Lecture 5: Ventilation and Gas Exchange Flashcards
What are the two types of ventilation? Definitions and what are their respective equations? UNITS!
1.Minute Ventilation= Frequency X Tidal Volume (total air moved into lung in one minute). Units: liters/min 2. Alveolar ventilation= frequency X (tidal volume- dead space) (total air moved into respiratory zone in one minute) Units: Liters/min
What are the two types of dead space? (definition)
Anatomic dead space: the air in the conductive zone of the airways that does not contribute to gas exchange Physiological dead space: total effective dead space. Same as anatomic dead space in normal individuals but increases in disease
The pressure of expired CO2 depends on what? What equation is this?
ratio of (dead space/tidal volume) Bohr equation
When you change diction of your breathing (normal vs slow,deep vs quick,shallow vs. increased dead space) which ventilate changes and which one is constant?
Constant: Minute Ventilation Change: Alveolar Ventilation
Of the following variables, what changes and how by a) slow, deep breaths b)quick shallow breaths c) increased dead space compared to normal -f, Vt, VE, Vd, Vt-Vd, VA
A. freq down, Vt up, Ve same, Vd same, Vt-Vd up, VA up B. freq up, Vt down, Ve same, Vd same, Vt-Vd down, VA down C. freq same, Vt same, Ve same, Vd up, Vt-Vd down, VA down
Work done by Respiratory Muscles is equal to what?
PressureXVolume
What force are the lungs working against in a static compliance curve? Dynamic compliance curve?
-Static: Elastic recoil and surface tension -Dynamic: elastic recoil, surface tension, and additional work against airway resistance
What is the relationship between work and ventilation rate? 1) At rest (FRC) 2) at increased ventilation rates 3) emphysema
1) consume about 3 ml O2/min (units for work) and this is small 2) at very high respiratory rates, you are using up a lot of O2/min 3) during emphysema, a small increase in ventilation leads to a large increase in work
Why does the work against elastic recoil greatest when you are taking fewer breathes (at a constant alveolar ventilation)?
When you are taking deeper breathes, larger tidal volumes means that you are working a lot harder against elastic recoil (remember compliance curve for system)
What is the relationship between airway resistance and work? Does it matter if flow is turbulent or laminar?
-linear. increased airway resistance means increased work -Yes, turbulent flow is less efficient and required more work
In restrictive disease, what work is a lot greater? What does this do to breathing? Same question for obstructive disease/
Restrictive: work against elastic recoil elevated. More breathes/min and shallower Obstructive: work against airway resistance elevated. Less breathes/min
What are the approximate composition of the elements found in our atmosphere?
Nitrogen: 78% Oxygen: 21% Argon: 1% CO2: 0%
What is the partial pressure equation? Units Calculate Partial pressure of nitrogen and oxygen?
Pgas= Total pressure X fraction of gas composition to the total Example: PO2= 760*0.21= 160 torr PN2= 760*.78= 600 torr
What is Henry’s Law trying to show? Equation?
-The quantity of gas that dissolves in a unit volume of liquid is determined by the solubility of the gas in that liquid and its partial pressure gas concentration= partial pressure of gas X solubility of gas
What is the partial pressure of water vapor in the body?
47 torr
What are the partial pressures of oxygen and CO2 in the following: ambient air, tracheal air, alveolar, arterial blood, mixed venous blood? YOU NEED TO KNOW THIS!
Ambient Air: Oxygen (160 torr) CO2(0) Tracheal air: Oxygen (150) CO2 (0) Alveolar air: Oxygen (100) CO2 (40) Arterial blood: Oxygen (95) CO2(40) Mixed Venous Blood: oxygen (40) CO2(45)
What factors affect diffusion and how? (Fick’s Law of Diffusion)
Diffusion constant (prop), Area (prop), pressure gradient (prop), distance (inver prop)
When looking at O2 and CO2 diffusion in the blood, what partial pressures of O2 and Co2 do we look at?
O2: ratio between alveolar pressure and mixed venous (100 and 40) CO2: ratio between alveolar pressure and mied venous (40 and 45)
What variable dictates diffusion of Co2 and O2 from the blood to the alveoli?
CO2: solubility constant is high O2: pressure gradient (driving force) is high
What is the diffusing capacity of the lung (definition)? What is the equation?
Diffusing capacity is the how good is the lung at diffusing oxygen from the alveoli into the capillary bed. Equation: Dl= V dot O2/ (PAO2-PVO2)
Why is carbon monoxide used as a surrogate for oxygen in the diffusion capacity equation? equation?
Oxygen has a large driving force so it is not a great marker for disease. CO is more sensitive detector. Dl(CO)= V dot CO/ PA CO
What determines alveolar gas content?
PO2
What two forces are working in opposition to control alveolar gas content?
Metabolism and ventilation
Increasing ventilation have a larger/smaller/or similar affects on CO2 than O2? Think about why you know this
larger When you hyperventilate, you are making your blood more basic (you know this from physiology class)
