29 Questions
What is the primary purpose of respiration?
To take O2 into the body for tissue utilization
How does gas movement between the lungs and tissues primarily occur?
Simple diffusion
Which gas has the highest partial pressure in human cells?
CO2
In which direction does CO2 move between the cells and venous blood?
From tissues to venous blood
What happens to PaCO2 levels if CO2 production increases while VA remains constant?
PaCO2 increases
What is the normal range for PACO2?
35 mmHg - 45 mmHg
What does the alveolar air equation account for?
The partial pressures of O2 and CO2 in alveolar air
What determines the partial pressure of N2 in alveolar gas?
Dalton's law
What is the normal ratio of CO2 compared to oxygen in the lungs?
0.8
Which gas has no role in gas exchange but occupies space and exerts pressure in the lungs?
Nitrogen
What is the prime determinant of partial pressure of CO2 (PACO2) in the lungs?
Volume of alveolar ventilation (VA)
What is the main barrier to gaseous diffusion in the lung?
Alveolar-capillary membrane
Which of the following is required for gases like CO2 or O2 to move between alveoli and the pulmonary capillary blood?
Alveolar epithelium
According to Fick's law, what factors contribute to more diffusion occurring?
Greater surface area, diffusion constant, and pressure gradient
In a normal lung, what does diffusion primarily depend on?
Gas pressure gradients
When will PaO2 not be any higher than 120 mmHg during hyperventilation?
At sea level when breathing room air
What occurs along pressure gradients in terms of pulmonary diffusion gradients?
Diffusion occurs
What accounts for 3/4 of the normal difference between PAO2 and PaO2?
Regional inequalities in V/Q
Which condition arises when venous blood enters areas with V/Q ratios of 0?
Alveolar shunts
What mainly causes regional variations in V/Q in the normal lung?
Gravity
Where do exchange units with V/Q values of 0 occur?
Alveolar shunts
Which part of the lung has a high V/Q ratio typically above 1?
Apices
What does mixing of well-oxygenated arterial blood with poorly oxygenated blood cause?
Dilution of O2 contents
Which gas has a higher solubility in plasma, leading to faster diffusion across the alveolar-capillary membrane?
Carbon dioxide (CO2)
What is the approximate time that blood leaving the lungs is normally exposed to alveolar gas for proper equilibration?
0.75 second
What is the typical PO2 of blood leaving the tissue capillaries after equilibration?
40 mmHg
What causes carbon dioxide to diffuse in the opposite direction, from blood into the alveolus?
Higher PCO2 in venous blood compared to alveolar gas
What is the primary cause of anatomic shunts that lead to a lower PaO2 than calculated PAO2?
Right-to-left anatomic shunts
Why does blood move from the tissue capillaries back into the cells after equilibration?
To release oxygen to the cells
Test your knowledge on gas exchange, transport of O2 and CO2, and the process of respiration in the context of Egan’s Chapter 12. Explore concepts such as diffusion of gases between tissues and blood, as well as the movement of O2 from the lungs to the tissues.
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