Topic 35 - Respiratory air fractions, and ventilation coefficient

Question 1

Words to include

Answer 1

Ventilation, spirometry

• Ventilation
  
  • Quantity of air entering and leaving the lung in unit time
• Functional fractions
  
  • Inspired and expired quantitiy of air
  • Degree of possible gas exchange
• Spirmoter

Respiratory air fractions

• Total Lung Capacity (TLC)
• Volume Tidal (VT)
• Functional Residual Capacity (FRC)
• Inspired Reserve Volume (IRV)
• Expiratory Reserve Volume (ERV)
• Residual Volume (RV)
• Volume Capacity (VC)
  
  • VC = VT + IRV + ERV
• Forced Vital Capacity (FVC)
  
  • VC related to unit time

Dead volume

• Ø contribute directly to gas exchange
• Anatomical dead space
  
  • Air fraction of upper and lower respiratory tract
  • Respiratory epithelium (ø)
• Physological dead space
  
  • Respiration (ø)
  • Epithelium
  • Anatomical dead space + alveolar dead space
• FRC + VD
  
  • “Used air” fraction
• VT - VD
  
  • Gas excange
  • “Fresh air” fraction

Ventilation coefficient

• Deepness of insipration
• V_coeff
  
  • Fresh air (VT - VD) / Used air (FRC + VD)
• Used air
  
  • FRC + VD
  • Air i dead space + proportion of air which earlier took part in gas exchange
• Fesh air
  
  • VT - VD
  • VT that takes part in gas exchange

Question 2

Topics to include in the essay

Answer 2

1. Ventilation (definition)
2. Spirometry
3. Respiratory air fractions
   
   • Dead volume
4. Ventilation coefficient

Question 3

Define ventilation

Answer 3

• Ventilation: The quantitiy of air entering and leaving the lung in unit time

Question 4

Respiratory air fractions

How can air fractions be measured?

Answer 4

Air fractions can be measured by the spirometer​

Question 5

Respiratory air fractions

Draw the graph, and name the fractions

Answer 5

• The inspired and expired quantitiy of air and volume of the air present in the lungs can be divided into functional fractions

1. Tidal Volume (TV)
2. Inspiration Reserve Volume (IRV)
3. Expiratory Reserve Volume (ERV)
4. Expiratory capacity (EC)
5. Functional Residual Volume (FRV)
6. Vital Capacity (VC)​​
7. Residual Volume (RV)
8. Inspiratory Capacity (IC)
9. Minimal volume (MV)
10. Total Lung Capacity (TLC)

Question 6

Respiratory air fractions

How to calculate vital capacity (VC)

Answer 6

VC = VT + IRV + ERV

Vital capacity is the maximal volume changes that can actively be attained

Question 7

Respiratory air fractions

Dead volume

Answer 7

• Anatomical and physiological dead space which does not contribute directly to the gas exchange
• Anatomical dead space
  
  • The air fraction of the upper and lower respiratory tracts
  • Volume of the airways, which are not covered by respiratory epithelium
• Physiological dead space
  
  • The former area and the areas excluded from respiration, covered by epithelium
  • ​Anatomical dead space + alveolar dead space
• Under normal conditions the alveolar dead space is low and thus the anatomic and physiological dead space are nearly equal
• FRC + VD
  
  • ​The sum of the amount of air in the dead space plus that proportion of air which earlier took part in the gas exchange = “used air” fraction
• VT – VD
  
  • Takes part in gas exchange (not in dead space) = “fresh air” fraction

Question 8

Ventilation coefficient

Answer 8

• The deepness of inspiration increases the proportion of fresh air to the used air already present, and thus improves gas exchange
• The deeper the inspiration the greater the VC therefore the more efficient is the respiration
• Used air
  
  • ​FRC + VD
  • The sum of the amount of air:
    
    • In the dead space
    • That proportion of air wihic earlier took part in gas exchange
• Fresh air
  
  • ​VT - VD
    
    • ​The part of VT that takes part in gas exchange
• VD = Volume Dead

Question 9

Consequence of taking the first breath

Answer 9

• Small amount of air will remain in the pulmonary tissue even after removing the lung frim the body and compressing it
  
  • This air-fraction appears in the tissue as minimal volume (MV), while taking the first breath
• That’s why the lung of the newborn (born live) is floating on the surface of the water, while in stillborn the lung will sink down