Respiratory - Ventilation Flashcards
Define:
Ventilation
How gas gets from the atmosphere to the alveoli
Define
Boyle’s law
The pressure and volume of a gas are inversely related
Increase V decrease P
How does Boyle’s Law apply to us?
When the diaphragm contracts, the volume of the thoracic cavity increases and intrapleural pressure decreases
Define
Henry’s Law: The amount of a gas that dissolves into a fluid is related to…
The solubility of the gas into the fluid
The temperature of the fluid and
The partial pressure of the gas
Increase Temp decrease solute solubility
How does Henry’s Law apply to us?
The chemical properties of O2 and CO2 will dictate how much of each gas is present in the blood
Define
Dalton’s Law
The total pressure of a gas mixture is equal to the sum of the pressures that each gas exerts independently
Add up partial pressures of all gases for total pressurue
PO2 = PB x FO2
What effect does increasing altidue have on fractional concentration of oxygen?
Increase altidue -> fractional concentration of oxygen remains unchanged
PO2 decreases
What occurs at the beginning of inspiration?
Ambient air brought into airways warmed and humidified
By larynx -> saturated w/water vapor
PP of other gasses diluted
PO2 in a humidified mixture: 150 mmHg
What affect does water vapor have on O2 in ventiliation?
% of O2 remains unchanged
PO2 is decreased
Define
Total Ventilation (VE)
Equation
Amount of air moved per minute
VE = VT x f
Total lVentilation = Tidal Volume x Respiratory Rate
What affect does anatomical dead space have on depth of breathing, VT and f?
VT and f increase
depth of breathing
What happens to the portion of inspired air that gets to site of gas exchange?
It remains in conducting airways
Useless for gas exchange
large effect on VE efficiency
500 mL air moved in and out -> 350 mL exchanged between atm and alveoli
Define
Anatomical dead space
Structure with no gas exchange
In conducting airways
What needs to be considered to determine alveolar ventilaton?
Dead Space
Alveolar dead space
In alveoli with poor circulation n
Insignificant in healthy lung - usully O
Lethal in diseased lung
Physiological Dead space
Anatomical + alveolar dead space
Usually the same as anatomical because alveolar is usually 0
Define
Alveolar Ventilation (VA)
VA = (TV - anatomic dead space) x resiratory rate
VA = (VT = VD) x f
more important than VE
How does “old” air enter the alveoli?
At end of expiration, “old” air from previous breath is in dead space
Next inspiration “old air pushed back into alveoli
Alevolar ventilation is best increased by…
increasing tidal volume
What two variables of Alveolar Ventilation can be altered?
TV and f
What is the relationship between Alveolar Ventilation and PaCO2
PaCO2 = partial pressue of CO2
They are inversely related
Increase ventilation decrease CO2
changing VA is the mechanism for regulating PaCO2
If you hyperventilate, PaCO2..
decreases
panic attack -> blow off alot of CO2
If you hypoventilate, PaCO2…
goes up
How do you determine if VA is adequate?
By looking at PaCO2
If PaCO2 is high, VA is not adequate for level of CO2
Not enough or too much ventilation
Eucapnia
VA
Normal
Hypercapnia
VA
Hypoventilation
decreased ventilation
Hypocapnia
VA
Hyperventilation
Increase ventilation
How do we measure the amount of O2 reaching the alveoli?
The Alveolar Gas Equation measures the partial pressure of O2 in the alveolus
assumes R is 0.8
Why is the Alveolar Gas Equation so important?
Allows us to calculate A-a gradient and determine the source of hypoxemia
PO2 in alveolus - PO2 in arterial blood
Define
Respiratory Quotient
Ratio of CO2 produced by VCO2 (by body) to O2 taken up (VO2)
Depends on the rate of metabolism and substrate burned
What causes the difference between PAO2 to PaO2?
In healthy individual, PAO2 very close to PaO2
A-a gradient
due to regional differences in Va/Q
Anatomic shunt (blood bypasses alveoli)
Bronchial veins drain into pulmonary veins
T or F
Alveolar ventilation is best increased by increasing respiratory rate
False
TV
T or F
A gas diffuses down its partial pressure gradient
True
T or F
Hypercapnia refers to excess CO2 in the arterial blood that is caused by hypoventilation
True
T or F
The volume of air that remains in the conducting airways, and thus not available for gas exchange, is known as alveolar dead space
False
Anatomic dead space
The pressure extered by the weight of the air in the atmosphere on objects on the earth’s surface
Atmospheric pressure
How much effort is required to stretch or distend the lungs
Compliance
The pressure and volume of a gas are inversely related
Boyle’s Law
