Topic 36 - Pressure changes during respiration, the respiratory work, compliance

Question 1

Words to include in pressure changes during respiration

Answer 1

• Total collapse of lung
  
  • Adhesional forces (fluid film)
    
    • Parietal pleura → visceral pleura
• Pressure relations
• Pulmonary pressure
  
  • Alveolar
  • Interpulmonary
  • Atmospheric pressure during apnea (760 mmHg)
• Pleural pressure
  
  • Interpleural
  • Negative
    
    • Lower than pulmonary pressure
    • Interpleural pressure is a closed cavity
• Transpulmonary pressure
  
  • P_{transpulmonary pressure} = P_alveolar - P_pleural

Pressure relations in different phases of respiration

• During apnea
  
  • Intrapulmonary pressure = atmospheric pressure
  • Balance
    
    • Collapsing tendency of lung
    • Expanding tendency of chest
• During inspiration
  
  • Pressure of pleural slit ↓
• During expiration
  
  • Retractive forces of lung
  • Intrapulmonary pressure rises above atmospheric pressure
  • Intrapleural pressure
• Müller’s experiment
  
  • Deep inspiration with closed epiglottis
  • Pulmoary pressure ↓
  • Intrapleural pressure ↓
  • Rumination
• Valsalva’s experiment
  
  • Forced expiration with closed epiglottis
  • Pulmonary pressure ↑
  • Intrapleural pressure ↑
  • Defecation
• Pneumothroax
  
  • Negative pressure from intrapleural space (ø)
  • Blood oxygen concentration ↓
  • Respiratory rate ↑
  • Heart rate ↑
  • Types:
    
    • ​Closed
    • Open
    • Valvular (tension)
• Emphysema
  
  • Septa between alveoli are damaged
  • Respiratory surface ↓

Question 2

Words to include in the respiratory work

Answer 2

• Inspiration
  
  • Collapsing tendency must be comvercome
    
    • Surface tension
    • Retractive forces of elastic elements
• Forced expiration

Resistance forces

• Friction
  
  • Respiratory tract
  • Smallest force in resistance
    
    • Laminar air flow
• Non-elastic tissue resistance
  
  • Diaphragm
  • Chest
  • Abdominal structures
• Total elastic restriction
  
  • Thoracic cavity
  • Strestch of:
    
    • Vertebral joints
    • Costal joints
  • Retractive forces of the lung
    
    • Resistance of interstitial elastic elements
    • Surface tension in the alveoli

Forces affecting the alveoli

• Open or closed state of alveoli
• Forces causing collapse
  
  • Retractive tendency of elastic elements
  • Surface tension
• Forces acting against collapse
  
  • Intrapulmonary pressure
  • Surface tension of neighboring alveoli
  • Presence of surfacant
• Transpulmonary pressure
• DPPC (Dipalmyoil Phosphatidile Choline + Peptides)
  
  • Surface tension ↓

Question 3

Words to include in compliance

Answer 3

• Ability of hollow organto change volume
• dV/dP
  
  • V: volume change
  • P: pressure change
• Amount of DPPC on alveolar surface
• DPPC max
• Inspiration
• Volume
• Pressure
• Increasing age = decreasing compliance (heart)

Question 4

Topics to include in the essay

Answer 4

1. Pressure changes during respiration
   
   • Types of pressure
   • Pressure relations in different phases of respiration
   • Experiments
   • Pathological conditions
     
     • Pneumothorax
     • Emphysema
2. The respiratory work
   
   • Resistance forces
   • Forces affecting the alveoli
3. Compliance

Question 5

Pressure changes during respiration

Give the types of pressure

Answer 5

• The moving of air is always dependent on the pressure relations

1. Pulmonary pressure
   
   • ​Alveolar
   • Intrapulmonary
   • Aroung atmospheric pressure (760 mmHg) during apnea (pause)
2. Pleural pressure
   
   • ​Intrapleural
   • Always negative
     
     • ​Means that it is lower than the pulmonary pressure
     • Reason: intraplueral space is a closed cavity, and gases in this cavity are being absorbed by the tissue constantly
3. Transpulmonary pressure
   
   1. ​P_tp = P_alv - P_pl

Question 6

Pressure changes during respiration

Pressure relations in different phases of respiration

Answer 6

• During apnea:
  
  • Intrapulmonary pressure = atmospheric pressure
  • The collapsing tendency of the lung an the expanding tendency of the chest maintain a balance
• During inspiration:
  
  • ​The pressure of pleural slit ↓
    
    • A result of the active work of the inspiratory muscles, which consequently takes the pressure in the lung beneath the atmospheric pressure:
      
      • ​Air flows into the lung
• During expiration:
  
  • ​Retractive forces of the lung makes the intrapulmonary pressure rise above atmospheric pressure

Question 7

Pressure changes during respiration

Experiments

Answer 7

• Pressure changes related to respiration gets stronger in case of closed epiglottis
• Müller’s experiment:
  
  • ​Deep inspiration with closed epiglottis
    
    • ​Pulmoary pressure ↓
    • Intrapleural pressure ↓
  • Ruminants uses this phenomen during rumination
• Valsalva’s experiment:
  
  • ​Forced expiration with closed epiglottis
    
    • ​Pulmonary pressure ↑
    • Intrapleural pressure ↑
  • U​​sed to equalise the pressure in the middle ear to the ambient pressure

Question 8

Pressure changes during respiration

Pathological conditions

Answer 8

• Pneumothorax
  
  • ​Partial or complete diapperance of negative pressure from the intrapleural space
  • Result:
    
    • Blood oxygen concentration ↓
    • Respiratory rate ↑
    • Heart rate ↑
  • Types of pneumothorax:
    
    • Closed
    • Open
    • Valvular (tension)
• Emphysema
  
  • ​The septa between the alveoli are damaged
  • Result: respiratory surface ↓

Question 9

The respiratory work

Answer 9

• Inspiration and forced expiration need muscle work (energy)
• At inspiration the collapsing tendency of lung must be overcome
  
  • Collapsing tendency is due to:
    
    • Surface tension
    • Retractive forces of elastic elements

Resistance forces

1. Friction
   
   • ​In the respiratory tract
   • The smallest force in resistance
     
     • ​Reason: laminar air flow
2. Non-elastic tissue
   
   • ​Diaphragm
   • Chest
   • Abdominal structure
3. Total elastic tissue
   
   • ​Thoracic cavity
   • Stretch of vertebral and costal joints
   • Retractive forces of the lung:
     
     • ​The resistance of the interstitial elastic elements
     • Surface tension in the alveoli

Forces affecting the alveoli

• Determinates the open or closed state of the alveoli
• Forces causing collapse
  
  • ​Retractive tendency of elastic elements
  • Surface tension
• Forces acting agianst collapse
  
  • ​Actula intrapulmonary pressure
  • Surface tension of neighboring alveoli
    
    • ​Dilate the alveolus next to it
  • Presence of surfacant
    
    • ​Reducing surface tension
• Result: transpulmonary pressure
• DPPC (Dipalmyol Phosphatdile Choline + Peptides)
  
  • Material reducing surface tension
  • The surface tension in the small alveoli is so high, that the open state can be maintained only by the presence of materials reducing surface tension

Question 10

Compliance

Answer 10

• Compliance: The ability of a hollow organ to change its volume
  
  • ​dV/dP
    
    • ​V: volume change
    • P: pressure change
• In physical objects the compliance is constant
• In living tissues, such as the lung it varies continuously during inspiration and expiration, because the thickness of the liquid film containing the surfactants changes during the breathing cycle
• Heart: compliance decrease with age

Compliance in the lungs

1. The changes in volume depends on the amount of available DPPC in the alveoli
   
   • ​During inspiration, the volume grows exponentially until all of the DPPC are used up
2. After this point, the expanding of the alveolar space requires expentionally higher amount of pressure per unti volum