O2 Transport

100 vocabulary flashcards covering the concepts of oxygen transport, Hb chemistry, the dissociation curve, and pulmonary shunting based on the lecture transcript.

Oxygen transport function

A function of both the blood and the heart to move oxygen between the lungs and tissues.

$$P_{O2}$$

The symbol representing the pressure of oxygen in a system.

Barometric pressure ($P_{B}$)

The atmospheric pressure, which is $760\,mmHg$ in Shreveport, Louisiana.

$$F_{iO2}$$

The fraction of inspired oxygen; for room air, it is $21\%$ or $0.21$.

$$P_{AO2}$$

The pressure of oxygen found in the alveoli, calculated using the alveolar air equation.

Water vapor pressure ($P_{H2O}$)

The pressure exerted by water vapor in the lungs, which is $47\,mmHg$ at body temperature.

Alveolar Air Equation

$$P_{AO2} = (P_{B} - 47) \times F_{iO2} - (P_{aCO2} \times 1.25)$$

$$P_{aCO2}$$

The partial pressure of carbon dioxide in arterial blood; normal is $40\,mmHg$.

Normal $P_{AO2}$

Approximately $100\,mmHg$ after accounting for water vapor and carbon dioxide.

$$P_{aO2}$$

The partial pressure of oxygen dissolved in arterial blood plasma.

Normal $P_{aO2}$ range

$80$ to $100\,mmHg$ for a normal adult.

$P_{aO2}$ Critical Value

$60\,mmHg$, below which the blood is significantly under-oxygenated.

$$P_{vO2}$$

The partial pressure of oxygen in venous blood; normal is approximately $40\,mmHg$.

$$S_{aO2}$$

The saturation of hemoglobin with oxygen in arterial blood, measured via an arterial blood gas machine.

$$S_{pO2}$$

The saturation of hemoglobin with oxygen as measured non-invasively by a pulse oximeter.

Medical Abbreviation: $c$ with a line over it

A medical abbreviation meaning 'with'.

Oxygen Toxicity

A condition caused by prolonged exposure to high concentrations of oxygen, creating free radicals that damage lungs.

Free Radicals

Highly reactive molecules created by supplemental oxygen that can trigger an inappropriate immune response against lung tissue.

Plasma dissolved oxygen

Oxygen that keeps its molecular form and dissolves into the liquid part of the blood; contributes to $P_{aO2}$.

Hemoglobin-bound oxygen

The majority of oxygen in the blood, which is bound to the hemoglobin protein inside red blood cells.

Normal $S_{aO2}$ range

$95\%$ to $100\%$.

Normal $S_{vO2}$ percentage

Approximately $75\%$.

Henry's Law

States that the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas.

Plasma solubility coefficient

$0.003\,mL$ of oxygen per $100\,mL$ of blood per $mmHg$ of pressure.

Deciliter ($dL$)

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

Dissolved oxygen formula

$P_{aO2} \times 0.003$; results in milliliters of oxygen per deciliter ($vol\%$).

Hemoglobin ($Hb$ or $Hgb$)

A large complex protein molecule found inside red blood cells that transports oxygen.

Molecules of Hb per Red Blood Cell

$280$ million molecules.

Heme portion

The four iron-containing pigment groups of a hemoglobin molecule where oxygen binds.

Globin portion

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

Ferrous state ($Fe^{++}$)

The specific chemical state iron must be in for oxygen to bind to hemoglobin.

$$HbA$$

The abbreviation for 'Adult Hemoglobin'.

Oxyhemoglobin ($HbO_{2}$)

Hemoglobin that is chemically bound to oxygen.

Deoxygenated hemoglobin ($Hb$)

Also called reduced hemoglobin; hemoglobin that is not bound to oxygen.

Cooperative Binding

The process where the binding of the first oxygen molecule to hemoglobin increases the affinity for the remaining three spots to fill quickly.

Hemoglobin oxygen capacity per molecule

Each hemoglobin molecule can carry exactly four oxygen molecules.

Volume Percent ($vol\%$)

A unit identical to milliliters of gas per $100\,mL$ (deciliter) of blood ($mL/dL$).

Normal Hemoglobin Range ($Hb$)

$12$ to $15\,g/dL$ or $12$ to $16\,g/dL$ depending on the population.

Hemoglobin oxygen binding constant

The fact that $1.34\,mL$ of oxygen can be carried by every $1\,g$ of fully saturated hemoglobin.

Bound oxygen formula

$Hb \times 1.34 \times S_{aO2}$ (where $S_{aO2}$ is expressed as a decimal).

Total arterial oxygen content ($C_{aO2}$)

The sum of oxygen bound to hemoglobin and oxygen dissolved in plasma.

$C_{aO2}$ Formula

$$(Hb \times 1.34 \times S_{aO2}) + (P_{aO2} \times 0.003)$$

Normal $C_{aO2}$ value

Approximately $20\,vol\%$ ($20\,mL/dL$).

Normal $C_{vO2}$ value

Approximately $15\,vol\%$ ($15\,mL/dL$).

Oxygen Delivery ($D_{O2}$)

The total amount of oxygen delivered to the tissues per minute, using cardiac output and arterial oxygen content.

$D_{O2}$ Formula

$$D_{O2} = \dot{Q} \times C_{aO2} \times 10$$

Cardiac Output ($\dot{Q}$ or $CO$)

The volume of blood pumped by the heart per minute; normal is approximately $5\,L/min$.

Normal Oxygen Delivery ($D_{O2}$)

Approximately $1000\,mL$ of oxygen per minute.

Oxygen Consumption ($V_{O2}$)

The amount of oxygen extracted and used by the tissues per minute; normal is $250\,mL/min$.

Arterial-Venous Oxygen Content Difference ($C_{(a-v)O2}$)

The difference between arterial and venous oxygen content; normal is approx $5\,vol\%$.

Oxygen Extraction Ratio

The percentage of oxygen delivered that is used by tissues; normal is $25\%$.

Myocardium oxygen extraction

The heart muscle extracts oxygen maximally at $75\%$ to $90\%$, unlike other tissues.

Oxyhemoglobin Dissociation Curve

A sigmoid-shaped graph showing the relationship between $P_{O2}$ and hemoglobin saturation ($S_{O2}$).

Association portion of the curve

The upper, flat portion of the curve occurring in the lungs where oxygen is loaded onto hemoglobin.

Dissociation portion of the curve

The lower, steep portion of the curve occurring in the tissues where oxygen is released.

$$P_{50}$$

The $P_{O2}$ at which hemoglobin is $50\%$ saturated; normal is $27\,mmHg$ at a $pH$ of $7.4$ and $37^{\circ}C$.

Right Shift of the curve

Describes a decreased affinity of hemoglobin for oxygen, helping to release oxygen to the tissues.

Left Shift of the curve

Describes an increased affinity of hemoglobin for oxygen, helping to load oxygen in the lungs.

Causes of a Right Shift

Increased temperature, increased $CO_{2}$, decreased $pH$ (acidosis), and increased $2,3-DPG$.

Causes of a Left Shift

Decreased temperature, decreased $CO_{2}$, increased $pH$ (alkalosis), and decreased $2,3-DPG$.

$2,3-DPG$ (or $BPG$)

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

Hypoxia

A condition of inadequate oxygen levels in the body tissues.

Hypoxemia

A condition of abnormally low levels of oxygen in the blood.

$D_{O2}$ Critical Threshold

The point ($< 500\,mL/min$) where oxygen delivery fails to meet tissue demands, leading to lactic acid formation.

Lactic Acid

A byproduct of anaerobic metabolism produced when tissues lack sufficient oxygen.

Cyanosis

A bluish discoloration of the skin or mucous membranes caused by high levels of deoxygenated hemoglobin.

Cyanosis Threshold

Occurs when there is $5\,g/dL$ of deoxygenated (reduced) hemoglobin in the capillaries.

Peripheral Cyanosis

Bluish tint found in the extremities (fingers, toes) often due to low blood flow.

Central Cyanosis

Bluish tint found in the lips, tongue, and mucous membranes, indicating dangerously low arterial saturation.

Polycythemia

An increased number of red blood cells/hemoglobin, which can cause cyanosis even if oxygen content is normal.

Anemia

A condition of low hemoglobin levels; severely anemic patients may not show cyanosis despite extreme hypoxia.

Shunt

Perfusion without ventilation; blood goes from the right heart to the left heart without being oxygenated.

Dead Space

Ventilation without perfusion; air is moving but no blood is there to pick it up.

Absolute (True) Shunt

A shunt where there is zero exposure to oxygen, such as anatomic holes in the heart.

Refractory to oxygen therapy

A characteristic of a true shunt where arterial oxygen does not improve much with supplemental oxygen.

Anatomic Shunt

A true shunt caused by structural defects, like a Ventricular Septal Defect ($VSD$).

Capillary Shunt

A true shunt occurring when pulmonary capillaries bypass non-ventilated (atelectatic) alveoli.

Atelectasis

The collapse of alveoli, which leads to capillary shunting.

Relative Shunt (Shunt-like effect)

Perfusion is exposed to some oxygen, but exchange is incomplete (e.g., pulmonary edema or fibrosis).

Venous Admixture

The mixing of shunted, non-oxygenated blood with oxygenated blood, which lowers the total $P_{aO2}$.

Normal Shunt Percentage

Less than $10\%$.

Life-threatening Shunt Percentage

$20\%$ to $30\%$.

Clinical Shunt Equation

An assessment that includes diffusion defects to provide a well-rounded picture of defects.

Alveolar-Arterial Gradient ($P(A-a)O2$)

The difference between alveolar oxygen and arterial oxygen pressure.

Shunt abbreviation

($Q_{S}/Q_{T}$)

Cyanide Poisoning

A type of poisoning that prevents tissues from consuming oxygen, resulting in a decreased arterial-venous difference.

Hyperthermia

An elevated body temperature or fever that increases oxygen consumption.

Hypothermia

A decreased body temperature that slows metabolism and decreases oxygen consumption.

Therapeutic Hypothermia

A medical treatment (temperature management) used to slow metabolism and prevent brain damage after cardiac arrest.

Skeletal muscle relaxation

Caused by sedation or paralytics, which decreases oxygen consumption ($V_{O2}$).

Packed Red Blood Cells ($PRBCs$)

The blood product derived from the blood bank used for transfusions.

Transfusion limitation

Clinical studies show transfusions increase hemoglobin but may not increase oxygen release to the tissues.

Shunt-like effects: Hypoventilation

Occurs when breathing is too slow or shallow to provide enough oxygen for equilibration.

Shunt-like effects: Pulmonary Edema

Fluid in the alveoli/interstitial space that acts as a diffusion barrier to oxygen.

Right Atrium

The location in the heart where mixed venous blood oxygen content is often measured ($C_{vO2}$).

Oxygen loading

The process occurring at the lungs where hemoglobin binds with oxygen ($Left\,Shift$).

Oxygen unloading

The process occurring at the tissues where hemoglobin releases oxygen ($Right\,Shift$).

Sigmoidal

The specific 's-shaped' curve of the oxyhemoglobin dissociation graph.

Anaerobic glycolysis

The metabolic process that produces factor $2,3-DPG$.