Oxygen and Carbon Dioxide Transport – Des Jardins (Lecture Notes)

Vocabulary flashcards covering key concepts from the notes on oxygen and carbon dioxide transport.

Total Oxygen Content

The sum of oxygen dissolved in plasma and oxygen bound to hemoglobin. CaO2 = (Hb × 1.34 × SaO2) + (PaO2 × 0.003).

Dissolved Oxygen in Plasma

Oxygen physically dissolved in plasma. Solubility is 0.003 mL O2 per 100 mL of blood per mmHg (PaO2).

Oxygen Bound to Hemoglobin

O2 carried by hemoglobin; each gram of Hb can carry up to about 1.34 mL of O2 when fully saturated; depends on Hb concentration and SaO2.

Hemoglobin (Hb)

Oxygen-transporting protein in red blood cells composed of four heme groups and four globin chains.

Heme

Iron-containing component of Hb that binds one O2 molecule at each of the four heme sites.

Alpha Chain

One of the globin polypeptide chains in Hb; normally two alpha and two beta chains per Hb molecule.

Beta Chain

One of the globin polypeptide chains in Hb; normally two beta and two alpha chains per Hb molecule.

Erythrocytes (RBCs)

Red blood cells; primary carriers of hemoglobin and thus O2 in the blood.

Normal Adult Hb Values (g/100 mL)

Male: 14–16 g/100 mL; Female: 12–15 g/100 mL.

SaO2 (Arterial Oxygen Saturation)

Percentage of Hb that is saturated with oxygen in arterial blood.

PaO2 (Arterial Oxygen Tension)

Partial pressure of oxygen in arterial blood (mmHg).

CaO2 (Arterial Oxygen Content)

Oxygen content of arterial blood; CaO2 = (Hb × 1.34 × SaO2) + (PaO2 × 0.003).

CvO2 (Mixed Venous Oxygen Content)

Oxygen content of mixed venous blood returning to the heart.

CcO2 (Pulmonary Capillary Oxygen Content)

Oxygen content of pulmonary capillary blood; CcO2 = (Hb × 1.34) + (PAO2 × 0.003).

Oxyhemoglobin Dissociation Curve

Relationship between PO2 and Hb saturation (SaO2); S-shaped curve with flat and steep portions.

Flat Portion (Oxyhemoglobin Curve)

High PO2 region where changes in PO2 produce little change in SaO2.

Steep Portion (Oxyhemoglobin Curve)

Low PO2 region where small decreases in PO2 cause large drops in SaO2.

Thebesian Veins

The coronary venous drainage into the left atrium, contributing to minor desaturation.

Bronchial Venous Drainage

Bronchial veins draining into pulmonary veins, causing venous admixture.

Alveolar Dead Space Ventilation

Alveoli that are ventilated but not perfused well, contributing to shunt-like effects.

Right Shift (Oxyhemoglobin Curve)

Decreased Hb affinity for O2; factors include acidosis (low pH), high CO2, increased temperature, and increased 2,3-DPG; promotes O2 unloading at tissues.

Left Shift (Oxyhemoglobin Curve)

Increased Hb affinity for O2; factors include alkalosis (high pH), low CO2, decreased temperature, and decreased 2,3-DPG; facilitates O2 loading in lungs.

2,3-Diphosphoglycerate (2,3-DPG)

RBC metabolite that decreases Hb’s O2 affinity; higher levels shift the curve to the right; increased in hypoxia and anemia.

Fetal Hemoglobin (HbF)

Hb present in fetal blood with higher O2 affinity than adult Hb, causing a left shift (lower P50).

Carbon Monoxide Binding (COHb)

CO binds Hb with ~210x greater affinity than O2, reducing O2 delivery and causing a left shift.

Total Oxygen Delivery (DO2)

Rate of O2 delivered to tissues; depends on cardiac output and arterial O2 content (DO2 ∝ CO × CaO2; influenced by PaO2, SaO2, Hb, and CO).

Oxygen Consumption (VO2)

Amount of O2 extracted and used by tissues per minute; also called oxygen uptake.

Arterial-Venous Oxygen Content Difference (CaO2 − CvO2)

Difference between arterial and venous O2 content; normally about 5 vol% indicating O2 extraction.

Oxygen Extraction Ratio (O2ER)

Fraction of delivered O2 that is extracted by tissues; O2ER = VO2/DO2 (also called oxygen coefficient or utilization ratio).

Pulmonary Shunting

Portion of cardiac output that moves from the right to the left heart without exposure to alveolar O2 (PAO2).

Anatomic Shunt

Right-to-left shunt where blood bypasses alveoli entirely; true shunt with venous admixture.

Venous Admixture

Mixing of deoxygenated venous blood with oxygenated arterial blood in the systemic circulation.

Causes of Absolute (Anatomic) Shunts

Congenital heart defects, intrapulmonary fistula, vascular lung tumors.

Capillary Shunts

Alveolar collapse/atelectasis, alveolar edema, or alveolar consolidation causing poor gas exchange.

Clinical Significance of Pulmonary Shunting

Shunt

Hypoxia Types (4)

Hypoxic (hypoxemic), anemic, circulatory (stagnant), and histotoxic hypoxia.

Cyanosis

Bluish discoloration of skin/mucous membranes; may appear when reduced Hb concentration reaches about 5 g/dL.

CO2 Transport in Plasma

CO2 transported in plasma as dissolved CO2, carbamino compounds, and bicarbonate (HCO3−).

CO2 Transport in Red Blood Cells

CO2 transported in RBCs as dissolved CO2, carbaminohemoglobin, and bicarbonate (HCO3−).

Formation of Bicarbonate (HCO3−)

CO2 reacts with water to form carbonic acid, catalyzed by carbonic anhydrase, producing bicarbonate for transport.

CO2 Elimination in Lungs

Bicarbonate is converted back to CO2 in the lungs and exhaled.

CO2 Dissociation Curve

Curve of CO2 content vs PCO2; CO2 content rises with PCO2; changes in PCO2 have a larger effect on CO2 content than changes in PO2 on O2 content.

Haldane Effect

Describes how deoxygenated blood carries more CO2 (loading) and oxygenated blood carries less CO2 (unloading).

Total Oxygen Content

The sum of oxygen dissolved in plasma and oxygen bound to hemoglobin. CaO2 = (Hb × 1.34 × SaO2) + (PaO2 × 0.003).

Dissolved Oxygen in Plasma

Oxygen physically dissolved in plasma. Solubility is 0.003 mL O2 per 100 mL of blood per mmHg (PaO2).

Oxygen Bound to Hemoglobin

O2 carried by hemoglobin; each gram of Hb can carry up to about 1.34 mL of O2 when fully saturated; depends on Hb concentration and SaO2.

Hemoglobin (Hb)

Oxygen-transporting protein in red blood cells composed of four heme groups and four globin chains.

Heme

Iron-containing component of Hb that binds one O2 molecule at each of the four heme sites.

Alpha Chain

One of the globin polypeptide chains in Hb; normally two alpha and two beta chains per Hb molecule.

Beta Chain

One of the globin polypeptide chains in Hb; normally two beta and two alpha chains per Hb molecule.

Erythrocytes (RBCs)

Red blood cells; primary carriers of hemoglobin and thus O2 in the blood.

Normal Adult Hb Values (g/100 mL)

Male: 14–16 g/100 mL; Female: 12–15 g/100 mL.

SaO2 (Arterial Oxygen Saturation)

Percentage of Hb that is saturated with oxygen in arterial blood.

PaO2 (Arterial Oxygen Tension)

Partial pressure of oxygen in arterial blood (mmHg).

CaO2 (Arterial Oxygen Content)

Oxygen content of arterial blood; CaO2 = (Hb × 1.34 × SaO2) + (PaO2 × 0.003).

CvO2 (Mixed Venous Oxygen Content)

Oxygen content of mixed venous blood returning to the heart.

CcO2 (Pulmonary Capillary Oxygen Content)

Oxygen content of pulmonary capillary blood; CcO2 = (Hb × 1.34) + (PAO2 × 0.003).

Oxyhemoglobin Dissociation Curve

Relationship between PO2 and Hb saturation (SaO2); S-shaped curve with flat and steep portions.

Flat Portion (Oxyhemoglobin Curve)

High PO2 region where changes in PO2 produce little change in SaO2.

Steep Portion (Oxyhemoglobin Curve)

Low PO2 region where small decreases in PO2 cause large drops in SaO2.

Thebesian Veins

The coronary venous drainage into the left atrium, contributing to minor desaturation.

Bronchial Venous Drainage

Bronchial veins draining into pulmonary veins, causing venous admixture.

Alveolar Dead Space Ventilation

Alveoli that are ventilated but not perfused well, contributing to shunt-like effects.

Right Shift (Oxyhemoglobin Curve)

Decreased Hb affinity for O2; factors include acidosis (low pH), high CO2, increased temperature, and increased 2,3-DPG; promotes O2 unloading at tissues.

Left Shift (Oxyhemoglobin Curve)

Increased Hb affinity for O2; factors include alkalosis (high pH), low CO2, decreased temperature, and decreased 2,3-DPG; facilitates O2 loading in lungs.

2,3-Diphosphoglycerate (2,3-DPG)

RBC metabolite that decreases Hb’s O2 affinity; higher levels shift the curve to the right; increased in hypoxia and anemia.

Fetal Hemoglobin (HbF)

Hb present in fetal blood with higher O2 affinity than adult Hb, causing a left shift (lower P50).

Carbon Monoxide Binding (COHb)

CO binds Hb with ~210x greater affinity than O2, reducing O2 delivery and causing a left shift.

Total Oxygen Delivery (DO2)

Rate of O2 delivered to tissues; depends on cardiac output and arterial O2 content (DO2 ∝ CO × CaO2; influenced by PaO2, SaO2, Hb, and CO).

Oxygen Consumption (VO2)

Amount of O2 extracted and used by tissues per minute; also called oxygen uptake.

Arterial-Venous Oxygen Content Difference (CaO2 − CvO2)

Difference between arterial and venous O2 content; normally about 5 vol% indicating O2 extraction.

Oxygen Extraction Ratio (O2ER)

Fraction of delivered O2 that is extracted by tissues; O2ER = VO2/DO2 (also called oxygen coefficient or utilization ratio).

Pulmonary Shunting

Portion of cardiac output that moves from the right to the left heart without exposure to alveolar O2 (PAO2).

Anatomic Shunt

Right-to-left shunt where blood bypasses alveoli entirely; true shunt with venous admixture.

Venous Admixture

Mixing of deoxygenated venous blood with oxygenated arterial blood in the systemic circulation.

Causes of Absolute (Anatomic) Shunts

Congenital heart defects, intrapulmonary fistula, vascular lung tumors.

Capillary Shunts

Alveolar collapse/atelectasis, alveolar edema, or alveolar consolidation causing poor gas exchange.

Clinical Significance of Pulmonary Shunting

Shunt

Hypoxia Types (4)

Hypoxic (hypoxemic), anemic, circulatory (stagnant), and histotoxic hypoxia.

Hypoxic (Hypoxemic) Hypoxia

Caused by inadequate oxygenation of arterial blood (e.g., due to low PaO2 or SaO2); common in respiratory diseases.

Anemic Hypoxia

Insufficient hemoglobin to carry adequate oxygen, even if PaO2 is normal (e.g., due to anemia or CO poisoning).

Circulatory (Stagnant) Hypoxia

Inadequate blood flow to tissues despite normal PaO2 and Hb content (e.g., due to heart failure or shock).

Histotoxic Hypoxia

Tissues are unable to utilize oxygen effectively, even if delivered adequately (e.g., due to cyanide poisoning interfering with cellular respiration).

Cyanosis

Bluish discoloration of skin/mucous membranes; may appear when reduced Hb concentration reaches about 5 g/dL.

CO2 Transport in Plasma

CO2 transported in plasma as dissolved CO2, carbamino compounds, and bicarbonate (HCO3−).

CO2 Transport in Red Blood Cells

CO2 transported in RBCs as dissolved CO2, carbaminohemoglobin, and bicarbonate (HCO3−).

Formation of Bicarbonate (HCO3−)

CO2 reacts with water to form carbonic acid, catalyzed by carbonic anhydrase, producing bicarbonate for transport.

CO2 Elimination in Lungs

Bicarbonate is converted back to CO2 in the lungs and exhaled.

CO2 Dissociation Curve

Curve of CO2 content vs PCO2; CO2 content rises with PCO2; changes in PCO2 have a larger effect on CO2 content than changes in PO2 on O2 content.

Haldane Effect

Describes how deoxygenated blood carries more CO2 (loading) and oxygenated blood carries less CO2 (unloading).