmHg → 0.00003mL O2 will dissolve in 1mL of plasma @ 37 C

• PaO2 of100 = 0.3 mL

**how much O2 is bound to Hb?

• 20mL/dL if PaO2 = 100mm

measured by 1.34mL O2 × 15 g% Hb = 20.1

(Hb’s O2 carrying capacity

each g% Hb can carry 1.34 mL of O2)

**what is the normal range for Hb in adults?

12-15 g/dL per 100mL blood

at 15 g/dL & 100% sat → Hb carries 20.1 mL O2

what is the Hb saturation & O2 partial pressure?

SaO2 = 97.5% at PaO2 of 100mmHg

SvO2 = 75% for PvO2 of 40 mmHg

what is cooperative binding?

each molecule of O2 bound makes the next molecule bind more quickly

**how do you calculate the total oxygen content (CaO2)?

(SaO2 × 1.34 x Hb) + (PaO2 x 0.003)

normal = 20 vol %

**what is the equation for CvO2?

(SvO2 × 1.34 x Hb) + (PvO2 x 0.003)

normal = 15 vol %

**what is the equation for CcO2?

(1.34 x Hb) + (PAO2 x 0.003)

Normal= 20

**what is the significance of the HbO2 curve?

• % Hb chemically bound to O2 at each O2 pressure

•relationship between amt of O2 dissolved and amt of O2 saturated

•flat portion → large changes in PO2 → small changes in SO2 & CaO2

PO2= 60 = 100mmHg

•curve portion → small changes in PO2 → large changes in SO2 & CaO2

**what is the normal p50?

27 torr

**what does the normal p50 represent?

• partial pressure where Hb is 50% saturated with O2

**what factors shift Oxyhemoglobin curve to the right?

•higher p50

(adds CO2)

tissue

• ↓ pH, Hb’s affinity for O2 = releases O2 into plasma (Bohr effect) & tissue

• ↑ PCO2, temp, 2-3 DPG

**what factors shift Oxyhemoglobin curve to the left?

•lower p50

lungs

• ↑ pH, Hb’s affinity for O2 = less O2 into plasma = less available tissue

• ↓ PCO2, temp, 2-3 DPG

**what factors cause changes in demand to O2 consumption? (increase or decrease VO2)

↑ exercise, seizures, shivering, hyperthermia

↓ skeletal muscle relaxation, peripheral shunting, certain poisons, hypothermia

**what is the equation for DO2 O2 delivery and normal value?

QT (CaO2 × 10)

normal value = 1000 mL/min

**what is the equation & normal value for VO2 O2 consumption?

QT (C(a-v)O2 × 10)

normal value = 250

**what is the equation for C(a-v)O2?

CaO2 - CvO2

normal is 5 vol %

**what is the equation for O2ER?

(CaO2 - CvO2) / CaO2

normal value= 25%

tissues extract 25% arterial O2

**what is the equation for Qs/Qt??

(CcO2 - CaO2) / (CcO2 - CvO2)

normal is <10%

intrapulmonary abnormalities = 10-20%

significant pulmonary disease - 20-30%

potentially life-threatening= >30%

**what can cause pulmonary shunting?

• part of QT where it moves from R to L of heart without being exposed to PAO2

• bypasses alveoli → enters pulm vascular system by bronchial venous changes

what is the result of pulmonary shunting?

\cdot venous admixture → mixing of shunted nonreoxygenated blood with reoxygenated blood in alveoli

\cdot reoxygenated blood loses O2

what is a absolute shunt?

• anatomic shunts → blood flows from R to L side of heart without coming in contact with alveolus for gas exchange

• capillary shunts → caused by alveolar collapse/atelectasis, alveolar fluid accumulation, alveolar consolidation

what is a relative shunt?

• when pulm capillary perfusion is in excess of A ventilation, ____ shunt, or shunt-like effect said to exist

•common causes → hypoventilation, V/Q perfusion mismatch, AC diffusion defects

what is hypoxemia?

• abnormally low arterial O2 tension

mild → 60 - 79

moderate → 40- 59

severe → <40

**what is hypoxia?

• inadequate level of tissue oxygenation → for aerobic cellular respiration

**what are the 4 types of hypoxia?

1. hypoxic hypoxia → inadequate O2 @ tissue cells caused by low arterial O2 tension (PaO2)

2. anemic hypoxia → normal PaO2, O2 carrying capacity for Hb is inadequate

3. circulatory hypoxia → blood flow to tissue cells is inadequate, O2 is not adequate to meet tissue needs

4. histotoxic hypoxia → inability of tissue cells to metabolize O2

what are 2 Hb abnormalities?

1. methemoglobin (metHb) → Hb w/ Fe++ oxidized to Fe+++

•cant combine to O2

•nitrate poisoning, oxidant drugs

2. sickle cell Hb → HbS crystallizes on deoxygenation