Respiratory Physiology III: Pulmonary Gas Exchange (Exam IV) Flashcards
Blood coming into the capillaries (before diffusion through the pulmonary artery):
PO2:
PCO2:
PO2: 40 mmHg
PCO2: 45 mmHg
In the alveoli:
PAO2:
PACO2:
PAO2: 100 mmHg
PACO2: 40 mmHg
Blood exiting the capillaries (after diffusion through the pulmonary vein):
PO2:
PCO2:
PO2: 100 mmHg
PCO2: 40 mmHg
When blood reaches the pulmonary veins, PO2 & PCO2 have reached:
Equilibrium
When blood enters the left heart the PO2 is actually at _____ & this is due to ____
PO2= 95 mmHg
Bronchial circulation
To calculate a partial pressure, you must determine the _____ of the gas to other molecules
Relative concentration
Refers to the pressure of one gas in a mixture of gases:
Partial pressure (Pgas)
Equation for partial pressure of a gas:
Pgas = PATM x Fractional concentration of gas
The atmospheric pressure (PATM) at sea level is ____ and air is composed of:
760 mmHg; 79% nitrogen & 21% oxygen
The fraction of inspired oxygen:
FiO2
Calculate the partial pressure of oxygen in our atmosphere:
PO2= 760 mmHg x 0.21
=160 mmHg
As air passes through the conducting zone of the lung, it is humidified creating:
Creating a partial (vapor) pressure for water
As air passes through the conducting zone of the lung, it is humidified creating a partial vapor pressure for water (PH20) which =47 mmHg. This addition of water does what to the partial pressure of oxygen:
Decreases it
Calculate the partial pressure of oxygen with the addition of the partial vapor pressure of water at 47 mmHg:
PO2= (760mmHg - 47mmHg) x 0.21
=149 mmHg
At normal alveolar ventilation & O2 absorption rates (250 mL/min), PAO2 is:
100 mmHg
Increasing alveolar ventilation will _____ PAO2
Increase
Equation for alveolar ventilation:
Alveolar ventilation = (TV-DS) x RR
According to the equation:
Alveolar ventilation = (TV-DS) xRR
You can increase alveolar ventilation by:
Increasing TV and/or increasing RR
A gas within a liquid also exerts a _____
Partial pressure
To calculate the partial pressure in a liquid solution, the ____ and the ____ of the gas are required
Relative concentration & solubility coefficient
Attractability of molecules to water
Solubility coefficient
If the solubility coefficient number is high:
The gas diffuses in the liquid quickly
Henry’s Law:
Partial pressure = (Concentration of dissolved gas) / (Solubility coefficient)
Concentration of dissolved gas equation:
(rearrangement of Henry’s Law)
Conc. of dissolved gas = solubility coefficient x partial presssure
At a constant temp, the amount of gas that dissolves in liquid is _____ to the partial pressure and the solubility
Directly proportional
Compare the solubility of CO2 to O2:
CO2 is more soluble than O2
Why would a patient who has trouble oxygenating their blood be able to transport and get rid of CO2 more easily?
Because CO2 is more soluble
The higher the partial pressure of the gas, the ______ we will be able to dissolve into the liquid
More
Gas exchange at the respiratory membrane depends on: (2)
- Transport rate through the respiratory membrane
- The rate of alveolar ventilation
An increase in alveolar ventilation will ______ PAO2 and gas exchange with an upper limit of ______ (which is _____)
Increase; 149 mmHg; the PAO2 of humidified air
The rate of alveolar ventilation has an upper limit of 149 mmHg. Describe a scenario where this limit might be surpasses:
Patients that are on oxygen may have a higher FIO2 (fraction of inspired oxygen) than 21% which would increase the partial pressure of oxygen
