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Basic Concepts and Devices
RT 31
Humidification
Basic Concepts
• Functions of the of the upper
airway: assure that inspired gas is:
– Warmed (convection).
– Humidified via evaporation from the
mucosa
– Filtered
• During exhalation:
– Expired gas transfers heat back to
the mucosa (convection)
– Condensation occurs on the mucosal
surfaces and water is reabsorbed by
mucus (rehydration)
Basic Concepts
• As gas travels through
the lungs it achieves
BTPS:
– Body temp ~ 37C
– Barometric pressure
– Saturation with water
vapor (100% relative
humidity @ 37C)
Basic Concepts
• The point at which this occurs is
called the isothermic saturation
boundary (ISB)
– Usually occurs ~ 5 cm below the
carina
– If the upper airway is bypassed or
VE is significantly higher than
norm,
• The ISB will be deeper into the
lungs and HUMIDITY therapy may
be indicated
Basic Concepts
• One of the most important,
but least understood, aspects
of pulmonary care is the role
of humidity therapy.
• Many care providers and
most patients do not
appreciate the role of
hydration in liquefying
secretions and facilitating the
natural flow of mucus from
the lower airways.
Basic Concepts
• Pulmonary patients need:
– adequate humidification of their inspired gases
– controlled fluid balance
– otherwise patients can become dehydrated.
• Dehydration can make secretions more viscous and inhibit the
mucociliary escalator activity of the airways, making secretions
difficult to dislodge.
• If these secretions block functional gas flow through the distal
airways infections, atelectasis and other respiratory problems
can easily occur.
Basic Physical Principles of Humidity
• Humidity is essentially the water vapor in a gas.
• This water vapor can be described in several ways,
as:
• 1. Absolute humidity - The actual content of water vapor in a gas
measured in milligrams per liter.
• 2. Potential humidity - The maximum amount of water vapor that a gas
can hold at a given temperature.
• 3. Relative humidity - The amount of water vapor in a gas as compared to
the maximum amount possible, expressed as a percentage
• 4. Body humidity - The absolute humidity in a volume of gas saturated
at body temperature of 37 C; equivalent to 43.8 mg/L
Formulas Used When Calculating
Humidity
• %RH=(absolute humidity/saturated capacity) x 100
– Refer to table 5-3 of Egan or 4-1 of Mosby.
Calculations are based on temperature. See example
on page 90 of Egan
• %BH = (absolute humidity/43.8mg/L) x 100
– See example on page 97 of Egan
• Absolute humidity: Refer to table 5-3 of Egan
Primary Humidity Deficit
• If the atmosphere's relative humidity is less than 100%, the air of the
atmosphere has what is referred to as a humidity deficit.
•
If outside air at 20°C has 14 mg/l of water vapor, and needs to have 17.3
mg/l to be fully saturated, it is said to have a primary humidity deficit of
3.3 mg/l.
– 17.3 mg/L (potential) – 14 mg/L (absolute) = 3.3 mg/L (primary deficit)
• Remember that the potential is based temp
• The primary humidity deficit occurs in the atmosphere and represents
the difference between what humidity there is and what there could be.
• Primary Humidity Deficit = Potential Water Vapor Content - Actual Water
Vapor Content
Secondary Humidity Deficit
• This is the moisture deficit in the inspired air that the nose and upper
airway need to compensate for.
– The amount of water vapor the body needs to add to inspired air to achieve
saturation at body temperature.
• When air is breathed into the nasal cavity and heated to body
temperature, its potential water vapor rises to 44 mg/l, which is the
potential water vapor content of air at 37°C.
• Therefore, unless the air of the atmosphere is at least 37°C and
fully saturated, there exists a moisture deficit.
• Secondary Humidity Deficit = 44 mg/l - Absolute Humidity.
How does a patient develop a
humidity deficit?
• Breathing a gas with little or
no humidity and very high
minute volume evaporation
of the respiratory mucosa
occurs
• Bypass of upper airway:
intubation, tracheostomy.
• Dehydration due to illness,
exposure, etc.....
• Please understand Figure 4-3
of Mosby, page 94.
Water Losses
• Insensible: skin and lungs
• Sensible: urine, GI tract, sweat
• Additive: vomiting, diarrhea,
suction from intestines, severe
burns, and fever
• For each degree of temperature
above 99F for over 24 hours,
1000m of fluid is required for
replacement
Water Vapor Correction
• Water vapor acts in most ways like any
other gas, it creates a partial pressure
when it’s in a mixture of gases.
• That partial pressure depends
– The amount of water vapor present
• Which in turn depends on the temperature.
• Unlike other gases in the air, changes in
the barometric pressure of the
atmosphere under normal conditions do
not have much impact on the partial
pressure of water.
Water Vapor Correction
• As a result, it is best to calculate the partial
pressures of the other gases in the air after
the partial pressure of water vapor has been
determined--especially when measuring the
air within the lungs.
• Inside the lungs, the partial pressure of
water vapor is approximately 47 mm Hg.
• This value is relatively constant because the
air entering the lungs is normally saturated
and at 37°C.
• By subtracting the partial pressure of the
water vapor from the total atmospheric
pressure, you will find what is referred to as
the dry gas pressure
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.
Importance of Humidity
If the upper airway were bypassed or dry
gases were inhaled, a series of adverse
reactions could occur, including:
– Slowing of mucus movement
– Inflammatory changes and possible
necrosis of pulmonary epithelium
– Retention of thick secretions and
encrustation
– Bacterial infiltration of mucosa
(bronchitis)
– Atelectasis
– Pneumonia
– Impairment of ciliary activity
Importance of Humidity
The general goals of humidity and
aerosol therapy are to:
1. Promote bronchial hygiene
2. Loosen dried and/or thick
secretions
3. Promote a effective coughs to
clear secretions
4. Provide adequate humidity in
the presence of an artificial
airway
5. Deliver adequate humidity
when administering dry gases
therapies
6. Delivering prescribed
medications
Clinical Evaluation of the Need for
Humidity and/or Aerosol Use
• Patient's age and ability to move normal
secretions
•
•
•
•
Neuromuscular status
Recent or planned surgeries
Trauma
Disease conditions
• The presence of any of these may impair the patient's ability to cough
and move secretions.
• Another problem may occur when patients develop very thick and
abundant amounts of secretions which cannot be moved with normal
muscle activity--making humidity or aerosol therapy necessary.
Indications for delivery of humidified
gases and aerosols
• Primary indications for
humidifying inspired
gases include:
• Administration of medical
gases
• Delivery of gas to the
bypassed upper airway
• Thick secretions in
nonintubated patients
Indications for delivery of humidified
gases and aerosols
• Additional indications
for warming inspired
gases:
– Hypothermia
– Reactive airway
response to cold
inspired gas
Mucociliary Blanket
• It’s natural escalator functions to
clear airways via function of the
ciliated mucosa.
• This mechanism occurs from the
larynx to the respiratory
bronchioles.
• Mucus is produced by goblet cells
and submucosal glands.
• Clara cells and tissue fluid
transudation also contribute to
airway secretions.
• A wave-like motion of the cilia then
move secretions upward toward the
larynx where it is either swallowed
or expectorated.
Mucociliary Blanket
Mucociliary Blanket
Sources of Mucus
• Secretion from goblet cells
and bronchial (mucous)
glands.
• The goblet cells, which are
distributed throughout the
epithelium of the mucosa,
synthesize and secrete
mucus into the airway.
Sources of Mucus
• The mucous glands,
which are in the
submucosa, are the
greater source of mucus.
• Chronic irritation or
disease can cause the
number and size of
goblet cells and mucous
glands to increase,
resulting in a larger and
more viscous mucous
blanket.
Effects of Mucous Layer
• Ciliary activity, which moves the mucus, can be adversely
affected if the mucous layer is changed.
– A higher ratio of gel to sol layer will affect the flow of
mucus by increasing cilia workload.
• a decrease in the watery sol layer
• or an increase in the viscous gel layer
– The cilia are capable of continuing to beat even if the
workload increases, but only to a certain level.
– If the cilia become tangled in the thick mucus or are
unable to penetrate the dense layer, the transport of the
mucous blanket would stop, causing secretions to
become retained in the respiratory tract.
Other factors that can impede ciliary activity
and the flow of mucus include:
• Tobacco smoke
• Local environmental
conditions
• Pathology of the
airway can impede
clearance due to
changes in the
epithelium.
Sign/Symptoms of Inadequate Airway
Humidification
•
•
•
•
Atelectasis
Dry, nonproductive cough
Increased airway resistance
Increased in incidence of
infection
• Increased work of
breathing
• Substernal pain
• Thick, dehydrated
secretions
Humidification Devices
• The purpose of humidifiers is to deliver a gas with
a maximum amount of water vapor content.
• May be heated or unheated, and the factors
affecting the efficiency of humidification devices
include:
– temperature
– time of exposure between gas and
water
– surface area involved in the gas/water
contact
Humidification Devices
• As temperature rises, the force exerted by the water
molecules increases, enabling their escape into the gas,
adding to the humidity.
– So the higher the tempthe more humidity
• Longer exposure of a gas to the water increases the
opportunity for the water molecules to evaporate during the
humidifier's operation.
• The greater the area of contact between water and gas, the
more opportunity for evaporation to occur.
Humidification Devices
• Space-efficient methods
– Bubble diffusion
– Aerosol
– Wick technologies
Humidification Devices
• Bubble diffusion:
– Stream of gas is directed underwater
– The gas is broken up into small bubbles
– As gas bubbles rise, evaporation increases the
water vapor content within the bubble
Humidification Devices
• Aerosol: spraying water particles into gas
– Aerosol (suspended water droplets) is generated
in the gas stream
– The greater the aerosol density (# of molecules),
the greater the gas/water surface area available
for evaporation
Humidification Devices
• Wick:
– Use porous waterabsorbent materials to
increase surface area
– A wick draws water into its
fine honeycombed
structure by means of
capillary action
– The surfaces of the wick
increase the area of contact
between the water and gas
Blow-By
• This “pass-over” type humidifier
directs a dry gas source over a water
surface area, and flowing it to the
patient.
• Because exposure area and time of
contact is limited and it is not heated,
this unit is not very efficient.
• These units are often used in
incubators and in certain ventilators,
although many times the use of a
heated element is added to improve
this humidification system
• Wick type or membrane type
Bubble Humidifier
•
•
•
•
•
•
•
•
Low-flow gas system
Provides flow lower than patient’s inspiratory
needs.
Oxygen or air is humidified at 30%-50% relative
humidity.
Gas is passed below the water’s surface in the
form of bubbles.
Increase exposure time result in good
humidification
Patient’s airway provide further humidification.
Should be used for NC use at 4lpm or above, but
the higher the flow rate the less the exposure
time.
Do not use with oximizers or venturi masks (these
are common mistakes in the clinical setting)
Jet Humidifier
• Forms aerosol
• Baffle system to break up particles into
smaller sizes
• Bernoulli’s principle
• Low flow
• Large-volume jets are used for bland aerosol
Ultrasonic Nebulizers
• Electrically powered
• Uses piezoelectric crystal to
generate aerosol
– Transducer converts radio
waves into high-frequency
mechanical vibrations (sound)
– These vibrations are
transmitted to a liquid surface
creating a geyser of aerosol
droplets
Mist tents and hood
• Kids don’t like things on their
face
• So tents and hoods are used to
deliver bland aerosols
• Sometimes referred to as croup
tents
• High flow rates should be used to
prevent CO2 build up
• Must use some kind of cooling
device to prevent heat retention:
refrigeration devices or even ice
Cascade Humidifier
• High Flow: Provide vapor to entire gas flow
• Used for mechanical ventilation, airway
bypass (artificial airways)
• 100% humidity
• Usually heated to body temperature
• Figure 4-7 of Mosby, page 99
Cascade Humidifier
• Gas enters the cascade and travels to the bottom of the
tower
• Then it moves up through a sheet of plastic consisting of
many tiny holes.
• Tiny bubbles are produced and dissipate into water vapor,
which are carried to the patient’s delivery circuit.
• No back flow is allowed due to one-way valves
• A heating element in the water reservoir heats the water to
form warm gas.
• Thermostat can be used to regulate and monitor
temperature.
Heat and Moisture Exchangers (HME) or
Artificial Noses
• Functions similarly to the upper
airway
• Captures s exhaled heat and
moisture and using it to heat and
humidify inhaled gas.
• Do not add heat or moisture--Use
the body’s own heat and moisture.
• Book statement: should be used
short term, flow less than 10 lpm,
and in the absence of thick
secretions
• Practical purposed: Used all the
time! Changed every 24 hours.
Heat and Moisture Exchangers (HME) or
Artificial Noses
• Light weight
• Less dead space
• Reduce accumulation of
condensation in tubing
• Decrease risk of infection
(maybe)
• If moisture remains on
filter for an extended
period of time, airway
resistance increases.
• Must be removed during
aerosol therapy
• Dead space volume limits
use for neonates and
pediatrics.
Aerosol Therapy
Basic Concepts and Delivery Systems
Aerosol Therapy
• 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
• 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.
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.
Particle Size
The particle size of an aerosol depends on the device used
to generate it and the substance being aerosolized.
Particles of this nature, between 0.005 and 50 microns, are
considered an aerosol.
The smaller the particle, the greater the chance it will be
deposited in the tracheobronchial tree.
 Particles between 2 and 5 microns are optimal in size for
depositing in the bronchi, trachea and pharynx.
Particle Size
• Heterodisperse:
– aerosol with a wide
range of particle sizes
(medical aerosols)
• Monodisperse:
– aerosol consisting of
particles similar in size
(laboratory, industry)
Deposition
• The aerosol particles are
retained in the mucosa of
the respiratory tract. They
get stuck!
• The site of deposition
depends on size, shape,
motion and physical
characteristics of the
AIRWAYS
Mechanism resulting in Deposition:
Inertial Impaction
• Moving particles collide with airway surface.
– Large particles (>5micros), upper and large airways
• Physics: the larger the particle, the more likely it
will remain moving in a straight line even when the
direction of flow changes.
• Physics: greater velocity and turbulence results in
greater tendency for deposition
Mechanism resulting in
Deposition
Table: Particle size and area of deposition.
Particle Size in Microns
1 to 0.25
1 to 2
2 to 5
5 to 100
Area of Deposition
Minimal settling
Enter alveoli with 95% deposition
Deposit proximal to alveoli
Trapped in nose and mouth
Mechanism resulting in
Deposition: 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
Mechanism resulting in
Deposition: Diffusion
• Actual diffusion particles
via the alveolar-capillary
membrane and to a lesser
extent tissue-capillary
membranes of respiratory
tract
• Lower airways: 2-5
microns
• Alveoli: 1-3 microns
• These values are from
your book
Deposition of Particles is also affected
by:
• Gravity –
– Gravity affects large particles more than
small particles, causing them to rain-out.
• Viscosity - The viscosity of the carrier gas plays
an important role in deposition.
• For example, if a gas like helium, which has a
low viscosity and molecular weight, is used as a
carrier gas, gravity will have more of an effect
upon the aerosol.
•
Helium is very light and hence can't carry
these particles well, leading to rain-out and
early deposition.
Deposition of Particles is also affected
by:
• Kinetic activity - As aerosolized particles
become smaller, they begin to exhibit the
properties of a gas, including the
phenomenon of "Brownian movement."
• This random movement of these small
(below lmm) particles causes them to
collide with each other and the surfaces of
the surrounding structures, causing their
deposition.
• As particle size drops below 0.1m, they
become more stable with less deposition
and are exhaled.
Deposition of Particles is also affected
by:
• Particle inertia (repeated) Affects larger particles which
are less likely to follow a course
or pattern of flow that is not in
a straight line.
• As the tracheobronchial tree
bifurcates, the course of gas
flow is constantly changing,
causing deposition of these
large particles at the
bifurcation.
Deposition of Particles is also affected
by:
• Composition or nature of the aerosol particles - Some
particles absorb water, become large and rain-out, while
others evaporate, become smaller and are conducted further
into the respiratory tree.
• 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.
Deposition of Particles is also affected
by:
• Heating and humidifying - As aerosols enter a
warm humidified gas stream, the particle size of
these aerosols will increase due to the cooling of
the gas in transit to the patient.
• This occurs because of the warm humidified gas
cooling and depositing liquid (humidity) upon the
aerosol particles through condensation.
Deposition of Particles is also affected
by:
• Ventilatory pattern - RCPs easily control this by
simple observation and instruction.
• For maximum deposition, the patient must be
instructed to:
– Take a slow, deep breath.
– Inhale through an open mouth (not through the nose).
– At the end of inspiration, use an inspiratory pause, if
possible, to provide maximum deposition.
– Follow with a slow, complete exhalation through the
mouth.
Aerosol vs. Systemic
• In many cases, aerosols are superior in terms of
efficacy and safety to the same systemically
administered drugs used to treat pulmonary
disorders.
• Aerosols deliver a high concentration of the
drugs with a minimum of systemic side effects.
• As a result, aerosol drug delivery has a high
therapeutic index; especially since they can be
delivered using small, large volume, and metered
dose nebulizers.
Methods of Aerosol Delivery
• Aerosols are produced in
respiratory therapy by
utilizing devices known
as nebulizers.
• There are a variety of
nebulizers in use today,
but the most common is
one in which the Bernoulli
principle is used through
a Venturi apparatus
Bernoulli’s Principle and
Nebulizers
• When gas flows through a tube, it exerts a lateral wall pressure within
that tube due to its velocity.
• As the gas reaches a smaller diameter in the tube, the velocity is
increased, which decreases lateral wall pressure.
• This decrease in diameter within the tube is at a structure called a jet.
• Just distal to the jet is a capillary tube that is immersed in a body of
fluid.
•
The decreased pressure is transmitted to the capillary tube and fluid is
drawn up it.
•
When the fluid reaches the jet, it is then atomized.
• See Mosby Figure 4-25, pg 115
Bernoulli’s Principle and
Nebulizers: The Baffle
• The absolute humidity that will be delivered from these
devices can be increased by the use of a heater.
• A baffle is distal to this atomization process in the stream
of gas/fluid flow.
– Nebulization takes place here as the liquid is impelled against
the baffle.
– This baffle causes the larger particles to coalesce and collect in
the reservoir.
•
The smaller particles will be delivered to the patient in
aerosol form.
Bernoulli’s Principle and
Nebulizers: The Baffle
• If the baffle is not used, the device is known as an
atomizer.
• When the baffle is used, it is then called a nebulizer.
• In addition to the physically placed baffle, any 90°
angle to gas flow can be considered a baffle.
• Large bore corrugated tubing should be used with
baffles.
• This will enable the aerosol particles to be delivered
to the patient.
Aerosol delivery is accomplished in a
variety of ways:










nasal spray pump
metered-dose inhaler (MDI)
dry powder inhaler (DPI)
jet nebulizer
small volume nebulizer (SVN)
large volume nebulizer
small-particle aerosol generator (SPAG)
mainstream nebulizers
ultrasonic nebulizer (USN)
intermittent positive pressure breathing
(IPPB) devices
Metered Dose Inhalers
• Metered dose inhalers (MDIs)
consist of a pressurized
cartridge and a mouthpiece
assembly.
•
The cartridge, which contains
from 150-300 doses of
medication, delivers a premeasured amount of the drug
through the mouthpiece when
the MDI is inverted and
depressed.
• See Mosby Figure 4-32, pg
119
Metered Dose Inhalers
• The particle size of the drug released is controlled by two
factors:
– the vapor pressure of the propellant blend
– the diameter of the actuator's opening.
• Particle size is reduced as vapor pressure increases,
and as diameter size of the nozzle opening decreases.
• The majority of the active drug delivered by an MDI is
contained in the larger particles, many of which are
deposited in the pharynx and swallowed.
Metered Dose Inhalers
• Successful delivery of medications with an MDI depends
on the patient's ability to coordinate the actuation of the
MDI at the beginning of inspiration.
• Proper instruction and observation of the patient are
crucial to the success of MDI of therapy.
• Patients need to be alert, cooperative, and capable of
taking a coordinated, deep breath. Patients should be
instructed to:
Metered Dose Inhalers
• Be sure to shake the MDI canister well before using.
• Hold the MDI a few centimeters from the open mouth.
• Holding the mouthpiece pointed downwards, actuate the MDI at
the beginning of a slow, deep inspiration, with a 4-10 second
breath hold.
• Late actuation, or at the end of the inspiration, or stopping
inhaling when the cold blast of propellant hits the back of the
throat will cause the medication to have only a negligible effect.
• Exhale through pursed-lips, breathing at a normal rate for a few
moments before repeating the previous steps.
• Patients should also be instructed to rinse their mouths after
taking the medication.
The advantages of MDI aerosol devices include:
• They are compact and portable.
• Drug delivery is efficient.
• Treatment time is short
Disadvantages
– They require complex hand-breathing coordination.
– Drug concentrations are pre-set.
– Canister depletion is difficult to ascertain accurate
– A small percentage of patients may experience adverse reactions to
the propellants.
– There is high oropharyngeal impaction and loss if a spacer or
reservoir device is not used.
– Aspiration of foreign objects from the mouthpiece can occur.
– Pollutant CFCs, which are still being used in MDIs, are released into
the environment until they can be replaced by non-CFC propellant
material
Reservoir Devices for MDI’s
(Spacers)
• These can be used to modify the aerosol discharged from an MDI.
The purposes of these spacers or extensions include:
• Allow additional time and space for more vaporization of the
propellants and evaporation of initially large particles to smaller
sizes.
• Slow the high velocity of particles before they reach the oropharynx.
• As holding chambers for the aerosol cloud released, reservoir
devices separate the actuation of the canister from the inhalation,
simplifying the coordination required for successful use.
• See Mosby, Figure 4-33, pg 121
Dry powder inhalers (DPIs)
• Consist of a unit dose formulation
of a drug in a powder form,
dispensed in a small MDI-sized
apparatus for administration
during inspiration.
• Because these devices are breathactuated, using turbulent air flow
from the inspiratory effort to
power the creation of an aerosol of
microfine particles of drug, they
don't require the hand-breath
coordination needed with MDIs.
Dry powder inhalers (DPIs)
• Cromolyn sodium and albuterol are the two primary drugs
available in powder form.
• Cromolyn sodium is dispensed in a device called the
Spinhaler, which pokes holes in capsules containing the
powdered drug.
• The albuterol formulation is dispensed in a device called the
Rotohaler, which cuts the capsule in half, dropping the
powdered drug into a chamber for inhalation.
• In both cases, a single-dose micronized powder preparation
of the drug in a gelatin capsule is inserted into the device
prior to inhalation.
• See Mosby Fig 4-39,40
The advantages of using DPI devices for
drug administration include:
• They are small and portable.
• Brief preparation and administration time.
• Breath-actuation eliminates dependence on patient's
hand-breath coordination, inspiratory hold, or head-tilt
needed with MDI.
• CFC propellants are not used.
• There is not the cold effect from the freon used in MDIs,
eliminating the likelihood of bronchoconstriction or
inhibited inspiration.
• Calculation of remaining doses is easy.
The disadvantages encountered when
relying on DPIs for drug administration
include:
• Limited number of drugs available for DPI delivery at this
time.
• Dose inhaled is not as obvious as it is with MDIs,
causing patients to distrust that they've received a
treatment.
• Potential adverse reaction to lactose or glucose carrier
substance.
• Inspiratory flow rates of 60Lpm or higher are needed
with the currently available cromolyn and albuterol
formulations.
• Capsules must be loaded into the devices prior to use.
Small volume nebulizers (SVNs)
• Gas powered (pneumatic) and
are a common method of
aerosol delivery to inpatients.
• There are a variety of different
SVNs available. Each has
specific characteristics,
especially in regard to output.
• Bernoulli’s principle:
make sure you
understand this concept
Small volume nebulizers (SVNs)
• Two subcategories: mainstream and sidestream.
• The mainstream nebulizer is one in which the main flow of
gas passes directly through the area of nebulization.
• The sidestream nebulizer is one in which the nebulized
particles are injected into the main flow or stream of gas as
with IPPB (Mosby 180-90) circuits.
• Don’t spend too much time on IPPB, just know basic
concepts and guidelines.
• The main difference, based upon their construction, is that
the larger particles tend to rain-out with a sidestream
nebulizer.
Advantages of SVN therapy:
• Requires very little patient coordination or breath
holding, making it ideal for very young patients.
• It is also indicated for patients in acute distress, or in the
presence of reduced inspiratory flows and volumes.
• Use of SVNs allows modification of drug concentration,
and facilitates the aeorsolization of almost any liquid
drug.
• Dose delivery occurs over sixty to ninety breaths, rather
than in one or two inhalations. Therefore, a single
ineffective breath won't ruin the efficacy of the treatment.
Disadvantages of SVNs include:
• The equipment required for use is expensive and
cumbersome.
• Treatment times are lengthy compared to other aerosol
devices and routes of administration.
• Contamination is possible with inadequate cleaning.
• A wet, cold spray occurs with mask delivery.
• There is a need for an external power source (electricity
or compressed gas).
Large-Volume Nebulizers
•
These units also have the capability for entraining room
air to deliver a known oxygen concentration.
• They can deliver varying concentrations of oxygen. When
using these units, you should always match or exceed the
patient's peak inspiratory flow rates.
• This assures delivery of oxygen and nebulized particles.
• These units produce particle sizes between two and ten
microns and may be heated to improve output.
Ultrasonic Nebulizers (USN)
• Ultrasonic nebulizers work on the principle that
high frequency sound waves can break up water
into aerosol particles.
• This form of nebulizer is powered by electricity
and uses the piezoelectric principle (ability to
change shape when a charge is applied).
• This principle is described as the ability of a
substance to change shape when a charge is
applied to it.
Ultrasonic Nebulizers (USN)
• Contains a transducer that has piezoelectric
qualities.
• When an electrical charge is applied, it emits
vibrations that are transmitted through a volume
of water above the transducer to the water
surface, where it produces an aerosol.
• The frequency of these sound waves is between
1.35 and 1.65 megacycles, depending on the
model and brand of the unit.
Ultrasonic Nebulizers (USN)
• Their frequency determines the particle size of the aerosol.
• The transducers that transmit this frequency are of two
types.
• One type is the flat transducer, which creates straight,
unfocused sound waves that can be used with various
water levels.
• The other type is a curved transducer, which needs a
constant water level above it because its sound waves are
focused at a point slightly above the water surface.
• If the water level falls below this point, the unit loses its
ability to nebulize.
Ultrasonic Nebulizers (USN)
• The particle size falls in the range of .5 to 3 microns.
• The amplitude or strength of these sound waves
determines the output of the nebulizer, which falls in the
range of 0 to 3 ml/minute and 0 to 6 ml/minute.
• Ultrasonic nebulizers also incorporate a fan unit to move
the aerosol to the patient. This fan action also helps cool
the unit.
• The gas flow generated by this fan falls in the range of
between 21 and 35 liters/minute. This flow of air also
depends on the brand and model of the unit.
Ultrasonic Nebulizers (USN)
• The transducer of an ultrasonic nebulizer is often found in
the coupling chamber, which is filled with water.
• This water acts to cool the transducer and allows the transfer
of sound waves needed for the nebulizer, which takes place
in a nebulizer chamber.
• The nebulizer chamber is found just above the coupling
chamber. These two chambers are usually separated by a
thin plastic diaphragm that also allows sound waves to pass.
• When studying ultrasonic nebulizers, remember that output is
controlled by amplitude, and particle size is controlled by
frequency.
The advantages of Ultrasonic
Nebulization are:
• High aerosol output
• Smaller stabilized particle size
• Deeper penetration into the tracheobronchial tree
(alveolar level)
• Useful in the treatment of thick secretions that are
difficult to expectorate, and they can help to stimulate a
cough.
• The therapy can be delivered through a mouthpiece or
face mask. Therapy can be given with sterile water,
saline or a mixture of the two.
Small-particle aerosol generator
(SPAG)
• This is a highly specialized
jet-type aerosol generator
designed to for
administering ribavirin
(Virazole), the antiviral
recommended for treating
high risk infants and
children with respiratory
syncytial virus infections.
Advantages of Aerosol Therapy as a
Whole:
• Systemic side effects are fewer and less severe than with
oral or parenteral therapy
• Inhaled drug therapy is painless and relatively convenient.
Aerosol doses are smaller than those for systemic
treatments.
• Onset of drug action is rapid.
• Drug delivery is directly targeted to the respiratory system.
Disadvantages as a Whole:
• Special equipment is often needed for its administration.
• Patients generally must be capable of taking deep, coordinated breaths.
• There are a number of variables affecting the dose of aerosol drug
delivered to the airways.
• Difficulties in dose estimation and dose reproducibility.
• Difficulty in coordinating hand action and breathing with metered dose
inhalers.
• Lack of physician, nurse, and therapist knowledge of device use and
administration protocols.
• Lack of technical information on aerosol producing devices.
• Systemic absorption also occurs through oropharyngeal deposition.
• The potential for tracheobronchial irritation, bronchospasm,
contamination, and infection of the airway.
The common hazards of aerosol
therapy are:
• Airway obstruction - Dehydrated secretions in the patient's airways
may absorb water delivered via aerosol and swell up large enough to
obstruct airways.
– To avoid this, watch the patient very closely and let him progress
with therapy at a reasonable rate. You may want to have suction
apparatus on hand.
• Bronchospasms - It is common for aerosol particles to cause this
condition (especially among asthmatics) and it is more prevalent when
administering a cold aerosol as compared to a heated one.
– If a very large amount of coughing occurs, stop therapy and give the
patient a rest. If this persists in farther therapy, stop treatment and
notify the physician.
The common hazards of aerosol
therapy are:
• Fluid overload - This can occur when administering continuous aerosol
therapy. It can happen quite frequently when treating infants or patients in
congestive heart failure, renal failure or patients who are very old and
immobile.
• In the infant, because of the smaller body size and possible underdeveloped
fluid control mechanism, a quantity of water that an adult can easily
handle will cause fluid overload.
• In a patient with congestive heart failure, any addition of fluid to the
vascular system will put an increased strain on the heart.
• In a patient with renal failure who is probably already in fluid overload, it
is easily seen that you will not want to increase the fluid volume.
• In older patients, the fluid control mechanisms may be impaired due to age.
Physician orders for aerosol therapy should contain
identification of:
•
•
•
•
•
•
•
Type of aerosol
Source gas (FI02)
Fluid composition (NaCl, water, etc.)
Delivery modality
Duration of therapy
Frequency of therapy
Temperature of the aerosol
Charting should include:
• time of administration
•
•
•
•
•
•
•
•
•
duration of therapy
type or composition of the aerosol (NaCl)
pulse
respiratory rate and pattern
breath sounds
characteristics of sputum
if sputum was or was not produced
the ease of breathing
benefits observed and any other relevant observations.
The reasons for administering aerosol
therapies include:
•
•
•
•
For bronchial hygiene
Hydrate dried secretions
Promote cough
Restore mucous blanket
• Humidify inspired gas
• Deliver prescribed medications
• Induce sputum lab culture
Bronchial Hygiene
Bronchial Hygiene
• Techniques designed to help mobilize and remove
secretions and improve gas exchange
• PDPV, CPT, modified breathing/coughing techniques,
and new devices
• Broad application is ineffective and expensive
• If combined with exercise, and used when indicated,
it can be a improve lung function
– Component of comprehensive respiratory care
Bronchial Hygiene
• Insufficient evidence to support or refute its use
with COPD, CB, or bronchiectasis
• Successful outcomes require:
knowledge of normal/abnormal physiology
patient evaluation and selection
clear definition of therapeutic goals
rigorous application of appropriate methods
on-going assessment
follow-up evaluation
Normal Clearance requires:
• a patent airway
• functional mucocilliary
escalator (larynx to
respiratory bronchioles)
• effective cough
most important
protective reflex
Four components to an effective
cough:
•
•
•
•
Irritation
Inspiration
Compression
Expulsion
Four components to an effective
cough:
• Irritation
Abnormal stimulation
provokes sensory
fibers to send impulses
to he brain’s medullary
cough center
Stimulus is either
inflammatory,
mechanical, chemical
or thermal
Four components to an effective
cough:
• Inspiration:
Cough center generates
a reflex stimulation of
the respiratory muscles
to initiate a deep
inspiration
Four components to an effective
cough:
• Compression
Reflex nerve impulses
cause glottic closure and
a forceful contraction of
the expiratory muscles
This causes rapid rise in
pleural and alveolar
pressure
Four components to an effective
cough:
• Expulsion
– Glottis opens
– Large pressure gradient is present
– Causes a violent, high-velocity, expulsive flow
combined with dynamic airway compression
creates a shearing force that displaces mucus for
the walls into the airstream
Abnormal Clearance is caused by
an alteration in
• Airway patency
• Mucociliary function
• Effectiveness of cough
reflex
Abnormal Clearance
• Airway patency
full airway obstruction
mucus plugging
can result in atelectasis with the
possiblitiy of deoxygenation due
to shunting
Inadequate humidification can
result in this
partial obstruction (reduced
airflow)
increase work of breathing
airtrapping
overdistention
VQ mismatch
Abnormal Clearance
• Mucociliary function
high FiO2 can impair
directly or due to
tracheobronchitis
Abnormal Clearance
• Effectiveness of cough
reflex
Abnormal Clearance
• Therapeutic interventions
• Abnormal clearance in the
presence of a pathogenic
organism may result in infection
• Infectious process 
inflammatory response and
release of chemical mediators
damage to airway epithelium
and increase mucus production
 cyclical activity
Phase Disruption
• Irritation
Anesthesia
CNS depression
Narcotics
Phase Disruption
• Inspiration:
•
•
•
•
Pain
Neuromuscular dysfxn
Pulmonary restriction
Abdominal restriction
Phase Disruption
• Compression
Laryngeal nerve damage
Artifical airway
No mucocillary escalator
Erosion of trachea
Prevent closure of glottis
Abdmonial muscle weakness
Abdominal surgery
Phase Disruption
• Expulsion
Airway compression
Airway obstruction
Abdominal muscle
weakness
Inadeaqute lung recoil
Diseases
• Internal obstruction or
external compression
FBO
Mucus hypersecretion
Inflammatory changes
Bronchospasm
Asthma
CB
Pneumonia
pneumonitis
• Tumor
• Kyphoscoliosis
Diseases
• Alteration in mucocilliary escalator
CF (viscous secretions)
Ciliary diskinetic syndromes (cilia don’t work right)
Bronchiectasis (occurs w/ CF & Ciliary diskinetic
syndromes)
Permenent airway damage
Dilated airway
Constant obstruction
Diseases
• Reflex
Neuromuscular
disorders
Muscular dystrophy
Amytrophic muscular
sclerosis
MS
Polymyelitis
• Cerebral palsy
Goals
• Mobilize and remove retained secretion
• Improve gas exchange
• Reduce WOB
Indications
• Acute
Acutely ill with copious secretions
Acute respiratory failure with clinical signs of retained
secretions
Lobar atelectasis
V/Q abnormalities due to unilateral lung infiltrates or
consolidation
Probably not helpful for:
Pneumonia without significant sputum production
COPD
Uncomplicated asthma
Indications
• Chronic: > 25-30
ml/day to be effective (
1 fluid oz or shot glass
full)
CF
Bronchiectasis
Ciliary dyskinetic
syndromes
Chronic bronchitis
Indications
• Prevention
Body position
Pt Mobilization
PDPV combined with
exercise to maintain
normal function in CF
– Possible NM disorders
Determining the need:
• Bedside assessment
Ineffective cough
Absent or increased sputum production
Labored breathing pattern
Decreased breath sounds
Crackles or rhonchi
Tachypnea, tachycardia
Fever
General physical fitness
Posture, muscle tone
Determining the need:
• Chart
H/O secretion retention or dz
process indicating such
Upper abdominal or thoracic
surgery
Age
H/O COPD
Obesity
Nature of procedure
Type of anesthesia
Duration of procedure
Intubation or trach
CXR: atelectasis or infiltrates
PFT
ABG
Bronchial Hygiene Methods: all can be used alone or
in combination with another
• PD & P includes
– postural drainage and turning
– Percussion
– Vibration
• Coughing and repulsion techniques
–
–
–
–
PAP adjunts
PEP
CPAP
Expiratory PAP (EPAP)
• High-frequency compression/oscillation methods
• Mobilization/exercise
Postural Drainage Therapy:
• Involves the use of gravity and mechanical energy to
Aid in mobilizing secretions
Improve V/Q balance
Normalize FRC
• Includes
Turning
Drainage
Percussion
vibrations
Turning
• Kinetic Therapy or continuous lateral rotational
therapy
• Done by
– Patient
– Caregiver
– Rotational bed
• RotoRest Delta Bed rotates continuously side to side (124 degree
angle over 3-4 minutes)
• Reposition can be accomplished by using automated inflation and
deflation of air-filled mattress compartments
Turning
• Primary Purpose
– Promote lung expansion
– Improve oxygenation
– Prevent retention of secretions
• Other benefits
– Reductions of venostasis
– Prevention of skin ulcers
Turning
• Absolute contraindications
– Unstable spinal chord injuries
– Traction of arm abductors
• Relative contraindications
–
–
–
–
–
–
–
Severe diarrhea
Marked agitation
Rise in intracranial pressure (ICP)
Large drops in blood pressure (>10%)
Worsening dyspnea
Hypoxia
Cardiac dysrhythmias
Turning
• Hazards
– Ventilator disconnection
– Accidental extubation
– Aspiration of ventilator condensate
– Disconnection of vascular lines or urinary
catheters
Turning
• Proning
– Used in pts with Acute Lung Injury (ALI)
– Improves oxygenation without negative effects on
hemodynamics
• May allow for lower FiO2 and lower pressure
• Not shown to improve survival though
Turning
•
Possible reasons for improved oxygenation
– Transpulmonary pressure in this position probably exceeds
the airway opening pressure in the lung regions where
atelectasis, shunt, and V/Q mismatch are most severe
– May shift blood away from shunt regions via gravity, which
induces recruitment of previously atelectatic but healthy
areas
– Reduces further injury from PPV
Postural Drainage
• Use of gravity to help move secretions from distal
lung segments
– May be coughed up
– Or suctioned out
• Affected lung segmental bronchus to be drained in a
vertical position relative to gravitational pull
• Positions are usually held for 3-15 minutes
– Depends on tolerance and condition
Postural Drainage
• Most effective if
– Sputum production is >25-30 ml/day
– Head-down positions exceed 25 degree below
horizontal
– Pt is adequetly hydrated
• Airwaymay need bland aerosol
• SystemicIV NS
– Performed every 4-6 hours
• Or as appropriate given pt response
Postural Drainage
• Technique
– Identify appropriate lobe or segment
– Determine position and need for position modification
given your assessment
•
•
•
•
Unstable hemodynamics
HTN
Cerebrovascular disorders
Orthopnea
– Schedule treatment at least 1.5-2 hours after meals to
prevent aspiration
– Assess need for pain meds
Postural Drainage
• Assess pt surroundings
–
–
–
–
Monitors
IV or other lines
NG
O2
• Explain procedure to the patient
– Secretions don’t always come up immediately.
– May take several txs to be successful
• Assess vitals and pulse-ox pre, during and post
• Assess breath sounds pre and post
• Encourage appropriate coughing techniques pre,
during, and post
Postural Drainage
• Other assessments
– Subjective response
– Breathing pattern, symmetrical movement, etc.
– Mental function
– Skin color
– SpO2
– ICP
Postural Drainage
• Recommended interventions
upon complications
– Hypoxia
• Give higher FiO2 during
procedure
• If hypoxia occurs during tx,
give 100% FiO2stop
therapyreturn to original
position
– Increased ICP
• Stop therapyreturn to
original position
Postural Drainage
• Recommended interventions
upon complications
– Acute hypotension during tx
• Stop therapyreturn to
original position
– Pulmonary Hemorrhage
• Stop therapyreturn to
original positioncall Doc
immediatelyO2maintain
airway
– Pain or injury
• Stop therapyreturn to
original position carefully
Postural Drainage
• Recommended interventions upon complications
– Vomiting/Aspiration
• Stop clear airway/suctionO2maintain airway return to
original positioncall Doc
– Bronchospasm
• Stop  return to original position O2call
Docbronchodilators as ordered
– Dysrhythmias
• Stop  return to original position O2call Doc
Postural Drainage
• Outcome assessment:
criteria indicating positive
response
• Should be assessed every
24 hrs for critical and
every 3 days for others or
upon change in status
– Worsening breath sounds is
not necessarily bad
• Example: diminished to
rhonchisecretions have
loosened
Postural Drainage
• Outcomes
–
–
–
–
–
–
–
–
Pt’s subjective response to treatment
Vitals and ECG
Breathing pattern, rate, chest expansion, etc.
Sputum production
Breath sounds
Chest X-ray
SaO2, SpO2, ABGs
Ventilator variables
Postural Drainage
• Charting
–
–
–
–
–
Date and time
Position(s)
Time in position(s)
Patient tolerance
Subject/objective indicators
of tx effectiveness
• Sputum color, viscosity,
volume
– Pre, during, post assessment
– Signature
Right Lung (3 Lobes)
Right Upper Lobe
Right Middle Lobe
Right Lower Lobe
Left Lung
Left Upper Lobe
Left Lower Lobe
Bronchi-Carina
Right Upper Lobe Bronchi
Right Middle Lobe Bronchi
Right Lower Lobe Bronchi
Left Upper Lobe Bronchi
Left Lower Lobe Bronchi
Right Upper Lobe Segmental
Anatomy : Apical
UPPER LOBES
Apical Segment/1
• Bed or drainage table
flat.
• Patient leans back on
pillow at 30 degree
angle.
• (Clap over area between
clavicle and top of
scapula on each side.)
Right Upper Lobe Segmental
Anatomy : Posterior
UPPER LOBES
Posterior Segment/3
• Bed or drainage table
flat.
• Patient leans over folded
pillow at 30 degrees
angle.
• (Clap over upper back on
each side of chest.)
Right Upper Lobe Segmental
Anatomy : Anterior
UPPER LOBES
Anterior Segment/2
• Bed or drainage table
flat.
• Patient lies flat on back
with pillow under knees.
• (Clap between clavicle
and nipple on each side
of chest.)
Right Middle Lobe Segmental
Anatomy : Medial
Right Middle Lobe Segmental
Anatomy : Lateral
RIGHT MIDDLE LOBE:
Lateral Segment-4
Medial Segment-5
• Foot of table or bed
elevated 14 inches or
about 15 degrees.
• Patient lies head down
on left side and rotates
1/4 turn backward.
Pillow may be placed
behind patient from
shoulder to hip.
• Knees should be flexed.
(Clap over right nipple
area.)
Right Lower Lobe Segmental
Anatomy : Superior
Right Lower Lobe Segmental
Anatomy : Posterior Basilar
Right Lower Lobe Segmental
Anatomy : Medial Basilar
Right Lower Lobe Segmental
Anatomy : Anterior Basilar
Right Lower Lobe Segmental
Anatomy : Lateral Basilar
Left Upper Lobe Segmental
Anatomy : Anterior
Left Upper Lobe Segmental
Anatomy : Apicoposterior
Left Upper Lobe Segmental
Anatomy : Anterior
Left Upper Lobe Segmental
Anatomy : Superior Lingular
Left Upper Lobe Segmental
Anatomy : Inferior Lingular
LEFT UPPER LOBE
Lingular Segment-Superior-4
Inferior-5
• Foot of table or bed
elevated 14 inches or
about 15 degrees.
• Patient lies head down
on right side and rotates
1/4 turn backward.
• Pillow may be placed
behind patient from
shoulder to hip. Knees
should be flexed.
• (Clap over left nipple
area.)
Left Lower Lobe Segmental Anatomy :
Anterior MedialBasilar
LOWER LOBES:
Anterior Basal Segment/8
• Foot of table or bed
elevated 18 inches or 30
degrees.
• Patient lies on side,
head down, pillow under
knees.
• (Clap over lower ribs just
beneath axilla.)
Left Lower Lobe Segmental
Anatomy : Superior
LOWER LOBES:
Superior Segment/6
• Bed or table flat. Patient
lies on abdomen with
pillows under hips
• (Clap over middle of
back below tip of scapula
on either side of spine.)
Left Lower Lobe Segmental
Anatomy : Lateral Basilar
LOWER LOBES:
Lateral Basal Segment/9
• Foot of table or bed
elevated 18 inches or 30
degrees.
• Patient lies on abdomen,
then rotates 1/4 turn
upward.
• Upper leg can be flexed
over a pillow for support.
(Clap over uppermost
portion of lower ribs.)
Left Lower Lobe Segmental
Anatomy : Posterior Basilar
LOWER LOBES: Posterior Basil
Segment/10
• Foot of table or bed
elevated 18 inches or 30
degrees.
• Patient lies on abdomen,
head down, with pillow
under hips. Upper leg
can be flexed over a
pillow for support.
• (Clap over lower ribs
close to spine on each
side of chest.)
Assignment for Upcoming Labs
• Memorize the segments
of the lungs
• Memorize the
appropriate positions
for each segment!
Percussion and Vibration
• Application of mechanical energy to the chest
wall
– Hands
– Pneumatic devices
• Percussionbreak secretions loose for TB tree
• Vibration aids in moving secretions toward
the central airways
Percussion and Vibration
• Unclear as to how much force or frequency
should be used to be effective
• Effectiveness is controversial
• Used in conjunction with postural drainage
• Percussion over the lobe or segment being
drained
Percussion
• This should be done with the hands in the
cupped position, with the thumb and fingers
closed to trap air.
Percussion
• Hold your arms with the elbows partially
flexed and wrists loose
• Rhythmically strike the chest wall in a waving
motion using both hands alternately in
sequence.
• Percuss back and forth in a circular pattern
over the specific segment for 3-5 minutes
Vibration technique
• Place hands on either side of the chest
• After the pt takes a deep breath, exert slightto-moderate pressure ont eh chest wall
• Initiate a rapid vibratory motion of the hands
throughout expiration
Mechanical Percussion and Vibration
• Devices have both frequency and force control
– 20-30 cycles/second
– 20-30 Hz
– Noise, excess force, mechanical failure and
electrical shock are all potential hazards
Coughing
• Directed cough (DC) to clear or mobilize
secretions is a component of bronchial hygiene
– Directed Cough is a deliberate maneuver that is
taught, supervised, and monitored.
• Forced expiratory technique (FET, or huff cough)
and manually assisted cough are examples of
directed cough.
Coughing
• Seeks to mimic the attributes of an effective
spontaneous cough (or series of coughs)
• To help to provide voluntary control over reflex
• To compensate for physical limitations
–
–
–
–
increasing glottic control
inspiratory and expiratory muscle strength
coordination
airway stability
• Patient should assume position best for
exhalation and allows for easy thoracic
compression
• •Surgical (Thoracic/Abdominal): Splinting to
limit pain and anxiety
"CASCADE TECHNIQUE"
• Breathe in slowly and deeply through the nose.
• Breathe out slowly and completely through
pursed lips.
• Breathe in slowly and deeply once again, then
hold breath briefly.
• Cough several times until lungs feel empty. The
cough should produce a sharp sound.
• Avoid taking sharp, quick breaths between
coughs.
Forced Expiratory Technique
"HUFF TECHNIQUE"
• Forced expirations of middle to low lung volume
without closure of the glottis
• Breathe in slowly and deeply through nose.
• Breathe out slowly and completely through pursed
lips.
• Breathe in slowly and deeply once again, then
hold breath briefly.
• Instead of coughing, let the air out in several short
bursts while saying "huff."
• A "huff" sound is produced rather than a sharp
sound.
"ASSISTED COUGH TECHNIQUE”
• Pt Breathes in slowly and deeply through the nose
and then out slowly and completely through
pursed lips.
• Pt Breathes in slowly and deeply once again, then
holds breath briefly.
• Assisting person places hands on pt’s sides at the
lower rib cage or on stomach above belly button.
• Pt coughs while the person assisting applies
gently pressure.
• Stop applying pressure when the patient is
finished breathing out, but don’t remove hands
PAP
• Positive airway pressure (PAP) adjuncts are used to
mobilize secretions and treat atelectasis and include
– continuous positive airway pressure (CPAP)
– positive expiratory pressure (PEP)
– expiratory positive airway pressure (EPAP).
• Cough or other airway clearance techniques are
essential components of PAP therapy when the
therapy is intended to mobilize secretions
PAP: CPAP
• The patient breathes from a pressurized circuit
against a threshold resistor (water-column,
weighted, or spring loaded) that maintains
consistent preset airway pressures from 5 to 20 cm
H2O during both inspiration and expiration
– (By strict definition, CPAP is any level of aboveatmospheric pressure.)
• CPAP requires a gas flow to the airway during
inspiration that is sufficient to maintain the desired
positive airway pressure.
PAP: CPAP
• Types of threshold resistors: all of these valves
operate on the principle that the level of PAP
generated within the circuit depends on the
amount of resistance that must be overcome to
allow gas to exit the exhalation valve.
• They provide predictable, quantifiable, and constant
force during expiration that is independent of the
flow achieved by the patient during exhalation
PAP: CPAP
• Underwater seal resistor:
– expiratory port of the circuit is submerged under a
column of water, the level of CPAP is determined
by the height of the column
• Weighted-ball resistor:
– consists of a steel ball placed over a calibrated
orifice, which is attached directly above the
expiratory port of the circuit
PAP: CPAP
• Spring-loaded:
– rely on a spring to hold a disc or diaphragm down over the
expiratory port of the circuit.
• Magnetic valve resistors
– contain a bar magnet that attracts a ferromagnetic disc
seated on the expiratory port of the circuit the amount of
pressure required to separate the disc from the magnets is
determined be the distance between them.
PAP: PEP
• The patient exhales against a fixed-orifice
resistor, generating pressures during expiration
that usually range from 10 to 20 cm H2O
• PEP does not require a pressurized external gas
source.
• The amount of PEP varies with the size of the
orifice and the level of expiratory flow produced
by the patient. The smaller the orifice the
greater the pressure.
PAP: PEP
• Thus the patient must be encourage to generated a
flow high enough to maintain expiratory pressure at
10-20 mm H2O
• Ideal I:E of 1:3 or 1:4
• The patient should perform 10-20 breaths through
the device and then perform 2-3 huff breath coughs
• This should be repeated 5-10 times during a 15-20
minute session
PAP: EPAP
• The patient exhales against a threshold resistor,
generating preset pressures of 10 to 20 cm H2O
(similar to CPAP expiration)
• EPAP does not require a pressurized external gas
source.
• EPAP utilizing threshold resistors does not
produce the same mechanical or physiologic
effects that PEP does when a fixed orifice
resistor is used.
• Further study is necessary to determine how
these differences affect clinical outcome.