Ventilation Mechanics

Question 1

Levels of respiration (x3)

Answer 1

• Tissue –> mitochondria
• Between tissue & blood (internal)
• Between blood & lungs (external)

Question 2

Aerobic respiration

Answer 2

• O2 utilization and CO2 production by metabolizing tissues

Question 3

Anaerobic respiration

Answer 3

• Production of ATP without the utilization of O2 (still produces CO2)
• Eliminating CO2 directly affects the pH of blood
• Anaerobic process is invoked to augment aerobic processes when the tissues need more energy (MI, intense exercise etc.) –> LA buildup

Question 4

Quiet inspiration/inhalation

Answer 4

• Contraction of diaphragm
• Elevation of lower ribs by contraction of external intercostals
  
  • Both of these contribute to increased thoracic capacity

Question 5

Forced inspiration/inhalation

Answer 5

• Downward movement of diaphragm
• Sternum + upper ribs elevated by sternocleidomastoids & scales: elevation of lower ribs by external intercostals
  
  • Increased thoracic capacity
• Pain can occur from intercostal muscle or diaphragm fatigue

Question 6

Expiration/exhalation

Answer 6

Quiet exhalation
- Elastic recoil of lungs & relaxation of musculature

Forced exhalation

• Muscles that compress abdominal viscera –> forces diaphragm upwards (abdominal muscles)
• Muscles that pull downwards inferior ribs (rectus abdominis, quadratus lumborum)
• Muscles that pull downwards + depress ribs (internal intercostal muscles)

Question 7

Why are the lungs able to move with the thoracic wall?

Answer 7

• Hydrostatic force created by the pleural fluid allows for this
• The water molecules act like a paste

Question 8

Rates of ventilation

Answer 8

Minute ventilation

• Rate at which air moves in & out of mouth
• Breathing frequency x Tidal volume

Alveolar ventilation

• Rate at which fresh air moves in & out of alveoli
• Less than minute ventilation due to dead space in lungs

Question 9

Impedances to ventilation

Answer 9

Elastance

• Measure of the stiffness of the lungs
• Property of elastic tissue & fluid in alveoli

Surfactant

• Water lining alveoli decreases lung compliance (increases lung elastance)
• Surfactant is a phospholipid released by Type 2 pneumocytes & reduces the surface tension of water (makes it easier to expand lungs)

Resistance

• Lungs w high resistance –> obstructed
• Airway diameter is the biggest factor

Question 10

Positive vs normal ventilation

Answer 10

Positive ventilation

• Lungs are inflated by increasing pressure inside alveoli
• Increased pressure = increased lung volume

Normal ventilation
- Lungs are expanded by reduced pressure surrounding the lungs to sub-atmospheric pressure (aka negative pressure)