Chapter 39 Humidity and Bland Aerosol Therapy
bland aerosol therapy
- Humidification therapy using inspired gas consisting of water, saline solution, or other substances without important pharmacologic action - used primarily to humidify, liquefy, or otherwise change the character of thick secretions.
Heated humidifiers evaporate more than how much water a day?
1 L H2O per day.
AARC guidelines for humidity
33 C within 2 C with a minimum of 30 mg/L of water vapor. Williams recommends 37 C 100%RH and 44 mg/L
When heated, the amount of water that a large volume nebulizer may produce is :
33-55 mg H2O/L
What is Humidity of air entering carina?
37 to 40 mg/L
Common problems with bland aerosol delivery systems
-cross contamination -infection -environmental safety -inadequate mist production -over hydration -bronchospasm -noise
Pass-over humidifier
Nonheated humidifier. Gas simply passes over the surface of the water, picking up moisture and delivering it to the patient. Provides a body humidity of approximately 25% because of the limited time of gas and water contact.
Aerosol
Spraying water particles into the gas
increase the temperature
The most effective was to increase the output of a humidification device is to :
passive humidifier
Type of humidifying device that uses exhaled heat and moisture to humidify the inspired gas; a heat and moisture exchanger (HME) is a passive humidifier.
Heated humidifiers
Used to increase the heat and water content of inspired gas for patients with bypassed upper airways and those receiving noninvasive mechanical ventilatory support.
humidifier
a device used to increase the moisture content of supplemental oxygen. this process occurs by evaporation of water from a surface to a gas that is not 100% saturated with water vapor.
Airway appliances used to deliver bland aerosol therapy include:
aerosol mask, face tent, T tube, tracheostomy mask, enclosures such as tents and hoods.
bubbler humidifier
breaks (diffuses) an underwater gas stream into small bubbles.
Important fact
delivery of inspired gas at 30 c or 34 c with 100% RH may not be sufficient to prevent airway epithelial damage occurring at 6 hour exposure.
vaporizer / humidifier
heat water to the point of expansion as a gas.
HME
heat/moisture exchanger; primary function of the upper respiratory tract; mainly the nose.
Servo-controlled heating system
in a humidifier, heating unit that monitors the temperature of gas delivered to the patient, adjusting the power to the heater based on the difference between the temperature setting and the temperature monitored by a thermistor probe placed downstream from the humidifier, at or near the patient airway connection.
use cool bland aerosol
in treating mild shortness of breath with stridor which treatment would be best?
what type of nebulizer uses a piezoelectric crystal to generate aerosol?
ultrasonic nebulizer
Isothermic Saturation Boundary
(ISB) is the point where inhaled gas reaches saturation (100% relative humidity at a body temperature of 37 degrees C); this point typically is 5cm below the carina.
What are the six types of heating elements?
- a hotplate element - wraparound type that surrounds the humidifier chamber - a yoke element - immersion type heater - heated wire in the inspiratory limb warming a wick/hollow fiber. - thin film high surface area broiler
Factors that can shift ISB
- breathes through mouth - breathes cold dry air - upper airway is bypassed (tracheal airway) - minute ventilation is higher than normal
Prolonged breathing of improperly conditioned gases through a tracheal airway can result in conditions?
- hypothermia - inspissation of airway secretions - mucociliary dysfunction - destruction of airway epithelium - atelectasis
four principles that affect the performance of a humidifier
- temperature - contact time - surface area - thermal mass
Heat Moisture Exchanger (HME)
1. also called the artificial nose 2. looks like a sponge filter -traps heat and moisture that naturally comes from the patient upon expiration and delivers the moisture and heat back to the patient on inspiration. Returns up to 70% 3. may become clogged with secretions-must be monitored 4. may cause increased ventilatory pressure 5. Best for short term humidification (transport or postop) 6. not indicated for thick copious secretions 7. disposable- never clean or rinse out just get a new one 8. short term vent for 24 hours of less. 9. eliminate problem of condensation 10. helpful in prevent of nosocomial infections and VAP 11. not to be used with small children or infants. add 5 o 90 ml of dead space.
What monitoring parameters should you utilize when using humidification during mechanical ventilation?
1. consistency of secretions 2. high temperature alarms if using HH 3. low temperature alarms if using HH 4. water levels and functions of the feed system
Indications for Heated humidification therapy include
1. managing hypothermia 2. bypassed.upper airway during mechanical ventilation
3 basic types of HME units
1. simple condenser humidifiers 2. hygroscopic condenser humidifiers 3. hydrophobic condenser humidifiers
Absolute Humidity (AH)
Actual content or weight of water in a given volume of gas. Expressed in mg/L
active humidifiers
Add H20 to gas by passing the gas over a H20 chamber (Passover humidifier) or through a saturated wick (wick humidifier), bubbling it through H20 (bubble through humidifier), or mixing it w/ vaporized H20 (vaporizer-phase humidifier)
Inspissated
Being thickened, dried, or made less fluid by evaporation
BTPS conditions
Body temp, 37 C; barometric pressure; saturated with water, 100% RH @ 37 C
Tubing is kinked or O2 flow too high
Bubble humidifier whistles by itself?
80%
Bubbler humidifier expected water vapor output?
How do you handle "rain out"?
Condensate can enter a persons airways and be aspirated. Circuits must be positioned to drain condensate away from the patient and checked often, with condensate drained frequently. Patients contaminate, bacteria colonized in condensate poses a risk for infection. All condensate should be treated as infectious waste.
bubble diffusion
Direct a stream of gas under water, or it is broken up into small bubbles.
Rule of Thumb
HME unites are better suited for short term use and during transport. Heated humidifiers should be used for patients requiring long term mechanical ventilation or for patients for whom the use of an HME unit is contraindicated.
Inspiration through the nose
Inhaled ambient air enters the nose, it warms to 28.5 C and picks up water vapor from the moist mucosal lining (evaporation) cooling the mucosal surface to 30.2 C
Humidity therapy
Involves adding water vapor and heat to the inspired gas. It is water in the gaseous or molecular form.
How does a Membrane Passover humidifier work?
It separates the water from the gas stream by means of a hydrophobic membrane causing water vapor molecules to easily pass through the membrane but blocking the liquid water/pathogens.
contraindications HME
Patients with thick, copious, or bloody secretions; patients with an expired tidal volume less than 70% of the delivered tidal volume; patients whose body temperature is less than 32 degrees C; patients with high spontaneous minute volumes greater than 10 l/min; and patients receiving in-line aerosol drug treatments.
Factors that affect output of bubbler humidifier
Relative humidity, absolute humidity, temperature
Exhalation through the nose
The expired gas (34.1 C) transfers heat back to the cooler tracheal and nasal mucosa which is 32.2 C at the end of exhalation. Condensation occurs on mucosal surfaces due to cooling gas holding less water vapor. Water is reabsorbed (rehydration).
Flows greater then 4 l/min
When should you start using humidification to avoid structural damage to epithelium and decreased ciliary motility and dried pulmonary secretions?
Wick type and membrane type
Which are types of passover humidifiers?
Benefit of wick and membrane type humidifier
don't transmit pathogens because aerosol is not produced. Maintain saturation at high flow rates. add little to no flow resistance.
Ultrasonic Nebulizer (USN)
electrically powered device that uses a piezoelectric crystal to generate an aerosol. ON BOARDS
equipment for aerosol therapy
large volume jet nebs ultrasonic nebs and aerosol generator
primary goal of humidification
maintain normal physiologic conditions in the lower airways
Inhales through mouth
pharyngeal temperatures are general 3 C lower with 20% RH less than breathing through nose.
Sputum induction
short term application of high density hypertonic saline (3 to 10%) aerosols to the airway to help mobilize pulmonary secretions for evacuation and recovery. Usually made using ultrasonic nebulization.
Recommended levels for gas delivered to the trachea include:
temperature range of 32 C to 35 C and RH 100%
Relative Humidity (RH)
the amount of water vapor present in air expressed as a percentage of the amount needed for saturation at the same temperature.
Surface are
the greater the area of contact between water and gas, the more opportunity there is for evaporation to occur. Pass over humidification pass gas over a large surface are.
Wick humidifier
uses absorbent material to increase the surface area for dry air to interface with heated water. No bubbling occurs, no aerosol is created.
What is "rain out"?
when gas cools, water vapor capacity decreases resulting in condensation.