Lecture 2: Alveolar Gas Exchange Flashcards
What is the function of anatomic dead space?
To direct air flow to alveoli
What is the easiest way to modify airway resistance?
Change bronchiole diameter (smooth muscle in airway walls)
What are examples of airway obstructions with normal oxygen diffusion?
Asthma
Chronic Bronchitis
How do you calculate the diffusion rate of a gas?
Diffusion Rate = [(surface area) x (diffusion constant) x (P1 - P2)] / distance
How much oxygen is exchanged every minute?
250 mL of O2
How much carbon dioxide is exchanged every minute?
200 mL of CO2
What does surface area correspond to?
Number of alveoli in the lungs
-also depends on number of open pulmonary capillaries
What makes up the thickness of the alveolar barrier?
Fluid Layer
Alveolar Epithelium
Interstitial Space
Blood Vessel Wall
What is more soluble - carbon dioxide or oxygen?
Carbon Dioxide
What does it mean to be “perfusion limited?”
Amount of blood is limiting factor for how much oxygen is diffused
What does it mean to be “diffusion limited?”
Ability of gas to cross is limiting factor for how much oxygen is diffused
What is the diffusion capacity of the lung for oxygen at rest?
21 mL O2/min/mm Hg
How is the diffusion capacity of oxygen calculated?
1.23 x Diffusion capacity of carbon monoxide
Describe the diffusion capacity for carbon dioxide?
Since carbon dioxide has such a high diffusion capacity, problems with CO2 will only be evident for people with extensive lung disease
What is LaPlace’s Law?
Pressure in alveolus = (2 x surface tension) / radius
- More surface tension = more pressure
- Smaller radius = more pressure
