1. Review of Humidity-Aerosol Therapy

2. Definitions of Esssential Terms
Absolute Humidity – Amount of water vapour actually present in the air (expressed in mg/litre). Sometimes called water vapour content.
Maximum Absolute Humidity – Amount of water vapour that the air can hold. Sometimes called water vapour capacity.
Varies directly with temperature.
Relative Humidity – The mathematical comparison of the above two. Content divided by capacity.

3. Essential Information for Doing Calculations of Relative Humidity
The maximum absolute humidity at body temperature is 44 mg/litre
This is sometimes called “Body Humidity”
Any relative humidity less than body humidity is called the “Humidity Deficit”

4. Indications for Humidifying and Warming of Gases
To humidify dry inspired gases
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

5. Equipment Used to Humidify Gases
Bubble Diffusion Humidifiers

6. Factors Affecting Performance of Bubble Humidifiers
Time of contact between gas and the water
Surface area available for evaporation to occur
Temperature of the gas

7. How Flow Lowers Water Temp.

8. Typical Wick-Type Humidifier

9. Fisher-Paykel Wick Humidifier

10. Hudson-RCI “Conchatherm”

11. Characteristics of Heated Humidifiers
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 a thermostat at home)
Heated wires can be employed to prevent condensation in tubing from gas cooling

12. Why Wick-Type Humidifiers Are Popular
Produce high vapour 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

13. 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

14. Artificial Noses Types of heat and moisture exchangers
Simple condensers
Hygroscopic Condenser Humidifiers (HCF)
Hydrophobic Condenser Humidifiers
Act by recycling exhaled heat and moisture
“Ideal” unit should be able to produce at least 30 mg/l – Most produce mg/l

15. Problems With HMEs
Increase in airflow resistance (particularly when mucus enters unit)
Drying and 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)

16. Why HMEs 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

17. Bland Aerosol Therapy Indications for
Tx of laryngotracheobronchitis (croup)
Tx of sub-glottic edema
Post-extubation edema
Postoperative management of upper airway
Presence of bypassed upper airway
Need for sputum induction

18. 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

19. Hazards and Complications of Bland Aerosol
Wheezing associated with bronchospasm
Infection
Overhydration
Patient discomfort
Caregiver exposure to contagious aerosols
Noise

20. Types of Nebulizers Used for Bland Aerosol Therapy
Large-volume jet nebulizers
Ultrasonic nebulizers

21. Schematic of Large-Volume Jet Nebulizer

22. Schematic of Ultrasonic Nebulizer (USN)

23. 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 indutions

24. Delivery of Inhaled Medications
Delivery systems
MDIs
DPIs
Small-volume jet nebulizers
Aka – HHNs; SVNs; wet nebs; med nebs; neb meds; acrons
USNs
Specialized aerosol systems

25. Definitions Aerosol Penetration Deposition Stability Retention
Clearance

26. Factors for Penetration and Deposition
Size of particle decides how far before depositing into the respiratory tract

27. Indications for Aerosols
Deliver medications
Humidify gases
Mobilize secretions

28. Hazards
Overhumidification
Bronchospasm
Infection

29. Examples of MDIs

30. Characteristics of MDIs
Exact same dose each actuation
High initial aerosol velocity
Currently uses chloroflourocarbon (CFC) propellant. Hydroflouroalkanes (HFA) will replace CFCs 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

31. MDI “Accessory” Devices
Holding chambers or spacers
Improve ease of administration
Decrease oral-pharyngeal deposition
Improve distribution of the mist
Flow-triggered MDIs
Currently only “Maxair” (pirbuterol) is available

32. Optimal Technique for Using MDI
Shake MDI first (Warm if cold)
Actuate into chamber
Inhale slowly and deeply
Maintain a 10-second breath hold
Allow 30 seconds between actuation

33. 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

34. Characteristics of DPIs
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 or in ventilator circuits

35. Brand Names Rotahaler – Albuterol Spinhaler – Intal
Turbuhaler – Terbutaline
Advair – Flovent and Salmeterol

36. 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

37. Disadvantages of DPIs
Some patients can’t generate the 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)

38. Small-Volume Nebulizers
Generally hold 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 %!
Should be used instead of MDI or DPI if patient is tachypneic

39. Disadvantages of SVNs Too complex for some patients to use
Requires assembly and periodic cleaning
Not easily portable like the MDI or DPI
Not all medications are available
No steroids currently available for SNV administration

40. Specialized Medication Nebulizers
Respigard II filters exhaled gas – Delivers very small particles (1-2 microns)
Circulair – 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

41. 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 the cigarette lighter adapter present in a car

42. Problems with USNs Expensive to purchase Prone to breaking down
Not all medications are available in multi-dose or unit dose forms
Medication must be manually added to unit prior to use