MEDICAL GASES Humidity and Aerosol Therapy First Year

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MEDICAL GASESHumidity and Aerosol Therapy

• First Year Respiratory Therapy
• MJC
• RsCr 220

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HUMIDITY THERAPY

• Add moisture to the gases we breathe
• Reduce upper airway swelling
• Maintain normal physiologic functions

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The Patient Needs Water

• Patients require hydration
• Normally through systemic hydration
• Respiratory signs of dehydration
• Crusty nasal passages
• Thick tenacious secretions
• Dry hacking cough
• Nosebleeds
• Dry mouth

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Respiratory Patients are Special

• Often have SUPER (0 humidity) dry gases
  delivered to them
• Have bypassed normalupper airways
• Need to heat and humidify

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Humidity Concepts

• Temperature effects humidity
• The warmer the air the more humidity it is
  capable to carry
• Weather, condensation and evaporation are results
  of changing conditions
• Water vapor content is measured in mg of water in
  liters of air (mg/L)
• Normal is 44 mg/L (100 humidity at 37oC)

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Definitions

• Water Vapor Pressure
• Exerts a pressure as part of the atmospheric
  pressure
• Normal is 47 mmHg in the lungs
• Daltons law of Partial Pressure (but more on
  that later with Gas Physics)
• Nitrogen, Oxygen and Carbon Dioxide exert their
  own partial pressure totaling 760 mmHg

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Definitions

• HUMIDITY
• Addition of water to gas delivered to airway
• Absolute Humidity
• Actual amount of water in air
• Relative Humidity
• Percentage of full saturation

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Definitions

• Body Humidity
• Fully saturated at body temperature
• 100 RH, 43.9 mg/L at 37C
• Body (Humidity) Deficit
• Difference between measured and fully sat
• Amount needed to achieve full saturation that
  temperature.

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Humidity Deficit
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I.S.B.

• Isothermic Saturation Boundary
• At or just below carina (end of trachea)
• Point at which inspired gases are fully 100
  saturated and warmed to body temperature
• 44 mg/L at 37oC

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Compromised ITB

• Upper airway is bypassed with artificial airway
• Environmental temperature or humidity drops
• Tidal volumes (breathing) increased

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The Bodys Normal Humidifier

• The nose is a efficient active humidifier which
  adds heat and moisture to the inspired gas.
• Nasal mucosa, vascular capillary beds, turbinates
  and conchae

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Reasons for Using Humidity Therapy

• Humidify Gases
• Thin Secretions
• Reduce Swelling
• Induce Sputum Samples

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Solutions Used

• Hypertonic (10) Sputum Inductions
• Greater tonicity then surrounding tissues
• Tend to draw fluid from surroundings
• Isotonic (Normal Saline) 0.9 - Breathing Tx
• Neither gains or loses water but maintains a
  steady size Body neutral
• Hypotonic Most Humidity Therapy
• Sterile Water

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Indications for Humidity Therapy

• Upper airway inflammation
• (Croup and Post extubation)
• Reduces swelling with vasoconstriction
• Humidity deficit
• Sputum induction

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Upper Airway Swelling

• Croup
• Post-Extubation

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Upper Airway Stridor

• Narrowing of the neck breathing passages
• Caused by swelling of inner lining
• Cool temperature causes decreased swelling and
  increased size of opening
• CROUP
• POST EXTUBATION

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Humidity Deficit

• Normal Humidification is Inadequate

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Respiratory Patients

• Usually patients in ICU with bypassed upper
  airway
• Trach or ET Tube
• Always heated
• Provide oxygen and humidity (sterile water)

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Sputum Inductions

• For patients unable to cough up on their own
• Nebulize 10 saline solution for 10 minutes
• The hypertonic saline draws out water from the
  tissues of the throat and trachea to help
  liquifey secretions for expectoration
• Could also use mucomyst to help break down the
  thick secretions
• Microbes then can be identified

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Goals of Humidity Therapy

• Provide adequate heat and humidity to the
  inspired gas
• Reduce airway swelling
• To aid in the removal of thick secretions
• To prevent airway response to cold air

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ANSI Standards

• American National Standard Institute states
  minimum standards for humidification
• Reminder Normal 44 mg/l or 100
• Upper Airway
• Output of 10 mg/L for unheated
• 50 RH at room temperature (22oC)
• Lower Airway
• At least 30 mg/L heated (100 at 30oC)

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Hazards of Humidification

• Just Right
• Too Little
• Too Much

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Hazards of Humidity Therapy

• Bronchospasm to cool mist
• Watch out for Asthmatics
• Infection
• Universal precautions
• Fluid overload
• Especially CHF and Newborns

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Underhumidification

• Caused by exposure to dry medical gases
• Thicken mucous and retained secretions
• Decreased mucocilliary transport
• Cold can cause bronchospasm

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Overhumidification

• Lead to excess body fluid retention
• Susceptible patients
• Efficiency of cilia is decreased
• Dilutes surfactants and collapsed alveoli
• Swelling of mucous layer and causing narrowing of
  air passages

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Systemic Hydration

• The most effective method to improve thick
  secretions is by
• Systemic Hydration with intravenous fluids

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Humidifier Types

• Bubble diffusers
• HME
• Wick
• Cascade, Babington, Passover

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Overall factors affecting humidity

• Need to design features into apparatus
• Temperature
• Has the greatest effect of all
• Heating allows for increased humidity
• Length of time
• Longer contact time increases humidity
• Surface area
• Greater surface area increases humidity

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Low-Flow Humidifiers

• Unheated
• Bubble Diffuser

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Bubble Humidifiers
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Bubble Humidifiers

• Used with nasal cannula only
• Adjust flow on flowmeter from 1 to 6 LPM
• Does NOT do well with high flows from flowmeter

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Diffuser Humidifier - Increases Surface Area of
Gas
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High-Flow Humidifiers

• CAPABLE OF BEING HEATED
• Aerosol Setup
• Concha
• Wick
• HME

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Large Volume Aerosol
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Large Volume Jet Aerosol Humidifier

• Called Aerosol set-up
• Always run at flush
• Flow restrictor in most brands limit flow to just
  12 or 13 liters

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Another Aerosol Setup
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Tandem Set-up
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50 Rule

• With very little air entrainment with high oxygen
  concentrations, total flows are pitiful
• Need to double the output in creative ways
• The most common way is to use two nebulizers teed
  in together in tandem

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Collection Bag

• All large bore circuits have a tendency to
  collect water
• This is mainly caused through condensation
• Also called rainout
• Best remedy is to place drain bag at lowest loop
  in the circuit.

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Too much water in the tubing

• Often the drain bag is poorly positioned
• Not at the bottom of the loop
• A gurgling sound can be heard when air passes
  through the collection of water
• The oxygen concentration is increased as the
  water acts as a restriction that messes up the
  entrainment ratios of the venturi device

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Collection Water Bag
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Fisher Paykel (Wick Humidifier)
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Wick Internal View
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Concha Humidifier
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Water in the line

• Can be limited with heated wires in tubing

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Heated Wire Circuit
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Servo Control

• Many modern ventilator circuits maintain a water
  free tubing with a feedback servo system that
  keeps the temperature constant
• Recommended temperature range from 34 to 35 and
  even 37oC
• But more on that with ventilator class

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Dated Little Seen Humidifiers

• Passover
• De Vilbiss
• Babbington

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Passover Humidifier
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Cascade Humidifier
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De Vilbiss
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Babbington Nebulizer
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Now for something new

• Heat Moisture Exchanger
• (HME)

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HME
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HME
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HME

• Can produce 70 90 body humidity
• For short term use
• Usually replaced every 24 hours (72 hrs max)
• Excessive secretions lead to blockage
• If secretions thicken, it should be replaced
• Considered passive (vs active) humidifier because
  it uses patient to heat unit

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Humidifiers

• Aid in the removal of thick secretions
• Sputum Inductions
• with Hypertonic Saline (10)

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SVN for Sputum Induction

• Use normal
• Small Volume Nebulizer
• Draws fluid out of tissue,
• causes mucous layer to
• increase and easier to
• effectively cough up sample.

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The End