Pulmonary Physiology

Question 1

Zones of Ventilation

Answer 1

Conductive Zone

• trachea
• bronchi
• terminal bronchi

Respiratory Zone

• respiratory bronchiole
• alveolar duct
• alveoli

Question 2

Conductive Zone

Answer 2

• the space air is conducted in and out of the lungs
• contributes to the delivery and removal of air to and from the alveoli
• trachea and mainstem bronchi are relatively rigid due to their connective tissue, multiple cartilage rings, and smooth muscle
  
  • the amount of cartilage decreases and the amount of smooth muscle increases as the number of branches increase
• the smallest conductive airways are the terminal bronchioles
• the diameter of the smaller airways changes in response to various stimuli which either constrict or dilate the smooth muscle
  
  • direct sympathetic control of the bronchial smooth muscle is limited
  • circulating epineprhine causes bronchodilation and local norepinephrine causes bronchodilation to a lesser extent
  • vagal fibres secrete acetylcholine, resulting in bronchoconstriction
  • mast cells release histamine and slow reacting substance of anaphylaxis resulting in bronchoconstriction
• participates in the exchange of air between the atmosphere and alveoli
  
  • no diffusion of oxygen and carbon dioxide
    
    • anatomic dead space (approximately 150 mLs in adults)
    • does not increase or decrease with breathing effort

Question 3

Respiratory Zone

Answer 3

Respiratory Bronchioles

• participate in diffusion of gases
• no cartilage rings
• very limited smooth muscle
• very small diameter of less tha 1 to 1.5 mm

Alveoli

• tiny, with a radius of about 100 micrometers
• primary function is gas exchange
• produce surfactant
  
  • a lipid substance produced by Type II alveolar epithelial cells
  • decrease the surface tension of hte alveoli and promotes expansion versus collapse of these tiny alveoli

Total volume within respiratory zones is normally about 3000mLs and can be adjusted greatly through effort and chest wall movements

Question 4

Pleural Fluid

Answer 4

• continually pumped into the lymphatic system, resulting in a slight amount of suction or vacuum between the two pleural membranes
• acts as a lubricant to enable the pleurae to slide over one another, plus it maintains tension to hold the two membranes together

Question 5

Compliance

Answer 5

• the tendency to accept change or the ‘ease’ in yielding to a damand
• the ‘ease’ or change in volume in relation to change in pressure
• the extent to which teh lungs expand in relation to pressure
• normal lung compliance of both lugns is about 200mL/cm water pressure
  
  • an increase in 1 centimeter of water pressure the lung volume increases by 200 mm
• compliance = change in volume​​ / change in pressure
• when compliance is high, a small change in pressure results in a large change in volume. When compliance is low, a large change in pressure is required for a small change in volume

Question 6

What are the four pressures which determine lung expansion and air flow?

Answer 6

1. atmospheric pressure (Patm)
2. pleural pressure (Ppl)
3. static recoil pressure (Pst)
4. alveolar pressure (Palv)

Question 7

Atmospheric Pressure

Answer 7

• pressure which exists outside the body
• includes the pressure of gases and water
• baromentric pressure
• main gases which exert pressure in the atmosphere are nitrogen and oxygen
  
  • in discussing lung pressure it is customary to set the atmospheric pressure to zero and express the remaining pressures in relation to zero
    
    • a pressure less than atmospheric pressure is a negative pressure, and a pressure greater than atmospheric pressure is expressed as a positive pressure

Question 8

Pleural Pressure

Answer 8

• pressure developed within the pleural space and exerted on the outer surface of the lung