REVIEW OF HUMIDITY-AEROSOL THERAPY by hcj

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									Review Aerosol and Humidity Therapy RsCr 224 REVIEW OF HUMIDITY-AEROSOL THERAPY Respiratory Care 224 Readings Wyka’s Foundations of Respiratory Therapy – Chapter 17 Mosby’s RC Equipment – Chapter 4 Egan’s Fundamentals Humidity and Bland Aerosol Therapy – Chapter 32 Various AARC Guidelines on Aerosol Therapy OUTLINE Humidity  Definitions, equipment (1.heated 2.non-heated 3.HMEs)  Bland Aerosol Therapy  Cool mist, sputum inductions Aerosol Therapy (Medicines)  Nebulizers, MDI, DPI  Specialized nebs Definitions of Essential Terms  Absolute Humidity - amount of water vapor actually present in the air (expressed in mg/liter). Sometimes called water vapor content.  Maximum Absolute Humidity - amount of water vapor that the air can hold. Sometimes called water vapor capacity.  varies directly with temperature  Relative Humidity - the mathematical comparison of the above two. Content divided by capacity  Body Humidity – the humidity of the lungs (100% saturated at 37oC)  Humidity Deficit – any humidity less than body humidity that needs to be made up by the body American National Standard Institute (with AARC) recommendations  Minimum of 10 mg/L for NON-intubated  Minimum of 30 mg/L for intubated patients (that bypass normal body humidification) Indications for Humidifying and Warming of Gases  To humidify dry inspired gases (> 4 LNC)  Thick mucous gel, retention of secretions, impaired cilia function, mucus plugging smaller airways leading to atelectasis and impaired pulmonary function (bronchoconstriction) eventually leading to destruction of cilia, damage to mucous glands and destruction of epithelial lining and basement membrane.  To overcome the humidity deficit when the upper airway is bypassed (trached patients or those with endotracheal tubes) Less common indications;  treatment of hypothermia  treatment of bronchospasm caused by cold air

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Review Aerosol and Humidity Therapy RsCr 224

EQUIPMENT USED TO HUMIDIFY GASES 1. Non-heated (Cool) Humidifiers 2. Heated Humidifiers 3. Heat Moisture Exchangers (HME) BUBBLE DIFFUSION HUMIDIFIERS  Used mainly with nasal cannula (are typically unheated) Factors Affecting Performance of Bubble Humidifiers  Time of contact between gas & the water  Surface area available for evaporation to occur  Temperature of the gas How Flow Lowers Humidity The bubble humidifier becomes less efficient with increased flow rates. HEATED HUMIDIFIERS  These are Hudson-RCI “Conchatherm”, Fisher-Paykel Wick, Puritan-Bennett Cascade  Water can be heated to maintain high humidity output  Temperature can be sensed “downstream” from the unit so that water temperature can be adjusted to maintain correct gas temperature (like thermostat at home)  Heated wires can be employed to prevent condensation in tubing from gas cooling Why Wick Type Humdifiers Are Popular  Produce high vapor output even at very high gas flows (>100 l/m)  Do not produce any water particles – Low risk of producing nosocomial infections  Have ability to utilize heated wire circuits  Have continuous-feed water systems Hazards & Problems Associated with Heated Humidifiers  Overheating leading to patient airway burns  Inadvertent overfilling of humidifier by therapist  Increased airway resistance created by pooling of condensate in circuit  Burns to caregivers from inadvertently touching heated metal surfaces ARTIFICIAL NOSES (HME)  Types of Heat & Moisture Exchangers: – Simple condensors – Hygroscopic Condenser Humidifiers (HCF) – Hydrophobic Condenser Humidifiers  Act by recycling exhaled heat & moisture

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Review Aerosol and Humidity Therapy RsCr 224 – “Ideal” unit should be able to produce at least 30 mg/l - Most produce 20 - 30 mg/l

Problems With HME’s  Increase in airflow resistance (particularly when mucus enters unit)  Drying & thickening of secretions can become a problem  Must be removed when administering “in-line” medication aerosol treatments  Lose efficiency in patients with high minute volumes (>10 l/m) Why HME’s Have Become Popular?  Significant cost savings can be realized compared to a standard ventilator circuit using a heated humidifier  Less therapist time needed to drain condensed water from circuit  Greater simplicity  However, in some cases “heated-wire” circuits may be actually cheaper than the HME

BLAND AEROSOL THERAPY Indications for;  Tx of laryngotracheobronchitis (croup)  Tx of sub-glottic edema  Post-extubation edema  Post-operative management of upper airway  Presence of bypassed upper airway  Need for sputum induction Contraindications to Bland Aerosol Therapy  Bronchospasm (evidence of current disease) – Asthma or Chronic Bronchitis patients who c/o SOB  History of airway hyperresponiveness – Those with a hx of asthma or other obstructive lung disease Hazards and Complications of Bland Aerosol  Wheezing associated with bronchospasm  Infection  Overhydration  Patient discomfort  Caregiver exposure to contagious aerosols  Noise Types of Nebulizers Used for Bland Aerosol Therapy  Large Volume Jet Nebulizers  Ultrasonic Nebulizers

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Review Aerosol and Humidity Therapy RsCr 224 Solutions Used for Bland Aerosol Therapy  Water - most irritating; cheapest to use – Normal Saline (0.9% NaCl) - least irritating; salt crystals can condense on water intake causing no aerosol to be produced  Hypertonic Saline - 5 or 10% - used only for sputum inductions

DELIVERY OF INHALED MEDICATIONS Basic Definitions Aerosol – liquid or solid particles which are suspended in a gas Stability – the ability of an aerosol particle to remain an aerosol particle Penetration – How far down the respiratory tract a particle is deposited Deposition – the fact that the particle stays in the respiratory tract (some small totally stable particles will be exhaled) Retention – absorbed in the respiratory tract Clearance – the fact that some particles are exhaled Factors that influence the penetration and deposition of aerosols >100 microns – do not enter the respiratory tract (filtered out) 10 – 100 microns – trapped in the nose and mouth 2 – 5 microns – deposited in the bronchial airways 1 – 2 microns – deposit in the alveoli < 1 microns – usually exhaled Implications – you want large 10 micron for upper airway swelling, 2 – 5 microns for bronchodilators in the airways and 1 – 2 microns for antibiotics and anti-inflammatories to the lung alveoli Indications for aerosol therapy  Humidification of the respiratory tract  Aid in mobilizing secretions  Deliver medications Hazards of aerosol therapy  Infection  Bronchospasm  Overhydration Delivery systems  MDI’s  DPI’s  Small volume jet nebulizers  aka: HHN’s; SVN’s; wet nebs; med nebs; neb meds; acrons  USN’s  Specialized aerosol systems 4

Review Aerosol and Humidity Therapy RsCr 224 METERED DOSE INHALERS (MDI’s)  Exact same dose each actuation  High initial aerosol velocity  Currently uses chloroflourocarbon (CFC) propellant. Hydroflouroalkanes (HFA) will replace CFC’s pending final approval.  Without using a “spacer” - up to 80% of aerosol lands in the oropharynx or mouth  10 - 20% reaches small airways  administration is very technique dependent MDI “Accessory” Devices  Holding chambers or spacers – Improve ease of administration – Decrease oral-pharyngeal deposition – Improve distribution of the mist  Flow-triggered MDI’s – Currently only “Maxair” (pirbuterol) is available Optimal Technique for Using MDI  Shake MDI first (warm if cold)  Actuate into chamber  Inhale slowly & deeply  Maintain a 10 second breath hold  Allow 30 seconds between actuation Disadvantages of MDIs  Coordination can be a problem – Requires use of additional spacer  High oral-pharyngeal deposition  Easy for patients to overuse  Some medications can be quite expensive  Some patients can run out without realizing DRY POWDER INHALERS (DPI’S)  Always are breath actuated since no propellant is used  Easier to self-administer - no spacer needed  Not very many drugs are available in this form  At least as good as MDI in terms of deposition and drug response  Can’t be used with young children & in ventilator circuits Optimal Technique for Using DPI  Patient must use high inspiratory flows – Best not used if patient is having severe SOB  Breath holding is not critical  Medication should be stored in a low humidity environment 5

Review Aerosol and Humidity Therapy RsCr 224 Disadvantages of DPIs  Some patients can’t generate high inspiratory flows needed  Assembly of unit can be difficult for some  Difficult to give high doses  Some pharyngeal deposition is unavoidable  Not that many medications available in this form (currently) SMALL VOLUME NEBULIZERS (Acorn tx)  Generally hold 2 - 6 ml of solution  Can be filled using “unit-dose” preparations or multi-dose vials  Generally require 4-8 l/m of flow to actuate  Can be driven with either oxygen or air – When using oxygen - FIO2 can be 40 - 90 %!!  Should be used instead of MDI or DPI if patient is tachypneic Disadvantages of SVNs  Too complex for some patients to use – Requires assembly & periodic cleaning  Not easily portable like the MDI or DPI  Not all medications are available – Only one steroid currently available for SNV administration (Pulmicort respule) Specialized Medication Nebulizers  Respigard II - filters exhaled gas - delivers very small particles (1-2 microns)  Circulaire - Uses a reservoir bag to conserve medication - enhances aerosol delivery  Continuous “HEART” Nebulizers - used for continuous drug administration (1-3 hours)  SPAG unit- used for administration of Ribavirin (not used any more) Small Volume ULTRASONIC NEBULIZERS  Produce very dense mists at very high outputs  Compact units; portable; easy to use  Used for delivery of “undiluted” medications (bronchodilators; antibiotics)  Some units can be powered by cigarette lighter adapter present in a car Problems with USNs  Expensive to purchase  Prone to breakdown  Not all mediations are available in multi-dose or unit dose forms  Medication must be manually added to unit prior to use The end

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