Pressure Flashcards
What is hydrostatic pressure?
Gravity pulling down the atoms and molecules stack around us
How is pressure measured?
Force per unit
What is “ideal gas laws?”
An understanding of the predictable behavior of gases under ideal conditions
What happens to pressure in a frozen “empty” bottle?
Pressure rises and volume drops
Is temperature and volume inversely proportional or directly proportional?
Inversely proportional
Jacques Alexandre Cesar Charles formula?
T=K*V
Temp in kelvin
If temperature goes up what happens to pressure?
It will rise as well
What does Boyles law assume?
Temperature is consistent
Joseph Louis Gay-Lussac law?
P=K*T
Is temperature and pressure directly proportional?
Yes
Carlo Avogadro law?
V/n= k
N= number of molecules
1 mole of gas occupies as much volume as any other mole of gas as long as?
Pressure and temp are held constant
What does STPD stand for?
Standard, Temperature, and Pressure Dry
Elements and measurements of “STPD?”
0 degrees Celsius
760mmHg
Ideal molar volume- 22.4L
Ideal molar volume for any gas?
22.4L
What is the point of the ideal molar volume?
A standard point from which to calculate density of a gas
Where does pressure come from?
Gas has:
mass
Takes up space
Compressible and expandable
Influenced by temp
Exerts pressure
Mass, volume, temperature all influence pressure
Combined ideal gas law?
P= nRT/V
What is the #1 mechanism of hypoxemia?
Low inhaled partial pressure of O2
Relationship between temperature and volume that follows Charles law?
They are directly related
Describe relationship between pressure and temperature that follows Gat-Lu’s sac law?
They are directly proportional
The relationship between gas and volume following Avogadro law?
Directly proportional
Percentage of nitrogen, carbon dioxide, and oxygen in the atmosphere?
N2-78%
O2-21%
CO2-0.03%
What happen to pressure, volume, and temperature if either changes?
Temp⬆️
pressure ⬆️
volume ⬇️
Combined ideal gas law for change in a closed system formula?
P1V1/T1 = P2V2/T2
Do gases separate from heavy to light?
No, they exert their pressure equally
Does FiO2 change in altitudes?
No, partial pressure of the gases changes
Define critical temperature?
The temperature when liquid cannot resist becoming gas
Critical temperature vs. boiling point?
Boiling point can rise and fall given different atmospheric pressure
Critical temperature is stable
Critical temperature of O2?
-183 Celsius
Critical temperature of nitrogen?
-147.1 Celsius
Critical temperature of water?
374 Celsius
Why is nitrogen and O2 true gases?
They stand above their critical temperature
Why isn’t water a true gas?
Water stands above it’s critical temperature
Gaseous form is vapor and compressed becomes liquid water
What is “molecular” humidity?
Water vapor
What is “particulate” humility?
Mist, fog, aerosol (tiny droplets suspended in air)
What is boiling point?
Temperature When vapor pressure of liquid exceeds atmospheric pressure
(Interplay between temperature and atmospheric pressure)
Explain boiling?
Atmospheric pressure pushes down on water surface
As the temperature rises, it creates more kinetic energy which weakens bonds and leads to water releasing vaporization breaking through
Two methods of conversion from liquid to gas?
Boiling and evaporation
Two forces that influence evaporation?
Saturation
Heat
What happens to the H2O capacity when temp drops?
Water Capacity drops
relative humidity rises
Absolute humidity drops
Formula for relative humidity?
Humidity content/ humidity capacity
Three quantifying measures for water content in the air?
Absolute humidity
Relative humidity
Partial pressure
Define absolute humidity?
The total weight of humidity in the air
Define relative humidity
The weight of water vapor in the air relative to how much the air can hold
How does a closed system create equilibrium?
Air becomes so saturated that molecules exchange.
From Fahrenheit to Celsius?
F - 32/1.8
Define BTPS?
Ideal qualities of water when it reaches Isothermic Saturation Boundary
Body temperature= 37C
Pressure= ATM
Saturation= carrying water caper at full potential for temperature
What is the weight associated with BTPS conditions
Air needs 43.8mgH2O/L to be saturated
What is a humidity deficit?
The difference between the what content in the atmosphere and how much we need in the respiratory tract in mgH2O/L
Define dew point?
When the air reaches 100 percent saturation and has to release water
Can occur in ventilators when temperature drops in tubing
Why is water pressure hard to calculate?
It has high variability because it come and goes
Conditions for STPD
0 Celsius
760mmHg
0% RH
Conditions for ATPD
? Celsius
? mmHg
0% RH
Conditions for ATPS?
? Celsius
? mmHg
100% RH
Second mechanism of hypoxemia?
Hypercarbia/hypoventilation
Mechanism of hypoxemia
Diffusion defect (thickness of membrane)
Low inhaled partial pressure of O2
Hypoventilation
How is the concentration of O2 diffused into blood determined by two factors of Henry’s law?
Concentration of O2 in blood at STPD
Pressure of O2 in gas
Four elements of Fick’s law that influence volume of gas diffusion?
Thickness of membrane
Surface area
Pressure gradient
Volume of gas diffusing across membrane
Why is CO2 19x more soluble than O2?
A larger solubility coefficient
A large carrying capacity in blood
Why does pascal’s principle not explain pressure in fluid bubbles of different sizes?
It assumes consistent volume
Also, it doesn’t account for the opposing pressure of surface tension.
smaller alveoli receive less flow than larger alveoli
According to LaPlace’s law, distending pressure and surface tension are? (Proportional)
Directly proportional
According to LaPlace’s law, distending pressure and radius are? (Proportional)
Inversely proportional
Explain how the result of Laplace law would be the flow of gas from small to large alveoli and eventually atelectasis?
Because the smaller alveoli have more pressure, the gases would flow to the larger alveoli.
With a smaller radius, the alveoli would have more surface tension and collapsing pressure
Example of hydrostatic pressure in the body?
Blood Pressure
What is hydrostatic and osmotic pressures use in the body?
A force that drives blood forward yet holds it in the vessel
What is semi-permeability?
A membrane permeable to solvents but not solutes
Where does fluid go if sodium is high outside of the cell?
Fluid leaves cells (hypertonic)
Role of oncotic pressure in the cell?
Hold fluid in the cell
Frank-Starlings formula
J=k(Pc-Pi)-a(pi(c)-pi(i))
What does “a” represent in the Franks-Starling formula?
Ability hold protein (Albumin)
What does pi represent in the Frank-Starling formula?
Oncotic
What does “J” represent in the Frank-Starling formula?
Constant
What does “K” represent in the Frank-Starling formula?
How tight
Process by which pressure is generated by solvents moving across a semi-permeable membrane?
Osmotic pressure moves the solvent against atmospheric pressure and gravity to equal solute to solvent concentrations.
Describe the “proof” that pressure in semi-permeable membrane has been made?
When the solutes in the U-tube rise against hydrostatic pressure and gravity
Explain three key physiological derangement’s using Starlings Law?
Elevated P(c): pulmonary edema (transudative)
Pi(c): low Albumin levels causing fluid in interstitial space
Pi(I): high levels of proteins in the interstitium or alveoli can cause fluid accumulation
Inflammable medical gases?
Gases that are flammable are not generally used for medical purposes
Safety factors to assess for gases?
Does it support life?
Is it combustible?
Is it flammable?
What is relative density?
Density of gas relative to air
Volume of one mole of ideal gas at STPD?
22.4L
The importance of density to RTs?
Less dense gases for severe obstructive or restrictive AWs
How do you calculate density using molar volume?
Gram weight/22.4L
Why is solubility of importance to us?
Level of solubility tells us the ease at which the gas will dissolve into the capillaries
What is critical pressure?
Pressure required to keep a substance liquid at critical temperature
Physical qualities of air detectable by human senses?
Odorless
Colorless
Transparent
Tasteless
Safety profile of air?
Non-flammable
Supports combustion
Supports life
Two big uses of medical air
To drive respiratory devices
To blend with oxygen to achieve a desired FiO2
Basic physical qualities of oxygen detectable by human senses?
Odorless
Colorless
Transparent
Tasteless
Safety profile of oxygen?
Non-flammable
Supports combustion
Supports life
Average partial pressure of oxygen at 760mmHg in (air, ISB, alveoli, arteries, tissue)
In air: 160mmHg
At ISB:150mmHg
In alveoli: 100-110mmHg
In arteries: 80-100mmHg
In the tissue: 10mmHg
How much seawater equals 1 atmosphere?
33ft of water
Four indications for hyperbaric therapy?
Rapid decrease in partial pressure of nitrogen (the bends)
Wound healing
Carbon monoxide toxicity
Air embolism
Factor by which hemoglobin has increased affinity to carbon monoxide?
Structural fires
Indoor charcoal fire
Automobile exhaust
250x
Name two ways that hyperbaric O2 therapy treat CO?
Floods system and dissolving in blood
Shortening half life
Wounding healing challenge that could respond to hyperbaric O2 therapy?
Non-healing wounds due to anaerobic bacteria
How does hyperbaric O2 therapy treat wound healing?
Flooding body with O2 can kill bacterium
How does hyperbaric therapy treat bends?
By raising the pressure, you can gradually lower it to reverse “the bends.”
Name the two ways we get oxygen?
Fractional distillation
Molecular filtration
What is molecular filtration?
A vacuum draws air into a cylinder with crystallized zeolites
Zeolites absorb nitrogen resulting in a lot of oxygen
Afterwards decompressed zeolites release nitrogen to be used again
Describe fractional distillation
oxygen under pressure limiting kinetic energy drops temperature causing condensation and turning liquid
Percent of saline in blood
0.9% 135-145
Does oncotic pressure change?
No
As hydrostatic pressure decreases, it becomes more influential
Laplace’s Law for a Sphere?
P= 2T/r
What is the body’s water capacity?
43.8
Physical qualities of CO2
Colorless
Transparent
Odorless to strong odor
Tasteless or slightly acidic
Safety profile of CO2
Non-flammable
Does not support combustion
Does not support life
How is CO2 administered?
Carbogen:
90:10
95:5
Reasons to use CO2
Hiccups
Atelectasis
Anxiety-related hyperventilation
Cerebrovascular condition
Physical qualities of helium?
Colorless
Transparent
Odorless
Tasteless
Safety profile of helium?
Non-flammable
Does not support combustion
Does not support life
Name of mixture of helium and O2?
Heliox
Ratio of heliox?
80 H2:20 O2
Most commonly used application for heliox?
Large airway obstruction
(Tumor growth)
What is the more controversial use of Heliox?
Smaller airway obstruction
(Asthma exacerbation)
Physical properties of Nitric oxide?
Colorless
Transparent
Tasteless
Slightly metallic odor
Safety profile of nitric oxide?
Non-flammable
Does not support life
Does support combustion
Patient population for nitric oxide?
To term and near-term neonatal
Off label: adults
Mechanism of action for nitric oxide?
Cause vasodilation
What is the unit dose of nitric oxide?
20 parts per million
Why doesn’t nitric oxide affect the systemic system?
Because it dissipates rapidly so it doesn’t have time to impact the systemic system
Physical properties of nitrogen?
Colorless
Transparent
Odorless
Tasteless
Safety profile for Nitrogen
Non-flammable
Does not support combustion
Does not support life
Medical uses of Nitrogen?
Powers pneumatic instruments in OR
Used to create zero-point reference gas for O2 analyzers
Explain the conservation of energy
Total energy in a system remain constant
(No gain or loss)
Can change form (potential to kinetic)
Define flow?
The movement of a volume of fluid in a specific period of time
Flow units used in for the ventilator?
L/minute
Flow units used for respiratory calculations?
L/second
Ficks formula
VDgas=A/T x Dgas (p1-p2)
What does “A” represent ficks law
Surface area
What does “T” represent ficks law
Thickness of membrane
What does “Dgas” represent in ficks law
Diffusability of gas
What does p1-p2 represent in Ficks law
Pressure gradient
Uses of nitrogen
Power devices
Creates zero point for O2 analyzers
Test patients tolerance for altitudes
Helps deliver different concentrations of oxygen
Bernoulli principle applications in Venturi
Bernoulli steady flow in a closed system
Venturi: steady flow in open system
Why is CO2 used for laparoscopic surgery
Will be absorbed by body
Won’t support combustion if electrocautery
Why is CO2 used for colonoscopy
Reduces patients discomfort after procedure
