Gas Laws, Partial Pressure + Solubility

These flashcards cover the key concepts of gas laws and their applications in respiratory physiology as discussed in the lecture.

What is the main purpose of gas laws in physiology?

To describe the behavior of gases in the respiratory system under various conditions.

What does Boyle’s Law state?

At constant temperature, the pressure of a gas is inversely proportional to its volume (P ⍺ 1/V).

How does Charles’s Law relate volume and temperature?

At constant pressure, the volume of a gas is directly proportional to its absolute temperature (V ⍺ T).

What does Gay-Lussac’s Law explain?

At constant volume, the pressure of a gas is directly proportional to its absolute temperature (P ⍺ T).

What is Avogadro’s Law about?

Equal volumes of gases at the same temperature and pressure contain the same number of molecules.

What is the Universal Gas Law equation?

PV = nRT, where P is pressure, V is volume, n is number of moles, R is the universal gas constant, and T is absolute temperature.

What does STPD stand for?

Standard Temperature (0℃) and Pressure (760 mmHg), Dry.

What is BTPS?

Body Temperature (37℃) and Pressure, Saturated with water vapour.

What does Dalton’s Law of Partial Pressures state?

The total pressure of a gas mixture is equal to the sum of the partial pressures of each gas.

If the total pressure is 740 mmHg, what is the partial pressure of gas X if it is 35% of the mixture?

The partial pressure of gas X is 259 mmHg.

What is Henry’s Law in relation to gas solubility?

The concentration of a gas that dissolves in a liquid is directly proportional to its partial pressure in that liquid.

What is the solubility constant for O2 at 37℃ according to the lecture?

0.03 ml (STPD) / L plasma / mmHg.

What happens to gas solubility in the presence of salts?

The presence of salts lowers the solubility of a gas in the liquid.

Describe gas diffusion in the context of tension gradients.

Gases diffuse down their tension gradient, which may not align with concentration gradients.

How is the composition of dry air characterized?

Dry air consists of approximately 20.93% O2, 0.03% CO2, and 79.04% N2.

What is the average partial pressure of oxygen in alveolar air?

About 100 mmHg.

How can residual volume be measured?

Using gas dilution methods or body plethysmography.

In gas dilution using helium, what is the formula for calculating RV?

RV = V1 x (C1 – C2)/C2.

What does body plethysmography measure?

The change in gas volume within the lungs based on pressure changes in a sealed box.

What occurs at the end of a maximum expiration in body plethysmography?

A shutter closes, and the subject makes respiratory efforts trying to inhale.

What conditions affect the solubility of gases in liquids?

Different gases have different solubilities, and solubility changes with temperature and the presence of solutes.

When does a gas reach equilibrium in a solution?

When the partial pressure of the gas in the solution equals the partial pressure of the gas above the liquid.

What is the significance of the kinetic energy and collision frequency of gas molecules?

They determine the pressure exerted by the gas.

What happens to gas volumes expressed at STPD?

They reflect gas volumes with chemical significance, such as O2 consumption and CO2 production.

What is the role of water vapor in moist inspired air?

It reduces the partial pressures of O2 and CO2 as air passes to the lungs.

Why might lung volumes be expressed at BTPS instead of STPD?

BTPS reflects the actual volumes of gases in the thorax at body temperature.

What are the variations of oxygen partial pressure in different alveoli during the respiratory cycle?

There can be a variation of ± 2 mmHg.

How does the pressure in the box relate to the volume change in body plethysmography?

Boyle's law is used to determine the change in gas volume (ΔV) based on pressure changes.

What pressure measurements are considered while applying Boyle’s law in lung gas measurements?

The pressure before and after the inspiratory effort (P1 and P2 for the box; P3 and P4 for the lungs).

What is the importance of gas composition when considering atmospheric pressure?

Understanding gas composition helps in calculating partial pressures and gas exchange in the lungs.

Why does the solubility of gases generally decrease with increasing temperature?

Higher temperatures increase kinetic energy, causing gas molecules to escape from the liquid saturation.