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Exchange of gases
NURSECONCEPTSCOACH
By. Ms. Saili Gaude
Assistant Professor
Shri Bhumika Nursing College, Parye Goa
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Exchange of gases occurs at 2
levels namely :
• Exchange between Lungs and
blood
• Exchange between blood and
Tissues
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EXCHANGE OF GASES

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Via Between Mechanis
m
Exchange
of
Respiratory
membrane
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LUNG -BLOOD
EXCAHNGE OF GASES
Alveoli &
Blood
capillaries
Bulk flow Oxygen &
Carbondioxide

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Component Characteristics
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RESPIRATORY
MEMBRANE
Respiratory membrane =
Epithelium of respiratory unit
+
Endothelium of pulmonary
capillary
• Very thin with average
thickness of 0.6u
• total surface area in each
lungs - 70sq.m
• Avg. pulmonary capillary
diameter - 8u

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PARTS
• Layer of surfactant
• Thin layer of alveolar
fluid
• Layer of alveolar
epithelium
• Basement membrane
of alveolar epithelium
Alveolar part
• Interstitial space
Mid alveolar &
Capillary
• Basement
membrane of
capillary
endothelium
• Capillary
endothelium
Capillary part
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Diffusion
DIFFUSION
01
Gases diffuse from area of high
pressure to low pressure by a
mechanism called bulk flow
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The volume of gas that diffuses
through the membrane each minute
for a pressure gradient of 1 mmHg
Oxygen- 21 ml/min/1mmHg
Carbon dioxide- 400 ml/min/1mmHg
Meaning
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Diffusion coefficient
A constant which is the measure of a
substance diffusing through the
concentration gradient
Diffusing capacity Diffusion capacity of
gases

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02
03
01
04
FACTORS AFFECTING
DIFFUSION
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Total surface area
The more the surface area
the more the diffusion
capacity
Molecular weight
of gas
Larger the molecule
difficult the diffusion
Pressure gradient
difference between
pressure of gases inside
alveoli and capillary
Solubility
The degree to which a gas
dissolves into the blood
Thickness of respiratory
membrane
Thicker the memberane difficult the diffusion

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01
DIFFUSION OF OXYGEN FROM
ATMOSPHERE TO ALVEOLI
Atmospheric air PO2= 159mmHg
Alveolar PO2= 104 mmHg
Oxygen moves from area of high pressure to area of low pressure
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02
DIFFUSION OF OXYGEN FROM
ALVEOLI TO BLOOD
Alveolar air PO2 = 104mmHg
Blood PO2 = 40mmHg
Oxygen moves from area of high pressure to low pressure
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02
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DIFFUSION OF CARBONDIOXIDE
FROM BLOOD INTO ALVEOLI
Alveolar air PCO2= 40mmHg
Blood PCO2= 46mmHg
Carbondioxide moves from are of high pressure to low pressure

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02
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DIFFUSION OF CARBONDIOXIDE
FROM ALVEOLI TO ATMOSPHERE
Atmospheric air PCO2= 40mmHg
Alveolar air PCO2= 0.3mmHg
Carbondioxide moves from area of high pressure to low pressure

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) EXCHANGE OF GASES BETWEEN
BLOOD AND CELLS
01
Diffusion of oxygen from blood to cell
02
PO2 in Blood = 95mmHg
PO2 in Tissues = 40 mmHg
Oxygen moves from higher pressure
to lower pressure
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Diffusion of Carbon dioxide from blood to
cell
PCO2 in Blood = 40mmHg
PCO2 in Tissues = 45mmHg
Carbon dioxide moves from higher
pressure to lower pressure

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It is the ratio between net output of
carbondioxide from tissues to
simultaneous net uptake of oxygen
by tissues
RESPIRATORY EXCHANGE
RATIO
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Carbohydrates - 1.0
Fat- 0.7
Proteins - 0.8
Balance diet - 0.825

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Thank You
Thank You
Nurseconceptscoach.com

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Exchange of gases - Transport of oxygen and carbondioxide

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Exchange of gases - Transport of oxygen and carbondioxide