Applied Physiology &
Chemistry
RT 210
Unit B
Mechanics of Ventilation:
Ventilation & Respiration




Ventilation is air movement in and out of the lungs
to allow external respiration to occur
Respiration is gas exchange across a permeable
cellular membrane
External respiration is gas exchange between
alveolar gas (air) and capillaries (blood)
Internal respiration is gas exchange between
capillaries and the tissues
The Lung - Thorax Relationship

Two opposing forces



Lungs tend to collapse due to elasticity
Chest wall tends to spring out
Linked together by the pleura




Negative pressure -4 to -5 cm H2O
Parietal pleura lines chest wall
Visceral pleura covers lung
Potential space between with small amount of
lubricant/pleural fluid between layers
Normal ventilation pressures

Inspiration, (intrapleural = -10 cm H2O,
intrapulmonary -3 cm H2O)





Diaphragm contracts and flattens
Chest cavity expands
Negative intrapulmonary pressure
Negative transairway pressure
Gas flows in through the mouth
Normal ventilation pressures

Expiration, (intrapleural = -5 cm H2O,
intrapulmonary = +3 cm H2O)




Diaphragm relaxes
Chest cavity recoils and decreases in size
Slight positive intrapulmonary pressure
Gas flows out through the mouth
Physics of Ventilation
Law of Laplace

P = 2 ST/r
surface tension tends to collapse alveoli
Surfactant allows different sized alveoli to be
connected without smaller emptying into the larger
alveoli and collapsing






Phospholipid
Decreases surface tension of the alveoli
Allows critical volume to be variable from alveoli to alveoli
Compliance-measures
dispensability of the lung

Compliance of the Lung = change in
volume divided by change in pressure
CL 
 volume (liters )
 pressure (cm H 2 O)
Compliance-measures
dispensability of the lung

Total compliance = lung and thorax (lung is
not measured out of thorax)



Pulmonary compliance = 0.2L/cm H2O
Thoracic compliance = 0.2L/cm H2O
Total compliance = 0.1 L/cm H2O
1
C total

1
C pulmonary

1
C thoracic
Compliance-measures
dispensability of the lung
Dynamic

volume
peak pressure
Pressure is peak pressure during gas flow
Static 
volume
plateau pressure
Compliance-measures
dispensability of the lung

Decreased or less compliance seen in:








Pulmonary consolidation
Pulmonary edema
Pneumothorax
Abdominal distension
ARDS
Pulmonary fibrosis
Thoracic deformities
Complete airway obstruction
Compliance-measures
dispensability of the lung

Compliance increases



Alveolar distension
Alveolar septal defect
Obstructive disorders-CBABE






C = Cystic Fibrosis
B = Bronchitis
A = Asthma
B = Bronchiectasis
E = Emphysema
Compliance is inversely related to elastance

Elastance is the property of resisting deformation
Resistance

Resistance =
Pr essure
Flow
Resistance

Laminar


Poiseuille’s Law states that flow rate varies
directly with radius of a tube
Small changes in airway radius will dramatically
affect flow and resistance


½ decrease in diameter increases resistance by 16
times
Turbulent (non laminar or eddy flow)


The higher the flow the more resistance
Resistance is also directly proportional to gas density
Resistance

Transitional


Tracheobronchial tree has both laminar and
turbulent flow caused in part by the directional
changes in the conductive airway
Reynold’s number



Less than 2000 is laminar flow
2000-4000 is laminar and turbulent or mixed flow
Greater than 4000 is turbulent flow
Resistance




Viscosity
Pressure Gradient
Bernoulli’s Principle
Coanda Effect
Lung Volumes


Relate to lung/thorax relationship,
compliance and surface tension
Four volumes and four capacities

IRV - Inspiratory Reserve Volume



Maximum inhalation following quiet inhalation
Normally 3.1 L
VT - Tidal Volume


Volume inspired or expired during quiet breathing
Normally 0.5L
Lung Volumes

Four volumes and four capacities (cont)

ERV - Expiratory Reserve Volume



Maximum exhalation following quiet exhalation
Normally 1.2L
RV - Residual Volume


Gas remaining in lung after maximum exhalation
Normally 1.2L
Lung Volumes

Capacities - consist of 2 or more volumes or
capacities

IC - Inspiratory Capacity




Made of IRV and VT
Maximum inhalation following quiet exhalation
Normally 3.6L
FRC - Functional Residual Capacity



Made of ERV and RV
Gas in lung following quiet exhalation
Normally 2.4L
Lung Volumes

Capacity (cont)

VC - Vital Capacity




Made of IRV, VT, and ERV
Maximum exhalation following a maximum inspiration
Normally 4.8L
TLC - Total Lung Capacity



Made of IRV, VT, ERV and RV
Gas in the lung following maximum inhalation
Normally 6L
FRC and Lung Compliance

FRC is most consistent volume - diaphragm at
rest






At FRC, equalization of opposing forces of pulmonary
and thoracic elasticity
As elasticity changes, FRC changes
At FRC, intrapleural pressure is normal -5 cm H2O
At FRC, intrapulmonary pressure equals ambient
pressure
With an increase in compliance, (decrease elasticity),
an increase in ease of inspiration but difficulty in
expiration
Decrease in compliance, decrease the ease of
inspiration
Classification of Ventilation

VE = Minute Ventilation



The amount of gas moved in 1 minute
Calculated by VT times (*) f
Can be measured by a respirometer





Vane- Draeger, Wright
Volume bellows spirometer
Venticomp bag
Vortex principle- Boum’s LS 75
Use a respirometer with a filter attached to
demonstrate measuring VE
Classification of Ventilation

VD= Dead space


Part of min. ventilation is "wasted", does not
reach alveoli where external respiration occurs
Anatomical (VDanat)


Alveolar (VDalv)


Fills space in the conductive airways
Alveoli that are not perfusion
Physiologic (VDphys)

All dead space combination of VDanat and VDalv
Classification of Ventilation

Dead space (cont)

Mechanical



Added dead space
Normally 1 cc per pound ideal weight (approx.
150cc)
Volume rebreathed
Classification of Ventilation

VA = Alveolar ventilation



Gas in perfused alveoli
Participates in external respiration
VA= (VT - VD)
Classification of Ventilation

Terms relating to dead space

Normal ventilation


Hypoventilation




Adequate ventilation to meet metabolic needs
Decreased alveolar ventilation
Can be caused by increased VD or decreased VT
Ventilation less than that necessary to meet metabolic
needs; signified by a PCO2 greater than 45 mmHg in
the arterial blood
Hyperventilation



Increased alveolar ventilation
Caused by decreased VD or increased VT
Ventilation more than necessary to meet metabolic
needs, signified by a PCO2 less than 35 mmHg in the
arterial blood
Ventilation and Perfusion

Ventilation = alveolar minute ventilation


VA = (VT - VD)* f
Perfusion = blood flow to the tissues
Ventilation and Perfusion

External respiration = gas exchange
between the alveoli and capillaries



Carbon dioxide leaves blood
Oxygen enters the blood
Respiratory Quotient -unequal exchange of CO2
produced vs. oxygen uptake or utilization
4 vol / CO2
RQ 
5 vol / O2

or
200ml CO2
 0.8
250ml O2
200 ml CO2 produced by 250 ml O2 used due to normal
metabolism in the Kreb’s cycle (CARC page 154 & 389).
Gas exchange unit

Normal unit


Dead space unit


ventilation without or in excess of perfusion
Shunt


Alveoli with capillary—relationship between
ventilation and gas flow are relatively equal
Perfusion without or in excess of ventilation
Silent unit

No perfusion, no ventilation
Regional Differences in Ventilation
& Perfusion
More ventilation to the bases


4 times more ventilation to bases than apices


Due to gravity’s effect on pleural pressures
On inspiration the transpulmonary pressure is greater at
the bases
More perfusion to bases



Due to gravity
20 times more perfusion to bases than apices
Ventilation/Perfusion ratio (V/Q)



V/Q = 4L alveolar minute volume 5L minute cardiac
output
Overall for the lung is 4:5 or 0.8
Regional Differences in Ventilation
& Perfusion

Diffusion





Whole Body Diffuision Gradients
Determinants of Alveolar Gas Tensions
Mechanism of Diffusion
Systemic Diffusion Gradients
Abnormalities


Impaired oxygen Delivery
Impaired Carbon Dioxide Removal
Shunting


Unoxygenated blood entering the left side of
the heart
Anatomical shunt

Normally 2-5% of cardiac output



Bronchial veins drains bronchial circulation
Pleural veins drains pleural circulation

Thebesian veins drains heart circulation
Absolute capillary shunt



Alveoli perfused but not ventilated
“True Shunt”
Refractory to O2 therapy
Shunting

Relative capillary shunt



V/Q mismatch
Areas where perfusion is in excess of
ventilation
Physiological shunt


Sum of anatomical, absolute and relative shunts
Causes


Decrease in ventilation
An increase in perfusion (increased CO)
Dead Space


"Wasted" ventilation
Types

Anatomical





Alveolar: Alveoli that have decreased perfusion
Physiological: Sum of anatomical and alveolar
Mechanical – added dead space
Causes



Conducting airways in tracheobronchial tree
An increase in ventilation
A decrease in perfusion (decreased CO)
Effect

Increased VD will decrease VA if VE remains constant
Effects of exercise & of high
pressure environs

Exercise


Increases CO2 production and O2
consumption
Aerobic versus anaerobic



Oxygen consumption correlates to alveolar
ventilation
At rest 250ml rises to 3500ml/minute (untrained)
to 5000ml/minute (trained athlete)
PaO2, PaCO2 and pH remain constant
Effects of exercise & of high
pressure environs

Exercise (cont)

Circulation






Increased sympathetic impulses stimulates heart rate
and perfusion to working muscles
Frank-Starling mechanism
Maximal heart rate
Muscle Work, Oxygen Consumption, and Cardiac
Output Interrelationships
The Training Influence
Body Temperature: Cutaneous Blood Flow
Relationship
Effects of exercise & of high
pressure environs
High altitude



Acclimatization
Major cardiopulmonary responses




increased alveolar ventilation via peripheral chemoreceptor
stimulation
Secondary polycythemia, increased RBC production due to
low oxygen levels
Development of respiratory alkalemia, due to the increased
alveolar ventilation and carbon dioxide elimination
Increased oxygen diffusion capacity in native high dwellers,
due to increased lung size
Effects of exercise & of high
pressure environs

Major cardiopulmonary responses (cont)




Increased alveolar arterial oxygen difference
Improved ventilation perfusion ratio
Increased cardiac output of non-acclimatized individuals
Increased pulmonary hypertension as a result of
hypoxic vasoconstriction
Solutions






Definition
Concentration
Osmotic pressure
Quantifying solute content and activity
Calculating solute content
Quantitative classification of solutions
Electrolytic Activity and Acid Base
Balance


Characteristics of acids, bases, and salts
Designation of acidity and alkalinity
Body Fluids and Electrolytes


Fluids
Electrolytes
Blood Gases


Define
Kreb’s [TCA] Cycle
Oxygen Transport
Dissolved


Henry's Law - weight of gas dissolving in
liquid is proportional to the partial pressure
of a gas

Bunsen solubility coefficient for O2



0.023ml of O2 can be dissolved in 1ml of plasma at
37°C and 760mmHg PO2
This allows us to determine the amount of O2
(expressed in ml) dissolved in 1ml of plasma using the
formula: 0.003 * PaO2
(ex: PaO2 of 100 mmHg = 0.3ml of dissolved O2 in
plasma)
Oxygen Transport

Graham's Law – rate of diffusion of a gas is
directly proportional to its solubility
coefficient and inversely proportional to the
square root of its density



CO2 is 20 times more diffusible than O2
CO is 200 times more diffusible than O2
Hemoglobin’s affinity for CO is 200 times more
than for oxygen.
Oxygen Transport

Combined with hemoglobin




Carries the most oxygen to the tissues
Doesn't exert a gas pressure
Calculate 1.34 * Hb * SaO2
Total oxygen content is sum of dissolved and
combined
Oxygen Transport

Oxyhemoglobin dissociation curve

Curve is sigmoidal due to Hb affinity for O2
at each of 4 binding sites



Last site has less affinity than 2nd & 3rd
In the steep portion minimal changes in PO2 will
cause drastic changes in saturation and total O2
content
P50 is where Hb is 50% saturated with O2 and is
normally a PaO2 of 27mm/Hg
Oxygen Transport
Oxyhemoglobin dissociation curve (cont)


A shift to right causes a decreased affinity
for O2, resulting in decreased saturation but
increased O2 to tissues





Factors causing shift to the right
Increased PCO2
Increased H+ (decreased pH)
Increased 2, 3 DPG
Increased temperature
Oxygen Transport
Oxyhemoglobin dissociation curve (cont)


A shift to the left causes increased affinity
for O2, resulting in increased saturation but
decreased O2 to the tissues





Factors causing shift to the left
Decreased PCO2
Decreased H+ (increased pH)
Decreased temperature
Decreased 2, 3, DPG
Oxygen Transport
Oxyhemoglobin dissociation curve (cont)


Bohr effect – the effect of H+ or CO2 on Hb
affinity for O2

At lungs – PCO2 is low




Shifts curve to left
Increased affinity for O2
pH increased in lungs causing shift to the left with an
uptake of oxygen into the blood
At tissues - PCO2 is high



Shifts curve to the right
Decreases affinity for O2
pH decreased in tissue causing shift to right releasing
oxygen to the tissue
Shift to Left
Shift to Right
(increased affinity) (decreased affinity)
H+ ( pH)
H+ ( pH)
PCO2
PCO2
Temperature
Temperature
2-3 DPG
2-3 DPG
P50 <27
P50 >27
↑ SaO2
↓ Sao2
Oxygen Transport

Total O2 content is determined by adding
the combined oxygen content with the
dissolved oxygen content

CaO2 = (0.003 * PaO2) + (1.34 * Hb *
SaO2)
Hypoxemia


Deficiency of oxygen in the arterial blood
Causes of hypoxemia

Decreased alveolar oxygen tension

Alveolar air equation
PAO2  F1O2 ( PBar  PH 2 O vapor) 
PaCO2
RQ
Hypoxemia

Causes of hypoxemia



Alveolar hypoventilation
Decreased hemoglobin saturation
Alveolar hypoventilation due to V/Q
abnormalities

Intrapulmonary shunting: blood going from right
to left heart without oxygenation
Hypoxemia

Responses to hypoxemia



Increased ventilation
Increased cardiac output
Types




Hypoxic
Anemic
Stagnant
Histotoxic
Hypoxia


Decreased oxygen to the tissues
Hypoxemic Hypoxia or Ambient Hypoxia


PaO2 decreased
Anemic Hypoxia or Hemic Hypoxia


Hb decreased
inability to accept O2 (CO poisoning)




Hb has 200 times more affinity for CO than O2
Normal HbCO is 0.5%
HbCO of 5-10% occurs after smoking
HbCO of 40-60% can cause death
Hypoxia

Stagnant Hypoxia or Circulatory Hypoxia


Histotoxic Hypoxia


Heart unable to deliver oxygenated blood to
tissues (low CO)
cells unable to accept or use oxygen (cyanide
poisoning)
Results


Anaerobic metabolism
Production of lactic acids is a by product of CO2
metabolism
Alveolar-Arterial Oxygen Difference
P(A-a)O2

Measurement of the pressure difference
between the alveoli and the arterial blood



In normal lungs O2 is readily transferred from
alveoli to blood and only a small PO2 difference
is present
Diseased lungs often have larger P(A-a)O2
because of diffusion defects
Has been used to estimate the percent
intrapulmonary shunt

On 100% O2, every 50 mmHg difference in P(A-a)O2
approximates a 2% shunt
Alveolar-Arterial Oxygen Difference
P(A-a)O2

An increase in P(A-a)O2 is strictly an
indication of respiratory defects in
oxygenation abilities


Most respiratory dysfunctions that produce
hypoxemia are accompanied by an increase in
P(A-a)O2
Normal value on room air is 10 to 15
mmHg
CO2 Transport

Carbon Dioxide


Produced from normal metabolism
The burning of glucose with O2 is carried in
plasma and in red blood cells
CO2 Transport
In plasma



Dissolved: approximately 8% of CO2
As Bicarbonate (HCO3):

CO2 + H2O form carbonic acid (H2CO3)
dissociates into bicarbonate and hydrogen ions
Equation

H2O + CO2 = H2CO3




H+ + HCO3¯
about 80% of C02 is transported as
bicarbonate
Attached to plasma proteins about 12%
CO2 Transport

In the red blood cells


Dissolved
As HCO3¯






HCO3¯ produced by hydrolysis of CO2
HCO3¯ diffuses out of cell
creates an electrical imbalance
Cl¯ enters the cell to bring balance
called the chloride shift or Hamburger phenomenon
Attached to the Hb molecule
CO2 Transport

Haldane Effect

The effect of O2 on CO2 transport


At the lungs, PO2 is increased & CO2 is unloaded
off Hb
At the tissues, PO2 is decreased & CO2 is loaded
on Hb
CO2 Transport

Terms relating to PaCO2

Hypocapnia or hyporcarbia


Hypercapnia or hypercarbia


CO2 below 35 mmHg
CO2 above 45 mmHg
Eucapnea

Normal CO2 (35-45 mmHg)
Buffer Systems (Acid Base Balance)
Purpose is to maintain the pH


Prevent rapid changes
Buffer systems


Open/Bicarbonate

Mainly the HCO3/H2CO3



Ventilatory
About 60%
Hb


Renal
About 30%
Buffer Systems (Acid Base Balance)
Closed/Noncarbonate


Blood



Intracellular
Phosphates, proteins, sulfates and ammonia
groups
Physiological roles of buffer systems


Bicarbonate
Noncarbonate
Henderson-Hasselbalch Equation
pH = pk + log




( HCO3 )
( H 2 CO3 )
pk = 6.10
normally HCO3¯= 24 mEq/L
normally H2CO3 = 1.2 mEq/L

HCO 3
20

H 2 CO3 1




log of 20 = 1.3
6.1 + 1.3 = 7.4 normal pH
10/1 = acidemia
30/1 = alkalemia
Normal Values (Arterial)
Absolute
pH
 PaCO2
 PaO2
 HCO3
 Base 0
 Hb
 O2 Sat
 O2 content

Range
7.4
7.35-7.45
40 mmHg
35-45
100 mmHg 80-100
24 mEq/L
22-26
0
+ or – 2
14 gm %
12-15
97.5 %
95 - 100%
20 volume % 18-20 volume %
Normal Values (Venous)
Absolute
pH
 PvCO2
 PvO2
 HCO3
 Base
 Hb
 O2 Sat
 O2 content

7.36
46
40
24
0
14
75
15 volume %
Acid Base Effects




Increased CO2 causes a decreased pH
Decreased CO2 causes an increased pH
Increased HCO3 causes an increased pH
Decreased HCO3 causes a decreased pH
Compensation

Kidneys




Excrete H+ which increase HCO3 to
compensate for an increased CO2
Excrete less H+ and more HCO3 to
compensate for decreased PCO2
May take 3 days to compensate
Excess Hydrogen Ion excretion & role of
urinary buffers
Compensation

Lungs


Increases CO2 to compensate for an
increased HCO3 (short term only)
Pharmacologically


Administer sodium bicarbonate (NaHCO3) to
increase pH
Administer ammonium chloride (NH3Cl) to
decrease pH
Interpretation

Method for interpretation




Categorize pH
Determine Respiratory Involvement
Determine Metabolic Involvement
Assess for Compensation
Interpretation
A. Values
pH PCO2 HCO3 B.E.
Respiratory Acidosis
1. Uncompensated
2. Partially Compensated
3. Compensated
Respiratory Alkalosis
4. Uncompensated
5. Partially Compensated
6. Compensated
Metabolic Acidosis
7. Uncompensated
8. Partially Compensated
9. Compensated
Metabolic Alkalosis
10. Uncompensated
11. Partially Compensated
12. Compensated
N
+
+
+
N
+
+
N
+
+
+
+
N
-
N
-
N
-
N
N
-
-
-
+
+
N
N
+
+
+
+
+
+
+
+
Interpretation
States


Respiratory Acidosis




Causes
Compensation
Correction
Respiratory Alkalosis





Causes
Clinical Signs
Compensation
Correction
Alveolar Hyperventilation Superimposed on Compensated
Respiratory Acidosis
Interpretation

Respiratory Acidosis












B.E.
+
+
+
N
+
+
N
+
+
Uncompensated
Partially Compensated
Compensated
+
+
N
-
N
-
N
-
Uncompensated
Partially Compensated
Compensated
N
N
-
-
-
Uncompensated
Partially Compensated
Compensated
+
+
N
N
+
+
+
+
+
+
+
+
Metabolic Alkalosis

HCO3
N
Metabolic Acidosis

PCO2
Uncompensated
Partially Compensated
Compensated
Respiratory Alkalosis

pH
Values
Interpretation
Metabolic Acidosis






Causes
Anion Gap
Compensation
Symptoms
Correction
Metabolic Alkalosis




Causes
Compensation
Correction
Metabolic Acid-Base Indicators



Standard Bicarbonate
Base Excess
Assessment of Hypoxemia

On room air with normal Hb and under
60 years old (PaO2 above 80mmHg = no
hypoxemia)




Normal = 80-100mmhg
Mild hypoxemia = PaO2 = 60-79mmHg
Moderate hypoxemia = PaO2 = 40-59mmHg
Severe hypoxemia PaO2 = less than
40mmHg
Assessment of Hypoxemia
O2 content




Mild hypoxemia 15-17 volume % (17)
Moderate hypoxemia = 12-14 volume % (15)
Severe hypoxemia = 12 volume % (12)
Over 60 years old



Subtract 1 mmHg for every year over 60
Severe hypoxemia is still PaO2 <40mmHg
*Review Table 7-2 CARC p122 “Relationship between Age and Normal
Predicted PaCO2
Assessment of Hypoxemia

Patients with abnormal Hb

Calculate total O2 content




(Hb * 1.34 * SaO2) + (0. 003 * PaO2)
Mild hypoxemia = CaO2 17 volume %
Moderate hypoxemia = CaO2 15 volume %
Severe hypoxemia = CaO2 12 volume %
Other Oxygenation Assessments






Oxygen Saturation (SaO2)
Arterial Oxygen Content (CaO2)
Alveolar-Arterial Oxygen Difference [P(A-a)O2]
Partial Pressure of Oxygen in Mixed Venous
Blood (PvO2)
Arteriovenous Oxygen Content Difference C(av)O2
Carboxyhemoglobin (HbCO)
Assessment of Acid Base Balance




Hydrogen Ion Concentration (pH)
Partial Pressure of Arterial Carbon
Dioxide (PaCO2)
Arterial Blood Bicarbonate (HCO3-)
Base Excess & Base Deficit
Control of Ventilation
Ventilation



Under control of autonomic or involuntary nervous
system
Is controlled by central and peripheral
chemoreceptors
Central chemoreceptors





Influenced by contents of the cerebrospinal fluid
(CSF)
CO2 diffuses freely in CSF
Increased CO2 in CSF will cause increased H+
Causes a stimulation of the inspiratory center
Control of Ventilation
Central chemoreceptors (cont)


Areas of the medullary center

Apneustic or pontine center


Allows deep inspiration
Pneumontaxic center



Limits inspiration from inspiration center
Causes decreased rate of time
Hering-Breuer (stretch receptors)

Inflation reflex message carried to brain via Vagus nerve

Located in smooth muscle of both large and small
airways

Limits inspiration
Peripheral Chemoreceptors
Carotid bodies




Responds to hypoxemia
Increases ventilation
Located in the bifurcations of the common carotid
arteries
Aortic bodies




Responds to hypoxemia
Usually effects heart more than ventilation
Located in the aortic arch
Handle Gas Cylinders With Care
States of Matter

Energy



Potential
Kinetic
Temperature



Absolute Zero
Scales
Heat Transfer
States of Matter
Forms



Solid
Liquid (Properties)







Pressure
Buoyancy
Viscosity
Cohesion & Adhesion
Surface Tension
Capillary Action
Gas
States of Matter
Changes


Liquid to Solid



Liquid to Gas (Vapor)




Melting
Freezing
Evaporation
Vapor Pressure
Humidity
Water

How its behavior is different from other compounds when
it freezes or melts
Gases


Molecules continuously moving
Avogadro’s law



1 gram atomic weight of any substance 6.02
* 1023 atoms
This is known as 1 mole.
1 mole of a gas at STPD occupies 22.4 L
Pressure
PB= barometric pressure
Normal barometric pressure is






760mmHg
14.7 PSI
1034cm H2O
33ft of water
Water vapor (or humidity) exerts pressure


Partial pressure of H2O (PH2O) at 100% RH at 37
degrees C = 47mmHg
Pressure

Dalton's law


The sum total of the individual partial
pressures of gases in the atmosphere are
equal to the barometric (PB = PN2 + PO2
+PTrace gases)
The pressure of each gas will be exerted
when separated from a mixture (PN2 = PB *
%N2)
Concentrations of Atmospheric
Gases





Oxygen 20.95%
Nitrogen 78.08%
Argon 0.93%
Carbon Dioxide 0.03%
Trace Gases 0.01 %
Application of Dalton's Law To The
Lung



Partial pressure of a gas equals Pbar *
concentration (example: 760mmHg * 0.21 =
159mmHg for O2)
In the lung the water vapor exerts a pressure
of 47mmHg thus it changes the pressure of
the atmospheric gases in the alveoli (example:
Pbar= 760mmHg – 47mmHg = 713mmHg)
Because of the change in the barometric
pressure in the alveoli the partial pressure of
O2 also changes (example: PO2 = 713mmHg *
0.21 = 149mmHg)
Application of Dalton's Law To The
Lung


In the lungs the CO2 is higher than in the
atmosphere and affected by the respiratory
quotient (the unequal exchange of O2 for CO2)
PaCO2
149 
Example: 149mmHg0–.850mmHg = 99mmHg
(99mmHg is alveolar partial pressure of
oxygen)
Application of Dalton's Law To The
Lung
Ideal Alveolar Gas Equation



In addition to the effects of PH2O on partial
pressure of gases in the alveoli, the carbon dioxide
diffusing from the bloodstream into the alveoli will
further decrease alveolar PO2
Since carbon dioxide is leaving the bloodstream, (a
closed system), and entering the respiratory tract,
(an open system), there is an indirect relationship
between the pressures of carbon dioxide and
oxygen
Application of Dalton's Law To The
Lung

Ideal Alveolar Gas Equation (cont)



Increases in PACO2 result in decreases in
PAO2
This indirect relationship basically involves
only carbon dioxide and oxygen because
they are the only metabolically active gases
Dalton's Law must be modified to account
for incoming carbon dioxide when applied to
alveolar
Application of Dalton's Law To The
Lung

Ideal alveolar gas equation
PAO2 = FIO2 * (Pb - PH2O) - PCO2 / RQ






PAO2 = pressure of O2 in the alveoli
Pb = barometric pressure
PH2O = water pressure
FIO2 = fraction of inspired oxygen
PACO2 = pressure of CO2 in the alveoli
RQ = respiratory quotient
Application of Dalton's Law To The
Lung

A modification of the above equation maybe
used with reasonably accurate results
PAO2 = (PB - PH2O)(FIO2) - PACO2

In both equations, PaCO2 is always
considered equal to PACO2 because of the
rapid equilibration of carbon dioxide (20 *
faster or easier than O2)
Gas Laws

Ideal Gas Law

If mass is constant then
P1V 1 P 2V 2

T1
T2
Gas Laws

Boyle's Law

If temperature and mass are constant then
volume and pressure are inversely
proportional
P1V1 = P2V2
Gas Laws

Charles' Law

If pressure and mass are constant then
temperature and volume are directly
proportional
V1 V 2

T1 T 2
Gas Laws

Gay-Lussac's Law


If volume and mass remain constant,
pressure and temperature are directly
proportional
The triangle demonstrates the relationship
P1 P 2

T1 T 2
Gas Laws


All gas laws use temperature in Kelvin
(absolute temperature scale)
C + 273 = Kelvin
Relationships of Gas Laws
Volume
Boyle’s
m
Charles’
(constant)
Pressure
Temperature
Gay-Lussac’s
Examples

Ideal Gas Equation


A gas system has volume, moles, and temperature of 9160ml,
0.523 moles & 324K, respectively. What is the pressure in torr?
P=x
V = 9160ml = 9.16L
n = 0.523 moles
T = 324K
(0.523 * 62.4 * 324) ÷ 9.16 = 1160 torr
How many moles of gas are contained in 890 ml at 21°C
and 750 mmHg pressure?
n = PV/RT
(750 mmHg ÷ 760mmHg atm-1)(0.89L) ÷ (0.08206L at mol-1K1)(294K)
(0.9868) * (0.89) ÷ (24.12564)
0.878252 ÷ 24.12564
n = 0.0364
Examples

Boyle’s Law

A gas system has initial pressure and volume of 3.69
atm and 5440ml. If the pressure changes to 2.38
atm, what will the resultant volume be in ml?
P1(V1) = P2 (V2)
3.69 * 5440 = 2.38x
20073.6 = 2.38x
x = 8434.29
Examples
Boyle’s Law (cont)



A gas occupies 12.3L at a pressure of 40.0 mmHg.
What is the volume when the pressure is increased
to 60mmHg?
40 * 12.3 = 60x
x = 8.2L
If a gas at 25°C occupies 3.6L at a pressure of
1atm, what will be its volume at a pressure of
2.5atm?
1atm * 3.6L = 2.5x
x = 1.44L
Examples

Charles’ Law


A gas system has an initial temperature of
308.9K with the volume unknown. When the
temperature changes to -230.4°C the volume
is found to be 1.67L. What was the initial
volume in L?
x
1.67

-230.4°C =>42.6K
308.9 42.6
42.6 x  515.863
x  12.11
Examples

Charles’ Law (cont)


Calculate the decrease in temperature when
2L at 20°C is compressed to 1L.
2L * 293 = 1x
x = 146.5
A 600ml sample of nitrogen is warmed from
77°C to 86°C. Find its new volume if the
pressure remains constant.
600ml ÷ 350 = 359K
Examples

Guy-Lussac’s Law

A container is initially at 47mmHg and 77K (liquid
nitrogen temperature). What will the pressure be
when the container warms up to room temperature of
25°C?
Ans: 180mmHg

A gas thermometer measures temperature by
measuring the pressure of a gas inside the fixed
volume container. A thermometer reads a pressure of
248 torr at 0°C. What is the temperature when the
thermometer reads a pressure of 345 torr?
Ans: 107°C
Examples

Guy-Lussac’s Law (cont)

A vessel has a pressure of 18.9 lb/in2 at
20°C. What temperature is necessary to
lower the pressure to 14.2 lb/in2?
Ans: -53°C
Review Characteristics of Medical
Gases






Oxygen
Air
Carbon Dioxide
Helium
Nitrous Oxide
Nitric Oxide
Agencies Regulating Gas
Administration
DOT - Department of Transportation



HHS - Department. of Health & Human Services




Before 1970, was called ICC – Interstate Commission
Regulates construction, transport and testing of cylinders
Formerly called HEW - Department. of Health, Education and
Welfare
FDA - Food & Drug Administration - is part of HHS - regulates
the purity of gases
OSHA Occupational Safety & Health Administration responsible for occupational safety
Recommending Bodies
CGA - Compressed Gas Association - created safety
systems
NFPA - National Fire Protection Assn.




Fire prevention
Governs storage
Z-79 – Committee of American National Standards for
Anesthetic Equipment, which includes






Ventilator devices
Reservoir bags
Trachea tubes and their connectors
Humidifiers
Other related equipment
Safety Systems for Cylinders
Color coding for E cylinders (not mandatory for
larger cylinders)









Oxygen – green (white internationally)
Carbon dioxide – grey
Nitrous oxide – blue
Cyclopropane – orange
Helium – brown
Ethylene – red
Air – yellow
Nitrogen – black
Safety Systems for Cylinders

Pin Index Safety System






E cylinders and smaller
High pressure (greater than 200psi)
Yoke & pin connections
Oxygen 2-5 position
Air 1-5 position
CO2 1-6 position
Safety Systems for Cylinders

American Standard Safety System



Larger than E cylinders
High pressure
Nipple & threaded nut
Safety Systems for Cylinders

Diameter Index Safety System



Low pressures (less than 200 PSI)
All connections after the regulator
Threaded nut & nipple
Qualities of cylinder gases

Flammable Gases



Ethylene
Cyclopropane
Nonflammable Gases



Nitrogen
Carbon dioxide
Helium
Qualities of cylinder gases

Gases that support combustion


Oxygen
Oxygen mixtures





Helium/oxygen – heliox
Oxygen/carbon dioxide – carbogen
Oxygen/nitrogen
Oxygen/nitrous oxide
Nitrous oxide
Qualities of oxygen









Colorless
Odorless
Tasteless
Atomic weight = 16gms
Molecular weight = 32gms
Critical temperature
-118.8ºC or -181.1ºF at 49.7 atm
Above this temperature it cannot remain a liquid
Fractional distillation
Cylinder marking and testing

Front




DOT-3AA 2015 PSI– these are DOT
specifications and service pressure
Serial number
Ownership markings
Manufacturers mark
Cylinder marking and testing

Back





Original hydrostatic testing
Specifications
Retest dates
Inspectors mark and specifications
Cylinders are filled to 5/3 maximum
pressure every 5-10 years (hydrostatic
testing)
Cylinder Filling and Duration


Can be overfilled by 10% to hold 2200
PSI
Duration of flow in minutes =
Tank pressure  Tank factor
liter flow
Cylinder Filling and Duration
Tank factors for O2 duration of flow




E = 0.28
G = 2.41
H = 3.14


These factors are used to calculate absolute duration
times; however, in practice a safety factor must be utilized
to insure no interruptions in gas therapy to the patient
Cylinder capacities



E = 22 ft3 or 616 liters @ 2200 psig
G = 187 ft3 or 5308 liters @ 2200 psig
H = 244 ft3 or 6908 liters @ 2200 psig
Cylinder Handling
Keep in carrier or stand
No flames/smoking
Proper technique in attaching regulators









Remove cap
Turn on gas momentarily (away from people)
“cracking”
Place and tighten regulator
Turn on gas
Adjust flow
Bleed off pressure when not in use
Cylinder Handling


Store with cap on to prevent breaking
stem
Cylinder testing


Every 5- 10 years
Water displacement measured to check for
expansion with 5/3 maximum pressure
Gaseous bulk systems three
general types
Standard





Large H or K size cylinders banked into a manifold
system
Primary bank
Reserve bank (automatically switches to this when
primary system drops to a preset lower pressure
limit
Six or more cylinders manifolded together. Alarms
are activated when reserve switches on or
malfunction occur. Cylinders are replaced as
needed.
Gaseous bulk systems three
general types
Fixed cylinders



Large bank of permanently fixed cylinders (up to
75)
Refilled on site by a liquid O2 truck that converts
the liquid into gas to fill tanks
Trailer units (2200 PSI)



Very large cylinders mounted on trailers towed to a
central location for connection
When low or in need of maintenance replaced with
fresh trailer
Gaseous bulk systems three
general types
Liquid Oxygen Systems



Liquid O2 is stored at -183°C or -297°F in thermos bottle type
storage vessels (inner and outer steel shells separated by a
vacuum)
Pressure readings do not indicate remainder of O2 because
the liquid O2 doesn't exert gas pressure




Weight will indicate remainder of O2
Pressures not to exceed 250 PSI in containers in LOX containers
Specifications for bulk systems by NFPA
Piping systems


Locate zone valves in hospital
Do not turn off unless directed by fire chief
Gaseous bulk systems three
general types
Liquid Oxygen Systems (cont)


Most economical
1 ft3 of liquid O2 = 860 ft3 of gaseous O2 @
ambient temperature




Liquid O2 cylinders are used when usage too large for and
not large enough for a permanently liquid vessel (come in
various sizes see textbook)
Fixed station (stand tanks) are large spherical with gaseous
equivalents up to 130,000 cubic feet. Refilled by service
tank trucks.
All liquid O2 tank containers are equipped with 50 PSI
reducing valves.
Liquid O2 duration (in minutes)
Pounds of liquid O2 * 344 =
Liters per minute
Gaseous bulk systems three
general types
Safety precautions for bulk O2



Must have 24 hour reserve or back-up supply
Procedure for total system failure should be known
Oxygen Concentrators


Membrane




Thin membrane-1 µm thick
Oxygen and H2O pass through membrane faster than nitrogen
Delivers an FIO2 of about 40%
Molecular Sieve





Uses a sieve filled with sodium-aluminum silicate
Air is forced through the sieve
The nitrogen is scrubbed from the air
Delivers an FIO2 of about 90% at 2 LPM
At higher flows the FIO2 decreases
Regulators

Reduce high tank pressure to low
working pressure


Usually 50 PSI
Single stage regulator


Reduces tank pressure to 50 PSI in 1 step
Has one pressure relief valve (about 200
PSI)
Regulators
Multi-stage regulator




Reduces tank pressure to working pressure in 2 or
more steps
Each stage has a pressure relief valve
The more stages the less fluctuation of working
pressure
Preset regulator



Single or multi-stage regulator that is set to have
pressure reduced to set working pressure (usually
50 PSI)
Has no way to adjust working pressure
Regulators

Adjustable regulator

Single or multi-stage regulator in which working
pressure may be set variably
Flowmeters


Control and indicate flow
Thorpe Tube

Vertical funnel shape tube with float

Must be kept vertical to be accurate
Flowmeters
Compensated Thorpe Tube Flowmeter




Needle valve adjustment is distal (after or
downstream) to the float
Indicated flow is accurate in the presence of
back pressure to check for compensation:
Label calibrated at 70ºF, 50 PSI



Visualize needle valve placement
Turn unit off and plug into pressure
Float will rise, then fall
Flowmeters

Uncompensated Thorpe Tube Flowmeter


Needle is proximal (upstream or before) the
float
Flow meter reading will be lower than what
is delivered to the patient if back pressure is
present
Flowmeters

Kinetic Flowmeter


Has plunger instead of float
All other areas of Thorpe tubes apply
Flowmeters
Flowmeters

Bourdon Gauge



Measures pressure but reads flow
Flow delivered to patient is less than flow
shown on the gauge if back pressure is
present
Works in any position
Flowmeters

Use of oxygen flowmeters with helium



Due to density of gases flow will not be
accurate
80% helium, 20% O2 flow will be 1.8 times
the meter reading
70% helium, 30% O2 flow will be 1.6 times
the meter reading
Compressors




Piston
Diaphragm
Centrifugal
Assembly & Troubleshooting (White p15)
Valves
Direct Acting
Diaphragm
Safety Features
Reducing









Single stage
Modified Single stage
Multistage
Safety Features
Regulators
Conservation


List current manufacturer and model
Describe how each acts as a
conservation option
Blenders

See textbook