Understanding Lung Volumes and Breathing Mechanics

The amount of air either inhaled or exhaled during rest

Tidal Volume (TV)

The amount of air forcibly inhaled beyond the TV

Inspiratory Reserve Volume (IRV)

The amount of air forcibly exhaled beyond the TV

Expiratory Reserve Volume (ERV)

The amount of air that remains in the lungs after maximal exhalation

Residual Volume (RV)

Total amount of air that can be inspired (TV + IRV)

Inspiratory Capacity (IC)

The amount of air left in the lungs after a quiet exhalation (ERV + RV)

Functional Residual Capacity (FRC)

The amount of air forcibly exhaled after a forceful inspiration (TV + IRV + ERV)

Vital Capacity (VC)

The maximal amount of air the lungs can hold (TV + IRV + ERV + RV)

Total Lung Capacity (TLC)

Air movement from the external environment to the alveoli in the lungs

Inhalation

The respiratory gas we INHALE (breathe in)

Oxygen (O2)

Air movement from the alveoli in the lungs to the external environment

Exhalation

The respiratory gas we EXHALE (breathe out)

Carbon Dioxide (CO2)

When the diaphragm CONTRACTS, it

Flattens

When the diaphragm CONTRACTS, the VOLUME of the thoracic cavity

Increases

When the diaphragm CONTRACTS, the PRESSURE in the thoracic cavity

Deacreases

When the diaphragm CONTRACTS, air moves

In

When the diaphragm RELAXES, it becomes

Dome shaped

When the diaphragm RELAXES, the VOLUME of the thoracic cavity

Decrease

When the diaphragm RELAXES, the PRESSURE in the thoracic cavity .

Increases

When the diaphragm RELAXES, air moves

Out