Respiration Part 5 Flashcards
What are the Factors that Affect the Pressure of Gas dissolved in a fluid?
•Concentration
• Solubility coefficient of ;
02: 0.024
CO2: 0.57
What does this stand for?Do A P•A•S•T/d MW
• D: diffusion rate
• A P: pressure difference
• T: temperature
• A: cross-sectional area of the pathway
• S: solubility of the gas
• d: the distance of diffusion
• MW: molecular weight of the gas
What does S/dVMW mean?
diffusion coefficient of the gas;
oxygen 1.0 carbon dioxide 20.3 carbon monoxide 0.81
What is the normal gas pressure of O2 in Venous blood,Arterial blood,alveoli and atmosphere?
PO2 in Venous blood:40mmHg
in Arterial Blood:100mmHg
In Alveoli :105mmHg
In the Atmosphere:160mmHg
What is the normal gas pressure of CO2 ?
In Venous blood:46mmHg
In Arterial blood:40mmHg
In Alveoli:40mmHg
In Atmosphere:0.3mmHg
Where does GAS EXCHANGE BETWEEN ALVEOLI AND
BLOOD occur?
Respiratory membrane
What does the respiratory membrane consist of?
•layer of fluid lining the alveolus and
containing surfactant
‹ the alveolar epithelium
• an epithelial basement membrane
• a thin interstitial space between the alveolar epithelium and the capillary
membrane
• a capillary basement membrane
• the capillary endothelial membrane
What is the thickness of the respiratory membrane?
0.6 micrometers
What are Factors affecting gas exchange across
the respiratory membrane?
a) Thickness of the membrane
b) Surface area of the membrane
c) Diffusion coefficient of the gas d) Partial pressure of gases across
the membrane (driving force)
e) Ventilation/perfusion ratio
What is Ventricular/Perfusion Ratio
VA/Q
= (4.2 L/min)/(5 L/min)
=0.84
What is the Main effect of Ventilation/perfusion ratio?
Decrease the POz of systemic arterial blood
Distribution of ventilation and perfusion is different:
• VA/Q at the bottom of the lung: 0.63
at the apex of the lung: 3.3
What is the V̇A/Q̇ ratio at the top (apex) of the lung?
3.3 (indicating high ventilation relative to perfusion)
What is the V̇A/Q̇ ratio at the bottom (base) of the lung?
0.63 (indicating low ventilation relative to perfusion)
What is a physiologic shunt?
A condition where the amount of blood fails to be oxygenated due to low V̇A/Q̇, resulting in decreased PaO₂.
What happens to PaO₂ in a physiologic shunt?
: PaO₂ decreases (PaO₂ ↓
What is physiologic dead space?
A condition where there is ventilation without adequate perfusion, leading to increased V̇A/Q̇.
What happens to PaO₂ in physiologic dead space?
PaO₂ increases (PaO₂ ↑).
What is Diffusing capacity of lung?
volume of air that diffuses through the respiratory
membrane per minute caused by unit partial pressure
What is the formula for DL?
DL=V/(PA-PC)
• PA: pressure of the gas in the alveoli
• PC: pressure of the gas in the pulmonary capillary blood
What is the purpose of DL?
To evaluate the ability of respiratory gases to pass through the
respiratory membrane.
• DL of Oz: 20mL/(min.mmHg)
Characteristics of gas exchange between tissues and blood
• Intracellular PO, is lower and PCO, is higher than in blood • Net diffusion of oxygen from blood into cells, and carbon dioxide
from cells into blood
What occurs during the TRANSPORT OF OXYGEN IN BLOOD?
~1.5% of O2 is dissolved in plasma (physical dissolution)
• ~ 98.5% of O2 is chemically combined with hemoglobin inside RBCs
What is hemoglobin?
O2 binding protein in red blood cells
It has 4 binding sites
Hemoglobin is the gas-transport
molecule inside
erythrocytes
What is the formula for O2 binding to hemoglobin ?
Hb + 02>Hb O2 (oxyhemoglobin)
It’s a reversible combination
