Rt 9 to 10 ch

Temperature and Gas Pressure

When the volume and mass stay the same, increasing the temperature increases gas pressure. Decreasing the temperature lowers gas pressure.

Anaerobic Respiration

Anaerobic respiration is cellular respiration that occurs without oxygen.

What causes the lactic acid buildup?

Without oxygen, cells cannot make energy normally. The body switches to anaerobic respiration, which produces lactic acid as a waste product.

What causes the lactic acid buildup?

Without oxygen, cells cannot make energy normally. The body switches to anaerobic respiration, which produces lactic acid as a waste product.

Respiratory Quotient

Respiratory quotient (R) compares the amount of carbon dioxide produced to the amount of oxygen consumed. Normal value:
200/250= 0.8. This means the body normally produces slightly less CO₂ than the amount of O₂ it uses.

Inspired Oxygen

FiO₂ (fraction of inspired oxygen) describes the amount of oxygen entering the body during inspiration.Room air FiO₂ = 21%

FiO₂

Oxygen in the air being inhaled

PAO₂

• Oxygen inside the alveoli

PaO₂

• Oxygen dissolved in arterial blood

As air moves into the lungs:

• it mixes with old air

• becomes humidified

• oxygen level decreases

Diffusion

Diffusion is the movement of particles from an area of high concentration to an area of low concentration. Oxygen moves from the alveoli (high oxygen concentration) into the pulmonary capillary blood (low oxygen concentration).

Gay-Lussac’s Law

When volume and mass stay constant, the temperature of a gas is directly proportional to its pressure.

Dalton’s Law

Dalton’s law states that the total pressure of a gas mixture equals the sum of the partial pressures of each gas. It helps explain:

• oxygen pressure in the lungs

• carbon dioxide pressure in the lungs

• how gases diffuse across the alveolar membrane

Each gas has its own partial pressure that helps drive diffusion.

Alveolar Dead Space

Alveolar dead space occurs when alveoli are ventilated but not perfused with blood.

What happens to gas exchange in alveolar dead space?

Gas exchange cannot occur because:

• air reaches the alveoli

• but blood flow is missing

Without blood flow:

• oxygen cannot enter blood

• carbon dioxide cannot leave blood

Normal PaO₂

Normal PaO₂ is about 80–100 mm Hg.

What does PaO₂ measure?

PaO₂ measures the amount of oxygen dissolved in arterial blood.

It shows how well oxygen moves from the lungs into the bloodstream.

Chronic Hypoxic Pulmonary Vasoconstriction

Chronic hypoxic pulmonary vasoconstriction can lead to cor pulmonale (right-sided heart failure).

Why does the right side of the heart become stressed?

Low oxygen causes pulmonary blood vessels to constrict.

This increases resistance in the lungs, so the right side of the heart must pump harder to move blood through the lungs.

Over time:

• the right ventricle enlarges

• heart strain develops

• right-sided heart failure can occur

Cerebrospinal Fluid (CSF)

CSF is a clear, colorless fluid that surrounds the brain and spinal cord.

What does this fluid help protect?

CSF:

• cushions the brain and spinal cord

• maintains pressure in the CNS

• removes waste products

• helps protect nervous tissue from injury

Apneustic Breathing

Apneustic breathing is prolonged inspiration followed by shortened exhalation.

What part of the nervous system is usually involved?

Usually caused by damage to the:

• pons

• pneumotaxic center

• brainstem

Common causes:

• stroke

• brain injury

• drug overdose

Blood-Brain Barrier

The blood-brain barrier is a thin semipermeable membrane that protects the central nervous system from contaminants in the blood.

Agonal Breathing

Agonal breathing is irregular, gasping, labored breathing often seen near death or after cardiac arrest.

Why is this breathing pattern an emergency sign?

It usually means:

• the brain is not getting enough oxygen

• cardiac arrest may be occurring

• the person is critically ill

Emphysema and Diffusion

Emphysema causes breakdown of elastin and destruction of alveolar walls, reducing surface area for diffusion.

How does loss of alveolar surface area affect oxygenation?

Less alveolar surface area means:

• less space for oxygen to diffuse into blood

• reduced gas exchange

• lower oxygen levels in the blood

Patients may develop:

• shortness of breath

• hypoxemia

• CO₂ retention

Explain how temperature affects gas pressure.

When temperature increases:

• gas molecules move faster

• collisions increase

• pressure increases

When temperature decreases:

• molecules move slower

• pressure decreases

Difference between FiO₂, PAO₂, and PaO₂

FiO₂

Amount of oxygen being inhaled.

PAO₂

Amount of oxygen inside alveoli.

PaO₂

Amount of oxygen dissolved in arterial blood.

Why does emphysema make gas exchange harder?

Emphysema destroys alveolar walls and decreases surface area available for diffusion.

This means:

• less oxygen enters blood

• less carbon dioxide leaves blood

Gas exchange becomes inefficient.

Difference between dead space and normal gas exchange

Normal gas exchange

Air reaches alveoli AND blood flow is present.

Dead space

Air reaches alveoli but blood flow is absent or reduced.

Without blood flow, gas exchange cannot occur.

Why can chronic lung disease lead to right-sided heart strain?

Chronic low oxygen causes pulmonary blood vessels to constrict.

This raises pressure in the lungs, forcing the right side of the heart to pump harder.

Over time this may lead to:

• pulmonary hypertension

• cor pulmonale

• right-sided heart failure