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Flashcards in Respiratory Physiology Deck (212)
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121

Surfactant layer during inspiration

  • Thicker
  • Lower number of DPPC on air-liquid interface
  • Only molecules on the surface can display tension-reducing effect

122

As the alveolus expands, DPPC...

  • Can act on a larger surface area
  • Surface tension gets smaller

123

Smaller changes in pressure may result in...

High unit volume changes

124

DPPC max

  • DPPC molecules used up
  • Further volume increase requires exponential pressure increase

125

Amount of DPPC on the alveolar surface

126

Changes in volume depend on...

DPPC availability in the alveoli

127

Surfactant is produced by...

Type II alveolar cells

128

Respiratory gas exchange is determined by...

  • Partial pressure
  • Diffusion conditions
  • Surface size
  • Metabolic activity (O2 consumption)

129

Dalton's law

  • Calculate partial pressure
  • P/Ptotal = V / VT

130

Henry-Dalton's law

  • Expresses how a gas is diluted in fluid
  • C = alpha x P

131

  • STPD
  • BTPS

  • Standard temperature and pressure
    • 760mmHg
    • 0°C
    • Free of water vapour
  • Body temperature and pressure
    • 760mmHg
    • 37°C
    • Saturated with water vapour

132

Partial pressure

Measure of how much gas is present

133

Partial pressure of oxygen in the air

160 mmHg

134

DCO2 =

20 x DO2

135

What binds 70x less O2 than the blood?

Plasma

136

Average O2 consumption of animals

300 mlO2/min/100kg

137

O2 consumption rate during forced physical performance

6000 mlO2/min/100kg

138

1 Hb binds ... O2

4

139

Speed of haemoglobin saturation

10 msec

140

Factors affecting haemoglobin O2 affinity

  • Body temp
  • Partial pressure CO2
  • 2,3-DPG concentration
  • pH
  • CO
  • Myoglobin

141

Oxygen saturation curve shape

Sigmoidal

142

Why is O2 saturation curve sigmoidal?

  • The binding of the first O2 facilitates the next
  • By allosteric stimulation

143

Normal arterial and venous blood saturation %

A: 95%

V: 75%

144

A shift to the right of the O2 saturation curve can be caused by...

  • Increase pCO2
  • Increased pH
  • Increased Temperature
  • Increased 2,3-DPG

145

What is shown in the figure?

Change of O2 affinity of hemoglobin by pCOchange

146

What is shown in the figure?

Change of O2 affinity of hemoglobin by pH change

147

Bohr shift

  • Decreased CO2 → pH increase
  • Haemoglobin picks up more oxygen

148

What is shown in the figure?

Change of O2 affinity of hemoglobin by temperature change

149

What is shown in the figure?

Change of O2 affinity of hemoglobin by 2,3 DPG change

150

Describe the effect of 2,3-DPG increase

  • By-product of 2,3-DPG displaces O2 from Hb
  • Saturation curve shifts to the right
  • More O2 is given to the tissues