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Flashcards in Respiratory Physiology Deck (212)
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91

Formula for transpulmonary pressure

Ptp = Palv - Ppl

92

During apnea, pulmonary pressure is equal to...

Atmospheric pressure

93

Pulmonary pressure

94

Intrapleural pressure

95

Volume

96

Apnea

97

Inspiration

98

Expiration

99

Müller's experiment

  • Deep inspiration with a closed epiglottis
  • Pulmonary and intrapleural pressure decreases

100

Valsava experiment

  • Forced expiration with closed epiglottis
  • Pulmonary + Intrapleural pressure increase

Used to equalise pressure in the ear

101

Pneumothorax

  • Loss of intrapleural negative pressure
  • Small: Escaped air can be reabsorbed from the pleural cavity
  • Large: Air needs to be drawn out of the pleural cavity

102

Closed pneumothorax

  • Small hole in thoracic wall/lung
  • Air gradually absorbed, IP pressure returns

103

Open pneumothorax

  • Large hole
  • IP is atmospheric

104

Valvular/tension pneumothorax

  • Flap of tissue acts as a valve over the hole
  • Allows air entry during inspiration
  • Doesn't allow escape during expiration
  • Lung severely collapses

105

Emphysema

  • Septa between alveoli are damaged
  • Reduced respiratory surface

106

Resistance forces which need to be overcome during inspiration

  • Friction
  • Non-elastic tissue resistance
  • Total elastic resistance

107

Friction force effect on inspiration

  • Smallest force of resistance
  • Caused be turbulent air flow

108

Non-elastic tissue resistance during respiration

  • Caused by:
    • Diaphragm
    • Chest
    • Abdominal structures

109

Total elastic resistance of inspiration

  • Stretch of vertebral + costal joints
  • Retractive forces
    • Resistance of interstitial elastic elements
    • Surface tension in the alveoli (Strongest)

110

Surface tension

  • Cohesive forces
  • Internal pressure
    • Causes liquid surfaces to contract to minimal area

111

Forces causing the collapse of alveoli

  • Retractive tendency of elastic elements
  • Surface tension

112

Forces acting against collapse of alveoli

  • Actual intrapulmonary pressure
  • Surface tension of neighbouring alveoli
  • Presence of surfactant

113

The result of alveolar dilating and retracting forces...

Transpulmonary pressure

114

The open state of alveoli can be maintained only by...

Materials reducing surface tension

115

DPPC

  • Reduces surface tension
  • If not present:
    • Fatal alveolar collapse
    • Plasma filtrated into alveoli (Reduced diffusion)

116

DPPC deficiency occurs genetically in...

  • Calves
  • Causes early postnatal death

117

How does lack of DPPC cause death?

  • Intrapleural pressure higher (30mmHg)
  • Alveolus cannot stay open against larger wall tension

118

delta V / delta P =

Compliance

119

Compliance

The ability of a hollow organ to change its volume

120

Figure showing compliance in the lungs