Oxygen Equilibrium and Transport Practice Flashcards

Flashcards covering oxygen pressures, hemoglobin characteristics, calculated oxygen content, and factors affecting the oxyhemoglobin dissociation curve.

$$P O_2$$

The partial pressure of oxygen in a system.

$$P_B O_2$$

The barometric pressure of oxygen, calculated by multiplying the barometric pressure (e.g., $760\,mmHg$) by the factional concentration of oxygen ($F_i O_2$).

$$P_A O_2$$

The partial pressure of oxygen found in the alveolar air.

Alveolar Air Equation

The calculation used to determine the amount of oxygen in the alveoli, expressed as $P_A O_2 = (P_B - P_{H_2 O}) \times F_i O_2 - (P_a C O_2 \times 1.25)$, where $P_{H_2 O}$ is typically $47\,mmHg$.

$$P_a O_2$$

The partial pressure of oxygen in the arterial blood, with a normal range of $80$ to $100\,mmHg$.

$$P_v O_2$$

The partial pressure of oxygen in the venous blood, which normally measures approximately $40\,mmHg$.

$$S_a O_2$$

The arterial oxygen saturation, representing the percentage of hemoglobin saturated with oxygen in arterial blood as measured via an arterial blood gas machine.

$$S_p O_2$$

The percentage of saturated hemoglobin as measured non-invasively by a pulse oximeter.

$$F_i O_2$$

The fraction of inspired oxygen, which is $0.21$ ($21\%\text{)}$ for room air.

Oxygen Toxicity

A condition caused by excessive supplemental oxygen ($F_i O_2$ of $50\%\text{}$ or more) that creates free radicals and can lead to an inappropriate immune response and conditions like ARDS.

Deciliter ($dL\text{)}$

A unit of measurement equal to $100\,mL$ of blood.

Henry's Law

A law stating that the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas.

Solubility Coefficient of Oxygen

The constant used to calculate oxygen dissolved in plasma, which is $0.003\,mL/dL/mmHg$.

Hemoglobin ($Hb\text{)}$ Carrying Constant

A constant representing the amount of oxygen bound to hemoglobin when it is $100\%\text{}$ saturated, equal to $1.34\,mL$ of oxygen per gram of hemoglobin.

$$C_a O_2$$

The total oxygen content in arterial blood, calculated as the sum of oxygen bound to hemoglobin and oxygen dissolved in plasma.

Volume Percent ($vol\%\text{)}$

A measurement of oxygen content expressed as milliliters of oxygen per deciliter of blood ($mL/dL\text{)}$.

Heme

The four iron-containing pigment groups of a hemoglobin molecule where individual oxygen molecules bind.

Globin

The protein portion of hemoglobin composed of four polypeptide chains (two alpha and two beta chains).

Adult Hemoglobin ($HbA\text{)}$

A large complex protein molecule found inside red blood cells; one red blood cell contains approximately $280\text{ million}$ hemoglobin molecules.

Oxyhemoglobin ($Hb O_2\text{)}$

Hemoglobin that is chemically combined with oxygen molecules.

Deoxygenated/Reduced Hemoglobin ($Hb\text{)}$

Hemoglobin that is not bound to oxygen.

Cooperative Binding

The process where the binding of one oxygen molecule to hemoglobin facilitates the rapid binding of the remaining three molecules.

Oxyhemoglobin Dissociation Curve

A sigmoid (S-shaped) curve that illustrates the non-linear relationship between hemoglobin saturation and the partial pressure of oxygen in the plasma.

$$P_{50}$$

The partial pressure of oxygen at which hemoglobin is $50\%\text{}$ saturated, which is normally $27\,mmHg$ at a $pH$ of $7.4$ and a temperature of $37\,^\circ\text{C}$.

Affinity

The attraction or binding strength between hemoglobin and oxygen.

Right Shift

A shift in the dissociation curve that increases the $P_{50}$ and decreases hemoglobin's affinity for oxygen, promoting oxygen unloading at the tissues.

Left Shift

A shift in the dissociation curve that decreases the $P_{50}$ and increases hemoglobin's affinity for oxygen, promoting oxygen loading in the lungs.

$$2,3\text{-DPG (or BPG)}$$

A metabolic intermediary produced in red blood cells that decreases hemoglobin's affinity for oxygen.

Bohr Effect

The way changes in $P CO_2$ and $pH$ affect the position of the oxyhemoglobin dissociation curve.