07 Humidity Therapy

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					MEDICAL GASES
Humidity and Aerosol Therapy

    First Year Respiratory Therapy

    MJC
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HUMIDITY THERAPY


  Add moisture to the gases we breathe
  Reduce upper airway swelling
  Maintain normal physiologic functions
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
       Dalton’s 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 Body’s 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
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
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
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
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
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
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
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)
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%)
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




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