Hemodynamics and Fick's Law Quiz

12 Questions

Which area of the respiratory system is responsible for gas exchange?

Respiratory bronchioles

What factor determines the volume of alveolar ventilation (VA)?

Tidal volume (TV)

What is the main reason for a decrease in alveolar ventilation (VA) during shallow rapid breathing?

Decrease in tidal volume

Which component is considered the gold standard for monitoring hemodynamic measurements and evaluating cardiovascular disease?

Left ventricular pressure-volume loops

What is the main factor responsible for the resistance to blood flow through a blood vessel?

Arteriole radius

How does vasoconstriction affect blood flow in blood vessels?

Decreases blood flow

What is the formula for cardiac output (Q) according to Fick's Equation?

Q = HR x SV

In Fick’s Law of diffusion, what does V gas represent?

Volume of gas diffused

How is blood flow (BF) related to the radius of an arteriole according to the text?

BF is inversely proportional to the radius

What does Alveolar ventilation (VA) in the text equation represent?

Volume of fresh air reaching lungs

During low-intensity exercise, why does tidal volume increase according to the text?

To prevent acidosis by expiring CO2

Which factor contributes to an increase in breathing frequency during high-intensity exercise?

Buildup of metabolites

Study Notes

Fick's Equation and Hemodynamics

VO2 (oxygen uptake) is calculated by multiplying cardiac output (Q) with the arteriovenous oxygen difference (a-vO2).
Cardiac output (Q) is the product of heart rate (HR) and stroke volume (SV).
Ejection fraction (EF) is the ratio of stroke volume to end-diastolic volume (EDV).
Mean arterial pressure (MAP) is the average pressure in the arterial system and is calculated by taking 2/3 of the diastolic blood pressure (DBP) and 1/3 of the systolic blood pressure (SBP).

Blood Flow and Resistance

Blood flow is inversely proportional to the radius of the blood vessel to the fourth power (Q ~ r^4).
Doubling the radius of an arteriole would increase blood flow by 16 times.
The sympathetic nervous system controls blood vessel radius, which affects blood flow.
Vasoconstriction (decrease in radius) decreases blood flow, while vasodilation (increase in radius) increases blood flow.

Fick's Law of Diffusion

The rate of gas diffusion (V gas) is proportional to the surface area (SA), the difference in partial pressures (P1 – P2), and the solubility of the gas (DC).
V gas = [SA x (P1 – P2) x DC] / T, where T is the thickness of the membrane.

Ventilation and Alveolar Ventilation

Ventilation (Ve) is the amount of air moved in or out of the lungs per minute and is calculated by multiplying tidal volume (TV) with breathing frequency (fb).
Alveolar ventilation (VA) is the volume of fresh air that reaches the respiratory zone of the lung and is calculated by subtracting dead space volume from tidal volume (VA = TV - DS).
VA is approximately 10 L/min under normal conditions, but decreases during shallow rapid breathing.

Partial Pressure of Gases

Partial pressure of a gas (PIO2) is calculated by multiplying barometric pressure with the percentage of the gas in air.
At sea level, PIO2 is approximately 159 mmHg.
Arterial oxygen pressure (PaO2) is approximately 100 mmHg at rest, while arterial carbon dioxide pressure (PaCO2) is approximately 40 mmHg at rest.

Cardiovascular Hemodynamics

Left ventricular pressure-volume (PV) loops are used to monitor hemodynamic measurements and evaluate cardiovascular disease.
The change in pressure drives blood flow, and the radius of the blood vessel affects resistance to flow.
Vasoconstriction and vasodilation affect resistance, which affects blood flow.
Preload, afterload, and contractility affect the pressure-volume loops, which impact cardiac output.