# Diffusion

Describe Dalton's Law--the law of partial pressures

the total pressure exerted by a mixture of gases is equal to the sum of the pressures exerted independently by each gas in the mixture.

Explain how Dalton's law relates to the partial pressure of atmospheric gases

In addition, the pressure exerted by each gas--its partial pressure--is directly proportional to the percentage of that gas in the gas mixture. The pressure produced by a particular gas is completely unaffected by the presence of another gas. Each gas in

Identify the % and partial pressure of the gases that compose the barometric pressure:
Nitrogen

Atmospheric PN2 =0.7808 x 760 = 593.408 mm Hg

Identify the % and partial pressure of the gases that compose the barometric pressure:
Oxygen

Atmospheric PO2 = 0.21 x 760 = 159.6 mm Hg

Identify the % and partial pressure of the gases that compose the barometric pressure:
Argon

Atmospheric PAr = 0.0093 x 760 = 7.068 mm Hg

Identify the % and partial pressure of the gases that compose the barometric pressure:
Carbon Dioxide

Atmospheric PCO2 = 0.0003 x 760 = .228 mm Hg

Differentiate between pressure gradients and diffusion gradients

pressure gradient: the movement of gas from an area of high pressure (high concentration) to an area of low pressure (low concentration).
-The primary mechanism responsible for moving air in and out of the lungs during ventilation.
-during ventilation alw

Identify the partial pressure of the gases in the air, alveoli, and blood:
Oxygen (Po)

Dry Air
159.0
Alveolar Gas
100.0
Arterial Blood
95.0
Venous Blood
40.0

Identify the partial pressure of the gases in the air, alveoli, and blood:
Carbon dioxide (Pco)

Dry Air
0.2
Alveolar Gas
40.0
Arterial Blood
40.0
Venous Blood
46.0

Identify the partial pressure of the gases in the air, alveoli, and blood:
Water (PH2O) vapor

Dry Air
0.0
Alveolar Gas
47.0
Arterial Blood
47.0
Venous Blood
47.0

Identify the partial pressure of the gases in the air, alveoli, and blood:
Nitrogen (PN)

Dry Air
600.8
Alveolar Gas
573.0
Arterial Blood
573.0
Venous Blood
573.0

Calculate the ideal alveolar gas equation

The alveolar O2 tension (PAO2)
PAO2 = [PB-PH2O] FIO2 -PaCO2 (1.25) or PAO2 = [PB-PH2O] FIO2 - PaCO2 / 0.8
PAO2 is the partial pressure of oxygen in the alveoli
PB is the barometric pressure
PH2O is the partial pressure of water vapor in the alveoli (PH2O

Name the nine major structures of the alveolar-capillary membrane through which a gas molecule must diffuse

1. the liquid lining the intra-alveolar membrane
2. the alveolar epithelial cell
3. the basement membrane of the alveolar epithelial cell
4. loose connective tissue (the interstitial space)
5. the basement membrane of the capillary endothelium
6. the capi

Describe how oxygen and carbon dioxide normally diffuse across the alveolar-capillary membrane

The venous blood entering the alveolar-capillary system has an average O2 tension (Pvo2) of 40 torr and an average CO2 tension (Pvco2) of 46 torr. As blood passes through the capillary, the average alveolaroxygen tension (PAo2) is about 100 torr, and the

Describe the clinical connection associated with pulmonary disorders that increase the alveolar-capillary thickness

Disorders that cause the alveolar-capillary thickness to increase; pulmonary edema, pneumonia, interstitial lung diseases( scleroderma, sarcoidosis,or Goodpasture's syndrome), acute respiratory distress syndrome (ARDS), and respiratory distress syndrome (

Explain how Fick's Law relates to gas diffusion

The law states that the rate of gas transfer across a sheet of tissue is directly proportional to the surface area of the tissue, to the diffusion constants and to the difference in partial pressure of the gas between the two sides of the tissue, and it i

Describe how the following relate to the diffusion constants in Fick's law:
Henry's Law

Gardenhire's slide:
Amount of gas that dissolves in a liquid is proportional to the partial P of the gas.
Solubility coefficient @ 37�C:
O2 = 0.024 ml/mmHg/ml H2O
CO2 = 0.59 ml/mmHg/ml H2O
24:1
Textbook:
the amount of a gas that dissolves in a liquid at a

Describe how the following relate to the diffusion constants in Fick's law:
Graham's Law

states that the rate of diffusion of a gas through a liquid is;
1. directly proportiaonal to the solubility coefficient of the gas
2. indirectly proportional to the square root of the gram-molecular weight (GWM) of the gas.
The relative rates of diffusion

Describe the clinical connection associated with hyperbaric oxygen therapy and the clinical application of Henry's Law

Hyperbaric Oxygen Therapy (HBOT) also known as hyperbaric medicine. Is the therapeutic application of oxygen at pressures greater than 1 atm. A patient receiving HBOT is placed in a sealed hyperbaric chamber and exposed to selected oxygen concentration at

Describe the clinical connection associated with oxygen toxicity

can deveolp within 24 hours in response to high partial pressures of inspired O2 (Po2), and with longer exposure times to inspired oxygen concentrations (FIo2) above 0.50. The higher the inspired Po2 and the longer the exposure, the more likely oxygen tox

Describe the clinical connection association with respiratory disorders that decrease the alveolar surface area

A # of respiratory disorders can drastically reduce the alveolar surface area ("A" component in Fick's law). Emphysema breaks down the walls of adjacent alveoli and pulmonary capillaries, the alveoli merge together into large air sacs (bullae). Emphysema

Define perfusion limited, and explain how it relates to a gas such as nitrous oxide

Perfusion means that the transfer of gas across the alveolar wall is a function of the amount of blood that flows past the alveoli.
N2O relation:
When N2O moves across the alveolar wall and into the blood, it does not chemically combine with hemoglobin. T

Define diffusion limited, and explain how it relates to a gas such as carbon monoxide

means that the movement of gas across the alveolar wall is a function of the integrity of the alveolar-capillary membrane itself.
Carbon monoxide relation:
When CO moves across the alveolar wall and into the blood, it rapidly enters the RBCs and tightly b

Describe how oxygen can be classified as perfusion or diffusion limited

Perfusion:
When O2 diffuses across the alveolar wall and into the blood, it enters the RBCx and combines with Hb--but not with the eagerness as CO. Hb quickly becomes saturated with O2 and once this occurs, O2 in the plasma can no longer enter the RBCs. T

Describe the clinical connection associated with why a decreased DLCO is a classic diagnostic sign of emphysema

The S/S associated with emphysema appear very similar to other COPD. The classic pulmonary function diagnostic test that verifies that a patient has emphysema is a decreased DLCO. This is because of the alveolar-capillary destruction (decreased alveolar s

Pressure Gradient vs Gas Diffusion-In reference to the alveoli

the alveoli by means of a pressure gradient, or the alveoli by way of the pulmonary capillary blood flow. each individual gas can move according to its own diffusion gradient. 2 different gases (O2 & CO2) can move (diffuse) in opposite directions based on

Water Vapor Pressure

Alveolar gas is 100% humidified @ body temperature.
Absolute humidity 44 mg/dL
Water vapor P 47 mmHg

Factors that affect Measured DLCO:
Age

The DLCO progressively increases between birth and 20 years of age. After age 20, the DLCO decreases as a result of the normal anatomic alterations of the lungs that reduce the overall alveolar-capillary surface area.

Factors that affect Measured DLCO:
Lung volume

The DLCO is directly related to an individuals lung size. Thus greater the subject's lung volume, the greater the DLCO.

Factors that affect Measured DLCO:
Body size

As a general rule, the DLCO increases with body size. The size of the lungs is directly related to the subject's ideal body size. Thus the larger the subject, the greater the lung size and the higher the DLCO.

Factors that affect Measured DLCO:
Body position

The DLCO is about 15% to 20% greater when the individual is in the supine position, compared with the upright position.

Factors that affect Measured DLCO:
Exercise

The DLCO increases with exercise. This is most likely because of the increase cardiac output, and capillary recruitment and distention, associated with exercise.

Factors that affect Measured DLCO:
Alveolar PO2 (PAO2)

The DLCO decreases in response to a high PAO2. This is because O2 and CO both compete for the same hemoglobin sites.

Factors that affect Measured DLCO:
Hemoglobin concentration

Anemia: Patients with low hemoglobin content have a low CO-carrying capacity and therefore a low DLCO value.
Polycythemia: Patients with high hemoglobin content have a high CO-carrying capacity and therefore a high DLCO value.

Factors that affect Measured DLCO:
Carboxyhemoglobin

Individuals who already have CO bound to their hemoglobin (smokers or fire fighters overcome by smoke inhalation) generate a "back pressure" to alveolar PCO. This condition decreases the pressure gradient between the alveolar CO and the blood CO, which in

Summary O2 cascade

Dry gas 159 mmHg
Conducting airways149
End exp gas 114
Alveolar 101
Arterial blood 97
Mean systemic Capillary pressure 40
Cellular cytoplasm <40
Mitochondria 3-23
Reason for change
Addition of water vapor
Mixing of deadspace
Addition of CO2
Intrapulmonary

Temp Conversion (C to F)

F = [C x 9 / 5] + 32

Temp Conversion (F to C)

C = (F - 32) x 5 / 9

Temp Conversion (C to K)

K= C + 273

IDEAL GAS LAW

PV=nRT
P= Pressure
V= Volume
n= Number of molecules present
R= Gas constant (.08)
T= Temperature in Kelvin scale
If n remains constant:
P1xV1 = P2 x V2
T1 T2

BOYLE'S LAW

(P1 x V1 = P2 x V2)
If T remains constant, P will vary inversely to V.
Example:
Container with 200 mL
P of 10 cm H2O.
Volume is reduced 50%
New P= 20 cmH2O
P2 = P1 x V1 = 10 cmH2O x 200 mL = 20 cmH2O
V2 100 mL

CHARLES' LAW

(V1 / T2 = V2 / T2)
If P remains constant, V will vary proportional to T.
Example:
Balloon with 3L
T increased from 250K to 300K.
Volume is increased to 3.6L
V2 = V1 x T2 = 3L x 300K = 3.6L
T1 250K

GAY-LUSSAC'S LAW

(P1 / T1 = P2 / T2)
If V remains constant, P will vary proportional to T.
Example:
Container with 50 cmH2O
T increased from 275K to 375K.
Pressure in the container is increased to 68 cmH2O
P2 = P1 x T2 = 50 cmH2O x 375K = 68 cm H2O
T1 275K

stroke volume (SV)

The amount of blood pumped by the left ventricle of the heart in one contraction. The stroke volume is not all the blood contained in the left ventricle; normally, only about two-thirds of the blood in the ventricle is expelled with each beat. Together wi

Other Lung Disorders associated with decreased DLCO value

Lung Abnormality
hyperinflation and decreased DLCO
DLCO and FRC
decreased DLCO
increased FRC
Pulmonary Disorder
Emphysema, etc. (COPD)
Lung Abnormality
hypoinflation and decreased DLCO
DLCO and FRC
decreased DLCO
decreased FRC
Pulmonary Disorder
restricti

Clinical Application of Fick's Law

*The area (A) component of the law is verified in that a decreased alveolar surface area ( caused by alveolar collapse or alveolar fluid) decreases the ability of O2 to enter the pulmonary capillary blood.
*The P1-P2 portion of the law is confirmed in tha

Water Vapor Pressure (PH2O)

47 torr

absolute humidity

44 mg/L

Alveolar CO2 Pressure (PACO2)

40 torr

Partial Pressure of Oxygen in the Alveoli

100 torr

Partial Pressure of Oxygen in the Atmosphere

159 torr

average O2 tension (Pvo2)

40 torr

average CO2 tension (Pvco2)

46 torr

average alveolar O2 tension (PAO2)

100 torr

average alveolar CO2 tension (PACO2)

40 torr

O2 is _____ limited (either diffusion or perfusion)

perfusion limited, which means the gas transfer from alveoli to blood can only be improved by increasing blood flow

CO2 is _____ limitied (either diffusion of perfusion)

diffusion limited so the transfer of gases can only be improved by improving diffusion parameters, such as the driving pressure of gas

diffusion rate for a gas in a gas is _____ with increased molecular weight (faster or slower)

slower

Why can't we use the molecular weight stuff in our body like in the last question.

Because gas is dissolved in liquid in the body so you have to take into effect solubility. CO2 is more soluble than oxygen so it diffuses faster, even though it has a higher molecular weight than oxygen

give the equation for Fick's law of diffusion

volume of air tranferred per unit time= DAP/X
d is diffusion coefficient (found by solubility/square root of MW)
A is surface area
P is change in pressure
X is length or thickness of a membrane

so according to Fick's law of diffusion, what are some factors that can affect diffusion?

diffusion coefficient (which has solubility and mw involved)
surface area
change in pressure
and length or thickness or a membrane

Tell whether CO and Nitrous oxide are diffusion or perfusion limited

CO is diffusion limited (CO2 is as well): you don't reach an equilibrium of Alveolar and arterial
Nitrous oxide is perfusion limited (and so is O2)

how do you improve gas transfer if something is perfusion limited?

increase the blood flow (ex: increase CO)

how do you improve diffusion rate if something is diffusion limited?

increase the partial pressure of alveolar gas (think back to Fick's law of diffusion and use those parameters.. though you cant cahnge SA, etc so that's why you change the pressure)

so oxygen is perfusion limited. Can it ever become diffusion limited?

yes. With fibrosis, equilibration takes longer and might not equilibrate if thick enough and get O2 to be diffusion limited. Also, at high altitudes people with fibrosis get worse because there is less driving pressure

can someone completely healthy have their oxygen become diffusion limited?

yes. If they exercise at high altitude

what is the equation for diffusion capacity (DL)?

DL= V/PA-Pa

when DLCO is increased, diffusion of the respiratory gases is ______. When DLCO is decreased, diffusion of the respiratory gases is ______

increased
decreased.
Use this because it's easier to determine the DLCO since the PaCO is O (extremely diffusion limited)

is DLCO higher or lower when supine?

higher

DLCO is _____ to body size

proportional

does DLCO go up or down with exercise? why?

it goes up bc recruitment of more blood vessels increases the SA

does DL go up or down with emphysema? Why?

down bc the decrease in SA

how do fibrosis effect DL?

it effects the bottom of the equation at the thickness. you can't diffuse across a thicker membrane as easily

if you have an increase in hemoglobin, how does that effect DL?

you have an increase in DL because the hemoglobin acts to pull out O2

somebody at sea level breaths a mixture of 0.1% CO. The uptake of CO was 28 mL/min. What is the lung's diffusion capacity of CO (DLCO)?

You have to do a few steps to get to being able to answer this.
First, pressure at sea level is 760. Subtract 50 from that for the water vapor pressure to give for 710.. Multiply 710 * 0.001 and it equals 0.71mm Hg. This is the pressure of CO.
To get DLCO

in perfusion limited O2 exchange, is the PO2 at the end of the pulmonary capillary closer to PAO2 of PVO2?

PAO2

List factors influencing states of matter

gas laws.Pressue, volume, temperature
Boyles, Charles, Gay Lussac, and Dalton

What is melting point?

When a solid turns into a liquid

What is boiling point?

When a liguid turns into a gas
(212 F, 100 C, 373 K)

What is sublimation?

Solid skips the liquid phase and go into the a gas stage

What is evaporation

Liquid goes to a gas

What is Water Vapor

a measure of forces exerted when molecules hit surface and escape (true humidity)

What is Critical Pressure

The pressure need ti change a gas to liquid
(H2O-218 atm CP)

What is critical temperature

Gas that cannot be change back into a liquid
For Oxygen:
-118.8 C
-181 F
49.7 Atm

Describe how gas pressures are measured

You measure the tension and pressure that exerts
Force/Unit Area= Pressure (Pascal) Increase altitudes decrease pressure (Barometer)

Describe what effects gas pressures:
Daltons Law

P1+P2+P3=(Total Pressure)Pt

List the component gases in the atm

N=78%
O2=21%
CO2=.03%
Ar=93%

What are some characteristics of Oxygen?

no color, odorless, no taste
Slightly paramagnetic
Supports combustion

What is boyles law and what type of relationship does it have

P1V1=P2V2
Inverse relationship
example: Breathing

What type of relationship is Daltons Law

Direct relationship

What is Guy-Lussac Law and what type of relationship

P1/T1=P2/T2
Direct relationship
Example: Liquid oxygen turning into a gas-passive pressure , boiling water with a lid

What is Charles Law and what type of relationship

V1/T1=P2/T2
Direect relationship
Example: hot air balloon

What is ficks law of diffusion?

V=(A)(D)(P1-P2)/T
A- surface area
D- contants of diffusion
P1-P2: pressure gradient
T- membrane thickness

how does gas flow?

From high pressure to low pressure

What is the Alveolar Air Equation?

PAO2=(PB-PH2O) x FiO2) - (PCO2 x 1.25)

What is the formula to convert F to C

F(9/5 x C) + 32
Rule of thumb F should always be bigger than C

What is the formula to convert K to C

K=C+273

What is the formula to convert C to F

C=5/9 (F-32)

What factors affect diffusion and give an example of each

membrane thickness-fluid/mucus
Surface area-atelectasis
pressure gradient- BP

What does it mean when an object has potential energy

energy position or stored energy

What is kinetic energy

energy of motion.

Fick's law of diffusion

Amount of gas moving across a sheet of tissue is proportional to the area of the sheet, the gas diffusion constant, and difference in partial pressure, and inversely promotional to thickness

Diffusion constant for a gas

Proportional to gas solubility, but inversely proportional to the square root of its molecular weight (e.g. CO diffuses 20x more rapidly than O2 because of its much higher solubility, similar molecular weight)

Describe diffusion limited gas

E.g. CO: diffuses rapidly and tightly bonds to Hb such that as the cell moves through the capillary, the partial pressure of CO in blood hardly changes and CO continues to diffuse. Therefore amount of CO in blood is limited by diffusion properties of bloo

Describe perfusion limited gas

e.g. N2O: no binding with Hb, so partial pressure of N2 in blood rapidly reaches equilibrium. Therefore the amount of N2 in blood is limited by available blood flow and not by diffusion properties of blood-gas barrier --> perfusion limited

Is O2 diffusion limited or perfusion limited?

Under normal circumstances: perfusion limited (capillary partial pressure of O2 reaches equilibrium when RBC is about 1/3 of the way along the capillary); if diseased such that diffusion properties of the lung are impaired, becomes diffusion limited (bloo

PO2 gradient between alveoli and RBC under normal conditions

alveolar PO2: 100mm Hg; RBC PO2: 40mmHg; gives gradient 60 mm Hg

Equation for diffusing capacity of CO

DLCO = volume of CO transferred per unit time / alveolar partial pressure of CO (derived from Fick diffusion equation)

Describe single-breath method for measuring DLCO

Single inspiration/breathhold of dilute CO mixture; rate of disappearance of CO and alveolar partial pressure of CO are measured and DLCO calculated

Normal DLCO

25 mL/min/mmHg

Does DLCO increase or decrease with exercise?

Increases 2-3x, because of recruitment and distension of pulmonary capillaries

Diffusion resistance

diffusion of O2 through blood-gas barrier + reaction of O2 with Hb (the two are probably about the same)

Why is the reaction rate of O2 with Hb a limiting factor in oxygenation?

Reaction rate of O2 is fast, but there is so little time available in the capillary.

Why does changing PO2 affect reaction rate of CO?

High O2 mixture: O2 competes with CO for Hb, so measured DLCO is reduced; can be used to identify the separate contributions of the diffusion properties of blood-gas barrier and volume of capillary blood

Carbon dioxide transfer into blood: how fast? Diffusion or perfusion limited?

20x faster than O2 because of higher solubility of CO2; probably not diffusion limited (but reaction of CO2 with blood is complex and there is some uncertainty)