Pulmonary Ventilation

Ventilation

Movement of air in and out of lungs due to pressure gradients

Boyles Law

Gas pressure and volume are inversely related.

Increased volume = decreased pressure

How do gas molecules flow?

Areas of high to low pressure.

What happens when lung volume increases?

Pressure in lung decreases relative to outside the lung and the air flows in.

What happens when lung volume decreases?

Pressure in the lung increases relative to outside the lung and air flows out.

How do you change the volume of the lungs?

Diaphragm contracts and increases the volume of the lungs to help with inhalation

Quiet inspiration

Muscles: Diaphragm and external intercostals

Action: Descend toward abdominal cavity and remain contracted to increase width

Change in V: Increases

Forced inspiration

Muscles: Diaphragm, external intercostals, scalenes, and sternocleidomastoid

Action: Contract more forcefully, elevates sternum and thoracic cage

Change in V: Increases

EX: Singing, holding breath

Quiet expiration

Muscles: Diaphragm

Action: Relax muscles, return them to original position

Change in V: Decreases

EX: Tital Volume

Forced expiration

Muscles: Obliques, rectus abdominis, and internal intercostals

Action: Push down and in, depresses thoracic cage

Change in V: Decreases

Why is intrapleural pressure normally negative?

The pressure in the lungs need to be greater than that of the cavity in order for the lungs to expand outward.

Pneumothorax

air in the pleural cavity, collapse/recoil

Treatment: chest tube- vacuum pump the outside air out of the lung

Factors influencing ventilation:

1. Airway resistance- anything that hinders airflow, inversely proportional to diameter

2. Pulmonary compliance- how easily the lungs and thoracic wall can expand

3. Respiratory volumes- tidal volume, inspiratory reserve volume, expiratory reserve volume, residual volume, and vital capacity

Bronchodilation

Allows max amount of airflow

Bronchoconstriction

Allows min amount of airflow

Alveolar surface tension

Produced by water molecules, causes an attraction which then leads to alveolar collapse. Re-inflation on inhale, but its hard on the body

How does surfactant prevent collapse?

Inserts itself between water molecules to keep them from sticking

Respiratory distress syndrome

Alveoli are stuck together

Distensibility

ability to stretch

Fibrosis

Excessive amount of stiff connective tissue that replaces healthy tissue. Leads to liver, heart, kidney disease, etc. Can decrease breathing

Thoracic wall flexibility

Impaired due to trauma or deformity