Unit 2, L4 Ventilation Flashcards
Equation for Ventilation
V = Frequency * volume so 15/min * 500 mL = 7.5 L/min
Boyle’s Law
Pressure-volume law. The volume of a given gas varies inversely with the applied pressure when temperature and mass are constant
Charles’ Law
Temperature volume law. The volume of a given amount of gas held at constant pressure is directly proportional to the Kelvin temperature
Gay-Lussac’s Law
Pressure-temperature law. The pressure of a given amount of gas at constant volume is directly proportional to the Kelvin temperature
Combined gas law
The ratio between the pressure-volume product and the temperature remains constant.
(P1V1)/T1 = (P2V2)/T2
Avogadro’s law
Volume-amount law. If the amount of gas in a container is increased, the volume increases
The ideal gas law
The state of an amount of gas is determined by its pressure, volume, and temperature
PV=nRT
Dalton’s Law of Partial Pressures
The total pressure of a mixture of non-reacting gases is the sum of their individual partial pressures
Amagat’s law of partial volumes
The volume of a gas mixture is equal to the sum of the component volumes of each individual component
Henry’s law of Gas Solubility
The concentration of a solute gas in a solution is directly proportional to the partial pressure of that gas above the solution
Henry’s Law of gas solubility and gas in solution example
Concentration is equal to partial pressure of gas above solution and stays constant. Exact relationship, so if he tells us there is 100 mmHg of pO2 above the solution, we know there is exactly 0.13 mM of oxygen dissolved in the solution
PAO2 definition and value
Alveolar partial pressure of oxygen, 100 mmHg
PaO2 definition and value
Arterial partial pressure of oxygen, 95 mmHg
PvO2 definition and value
Venous partial pressure of oxygen, 40 mmHg
Composition of ambient air
Mostly nitrogen, oxygen
Gas fractions
Sum of individual gas fractions = 1
1 = FN2 + FO2 + etc
Partial pressures (Dalton)
Sum of partial pressures = Total pressure
Barometric pressure is what value
760 mmHg at sea level
At sea level, what is the pressure equation?
P atm = 760 mmHg = PN2 + PO2 + etc
Partial pressure of N2 in atmospheric air
Its 79% N2, so 760 mmHg * 0.79 = 600 mmHg
Partial pressure of O2 in atmospheric air
21% O2, so 760 * 0.21 = 160 mmHg
Our atmospheric water vapor pressure is
160 mmHg O2
Equation for water vapor pressure
PIo2 = (Patm - P water) * FO2
150 mmHg = (760 mmHg - 47 mmHg) * 0.21
Water vapor pressure is always what value
47 mmHg
Ideal alveolar oxygen equation
The partial pressure of oxygen in the alveoli is the partial pressure of oxygen that enters the alveoli minus the partial pressure of oxygen that leaves the alveoli.
PAO2 = PO2 entering - PO2 leaving PaO2 = PiO2 - PACO2/R
The partial pressure of oxygen leaving the alveoli is the partial pressure of alveolar CO2 (PACO2) divided by the respiratory quotient (R)
Respiratory Quotient R is what, and what is the standard R
The ratio of CO2 eliminated to O2 consumed. Standard R for mixed diet is about 0.8
Ideal alveolar oxygen equation
PAO2 = PiO2 - PACO2/R
100 mmHg = 150 mmHg - (40 mmHg/0.8)
If you breathe 100% oxygen, what is the PAO2 (PACO2 is 45 mmHg, R is 0.8)
PAO2 = ((Patm-Pwater)*FO2)-PACO2/R X = ((760-47)*1.0)-45/0.8 X = 713-56 X = 657 mmHg
The amount of CO2 in the alveoli is _________ to the amount of CO2 produced by the tissue, and _________ to the ventilation rate
The amount of CO2 in the alveoli is directly proportional to the amount of CO2 produced by the tissue, and indirectly proportional to the ventilation rate
Alveolar ventilation equation
Va = VCO2/PCO2 * K
Va = Alveolar ventilation rate VCO2 = Rate of carbon dioxide exhalation PCO2 = Partial pressure of arterial carbon dioxide
Doubling ventilation will __________ PCO2
Halve PCO2
Halving ventilation rate will __________ PCO2
Double PCO2
Alveolar CO2 is determined by _________ and ________
Metabolism and ventilation (rate of elimination)
More ventilation occurs at ________ of the lungs than at the ______ of the lungs
More ventilation occurs at the base of the lungs than at the top of the lugns
Pleural pressure at the ___________ of the lungs is ___________ than pleural pressure at the __________ of the lungs
Pleural pressure at the bottom of the lungs is a little bit greater than pleural pressure at the top of the lung
Single Breath Nitrogen Test
Patient breaths in 100% O2 to TLC and didn’t breathe in any N2, but there was already N2 in the lungs from previous breaths. Initial breath out is 100% O2, then some N2 starts to come out with the mixture. Most of the lung is when you see a mixture of O2 and N2. Alveoli are slow to empty or the airways that are closed off to the O2 breathe will be at the very end, this is basically only N2. This is telling you that the O2 you inhaled didn’t make it into those spaces
Ventilation equations
Vt = VD + VA
VA = Vt - Vd
How to measure anatomic dead space
Fowler’s method, a single breath of oxygen. Breathe in 100% O2, mix with N2 that is already in the lungs, and some will stay at 100% in the conducting zone, and can measure the amount of N2 that is let out
Physiological dead space definition
Total volume of gas that does not participate in gas exchange. Anatomic dead space + alveolar dead space (ventilated but not perfused)
Measuring physiological dead space
Borh’s method, expired CO2. Measuring Co2 that comes out of the expired air, so breathing in CO2-free air, mix with lungs, and CO2 free air will stay in anatomic dead space. CO2 from alveolar space will be mixed in and we can measure that when it comes out
Equation for measuring physiological dead space using Borh’s method
VD = Vt * (PACO2-PECO2)/PACO2 VD = 500 * (40-28)/40 VD = 150 mL
