Factors Affecting Pulmonary Ventilation

Airway resistance

Anything that obstructs air flow through the respiratory tract.

What happens to airway resistance during inspiration?

It slightly decreases because the airways are pulled open as the lungs expand.

What happens to airway resistance during expiration?

It slightly increases because the airways narrow as the lungs recoil.

What happens to airway resistance during bronchodilation?

It decreases airway resistance because smooth muscle around the bronchioles relaxes, increasing the diameter of the bronchioles.

What happens to airway resistance during bronchoconstriction?

It increases airway resistance because smooth muscle around the bronchioles contract, decreasing the diameter of the bronchioles.

Alveolar surface tension

Caused by the hydrogen bonds that pull water molecules together in the alveoli.

When is the hydrogen bonding of water is at its strongest in the alveoli?

During expiration because the alveoli are at their smallest.

What might happen if the hydrogen bonds of water in the alveoli become too strong?

The alveoli will collapse.

What reduces alveolar surface tension?

Surfactant

Pulmonary compliance

The distensibility (or stretch) of the lungs and the chest wall

What happens to pulmonary compliance when surfactant in the alveoli decreases?

Pulmonary compliance decreases because hydrogen bonds will prevent the alveoli from stretching

What happens to pulmonary compliance when surfactant in the alveoli increases?

Pulmonary compliance increases because surfactant will weaken hydrogen bonds between water molecules this will prevent the alveoli from stretching

What allows for distensibility in the lungs?

Elastic tissue

What happens to pulmonary compliance when an infection damages the lung?

Pulmonary compliance decreases because this will destroy the lung’s elastic tissue

What role does the distensibility of the chest wall play during inspiration?

The lungs move alongside the chest wall during inspiration

What happens to pulmonary compliance when a broken rib prevents the chest wall from moving?

Pulmonary compliance decreases because the lungs move with the chest wall