Egan's Chapter 35- Humidity and Bland Aerosol Therapy

What is the process of humidity therapy?

The nose heats and humidifies gas on inspiration, while cooling and reclaiming H2O from the gas that is exhaled

What is humidity deficit?

Normal humidity range (44 mg/H20) minus actual humidity

What can happen if Isothermic saturation boundary shifts?

The body's normal heat and moisture exchange mechanisms can be compromised.

What is relative humidity?

The ratio between the amount of H2O in given volume of gas and the maximum amount it is capable of holding at that temperature.

What is absolute humidity?

The amount of H2O in a given volume of gas (measured in mg/L)

What is body humidity?

The relative humidity at body temperature (37 degrees Celsius) expressed as a percentage. Capacity of H2O at 37 Celsius is 44 mg of H2O

What is the term for inspired air that is not fully saturated at body temperature?

Humidity deficit

What is a humidifier?

A device that adds molecular H2O to gas, occurring by evaporation of H2O from a surface.

What is the temperature principle in regards to humidifier function?

The higher the temperature of gas the more H2O it can hold.

What is the purpose of a BUBBLE humidifier?

Usually used unheated with oxygen delivery systems to raise the water vapor content of gas to ambient levels by breaking underwater gas stream into small bubbles

What is the purpose of Passover in regards to humidifiers?

Directs gas over the water surface.

What are two types of Passover devices?

1. Simple reservoir type
2. Wick type: has an absorbent material that increases the surface area for dry air to interface with heated water.

What is a Heat-Moisture Exchanger (HME)?

An often passive humidifier that is also known as an artificial nose that does not add heat or water to system. It also captures exhaled heat and moisture, which is then applied to subsequent inhalation

What is added by using an HME?

30-90 mL of dead space

Which humidifier can deliver gas at 100% body humidity?

wick humidifier

What improves water output of bubble and Passover humidifiers?

Heat

Who are heating systems primarily used for?

Patients with bypassed upper airways and those receiving mechanical ventilation

What is a drawback of using heating systems?

Heating inhaled gas can expose patient to a risk of airway burns.

What can you do to avoid constant refilling of humidifier reservoirs?

Use a large water reservoir and utilize a gravity feed system.

What are characteristics of a manual reservoir feed system?

Simple large reservoir that is manually opened and refilled with sterile or distilled water.

What is a drawback of manual reservoir feed systems?

Cross contamination.

What is a characteristic of automatic reservoir feed systems

small inlet can be attached to a gravity-fed intravenous type bag and the tubing allows refilling without interruption. Floatation valve controls can be used to maintain humidifier reservoir fluid volume.

What is an advantage of using automatic reservoir feed systems?

Avoids need for constant checking and manual refilling.

What can help minimize condensation to reduce the risk of colonization?

wick or membrane type Passover humidifiers prevent formation of bacteria-carrying aerosols. No need to frequently change the circuit.

What types of liquid can be used in bland aerosols?

Sterile water & Sterile saline (hypotonic, isotonic and hypertonic)

How do Large-Volume Jet Nebulizers work?

Pneumatically powered and connected directly to a flow meter and a compressed gas source. Variable air-entrainment port allows air mixing to increase flow rates and to alter the FiO2

Formula for approximation for FiO2 (low flow device)

(4x L/m) +20

Mechanics of Large-Volume jet nebulizer

Liquid particles are generated by passing gas at high velocity through small et orifice. Low pressure at jet draws fluid from reservoir up siphon tube. H2O is then shattered into liquid particles. Smaller particles leave the nebulizer through the outlet p

What is an ultrasonic nebulizer?

Electrically powered device that uses a piezoelectric crystal to generate a very fine and consistently sized aerosol.

How does the crystal transducer in an ultrasonic nebulizer work?

Crystal transducer converts radio waves into high-frequency mechanical vibrations that produce the aerosol. Cuplent (liquid) takes vibration energy and transmits it to what is being delivered to the patient.

What are all airway appliances used with and why?

Large-bore tubing to minimize flow resistance and to prevent occlusion by the condensate.

What are drawbacks of utilizing enclosures?

Heat retention & CO2 build-up in tents.

What can be done to remedy heat retention in airway enclosures?

Handled differently by each manufacturer, Maxicool uses high fresh gas flows, others may use separate cooling devices.

What can be done to remedy CO2 build-up in airway tents?

High flows of fresh gas circulating continually through tent help "wash out" CO2 build up

What are the indications for bland aerosol administration?

--Presence of upper airway edema-cool, bland aerosol
--Laryngotracheobronchitis
--Subglottic edema
--Post extubation edema
--Post-op management of the upper airway
--Need for sputum specimens or mobilization of secretions

What're the contraindications for bland aerosol administration?

1.Bronchoconstriction
2.History of airway hyperresponsiveness

What are the hazards and complications when dealing with Bland Aerosol Therapy?

1.Wheezing or bronchospasm
2.Bronchoconstriction when artificial airway is used
3. Infection
4. Overhydration
5. Patient discomfort
6. Caregiver exposure to airborne contagions produced during coughing or sputum induction
7.Edema of airway wall
8.Edema as

list the 4 indications for humidity:

1.medical gas administration
2. hypothermia
3.cold air reactive airway
4. thick secretions

How can you estimate if an HME is performing well?

You can estimate if an HME is performing well at the bedside by visually confirming condensation in the flex tube between the airway and HME. Lack of condensate may be a clue that humidification is inadequate and that alternative systems may be appropriat

What're the primary indications for humidification therapy?

Humidifying dry medical gases
Overcoming humidity deficit created when upper airway is bypassed

What're the secondary indications for Humidification Therapy?

Managing hypothermia
Treating bronchospasm caused by cold air.

Know and understand "servo-controlled" heating systems.

Monitors temperature at or near the patient's airway using a thermistor probe.

What is the ISB?

Isothermic Saturated Boundary is the point where inhaled gas reaches saturation (100% RH at a body temp of 37 degrees C).

What does BTPS mean?

Below the ISB, temperature and RH remain constant (BTPS).

Temperature and humidity (increase/decrease) with inspiration and (increase/decrease) with exhalation.

Temperature and humidity decrease with inspiration and increase with exhalation.

When does the ISB shift deeper into the lungs?

The ISB shifts deeper into the lungs when a person inhales through the mouth.

Prolonged and severe shifts of the ISB can cause what?

Prolonged and severe shifts of the ISB can cause damage the airways and compromise the body's normal heat and moisture exchange mechanisms.

When airways are exposed to dry, cold gas, or air, what happens to the cilia?

When airways are exposed to dry, cold gas or air, ciliary motility is reduced... becoming irritable.

What happens to the production of mucus when the airways become irritable?

As the airways become irritable, the production of mucus increases and pulmonary secretions become thick.

When can prolonged breathing of improperly conditioned gases lead to serious consequences?

When the upper airway is bypassed via endotracheal tube or tracheostomy tube, prolonged breathing of improperly conditioned gases can lead to serious consequences.

Clinical signs and symptoms of inadequate airway humidification include:

Atelectasis - Usually due to mucus plugging of small airways from thickened mucus.
Dry, nonproductive cough - airway irritation from dry gas and lack of humidity.
Increases airway resistance - From irritated, swollen airways in combination of increases in

When the RH of inspired gas is greater than __% of BTPS conditions, no injury is believed to occur in the normal lungs.

When the Relative Humidity of inspired gas is greater than 60% of BTPS conditions, no injury is believed to occur in the normal lungs.

What is cool, humidified gas often used for?

Cool, humidified gas is often used with bland aerosol delivery (sterile water) to treat upper airway inflammation caused by croup, epiglottitis, and post-extubation edema. (Often referred to as a "cool mist aerosol")

The most common examples of a passive humidifier are __________________________.

The most common examples of a passive humidifier are heat and moisture exchangers (HME's)

What is a bubble humidifier?

direct gas through a tube or channel into the bottom of a water reservoir, where the gas stream produces bubbles that rise through the water and pass through the device outlet to the patient

What does increasing the height of the water column above the gas outlet do?

Increasing the height of the water column above the gas outlet increases the humidity content of the bubbles by allowing a longer contact time.

What do bubble humidifiers do to warn of flow path obstruction?

Bubble humidifiers incorporate gravity or spring-loaded pressure relief valves or "pop-off" valves to release high pressure (above 2 psi) to prevent rupture of the humidifier bottle and warn of flow path obstruction.

What is the bubble size on a bubble humidifier govern by?

Bubble size is govern by the design of the gas outlet at the bottom of the capillary tube.

Unheated bubble humidifiers can provide an AH level of ___-____/L.

Unheated bubble humidifiers can provide an AH level of 10 to 20mg/L.

What is a diffuser humidifier and what is it's purpose?

Diffuser humidifiers are designed to create a large number of small bubbles, allowing a greater surface area for gas and water interaction.

Why should you not add heat to a bubble humidifier?

Adding heat to a bubble humidifier can increase the absolute humidity (AH) in the gas... However, bubble humidifiers are designed for low flow oxygen and small bore tubing for nasal cannula use. Adding heat would cause condensation in the tubing and water

Some systems use ______ _____ _____ to prevent rain out and condensation.

Some systems use "heated wire" circuits to prevent rain out and condensation.

How do you generate Liquid aerosols?

Liquid particle aerosols are generated by passing gas at a high velocity through a small jet orifice.

What is the The Bernoulli Principle?

The resulting low pressure generated at the jet draws fluid from the reservoir up to the top of a siphon tube (capillary), where it is sheared off and shattered into liquid particles. (The Bernoulli principle)

What is baffling and when does it happen?

The larger, unstable particles fall out of suspension and strike the internal surface of the device... "baffling".

Jet nebulizers typically operate at a flow of __-___L/m.

Jet nebulizers typically operate at a flow of 6 to 15 L/m

What does humidity involve?

Humidity involves adding water vapor to inspired gas.

Heat and moisture exchange is one of the primary functions of the _______ _______.

Heat and moisture exchange is one of the primary functions of the respiratory tract.

What does the upper airways do?

The upper airways add heat and humidity to inspired gases during inhalation and cool and reclaim water during exhalation.

How are nasal mucosa kept moist?

The nasal mucosa are kept moist by secretions from mucus glands, goblet cells, transudation of fluid through cell walls, and condensation of exhaled humidity.

convection

During exhalation, the expired gas transfers heat back to the cooler tracheal and nasal mucosa by_____.

Explain the different temperatures between when a person inhales and exhales.

When a person inhales through the mouth at normal room temperature, temperatures at the hypopharynx are about 3 degrees C lower and the RH is about 20% less than when a person inhales through the nose.

What are devices with air entrainment ports used for?

Devices with air entrainment ports can be used to increase inspiratory flows by allowing for air mixing.

Depending on the design, input flow, and air entrainment setting, the total water output of an unheated, large-volume jet nebulizer can vary from __-___ mgH20/L.

26 to 35.

The Babington nebulizer incorporates a unique design to perform nebulization.
Fluid is spread over the surface of a glass sphere and struck by compressed gas passing from the inside of the sphere through one or more orifices on its surface.
The liquid is

Explain the Babington nebulizer.

Spinning disk devices

Centrifugal nebulizers
Operates on the principal that a spinning disk with a hollow shaft draws liquid from the reservoir.
As the liquid leaves the shaft, it is spread across the top of the disk and contacts a system of baffles (teeth) attached to the dis

USN

an electrically powered device that uses a piezoelectric ceramic transducer that vibrates at 1.3 to 2.3 mHz

USN's marketed as ____ ____devices are sold as room humidifiers for home use.

cool mist

What is the biggest disadvantage of a cool mist device?

The wet, large volume reservoirs of these devices can easily become contaminated, resulting in airborne transmission of pathogens.

Airway appliances used to deliver bland aerosol therapy include:

Aerosol masks
Face tents
T-Tube or T-piece connections
Tracheostomy masks

When are aerosol masks and face tents used for bland aerosol treatments?

The aerosol mask and face tent are used with patient who have intact upper airways.

When are T tubes used?

T-Tubes (T-pieces) are used for patients who are either intubated with an endotracheal tube or have a tracheostomy tube in place.

What are the biggest problems with bland aerosol delivery systems?

The most common problem with bland aerosol delivery systems involve infection control, environmental safety, inadequate mist production, overhydration, bronchospasm, and noise.

Large volume USN's

____ ____ ______ are capable of high water outputs and should never be used for continuous therapy.

What are the contraindications to Large Volume USN's?

Large volume USN's are capable of high water outputs and should never be used for continuous therapy.
Infants and small children are at the greatest risk.

Three common types of passover humidifiers are:

Reservoir humidifiers
Wick units
Membrane devices

What type of system is commonly used for mechanical ventilation?

Reservoir humidifiers:

How does a reservoir humidifier work?

Gas simply passes over heated water to pick up saturated water vapor and delivers this to the patient

Describe Wick Humidifiers.

Wick systems incorporate a wick-like material encased in a metal column that is heated and temperature controlled. (Concha Column)
The column is plugged into a water reservoir that continually feeds the column. (water fed system)
The column is inserted in

Wick systems incorporate a wick-like material encased in a metal column that is heated and temperature controlled called a ....

concha column

The wick system's concha column is plugged into a water reservoir that continually feeds the column

water feed system

Describe membrane humidifiers.

Membrane systems utilize a hydrophobic membrane that separates water from the gas stream.
Water vapor molecules can pass through the membrane, but liquid water cannot.

What's the vapotherm 2000?

A membrane cartridge system

Membrane systems humidify and heat oxygen flows up to __L/min.

Membrane systems humidify and heat oxygen flows up to 40L/min

What are membrane humidifiers used for?

This system has been used to provide high-flow oxygen via high-flow nasal cannula to a range of patients from infants to adults.

Current types of heating elements used for heated humidified systems?

Hot plate element. (Fisher & Paykel)
Wraparound. (Concha Column)
Yolk or collar heating element.
Immersion heater

Describe the servo-controlled heating system.

Humidifier heating systems generally have one;
regulates the power to the heating element.;
monitors temperature at both the unit delivering the heat and near the patient via probe placement in the circuit.
The temperature is adjustable, set, and regulate

____ _____ ________ are often used in combination with heated humidification to prevent condensation and water occlusion.

Heated wire circuits are often used in combination with heated humidification to prevent condensation and water occlusion.

What are contraindications for reservoir feed systems?

Manually refilling the reservoir can change the temperature of the water and change output humidification. (until the water re-heats)Refilling can also increase the risk of reservoir contamination.

Why are gravity feed systems incorporated into reservoir systems?

Gravity feed systems are incorporated into these systems to prevent abrupt water temperature changes and prevent the possibility of cross-contamination.
Gravity system utilize a small inlet port in the wall of the humidifier chamber attached to a gravity-

What are some of the contraindications of condensation?

Condensation can alter (raise FIO2 levels) when water pools and forms a bolus in corrugated tubing when venturi devices are incorporated as part of humidification devices (usually cool mist systems).

What is used to prevent pooling of water in tubing? Describe this and contraindications with it.

Drain bags are used to prevent pooling of water in corrugated tubing and prevents pooling in the tubing.Drain bags are inserted and placed in the lowest point of the tubing to ensure that gravity allows the water to flow into the bag at not pool in the tu

Accidental patient inhalation of contaminated water is highly possible if accumulated water is allowed to pool in tubing

This could cause serious bacterial lung infection and pneumonia.

Describe an HME.

HME's, or artificial nose, is classified as a passive humidifier.
HME's capture heat and moisture and uses it to heat and humidify the next inspiration.
HME's contain a condenser element with high thermal conductivity, usually consisting of metallic gauze

What is the moisture output range of an HME?

Moisture output ranges from 22 to 34 mg/L.

Who primarily uses HME's?

HME's are used primarily on patients who are intubated and on mechanical ventilation.

HME's are not recommended for patients who are ____________ or have ______ ______. They also aren't recommended for ______.

HME's are not recommended for patients who are dehydrated or have copious secretions; infants

Expectorated mucus has the potential to occlude HME's causing complete airway obstruction.

While using an HME what can cause complete airway obstruction?

HME's add 30 to 90 ml of mechanical dead space.

HME's add ____-____ml of mechanical dead space.

The American National Standards Institute (ANSI) recommends that the minimum level of humidity for intubated patients exceed _____.

30mg/L.

When adding humidification for intubated patients, the American National Standards Institute recommends that the minimum level of humidity exceeds 30mg/L. Air entering the carina has a humidification level of ___-____mg/L.
Current AARC clinical practice g

The American National Standards Institute (ANSI) recommends that the minimum level of humidity for intubated patients exceed 30mg/L.
Air entering the carina has a humidification level of 35 to 40mg/L.
Current AARC clinical practice guidelines recommends a

Who are heated humidifiers mainly used for?

Patients with bypassed upper airways and patients receiving mechanical ventilatory support