Gas Exchange and Blood Gas Transport Flashcards
Name the three Gas Laws
- Dalton’s Law
- Henry’s Law
- Fick’s Law
Which law states that in a mixture of gases, each gas will behave as if it were on its own?
Dalton’s Law
Which law states that there is a partial pressure caused by each gas that is INDEPENDENT of the other partial pressures for different gases?
Dalton’s Law
Abiding by Dalton’s law means, the sum of the _____________ of all the gases in a mixture will equal the ____________.
Partial Pressures; Total Pressure
The Normal Alveolar Gas Mixture Pressure is … (in mmHg)
760 (As a result of combining the Partial Pressures of O2 (100 mmHg), Co2 (40 mmHg), H2O (47 mm Hg), and N2 (573 mmHg)).
When a gas is in contact with the surface of a liquid, the amount of gas that will go into the solution is ____________ to the partial pressure of that gas. What Gas Law provides this answer?
Proportional; Henry’s Law
This law states that the rate of transfer of a gas through a sheet of tissue is proportional to the tissue area and the difference in gas partial pressure between the 2 sides and inversely proportional to the tissue thickness.
Fick’s Law
Three principles of Fick’s Law
Net Diffusion Rate of a Gas across a membrane is:
- Proportional to the difference in partial pressure between the pre- and post- tissue barrier.
- Proportional to the surface area of the membrane.
- Inversely proportional to the thickness of the membrane
What does P A and P a mean? (In reference to Gas Exchange in the lungs)?
P A = Partial Pressure of Alveoli
P a = Partial Pressure of Arteries
Draw the basic overview of the Gas Exchange in the Lung, WITH PO2 and PCO2 values!
Dried Inspired Air: PO2 = 160; PCO2 = 0
Humidified Bronchial Air: PO2 = 150; PCO2 = 0
Alveolar Air: PO2 = 100; PCO2 = 40
Mixed Venous Blood (aka Pulmonary Artery): PO2 = 40; PCO2 = 46
Systemic Arterial Blood (aka Pulmonary Vein): PO2 = 100; PCO2 = 40
What is the equation for the Alveolar Minute Volume Rate?
V(alveolar) = V(tidal) - V(deadspace)
*** Be able to manipulate this equation!
The total volume of gas entering the lungs per minute?
Tidal Volume
The volume of gas per unit time that reaches the alveoli?
Alveolar Volume
The volume of gas per unit time that does not reach these respiratory portions (alveoli), but does stay in the trachea/bronchi.
Dead Space Volume
What determines the partial pressure of Alveolar CO2 and arterial CO2?
Alveolar Ventilation Rate
The rate of CO2 production by the body should be _________ to the rate of the CO2 removed by the lungs at equilibrium?
Equal
The rate of alveolar ventilation is the ______ determinant of the rate of the total body CO2 excretion by the lungs.
SOLE
If you increase alveolar ventilation, then the PACO2 or the PaCO2 would __________.
Decrease
If you ________ alveolar ventilation, then the PACO2 or the PaCO2 would increase.
Decrease
Cessation of Breathing
Apnea
The rate at which gas enters or leaves the lung.
Ventilation
Shallow or slow breathing rate can give you a decreased minute ventilation rate of Alveoli (VA); However, there is NO change in PaCO2.
Hypopnea
What type of Ventilation can cause brainstem damage?
Hypopnea
Increased deep breathing rate giving an increased minute ventilation rate of Alveoli (VA); However, there is NO change in PaCO2.
Hyperpnea
What type of ventilation occurs with normal exercise or with a fever?
Hyperpnea
Increased breathing rate giving an increased minute ventilation rate of Alveoli (VA); this INCLUDES hypocapnea and Respiratory Alkalosis
Hyperventilation
“Loss of CO2 from blood.”
Hyperventilation
Hypocapnea
Decreased PaCO2
Which is more important for the body?
A. Depth of breathing?
B. Breaths per minute?
A. Depth of breathing!
More important because the gas inhaled needs to get into the alveoli for O2 transport in the body. If you have increased breaths per minute, you won’t necessarily be giving enough O2 for the body.
What is the Alveolar Gas Equation?
PAO2 = [FiO2 (760-47)] - (PaCO@ / 0.8)
PAO2 = Alveolar Partial Pressure of O2
FiO2 = Fraction of inspired air = % O2 inspired/100
Patm = Atmospheric Pressure = 760 mm Hg
PH2O = Pressure of Water = 47 mm Hg @ 100% humidity
PaCO2 = Arterial CO2 partial pressure
Respiratory Quotient = 0.8
VCO2 eliminated / VO2 consumed
Respiratory Quotient
RQ of 1.0 indicates?
Pure carbohydrate oxidation
RQ of 0.7 indicates?
Pure Fat Oxidation
At equilibrium, the rate of O2 consumption of the body will be _______ to the net rate of O2 entering the lungs.
Equal
There is a ______ relationship between FiO2 and PAO2.
Linear
PAO2 - PaO2
A-a gradient (Alveolar-arterial gradient for O2)
What is the point of the A-a gradient?
Assess the alveolar to capillary gas exchange. It is used in diagnosing the source of hypoxemia.
A large A-a gradient would indicate?
A more serious respiratory compromise!!!
Estimated Normal A-a gradient
(Age/10) + 10
How do we get the value of PAO2?
Use PaCO2 value from blood gas in the Alveolar Gas Equation
PAO2 = [FiO2 (760-47)] - (PaCO@ / 0.8)
What can cause a Large A-a gradient?
- Alveolar Membrane Disease
- Shunt
- Intertstitial Disease
- V/Q mismatch
All of these are considered Respiratory Compromise!
What is a Pulmonary Shunt?
A pulmonary shunt is a physiological condition which results when the alveoli of the lung are perfused with blood as normal, but ventilation (the supply of air) fails to supply the perfused region.
What is the V/Q ratio?
Ventilation Perfusion Ratio
Ideally, the oxygen provided via ventilation would be just enough to saturate the blood _______.
Completely. (in the V/Q ratio)
What is the function of the Oxyhemoglobin Dissociation Curve?
The oxyhemoglobin dissociation curve is an important tool for understanding how our blood carries and releases oxygen. Specifically, the oxyhemoglobin dissociation curve relates oxygen saturation (sO2) and partial pressure of oxygen in the blood (pO2), and is determined by what is called “Hemoglobin affinity for oxygen”; that is, how readily hemoglobin acquires and releases oxygen molecules into the fluid that surrounds it.
How do we measure the O2 % Saturation of Hb (SpO2 aka SO2)?
Pulse Oximeter
What is the normal PO2 value for healthy venous return?
40 mm Hg
What is the normal healthy PaO2 for systemic arterials?
100 mm Hg
What does the NORMAL Oxyhemoglobin Dissociation Curve mean?
Important Steps to Know:
- At 0 mm Hg PO2, you have 0% Sat of O2.
- At 40 mm Hg PO2, you have about 70% Sat of O2. Why? Because the venous blood is returning from the tissues to the lungs and O2 is binding to the Hb due to an increased affinity.
- From 40-100 mm Hg PO2, the Hb affinity for O2 decreases making it harder to fully saturate due to previous binding (0-40 mm Hg).
- At 100 mm Hg, blood has enough % Sat to go out as “oxygenated” blood to the heart and systemic circulation.
What are the factors that affect the Standard Oxyhemoglobin Dissociation Curve?
- Blood pH
- Effects of CO2
- Temperature and Exercise
- 2,3-DPG
- Carbon Monoxide (CO)
- Methemoglobinemia
- Fetal Hemoglobin
A decrease in blood pH (more acidic) will cause the Oxyhemoglobin Dissociation Curve to shift to the _________.
Right
An increase in blood pH (more basic) will cause the Oxyhemoglobin Dissociation Curve to shift to the _________.
Left
If the Oxyhemoglobin Dissociation Curve is shifted to the Right, what does this mean?
Decreased affinity for O2 (release of O2)
What causes a shift to the right on the Oxyhemoglobin Dissociation Curve?
CADET CO2 increase Acidity increase DPG increase Exercise increase Temperature increase
If the Oxyhemoglobin Dissociation Curve is shifted to the Left, what does this mean?
Increased affinity for O2 (loading of O2)
The amount of CO2 in can influence the ____.
pH
What type of blood carries more CO2?
Deoxygenated blood
Warmer muscles will hold O2 longer or release it quicker?
Release O2 quicker
Hyperthermia will cause a ______ shift
Right
Hypothermia will cause a ______ shift
Left
What is 2,3-DPG?
2,3 diphosphoglycerate. Created in erythrocytes during glycolysis.
Not needed to know, but this molecule interacts with the beta subunits of Hb which is why it causes decreased affinity for O2! So more will shift it right.
What abnormal hemoglobin will increase O2 affinity?
Methemoglobinemia
Fetal Hemoglobin has a _________ affinity for O2. What type of shift would this have RELATIVE to Normal Adult?
Increased. Left.
In the blood plasma, CO2 is
Mostly bound to bicarbonate. But has some dissolved, and some bound to plasma albumin forming a carbamino-protein complex.
Function of Bicarbonate?
Buffers H+
In RBCs, CO2 forms
Carbamino-Hb complex
What does the Carbamino-Hb complex do?
When O2 binds to Hb, it reduces affinity for CO2. Which is why venous blood carries more CO2 than arterial blood.
Chloride shifts into the RBCs to increase _____.
mOsm (milliOsmole)
70% of Bicarb from the RBCs goes into the ______ to do what?
Blood Plasma and serves as a buffer.