Transcript RT 21 Final Exam Review - Respiratory Therapy Files

RT 21 Final Exam Review
Law of Conservation
• Memorize the definition
• energy cannot be created or destroyed: energy can only be
transferred (transformed)
• All matter is comprised of molecules that are in constant motion. The
degree of this motion differs among three states of matter (solid,
liquid and gas) and their intermolecular forces
Kinetic Theory
• States that the atoms & molecules that make up
matter are in constant motion. Temperature
influences movement of molecules. Hot objects
move more than cold objects. Increasing kinetic
energy increases temperature. Thermal energy =
molecular Kinetic Energy + Potential Energy
States of Matter
• Solids: have a high degree of internal order; their atoms have a strong
mutual attractive force
• Liquids: atoms exhibit less degree of mutual attraction compared
with solids, they take the shape of their container, are difficult to
compress, exhibit the phenomenon of flow
• Gases: weak molecular attractive forces; gas molecules exhibit rapid,
random motion with frequent collisions, gases are easily
compressible, expand to fill their container, exhibit the phenomenon
of flow
Potential and Kinetic Energy
• Potential energy (Position) The strong attractive forces between
molecules that cause rigidity in solids
• Kinetic energy (Motion) Gases have weak attractive forces that allow
the molecules to move about more freely, interacting with other
objects that they come in contact with
• Internal energy and temperature: The two are closely related:
internal energy can be increased by heating or by performing work on
it. Absolute zero = no kinetic energy
States of Matter
• Liquid- solid phase changes (melting and freezing)
• Melting = changeover from the solid to the liquid state
• Melting point = the temperature at which melting occur
• Freezing = the opposite of melting 13.
• Freezing point = the temperature at which the substance freezes;
same as its melting point
Temperature
• Temperature: the amount of heat energy in matter expressed in
terms of a specific scale
• Celsius (used in health care) Body temperature 37 degrees C (+/-1) ;
Boiling point of water 100 degrees C; Freezing point of water 0
degrees C; Absolute 0 (no molecular movement) -273 C 16.
• Kelvin (used in research): Absolute 0 (no molecular movement) 0
Kelvin 17.
•
Temperature Conversions
•
• Kelvins = Celsius + 273 Example: Convert 37 C to Kelvins; Kelvins = 37 + 273 = 310 Kelvins
• To convert Kelvin temperatures to Celsius, subtract 273 as shown below: b.
•
Celsius = Kelvins - 273 c.
• Example: Convert 298 Kelvins to Celsius d.
•
Celsius = 298 K - 273 = 25 Celsius 18.
•
To convert Fahrenheit to Celsius, use the following formula:
• C = .55 x ( F- 32)
• Example: Convert 60 Fahrenheit to Celsius
•
C = .55 (60 - 32) = .55 x 28 = 15 Celsius
•
To convert Celsius to Fahrenheit, use the following formula:
•
F = (1.8 x C) + 32
•
Example: Convert 20 Celsius to Fahrenheit
•
F = (1.8 x 20) +32 = 36 + 32 = 68 Fahrenheit
Pressure
• A measurement of force per unit area, ie: pounds per square inch
(PSI)
• Absolute Pressure Scale: A pressure scale in which the 0 point is a
complete vacuum or the pressure at which all molecular motion
ceases. Absolute pressure includes atmospheric pressure. b.
• Gauge Pressure Scale: A pressure scale in which the 0 point is
atmospheric pressure or the pressure of the atmosphere pushing
down on a given point on the earth.
Absolute Pressure
• is zero-referenced against a perfect vacuum, so it is equal to gauge
pressure plus atmospheric pressure.
• ATMOSPHERIC PRESSURE AT SEA LEVEL IS 760 torr (mmHg)
• Positive pressure is above atmospheric pressure and negative pressure is
below atmospheric pressure
• Atmospheric pressure varies based on altitude
• Gauge pressure is zero-referenced against ambient air pressure, so it is
equal to absolute pressure minus atmospheric pressure. Negative signs are
usually omitted. To distinguish a negative pressure, the value may be
appended with the word "vacuum" or the gauge may be labeled a "vacuum
gauge."
• Differential pressure is the difference in pressure between two points.
(Delta P)
Pressure Conversion
• cmH20 (absolute) = cmH2O (gauge) + 1034
• Ex: Convert 100 cmH2O gauge to cmH2O absolute = 100 + 1034 = 1134
cmH2O Absolute
• torr (same as mmHg)
• torr is used to measure blood pressure and atmospheric pressure.
• 1 torr = 1 atm, measured by a Barometer
• At sea level 1 atm = 760 torr (mmHg)
• torr (absolute) = torr (gauge) + 760
• 1 torr (Torr) is equal to 1.36 centimeters of water (cmH2O)
• Ex: Convert 100 torr to cmH2O = 100 x 1.36 = 136 cmH2O
Negative Pressure
• negative or minus gauge pressure is frequently used in respiratory
care to describe gauge pressure conditions that are lower or less than
0 or atmospheric pressure. (same thing as vacuum pressure)
Critical temp and pressure
• Critical temperature:
• The temperature reached in which gaseous molecules cannot be
converted back to a liquid, no matter what pressure is exerted on
them. The highest temperature at which a substance can exist in a
liquid state.
• Critical pressure:
• The critical pressure of a substance is the pressure required to liquefy
a gas at its critical temperature.
Standard Measurements
• STPD:0 Celsius, 1 atmosphere (760 torr), dry -- used mainly in
chemistry, used in respiratory care to measure metabolic and
nutritional values. 27.
• BTPS: 37 Celsius, 1 atmosphere (760 torr), saturated -- the conditions
in the body, used in respiratory care to measure lung volumes.
• ATPS: room temperature, room pressure, saturated -- ambient or
room conditions, the temperature and pressure vary with the
conditions in the environment or room. Used in respiratory care to
convert room conditions to body conditions.
Atoms
• Basic unit of matter that consists of a dense central nucleus
surrounded by a cloud of negatively charged electrons. The atomic
nucleus contains a mix of positively charged protons and electrically
neutral neutrons. The electrons of an atom are bound to the nucleus
by the electromagnetic force. Likewise, a group of atoms can remain
bound to each other by chemical bonds based on the same force,
forming a molecule. An atom containing an equal number of protons
and electrons is electrically neutral, otherwise it is positively or
negatively charged and is known as an ion.
Atoms
An atom is classified
• according to the number of protons and neutrons in its nucleus: the
number of protons determines the chemical element, and the
number of neutrons determines the isotope of the element
Protons
Proton is a subatomic particle with a positive charge and a mass of 1
atomic mass unit and is located within the nucleus. When the number
of protons in the nucleus is equal to the number of electrons orbiting
the nucleus the atom is electrically neutral.The number of protons
contained in the nucleus = Atomic Number
• Each element has a different atomic number
• Ex: Oxygen atomic number is 8
Electrons and Neutrons
Neutron:
• Neutron is also in the atoms nucleus
• It is a subatomic particle with no electric charge and a mass of 1 amu
• The sum of the neutrons inside the nucleus he number of the protons = atomic mass
• Most atoms of elements can accommodate additional neutrons in their nucleus
• Oxygen, three variations with varying atomic mass
Electron
• is the lightest subatomic particle. It is a negatively charged particle. a.
• Its mass is only 1/1,840 the mass of a proton. An electron is therefore considered to be mass-less in comparison with
proton and neutron and is not included in calculating atomic mass of an atom.. Under ordinary conditions, electrons are
bound to the positively charged nucleus by the attraction created from opposite electric charges. b.
• An atom may have more or fewer electrons than the positive charge of its nucleus and thus be negatively or positively
charged as a whole; a charged atom is called ion. In plasma, electrons exist in free state along with ions.
Ions
An ion is a charged atom or molecule. It is charged because the number of
electrons do not equal the number of protons in the atom or molecule. An
atom can acquire a positive charge or a negative charge depending on
whether the number of electrons in an atom is greater or less then the
number of protons in the atom.
• When an atom is attracted to another atom because it has an unequal
number of electrons and protons, the atom is called an ION.
• If the atom has more electrons than protons, it is a negative ion, or
• ANION (a –will be applied)
• If it has more protons than electrons, it is a positive ion or
• CATION (a + will be applied) Ex: Na+ Cl-
Compound and Molecules
• A molecule is formed when two or more atoms join together
chemically. A compound is a molecule that contains at least two
different elements. All compounds are molecules but not all
molecules are compounds. Molecular hydrogen (H2), molecular
oxygen (O2) and molecular nitrogen (N2) are not compounds because
each is composed of a single element. Water (H2O), carbon dioxide
(CO2) and methane (CH4) are compounds because each is made from
more than one element.
Electrovalent (Ionic) Bonding
• Two or more elements combine with each other by transferring electrons.
One electron leaves outermost electron shell of one atom and enters
outermost shell of other atom Tendency in nature is for all atoms to seek
eight electrons in their outermost electron shell (RULE OF EIGHT)
• Ex: Na and Cl, Cl has 7 electrons in its outermost shell and Na has one.
When the two elements react NA transfers its lone electron to Cl making Cl
negatively charged, and sodium becomes positively charged since it lost an
electron. Creating ions of Na and Cl b.
• The bond that holds Na and Cl together is called electrovalent c.
• The electrostatic attraction between these opposite charges maintains
molecular integrity (NaCl)
Covalent Bonding
• Results from the sharing of one or more pairs of electrons to form covalent
molecules
• Example: two Oxygen Molecules
• Oxygen has two unpaired electrons in its outermost shell (total of 6), this
combines with two from another Oxygen molecule to form O2
• Some compounds are held together from a combination of both types of
bonds
• As elements react to form compounds, electrons are either shared or
transferred or both
• The electrons involved in these processes are called valence electron
Henry’s Law
• Henry’s Law
• Describes the diffusion rate, or dissolving of a gas molecules into
liquid. It states
• “For a given temperature, the rate of a gas’s diffusion into a liquid is
proportional to the partial pressure of that gas and its solubility
coefficient”. Does not apply to gases that chemically react with the
solvent
External respiration or breathing
• is a process of inhaling the air into the lungs and expelling the air that
contains more carbon-di-oxide from the lungs to the outer
environment. Exchange of gases in and out of the blood also takes
place simultaneously. External respiration is a physical process in
which oxygen is taken up by capillaries of lung alveoli and carbondioxide is released from blood.
Internal respiration or cellular respiration/tissue
respiration
• is a metabolic process during which oxygen is released to tissues and
carbon dioxide is absorbed by the blood. Once inside the cell the
oxygen is utilized for production of energy in the form of ATP
(adenosine triphosphate)
Solubility Coefficient of Oxygen
• (only O2 and Co2 are capable of diffusing into the blood under normal circumstances, Nitrogen does not
diffuse due to its large size)
• Determined by: Plasma as the solvent
• 760 torr (sea level barometric pressure) 1 atm
• Body Temperature
• Under these circumstances oxygen’s solubility coefficient has a value of 0.023. Meaning:
• 0.023 ml of Oxygen can be dissolved by 1 ml of plasma
• 0.023 ml O2/ml plasma / 760 torr PO2
• Solubility Coefficient of Oxygen Conversion
• Since 0.023 ml of Oxygen dissolves in 1 ml of plasma under a pressure of 760 torr of Oxygen, the amount of
oxygen able to be dissolved in 1 ml of plasma for each torr of oxygen is determined by:
• 0.023 ml O2 /ml Plasma = 0.00003 ml O2/ml plasma/torr PO2
• Further broken down to:
• 0.00003 mlO2/ml plasma/torr Po2 x 100 ml plasma= 0.003 ml O2/ 100 ml plasma/torr PO2
• CO2 diffuses about 22 times faster than O2 into the blood
CaO2 and PAO2
• Total Oxygen Content (formula to determine tissue oxygenation)
CaO2 = (Hb x 1.34 x SaO2) + (0.003 x PaO2) NORMAL 17-21vol%
• PAO2 = FIO2 (PB- PH2O) –PaCO2 /RQ
• PAO2 = Alveolar air equation; Normal 100 mmHg
• RQ is dropped if FIO2 is over 60%
Grahams Law
• States “the rate of diffusion of a gas through a liquid is directly
proportional to its
• solubility coefficient and inversely proportional to the square root of
its density”.
• Describes the diffusion rate of one gas into another gas.
• Gram molecular weight equals the number of particles in a given
amount of matter.
• Molecular weight of CO2 = 44.01 d.
• Molecular weight of Oxygen = 31.99
Density, Weight and Mass
• DENSITY: the mass per unit volume of a substance. The standard units
for density are grams per cubic centimeter (gm/cm3), but the density
of medical gases is usually expressed in grams per liter (g/l). 19.
• WEIGHT: measurement of the force of gravity acting upon an object
(usually the earth's gravity).
• MASS: measurement of the amount of matter present in an object
independent from the force of gravity acting on it.
Avogadro’s Law:
"Equal volumes of gases at the same temperature and pressure contain
the same number of molecules." Therefore, the gram molecular weight
(GMW) of a substance at STPD contains 6.023 X 1023 molecules and
occupies a volume of 22.4 liters. Avogadro's law can be used to find the
density of medical gases.
Density of gases:
Gases are influenced by changes in temperature and pressure
• Calculates under STP conditions
• Calculated by dividing volume occupied by 1 mole of gas at STP, that is
22.4 liters, into the gram of molecular weight of that gas
• Density = gram molecular weight / 22.4 liters d.
• Example:
• Density of O2 = Weight of O2 32g /22.4 liters = 1.43g/L f.
• Gases such as Helium have far less density
• Oxygen has higher density than air and tends to accumulate at the lowest
point (Ex: oxygen enclosure)
Specific Gravity
• The density of a material divided by or compared with the density of
a standard.
• In physics, the density of water is most often used as a standard.
• When finding the specific gravity of a medical gas, air is used as the
standard.
• This is done because it is useful to know how the density of a medical
gas compares with room air.
• When the specific gravity of a substance is calculated, the standard
must be indicated. This is done by indicating (Air = 1) for medical
gases or (Water = 1) for liquids.
Atmospheric Pressure
• (21% O2, 78% Nitrogen) At altitudes above sea level the atmospheric
pressure is lower because there is less air pushing down on the
surface. a.
• At sea level, 1 ATM = 760 torr, In Denver, 1 mile above sea level, 1
ATM = 680 tor.
At sea level:
• 760 mmHg
• 760 torr
• 1034 cmH2O
• 14.7 PSI
Air Pressure
• Because air is a fluid, force applied in one direction is distributed
equally in all directions. Thus the downward pull of gravity on air
molecules produces air pressure in all directions.
• As elevation goes up, barometric pressure goes down
Pressure Gradient
• Fluids (air and water) flow from areas of high pressure to areas of low
pressure.
• Change in pressure across a horizontal distance is a pressure
gradient.
• Greater the difference in pressure and the shorter the distance
between them, the steeper the pressure gradient and the high the
velocity of flow
• In the lung, flow travels to the alveoli based on the diameter of the
airway and also the pressure gradient.
Speed, Velocity and flow
• Speed is a measurement of an object’s movement in units of distance
or length /time, (ie cm/sec, miles per hour).
• Velocity is the speed of an object with its direction at a given instant,
(ie 50 miles/hour South).
• Fluid flow is a special kind of velocity expressed in units of
volume/time, ie ml/sec, l/min. Remember that a fluid is a substance
capable of flowing ---a gas or liquid.
Buoyancy and Viscosity
• Buoyancy – occurs because the pressure below a submerged object
always exceeds the
• Viscosity: the force opposing a fluid’s flow. The greater the viscosity of
a fluid, the greater the resistance to flow. Blood has a viscosity five
times greater than that of water
Pascal’s Law
• states that pressure exerted anywhere in a confined incompressible
fluid is transmitted equally in all directions throughout the fluid such
that the pressure ratio (initial difference) remains the same. a.
• Pascal’s Law states that when you apply pressure to confined fluids
(contained in a flexible yet leak- proof enclosure so that it can’t flow
out), the fluids will then transmit that same pressure in all directions
within the container, at the same rate.
Cohesion and adhesion:
• The attractive force between like molecules is cohesion.
• The attractive force between unlike molecules is adhesion.
• The shape of the meniscus depends on the relative strengths of
adhesion and cohesion.
• H20: Adhesion > Cohesion
• Mercury: Cohesion > Adhesion
Boiling, Saturation, Dew Point, Evaporation
• Boiling –heating a liquid to a temperature at which its vapor pressure
equals atmospheric pressure.
• Saturation –equilibrium condition in which a gas holds all the water
vapor molecules that it can.
• Dew point –temperature at which the water vapor in a gas begins to
condense back into a liquid.
• Evaporation –when water enters its gaseous state at a temperature
below its boiling poin
Pressure Conversion
• One approach to converting from one pressure scale to another
would be to memorize a conversion factor for each pressure scale. An
easier approach is to remember the value for 1 atmosphere in each of
the commonly used pressure scales.
• Remember: 1 ATM = 15 psi = 760 torr = 1034 cmH2O b.
• Then use the following equation to convert:
• New Pressure=
• 1 ATM in new scale
• ------------------------- x Given pressure Value
• 1 ATM given scale
Humidity/Aerosol
• Vapor pressure –Pressure water as a vapor or gas exerts and is part of the
total atmospheric pressure. Water vapor pressure in the lungs exert 47
mmHg
• Absolute Humidity –the actual amount (in mg./l) of water vapor in the
atmosphere
• Relative Humidity – the percent of water vapor in the air as compared to
the amount necessary to cause saturation at the same temperature.
• % Body Humidity –the relative humidity at 37 degrees Celsius
• Humidity Deficit – the amount of water vapor needed to achieve full
saturation at body temperature (44 mg/l - A.H)
Humidity/Aerosol
• Vaporization: the change of matter from a liquid to a gaseous form
• Water vapor pressure : the direct measure of the kinetic activity of water vapor
molecules
• Inadequate humidification:
• inspissated secretions
• Damage to tracheal epithelium
• Decrease in ciliary activity
• Retention of secretions
• Hypothermia
• Infection
• Blockage of airway
• Atelectasis
Humidity/Aerosol
Indications for humidity: Provide humidity for dry gases b.
• Correct humidity deficit in intubated or tracheostomized patients
• Treatment of hypothermia
• Correct bronchospasm induced by inspiration of cold air
Factors affecting humidifiers:
• Temperature
• Surface area of fluid exposed to water
• Time of contact with water
Water loss:
• Insensible: skin and lungs
• Sensible: urine, GI tract, sweat
• Additive: vomiting, diarrhea, suction from intestines, severe burns, and fever
Humidity/Aerosol
Importance of humidity:
• It is needed to maintain normal bronchial hygiene
• It promotes functions of the normal mucociliary escalator
• It maintains the body's vital homeostasis
Without humidity:
• the nearly 100 ml of mucus secreted daily would become quite thick
and tenacious.
• actual lung parenchyma would dry up, causing a loss of normal
compliance which would restrict lung movement and reduce
ventilation.
Humidity/Aerosol
Aerosol:
• It is important to remember that an aerosol is not the same as humidity.
• Humidity is water in a gas in molecular form, while an aerosol is liquid or
solid particles suspended in a gas.
• Examples of aerosol particles can be seen everywhere: as pollen, spores,
dust, smoke, smog, fog, mists, and viruses.
• Aerosol therapy is designed to increase the water content delivered while
delivering drugs to the pulmonary tree
• Deposition location is of vital concern
• Some factors that affect aerosol deposition are aerosol particle size and
particle number
Humidity/Aerosol
Aerosol Output:
• The actual weight or mass of aerosol that is produced by nebulization.
• Usually measured as mg/L/min also called aerosol density
• Aerosol output does not predict aerosol delivery to desired site of
action. c
Particle Size:
• The particle size of an aerosol depends on the device used to
generate it and the substance being aerosolized.
• Particles between 2 and 5 microns are optimal in size for depositing
in the bronchi, trachea and pharynx
Humidity/Aerosol
• Sedimentation: Particles settle out of aerosol suspension due to gravity. The bigger it is
the faster it settles! Medium particles: 1-5 microns, central airways. Directly proportional
to time. The longer you hold your breath the greater the sedimentation
• Diffusion: Actual diffusion particles via the alveolar-capillary membrane and to a lesser
extent tissue-capillary membranes of respiratory tract
• Gravity: affects large particles more than small particles, causing them to rain-out.
Hypertonic solutions
• absorb water from the respiratory tract, become larger and rain-out sooner.
Hypotonic solutions
• tends to lose water through evaporation and are carried deeper into the respiratory tract
for deposition.
Isotonic solutions (0.9% NaCl)
• will remain fairly stable in size until they are deposited
DO2
• DO2:
• The delivery of oxygen to the tissues per minute is calculated from:
DO2 = [1.39 x Hb x SaO2+ (0.003 x PaO2)] x Q
GAS LAWS
• Moles: the SI unit for amount of substance is the mole, mol. Since we can’t count molecules, we
can convert measured mass (in kg) to the number of moles, n, using the molecular or formula
weight of the gas. By definition, one mole of a substance contains approximately 6.022 x
10. particles of the substance. You can understand why we use mass and moles!
Boyles Law:
• The volume that a gas occupies when it is maintained at a constant temp. is inversely proportional
to the absolute pressure exerted on it.
• Boyle determined that for the same amount of a gas at constant temperature,
• p * V = constant
• This defines an inverse relationship: when one goes up, the other comes down.
• Boyle’s Law can be used to predict the interaction of pressure and volume.
• If you know the initial pressure and volume, and have a target value for one of those variables,
you can predict what the other will be for the same amount of gas under constant temperature
Gas Laws
Charles Law: If pressure remains constant, the volume of a gas varies
directly with the temperature, expressed in Kelvin.
• As the temperature increases, the volume of the gas will increase.
• As the temp. decreases, the volume will also decrease
Combined Gas Law: “The state of an amount of gas is determined by its
pressure, volume, and temperature” The absolute pressure of a gas is
inversely related to the volume it occupies & directly related to its absolute
temp. 5.
Gay-Lussac’s Law: “With volume remaining constant, pressure and
temperature are directly related
Dalton’s Law“The sum of the partial pressures of a gas mixture equals the
total pressure of the system and that the partial pressure of any gas within a
gas mixture is proportional to its % of the mixture”
Week 6-7 GAS EXCHANGE
Ventilation: The mechanical movement of air into and out of the lungs
Respiration: The interchange of gases between an organism and the medium in which it
lives the taking in of oxygen, its use by the tissues, and the giving off of carbon dioxide 3.
• FIO2 –ractional inspired oxygen concentration expressed as decimal. 100% is written as
1.00
• PAO2 –partial pressure of oxygen in the alveolus expressed in mmHg
• PB–barometric pressure expressed in mmHg
• PaO2 –partial pressure of oxygen in the arterial blood expressed in mmHg
• SaO2 – saturation of the hemoglobin by oxygen expressed as a percentage
• PACO2–partial pressure of carbon dioxide in the alveolus expressed in mmHg 9.
• PaCO2 – partial pressure of carbon dioxide in the arterial blood expressed in mmHg 10.
• PvO2–partial pressure of oxygen in the venous blood expressed in mmHg
Gas Exchange
• PvCO2 – partial pressure of carbon dioxide in the venous blood expressed in mmHg
• R –respiratory quotient: Total exchange of oxygen for carbon dioxide expressed as a ratio
of carbon dioxide produced to the volume of oxygen consumed; normal value is 0.8 13.
• Diffusion: Gas movement between the lungs and the tissues occurs via simple diffusion
The partial pressure of inspired 02 (PI02) = 159mmHg, Capillary Ca02 = 40 mmHg,
intracellular P02 is approx. 5 mmHg. This pressure gradient allows for the diffusion of
oxygen from the lungs to the cell.
Barriers to diffusion:
• Alveolar epithelium
• Interstitial space
• Capillary endothelium
• Erythrocyte membrane
Ficks
• Fick’s First Law of Diffusion
• Vgas= (A x D) (P1–P2) /T
• Vgas is the movement of a volume of gas through a biological
membrane
• A is the cross-sectional area available for diffusion
• D is the diffusion coefficient
• T is the thickness of the membrane
• (P1 – P2) is the partial pressure gradient across the membrane
Time Limits to Diffusion
• Red blood cells (RBC’s) are normally in contact with the alveolus in
the pulmonary capillary for 0.75 seconds. During heavy exercise, a
0.25 sec. transit time is still sufficient for full equilibration of gas
diffusion.
• Saturation of the RBC is normally accomplished in < 0.5 seconds
• The time available for diffusion in the lung is mainly a function of the
rate of pulmonary blood flow
A-a Gradient
• Difference in partial pressure between the alveolar gas and the
arterial value
• Expressed as P(A-a)O2
• P(A-a)O2 = PAO2-PaO2
• Normal = (on 21%) less than 4mmhg for every 10 years in age
• Normal value: 5-10mmHg on R/A and < 65mmHg on 100%
• On 100% 02 every 50mmhg difference in P(A-a)02 = 2% shunt
Hypoxic pulmonary vasoconstriction
• Hypoxic pulmonary vasoconstriction: physiologic protective
mechanism which prevents right to left shunting of blood. Right to
left shunt causes hypoxemia unresponsive to oxygen therapy
• a/A Ratio: Ratio between the partial pressure of the alveolar gas and
the partial pressure of the arterial gas or how much oxygen is getting
from the alveoli to the blood a.
• Expressed as: PaO2/PAO2
• Normal value: > 75%
V/Q. Shunt. Deadspace
V/Q: V/Q mismatch: Ambiguous term, simply means there is a problem with either ventilation or perfusion or
both resulting in hypoxemia. Initial treatment it to give Supplemental O2; assess via pulse-ox
• If the V/Q mismatch does not improve with Oxygen, it is deemed a “shunt” and will require positive
pressure.
• Refractory hypoxemia (V/Q that doesn’t respond to O2 alone, = shunt = positive
• pressure)
Shunt:
• Perfusion without effective ventilation
• Treatment: Positive pressure
DEAD SPACE:
• Ventilation without perfusion
• Treatment depends on cause
• Heart not pumping effectively
• Pulmonary emboli (blood clot preventing blood flow, vasoconstriction
Blood carries oxygen in two forms
Plasma: Oxygen first dissolves in plasma.
• Relates to Henry’s Law which states that there is a direct relationship
between the partial pressure of the gas over the liquid. Amount of
oxygen carriage = 0.03 x PaO2
Red Blood Cell. The major source of oxygen carriage. Each red blood
cell consists of 4 Heme complex’s, each with its own iron ion. Oxygen
molecules bind to these Heme complexes via the iron ion. When all the
Heme complex’s are bound with O2, the Hb is converted to its
oxygenated state and referred to as: Oxyhemoglobin (HbO2)Each gram
of normal Hb can carry approx. 1.34 ml of oxygen
HBO, VO2
Diseases for which hyperbaric oxygen therapy is indicated:
• Arterial gas embolism
• Decompression sickness (the bends)
• Severe carbon monoxide poisoning
• Wound healing
Oxygen Consumption: Approximately 250 ml of oxygen are used every
minute by a conscious resting person (oxygen consumption) and therefore
about 25% of the arterial oxygen is used every minute. The hemoglobin in
mixed venous blood is about 70-75% saturated
• VO2 = Q x (CaO2-CvO2) mlO2/min
FLUID DYNAMICS
Hydrodynamics: The study of fluids in motion
Law of Continuity: Explains the relationship between the cross-sectional area
of a tube through which fluid is flowing and the velocity of the flowing fluid
when the flow rate is constant. Cross-sectional area and velocity are
inversely related (meaning as the area is decreased, the velocity increases) 3.
• Flow patterns: As gas travels down the tracheobronchial tree it takes on a
distinct flow characteristic
• Laminar (lower airway)
• Turbulent (upper airway)
• Transitional (bifurcation of bronchi
Flow Patterns
• Natural flow patterns: Nose/trachea = turbulent, this allows
entrapment of particles in the nasal concha. As the airway increase in
cross sectional area, the velocity decreases turning the flow into
laminar. The transition of turbulent to laminar is called transitional
flow
• Laminar: Laminar flow patterns depend on the airway size and
resistance to flow
• Obstructions to flow (mucus, swelling…) cause turbulent flow
patterns
Flow Patterns
• Laminar flow turns into turbulent flow when the velocity of flow exceeds a
certain value (critical velocity) which is a function of the viscosity and density of
the fluid
• Streamed lined horizontally moving molecules
• Laminar Flow in a tube has its greatest velocity in the center of the tube and
least on the edges of the tube e.
• This is called Parabolic velocity
Laminar to Turbulent:
• High linear gas velocity
• High gas density
• Low gas viscosity
• Large tube diameter
Flow Patterns
Turbulent:
• Non linear patterns of eddies. The velocity of the flow is equal through the tube
everywhere in the tube unlike laminar
Reynolds Number:
• dimensionless quantity that is used to help predict similar flow patterns in
different fluid flow situations. defined as the ratio of inertial forces to viscous
forces and consequently quantifies the relative importance of these two types of
forces for given flow conditions. Less 2000= Laminar, More 2000= turbulent 9.
Viscosity: The internal force that opposes the flow of fluids (equivalent to the
frictional forces between solid substances)
• The greater the viscosity, the greater the opposition to flow
• The stronger the cohesive forces, the greater the viscosity
Poiseuille’s Law:
• Fluid viscosity, tube length and radius determine resistance to flow.
• As the radius of a tube decreases by ½, resistance increases 16 times.
• Increased resistance to flow can be caused by a decreased airway size secondary to an
increase in airway secretions, bronchospasm, intubation, etc.
• The law that the velocity of a liquid flowing through a capillary is directly proportional to
the presence of the liquid and the fourth power of the radius of the capillary and is
inversely proportional to the viscosity of the liquid and the length of the capillary. d.
The variables in Poiseuille’s Law are:
• The driving pressure gradient (the heart pumping)
• Viscosity of the fluid (a person who is anemic can affect the viscosity of his/her blood)
• Tube length
• Fluid flow
• Tube radius
Bernoulli’s Principle
• Bernoulli’s Principle: Describes relationship between lateral wall
pressure and velocity form an incompressible fluid flowing through a
tube in laminar fashion
• When a fluid flows through a tube of uniform diameter, pressure
decreases progressively over the tube length.
• As fluid passes thru a constriction, the pressure drop is much greater
• Venturi Principle:“The pressure drop that occurs as the fluid flows
thru a constriction in the tube can be restored to the preconstriction
pressure if there is a gradual dilation of the tube”.
Osmosis/Diffusion
• DIFFUSION: the process by which molecules intermingle as a result
of their random motion or the movement of molecules from an area
of high concentration to an area of low concentration.
Solvent and Solute
• When describing the characteristics of solutions, the following terms are
used:
• A. Solvent: a liquid in which another substance is dissolved.
• B. Solute: a substance that is dissolved in a liquid.
• There are two important parts of a solution. The liquid used to make the
solution is called the solvent. The best known solvent of all is water.
Because of its unique properties, water dissolves a remarkable number of
other substances – gases, liquids and solids. Solutions that use water as a
solvent are known as aqueous solutions.
• There are many other liquids that can be solvents, however. These are
called non-aqueous solvents
Solvent and Solute
• The substance that is dissolved in a solvent is called the solute The
solute is commonly a solid, but it can also be a gas or a liquid.
Substances that dissolve in a particular solvent are designated as
soluble, while substances that do not dissolve are insoluble
• Solution is a homogeneous mixture.
Semi-permeable Membrane
• a membrane which allows the passage of solvent but not solute
molecules.
• type of biological membrane that will allow certain molecules or ions
to pass through it by diffusion and occasionally specialized "facilitated
diffusion”
Osmosis
• The diffusion of the molecules of a solvent across a semi-permeable
membrane while the molecules of the solute are left behind. It is
important to remember the solvent molecules are diffusing from
high to low concentration, the solute molecules cannot diffuse
through the membrane.
Osmotic Pressure
• The pressure required to stop movement of pure solvent across the
membrane.
• Example: The osmotic pressure of 1% NaCl would be that pressure which
would stop diffusion of pure water through a membrane to a solution of
1% NaCl. The greater the osmotic pressure, the faster water will dilute
the solution.
• Ex: Plasma
Osmotic Pressure
• ISOTONIC: an isotonic solution has the same osmotic pressure as the
reference solution, ie: 0.9% NaCl or normal saline is isotonic
compared to tissue, so normal saline would not cause water to move
into or out of tissue cells via osmosis.
• HYPERTONIC: a hypertonic solution has a greater osmotic pressure
than the reference solution, ie: 3% NaCl is hypertonic compared to
tissue, so 3% NaCl would cause water to move out of tissue cells via
osmosis.
Diffusion of solvents
• A solvent diffuses through a semi-permeable membrane toward
the:
• 1. the hypertonic solution.
• 2. the solution with the greatest osmotic pressure
• 3. the solution with the greatest solute concentration.
Diffusion of solvents
• A solvent diffuses through a semi-permeable away from the:
• 1. the hypotonic solution.
• 2. the solution with the lowest osmotic pressure.
• 3. the solution with the lowest solute concentration.
Pharmacology
• The study of substances that interact with living systems through
chemical processes
• DRUG: Any substance that interacts with a molecule or protein that
plays a regulatory role in living systems.
• Includes oxygen and other therapeutic gases along with our inhaled
aerosolized medications
Definitions
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•
•
•
•
•
•
•
•
Endogenous: Substances made inside body
Exogenous: substances made outside the body
Hormones: are endogenous drugs
Toxin: poisons of biologic origin
Receptors: Specific molecule, usually a protein, that interacts with a
specific chemical that then causes a change in the specific molecule,
causing a change in regulatory function
BETA 2 = Epinephrine
Musucarinic= AcH
Lock that a key fits into; ex:
Lock receptor and epinephrine the key to opening the lock
Definitions
• Agonist: any drug that binds to a receptor and activates the receptor
• Drug that fits into a receptor, will then activate and a chemical reaction occurs within the cell.
When agonist leaves the binding site it deactivates the receptor.
• SABA: Short acting Beta Adrenergic
• Ex: Albuterol, Xopenex (for quick relief)
• LABA: Long acting Beta Adrenergic
• Ex: Serevent, Foradil, Brovana (preventative)
• Antagonist: any drug that binds to a receptor and prevents the activation of the
receptor
• Can be called competitive antagonist; competes with the agonist for binding site.
• RT’s antagonist drug= Atrovent (short acting), Spiriva (long acting)
• Blocks Ach from attaching to Musacarinic receptors
Definitions
• Chemical Antagonist: binds directly with an agonist, instead of the
receptor site, to prevent the agonist from reaching the receptor. Ex:
Heparin
• Absorbed: drug must be able to absorb into the body to work
• Delivery: Must be able to get to intended site to work; gut, intestines,
liver, blood…then to site of action
• Elimination: drugs must be eliminated at a reasonable rate. Affected
by kidney or liver problems
• Synergism the interaction of elements that when combined produce a total effect that is greater than
the sum of the individual elements, contributions, etc.
Definitions
• Action (mode of action, intended drug effect)
• Side effect (not intended effect, nausea/tachycardia…)
• Half life time required for concentration of a drug in the body to decrease by 50%. Half-life also represents
the time necessary to reach steady state or to decline from steady state after a change
• Tolerance decrease in susceptibility to the effects of a drug due to its continued administration.
• Tachyphylaxis rapid decrease in response to a drug after administration of a few doses. Initial drug
response cannot be restored by an increase in dose
• Potentiation The action of a substance, at a dose that does not itself have an adverse action, in
enhancing the effect of another substance
Definitions
• Anticholinergic actions
• inhibition of parasympathetic response manifested by dry mouth,
decreased peristalsis, constipation, blurred vision, and urinary retention.
• Bioavailability
• fraction of active drug that reaches its action sites after administration by
any route. Following an IV dose, bioavailability is 100%; however, such
factors as first-pass effect, enterohepatic cycling, and biotransformation
reduce bioavailability of an orally administered drug.
• cholinergic response
• stimulation of the parasympathetic response manifested by diaphoresis,
salivation, abdominal cramps, diarrhea, nausea, bronchoconstriction and
vomiting
Pharmacokinetic Phase
• Describes the time course and disposition of a drug in the body based
upon absorption, distribution, metabolism, and elimination and the
effects and routes of excretion of the metabolites of the drug
Pharmacokinetic Phase
• Ionized drugs have minimal side effects generally; non-ionized
drugs have greater side effects
Pharmacodynamic Phase
• Describes the mechanism of action of a drug (how it actually
works in the patients body)
• Effects are caused by combining a drug with a matching
receptor
Neurotransmission
• Neuron: basic cell of the nervous system, provide instant method of
cellular communication
• Don’t confuse nerve with neuron, nerve is a collection of neuron axon
fibers
• The signals in nerves can run both ways
• Efferent (out)
• Afferent (in)