Oxygen Transport

Vocabulary practice flashcards covering oxygen transport, dissolved oxygen, hemoglobin dynamics, formulas, and shifts in the oxyhemoglobin dissociation curve.

Dissolved Oxygen

The portion of oxygen that dissolves in blood plasma and moves freely in its normal gaseous state, which is measured clinically as $\text{PO}_2$.

Oxygen Solubility Coefficient

The factor of $0.003\,\text{mL}$ of $\text{O}_2$ dissolving in $100\,\text{mL}$ of blood for every $1\,\text{mmHg}$ of $\text{PO}_2$ at normal body temperature.

Normal Dissolved Oxygen at $100\,\text{mmHg}$ $\text{PO}_2$

A concentration of $0.3\,\text{mL}$ of dissolved oxygen in every $100\,\text{mL}$ of blood, calculated as $100\,\text{mmHg} \times 0.003$.

Hemoglobin A (HbA)

The primary adult hemoglobin molecule consisting of four heme groups (an iron-containing non-protein portion) and four polypeptide chains forming globin (two identical $\alpha$ chains and two $\beta$ chains).

Deoxyhemoglobin

Hemoglobin in its uncombined or reduced form ($\text{Hb}$), which reacts reversibly with molecular oxygen ($\text{O}_2$) to produce oxyhemoglobin ($\text{HbO}_2$).

Oxyhemoglobin ($\text{HbO}_2$)

The compound formed when iron in hemoglobin reversibly binds oxygen; hemoglobin reaches $100\%$ saturation when four oxygen molecules are bound to a single hemoglobin molecule.

Sickle Cell Hemoglobin (HbS)

A hemoglobin variant featuring an altered amino acid sequence on the $\beta$ chain, changing the structural properties of hemoglobin and the morphology of the red blood cell.

Oxygen Carrying Capacity of Hemoglobin

The standard carrying constant equal to $1.34\,\text{mL}$ of $\text{O}_2$ carried per gram of hemoglobin when fully saturated.

Normal Arterial Hemoglobin Saturation ($\text{SaO}_2$)

A normal arterial saturation value of approximately $97\%$, reduced from $100\%$ by normal anatomical and physiological shunting via Thebesian veins, bronchial veins, and under-ventilated alveoli.

Total Arterial Oxygen Content ($\text{CaO}_2$)

The total volume of oxygen carried in arterial blood, calculated as $(\text{Hb} \times 1.34 \times \text{SaO}_2) + (\text{PaO}_2 \times 0.003)$, with a normal range of $16\text{--}20\,\text{vol}\%$.

End-Capillary Oxygen Content ($\text{CcO}_2$)

The oxygen content calculated in the pulmonary capillary blood, expressed as $(\text{Hb} \times 1.34 \times \text{ScO}_2) + (\text{PAO}_2 \times 0.003)$.

Total Oxygen Delivery ($\text{DO}_2$)

A measure of cardiopulmonary delivery calculated as $\text{CO} \times (\text{CaO}_2 \times 10)$, with a normal value of $900\text{--}1150\,\text{mL}\,\text{O}_2/\text{min}$.

Oxygen Dissociation Curve

An S-shaped curve illustrating the percentage of hemoglobin bound to oxygen at each given partial pressure of oxygen ($\text{PO}_2$).

Steep Portion of the Oxygen Dissociation Curve

The slope of the curve between $10$ and $60\,\text{mmHg}\,\text{PO}_2$, where rapid combination occurs and reductions below $60\,\text{mmHg}$ produce large drops in oxygen bound to hemoglobin.

Flat Portion (Plateau) of the Oxygen Dissociation Curve

The plateau between $70$ and $100\,\text{mmHg}\,\text{PO}_2$ that serves as a safety zone for oxygen uploading in the lungs; further increases above $100\,\text{mmHg}$ add very little oxygen to the blood.

$$P_{50}$$

The partial pressure of oxygen at which hemoglobin is $50\%$ saturated, having a normal value of $27\,\text{mmHg}$.

Right Shift of the Oxygen Dissociation Curve

A displacement characterized by an increased $P_{50}$ and lower hemoglobin affinity for oxygen, improving oxygen unloading to the tissues.

Left Shift of the Oxygen Dissociation Curve

A displacement characterized by a decreased $P_{50}$ and higher hemoglobin affinity for oxygen, improving uploading in the lungs but limiting oxygen unloading to the tissues.

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

A substance formed in red blood cells during anaerobic glycolysis; elevated levels shift the curve to the right, whereas low levels (as seen in stored blood) cause a shift to the left.

Fetal Hemoglobin (HbF)

A hemoglobin variant that possesses a greater affinity for oxygen than adult hemoglobin ($\text{HbA}$), shifting the curve left to enhance maternal-fetal oxygen transfer before progressively disappearing after $1\,\text{year}$ of life.

Carboxyhemoglobin (COHb)

Hemoglobin bound to carbon monoxide, which binds with $210$ times greater affinity than oxygen, blocking oxygen attachment and shifting the curve left to limit tissue unloading.

Normal Blood Gas Values

Standard clinical ranges for blood gases: arterial values include $\text{pH}\ 7.35\text{--}7.45$, $\text{PaCO}_2\ 35\text{--}45\,\text{mmHg}$, $\text{HCO}_3^-\ 22\text{--}28\,\text{mEq/L}$, and $\text{PaO}_2\ 80\text{--}100\,\text{mmHg}$; venous values include $\text{pH}\ 7.30\text{--}7.40$, $\text{PvCO}_2\ 42\text{--}48\,\text{mmHg}$, $\text{HCO}_3^-\ 24\text{--}30\,\text{mEq/L}$, and $\text{PvO}_2\ 35\text{--}45\,\text{mmHg}$.