Gases Flashcards
What is the summation of the major gas laws?
PV=nRT
What is the overall concept of Boyle’s Law?
At constant temperature, the volume of a gas is inversely proportional to the pressure it exerts
What is the overall concept of Avogadro’s Law?
Equal volume of gas at the same temperature and pressure contain the same number of molecules
What is the overall concept of Charles’ Law?
At a constant pressure, the volume of a gas is proportional to its absolute temperature
What is the “R” in PV=nRT?
Gas constant
What is the overall concept of Graham’s Law?
Rate of diffusion of a gas is inversely proportional to the square root of its molecular weight
What is the overall concept of Henry’s Law?
The quantity of gas that can dissolve in a fluid is equal to the partial pressure of the gas multiplied by the solubility coefficient
What is the overall concept of Dalton’s Law of Partial Pressures?
The pressure exerted by a mixture of gases is equal to the sum of the individual partial pressure exerted by each gas
What is the vapor pressure of water?
Pressure that is exerted by the water molecules to escape from the liquid to air
The vapor pressure of water is due to what action?
Molecular motion
The vapor pressure of water is proportional to what?
Temperature
At body temperature (37 degrees Celsius), what is the vapor pressure of water?
47 mmHg
What effect does increased temperature have on molecular motion?
Increased
If temperature increase, how is the vapor pressure of water affected?
Also increases
What two gasses change in number the most dramatically as air goes from the atmosphere into our lungs?
Water vapor and carbon dioxide
What happens to the atmospheric air as it goes from the atmosphere into our lungs?
Dilution of water vapor from respiratory passageways and CO2 from the blood
What gasses diminish as the atmospheric air enters our lungs?
Nitrogen and oxygen
What are the most abundant gasses in the atmospheric air?
Nitrogen, oxygen, and argon (in that order)
What is the relationship between respiratory membrane diffusion and temperature?
Proportional (but temperature stays relatively constant)
What is the relationship between respiratory membrane diffusion and solubility?
Proportional
What is the relationship between respiratory membrane diffusion and cross-sectional area?
Proportional (but area varies overall)
What is the relationship between respiratory membrane diffusion and the square root of molecular weight?
Inversely proportional (but weight is fixed)
What is the relationship between respiratory membrane diffusion and the concentration gradient?
Proportional (gradient varies)
What is the relationship between respiratory membrane diffusion and the distance involved?
Inversely proportional (distance varies)
Solubility and the square root of molecular weight are considered what features?
Properties of the gas (therefore are constant)
Which is more diffusible: carbon dioxide or oxygen?
CO2 by 20X
Which is more diffusible: nitrogen or oxygen?
Oxygen (nitrogen is half as diffusible)
Where are oxygen levels lower: atmosphere or alveoli?
Alveoli
Where are carbon dioxide levels higher: atmosphere or alveoli?
Alveoli
What makes up the two layers of the respiratory membrane?
Alveolar epithelium, capillary endothelium
About how thick is the respiratory membrane?
.5-.6 microns
What is the total surface area of the respiratory membrane?
50-100 square meters
About how many milliliters of pulmonary capillary blood is seen in the respiratory membrane?
60-140 mL
When does oxygen diffusion of the respiratory membrane increase?
Exercise
As one expires a normal tidal volume (500 mL), how do oxygen and carbon dioxide levels change?
Oxygen falls, carbon dioxide rises
What makes up the middle 150 mL of expired air?
Mixture of dead space and alveolar air
What makes up the last 250 mL of expired air?
Alveolar air
What makes up the last 100 mL of expired air?
Dead space
Does each normal breath turn over the total alveolar air volume?
No, small percentage
Approximately how many breaths are necessary for complete turnover of alveolar air?
6-7
Why is a slow turnover rate of alveolar air beneficial?
Prevents large changes in gas concentration in alveoli from breath to breath (acts as a buffer)
What is the usual rate of alveolar ventilation to pulmonary capillary perfusion?
4L/5L = .8 overall V/P ratio
What is usually the cause of a decrease in the ventilation to perfusion ratio?
Problem with decreased ventilation
What is usually the cause of an increase in the ventilation to perfusion ratio?
Problem with decreased perfusion of lungs
During decreased ventilation-perfusion ratios, the alveolar PO2 and PCO2 change to look more like what blood averages?
Venous (alveolar PO2 decreases to 40 mmHg and alveolar PCO2 increases 45 mmHg)
What is the result of a decreased ventilation-perfusion ratio?
Physiologic shunt blood and blood that is not oxygenated as it passes the lung
What is the overall concept of a decreased ventilation-perfusion ratio?
Not enough ventilation for the amount of pulmonary blood flow (perfusion)
What is the overall concept of an increased ventilation-perfusion ratio?
Not enough pulmonary blood flow (perfusion) for the amount of ventilation
During increased ventilation-perfusion ratios, the alveolar PO2 and PCO2 change to look more like what levels?
Atmospheric levels (alveolar PO2 increases toward 149 mmHg, alveolar PCO2 decreases toward 0 mmHg)
What is the result of an increased ventilation-perfusion ratio?
Increase of physiologic dead space
What is the result of a V/P ratio of .2?
Increased physiologic shunt blood (ratio decreased)
What is the result of a V/P ratio of 4?
Increased physiologic dead space (ratio increased)
What is VO2 maximum?
Maximum oxygen that can be absorbed from the lung and delivered to the tissue per minute
What is used as the best measure of cardiovascular fitness?
VO2 maximum
What limits VO2 maximum measurements?
Cardiac output (NOT pulmonary ventilation)
During exercise training, what measurements are able to be improved and which stay constant?
VO2 maximum improves, maximum heart rate stays constant
Why is VO2 maximum able to improve due to exercise training?
Due to increase in maximum stroke volume
What is the average VO2 maximum level of a cardiac patient? Sedentary person? Endurance athlete?
- 5L/min - cardiac patient
- 0L/min - sedentary person
- 0L/min - endurance athlete
What is oxygen uptake at rest?
25%
Which stays constant and which decreases during exercise: AO2 or VO2?
AO2 stays constant
VO2 decreases
Where is the majority of the oxygen located when carried from lungs to tissue?
Bound to hemoglobin (97%)
Where is the remaining oxygen located when carried from lungs to tissue that is not bound to hemoglobin?
Dissolved (3%)
What is the function of hemoglobin?
Increases carrying capacity 30-100 fold
Where is the majority of carbon dioxide located when carried from tissues to the lungs?
Bicarbonate ion (70%)
Where is the remaining carbon dioxide located when carried from tissues to the lungs that isn’t in bicarbonate ions?
23% bound to hemoglobin and other proteins
7% dissolved
Why isn’t the amount of oxygen carried from the lungs to tissues equal to the amount of carbon dioxide carried from the tissues to the lungs?
20% of oxygen transported ends up as metabolic water
What is the difference between the amount of oxygen and carbon dioxide transported between lungs and tissue?
5/4 (oxygen to carbon dioxide)
What is the pH of oxygenated arterial blood?
7.41
What is the pH of deoxygenated venous blood?
7.37
Which is slightly more acidic: arterial or venous blood?
Venous blood
How can exercise affect the pH of venous blood?
Could drop to 6.9
What counteracts against the slightly more acidic venous blood?
Blood buffers
What is the ratio of CO2 output to O2 uptake?
4/5 = .8
What happens to 80% of the oxygen in cells?
Converted to carbon dioxide
What happens to 20% of the oxygen in cells?
Converted to metabolic water
How does increased fatty acid utilization for energy affect the amount of metabolic water created from oxygen in cells?
Increases to a maximum of 30%
In what situation is no metabolic water generated from oxygen in the cells? What is the result?
If only carbohydrates are being used for energy
Result = all oxygen is converted to carbon dioxide
When only carbohydrates are being used for energy, how does the ratio of CO2 output to O2 uptake change?
Ratio approaches 1
How is hemoglobin affected by decreased partial pressure of oxygen?
Hemoglobin releases more oxygen
In which vascular structures do we see 97% saturation of PO2?
Arteries (95 mmHg)
In which vascular structures do we see a 70% saturation of PO2?
Veins (40 mmHg)
What change in PO2 causes a large release of oxygen from hemoglobin?
SLIGHT decrease in PO2 (due to sigmoid shaped curve)
Why does a slight decrease in PO2 elicit the greatest release of oxygen from hemoglobin?
Steep portion of curve below a PO2 of 40 mmHg
Increases in what things leads to a shift toward oxy-hemoglobin dissociation (right)?
Increased temperature, CO2 (Bohr effect), 2,3-diphosphoglycerate (2,3 DPG)
What kind of change to pH can promote dissociation in tissues (right shift)
Drop in pH
What kinds of things can promote association (left shift)?
Decreased CO2, temperature, and 2,3 DPG
What is the location for association (left shift)?
Lung
What is the location for dissociated (right shift)?
Tissues
What is the major factor influencing the release of oxygen from hemoglobin?
Partial pressure of oxygen (PO2)
What is an example of a location where PO2 is 40 mmHg?
Superior or inferior vena cava (mixed venous blood)
What is the PO2 of oxygenated arterial blood?
95 mmHg