Humidity & Bland Aerosol therapy (ch. 38)

- with high fresh gas flows to prevent heat buildup - use of a separate cooling device

How can you the RT prevent heat retention in enclosures? (2)

You should switch him over from an HME to a heated humidifier

Mr. Jones is on a mechanical ventilator with an HME. You, the RT, noticed his secretions are becoming copious and increasingly tenacious. What should you do?

false. HMEs add 30 to 90 ml of mechanical dead space, exceeding the tidal volume of the infant.

T/F: HME are recommended for infants and small children

false. evidence suggest that long term HME are correlated to blocked tracheal tubes

T/F: HME are used for long term vent patients

true

T/F: below the ISB, temperature and relative humidity remains constant

false. circuit contamination usually occurs from the patient to the circuit

T/F: circuit contamination usually occurs from the circuit to the patient

true. only water vapor molecules

T/F: liquid water (and pathogens) cannot pass through a membrane humidifier

there are no contraindications

What are the contraindication for inspiration of humidified gas during mechanical ventilation

-manual systems -automatic systems

What are the two different types of reservoirs and feed systems

- CO2 buildup - heat retention

What are the two problems with enclosures?

- mouth breathing - breathing cold, dry air - when the upper airway is bypassed - higher than normal minute ventilation

What factors can cause the ISB to shift distally (deeper into the lungs)?

-33 degrees c within 2 degrees c -with a minimum of 30 mg/L

What is the AARC clinical practice guidelines recommended for appropriate temperature and humidity of inspired gas delivery to mechanically ventilated patients with artificial airways

there must be at least 60% of inspired humidity or else damage can occur within MINUTES.

What percentage of inspired humidity must be present to prevent injury to the lungs?

a reduction of 20mg/L absolute humidity below BTPS

What results in less than 60% relative humidity?

1- using a condensing element of low thermal conductivity (e.g. paper, wool, or foam) 2- impregnating this material with a hygroscopic salt (calcium or lithium chloride)

a hygroscopic condenser HME provides higher efficiency by what two things?

with 70% efficiency or better and at least 30 mg H20/L (water vapor)

according to the ISO (international organization for standardization) how should the ideal HME perform?

15-20 mg/L

an unheated bubble humidifier provides about how much absolute humidity?

above the ISB

at what point does temperature and humidity decrease during inspiratory, and increase during expiration?

-hypothermia -inspissation of airway secretions -mucocillary dysfunciton -destruction of airway epithelium -atelectasis

breathing improperly conditioned gases through a tracheal airway can result in? (5)

trying not to change the circuit at all unless it becomes visibly soiled

how can we prevent cross contamination with a ventilatory circuit?

by maintaining heat in the circuit can prevent formation of condensate (such as: heating wire elements inserted into the ventilator circuit, insulation, or increasing the thermal mass of the circuit)

how can you the RT prevent the formation of condensation?

by providing sufficiently high gas flow rates to help "wash out" the CO2

how can you the RT reduce the build up of CO2 in enclosures?

by secretions from the: -mucous glands -goblet cells -transudation of fluid through cell walls -condensation of exhaled humidity

how is the nasal mucosal lining kept moist?

ultrasonic nebulizer

this device is an USN that is electrically powered, and uses a piezoelectric crystal to generate aerosol

large- bore tubing

this device is required to minimize flow resistance and prevent occlusion by condensation

aerosol

this is Suspension of water particulate form (or a mist) in gas that can be inhaled. (nebulizers)

humidifier

this is a device that adds molecular water to gas

HME

this is a passive humidifier often described as the artificial nose

relative humidity

this is a ratio between the amount of water in a given volume of gas and the max amount it is capable of holding at that temperature (capacity)

nasal mucosa (it's very vascular)

this is responsible for actively regulating temperature in the nose

absolute humidity

this is the amount of water in a given volume of gas.

humidity

this is water in a gaseous form, or vapor in the environment.

mucosa lining

this lines the sinuses, trachea, and bronchi aiding in heating and humidifying inspired gases

simple reservoir type

this passover directs gas over the surface of a volume of water

hydrophobic condenser HME

this type of condenser uses a water repellant element with a large surface area and low thermal conductivity

bubble- diffusion (bubble humidifier)

this type of humidifier directs a stream of gas underwater, where it is broken up into small bubbles. As the gas bubbles rise to the surface, evaporation increases the water vapor content within the bubble

passover

this type of humidifier directs gas over a surface of water

vaporizer humidifier

this type of humidifier simply heats water to the point of expansion as a gas

aerosol humidifier

this type of humidifier sprays water particles into the gas

wick

this type of humidifier uses porus water- absorbent materials to draw the water (similar to a sponge) into its fine honeycombed structure by means of capillary action

membrane- type humidifier

this type of passover separates the water from the gas stream by means of a hydrophobic membrane

wick humidifier

this type of passover uses an absorbent material to increase the surface area for dry air to interface with heated water

the longer a gas remains in contact with water, the greater the opportunity for evaporation to occur

Explain how contact time affects the performance of a humidifier

the greater the area of contact between water and gas, the more opportunity there is for evaporation to occur

Explain how surface area affects the performance of a humidifier

the greater the mass of water or the core element of a humidifier, the greater is its capacity to hold and transfer heat.

Explain how thermal mass affects the performance of a humidifier

they are associated with a lower incidence of ETT occlusion

HMEs that deliver at least 30 mg H2O/L should be used because?

ultrasonic nebulizer

If your patient is prone to bronchospasm, should you use a large volume nebulizer or an ultrasonic nebulizer?

3 degrees c 20% less relative humidity

When a person inhales through the mouth at a normal room, pharyngeal temperatures are normally _____ degrees c less, with ____% less relative humidity

for patients with bypassed upper airways and patients receiving noninvasive mechanical ventilatory support

When would we use a heated humidifier?

for the treatment of: - croup -epiglottis -postextubation edema

When would you the RT use cool humidified gas? (3)

when using moderate to high FiO2 levels

When would you use a tracheostomy mask for a trach patient?

-because of the low ratio of gas volume to moist and warm surfaces -because of smaller vascular squamous epithelium lining the oropharynx and hypo pharynx

Why is the mouth less effective at heat and moisture exchange than the nose? (2)

by producing a high- density aerosol. You would set the amplitude high and the flow rate low.

You the RT are called to do a sputum induction using a USN (ultrasonic neb). How you do this?

by maximizing aerosol delivery per minute. You would set the flow rate to match (and slightly exceed) the patients inspiratory flow rate, and set the amplitude at the maximum

You the RT are called to try and help mobilize secretions using a USN (ultrasonic neb). How would you do this?

active humidification

during noninvasive ventilation, what type of humidification is suggested?

simple condenser HME contains a condenser element with high thermal conductivity, usually consisting of metallic gaze, corrugated metal, or parallel metal tubes

explain how a simple condenser works

an active HME adds heat, humidity, or both to inspired gas by chemical or electrical means

explain how an active HME works

the greater the temperature of a gas, the more water vapor it can hold (increasing capacity)

explain how temperature affects the performance of a humidifier

An active humidifier is actively adding heat or water, or both to the device-patient interference) a passive humidifier recycles exhaled heat and humidify from the patient

explain the difference between an active and a passive humidifier

the expired gas transfers heat back to the cooler tracheal and nasal mucosa by convection

explain the heating process performed during exhalation?

the nose heats and humidifies gas on inspiration

explain the heating process performed during inspiration?

-ciliary motility is reduced -airways become more irritable -mucus production increases -pulmonary secretions become inspissated

explain what happens to the airway when exposed to relatively cold, dry air:

because in cold environments, the formation of condensation may exceed the ability of the mucus to reabsorb water, resulting in a runny nose

explain why Tim has a runny nose when he stands outside in 23 degree weather

1- results in less water being used 2- reduces need for draining the tubes 3- less infection risk for patients and health care workers

explain why you the RT would want to decrease condensation (3)

t- tube

for a tracheostomy patient, which airway application is most common?

1- hotplate 2-wrap around type 3- yolk/ collar 4- immersion- type heater 5- heated wire 6- a thin-film

list the 6 types of heating elements

-bubble -passover -nebulizers of bland aerosol -vaporizers

list the active humidifiers

- atelectasis - dry, nonproductive cough - increased airway resistance - increased incidence of infection - increased work of breathing - patient complaint of substernal pain and airway dryness - Thick, dehydrated secretions

list the clinical signs and symptoms of inadequate airway humidification? (7)

condensation, cross contamination, and ensuring proper conditioning of the inspired gas

list the common problems seen with humidification systems

1- bronchoconstriction 2- history of airway hyper-responsiveness

list the contraindications to bland aerosol administration

- aerosol mask - face tent - t tube - tracheostomy mask

list the four types of airway appliances

-temperature -surface area -time of contact -thermal mass

list the four variables that affect the quality of performance of a humidifier

- high flow rates during disconnect may aerosolize contaminated condensation (HH) - under-hydration and mucous impaction (both) - increased WOB (both) - hypoventilation caused by increased dead space (HME) - elevated airway pressure pressures caused by condensation (HH) - ineffective low-pressure alarm during disconnection (HME) - patient- ventilator dyssychrony and improper ventilator function caused by condensation in the circuit (HH) - hypoventilation or gas trapping caused by mucus plugging (both) - hypothermia (both) - potential for burns to caregivers from hot metal (HH) - potential electrical shock (HH) - airway burns or tubing meltdown if hearted wire circuits are covered or incompatible with humidifier (HH) - possible increased resistive work of breathing caused by mucous plugging (HME or HH) - inadvertent overfilling resulting in unintended tracheal lavage (HH) - inadvertent tracheal lavage from pooled condensate in circuit (HH)

list the hazards and complications associated with the use of heated humidifiers and HME during mechanical ventilation (15)

- wheezing or bronchospasm - bronchoconstriction when artificial airway is used - infection - over hydration -patient discomfort - caregiver exposure to airborne contagions produced during coughing or sputum induction - edema of the airway wall - edema associated with decreased compliance and gas exchange and with increased airway resistance - sputum induction by hypertonic saline inhalation can cause bronchoconstriction in patients with chronic obstructive pulmonary disease, asthma, cystic fibrosis, or other pulmonary diseases

list the hazards and complications of bland aerosol therapy (9)

- presence of upper airway edema - laryngotracheobronchitis - subglottic edema -postextubation edema - postoperative management of the upper airway - presence of a bypassed upper airway - need for sputum specimens or mobilization of secretions -stridor - brassy, crouplike cough - hoarseness after extubation - history of upper airway irritation and increased WOB

list the indications for bland aerosol administration (11)

- cross contamination - environmental exposure - inadequate aerosol output - over-hydration - bronchospasm

list the most common problems with bland aerosol therapy

passive HME (heat and moisture exchangers) (be mindful that there is an active HME!)

list the passive humidifier

temperature: 29-32 degrees c relative humidity: 95% absolute humidity: 28-34

list the recommended heat and humidity levels for the hypopharynx

temperature: 20-22 degrees c relative humidity: 50% absolute humidity: 10 mg/L

list the recommended heat and humidity levels for the nose/mouth

temperature: 32-35 degrees c relative humidity: 100% absolute humidity: 36-40 mg/L

list the recommended heat and humidity levels for the trachea

-Managing hypothermia -Treating bronchospasm caused by cold air

list the secondary indications for humidification therapy

1- passover humidifiers can maintain saturations at high flow rates 2- they add little or no flow resistance to spontaneous breathing circuits 3- they do not generate any aerosols, and they pose a minimal risk for spreading infections

list the three advantages of a passover humidifier

-Humidifying dry medical gases(flows>4L/min =heat loss and water loss of the mucosa) -Exposure to cold dry air creates decrease ciliary motility, airway becomes irritable, mucus decreases and pulmonary secretions become inspissated. -Overcoming the humidity deficit created when the upper airway is bypassed

list the three primary indications for humidification therapy

1- simple condenser humidifiers 2- hydroscopic condenser humidifiers 3- hydrophobic condenser humidifiers

list the three types of HMEs

-simple reservoir type -wick type -membrane type

list the three types of passover humidifiers

humidity is water in the gas phase bland aerosol consists of liquid particles suspended in a gas

simply put, what is the difference between humidity and bland aerosol

30 degrees c

temperatures on an HME or HH should never be below?

37 degrees c

temperatures on an HME or HH should never exceed pass?

patients with intact upper airways

what are aerosol mask used for?

37 degrees c and 100% relative humidity

what are normal BTPS conditions?

patients who are orally or nasally intubated or who have a tracheostomy

what are t-tubes used for?

1- the temperature difference across the system 2- the ambient temperature 3- the gas flow 4- the set airway temperature 5- the length, diameter, and thermal mass of the breathing circuit

what are the five factors influencing the amount of condensation?

only for patients who have a tracheostomy

what are tracheostomy mask used for?

- large volume jet nebulizer - ultrasonic nebulizer

what devices can generate bland aerosol? (2)

-promotes vasoconstriction -decreases edema -reduces airway obstruction

what do enclosures devices promote?

- patients response (pain, discomfort, dyspnea, restlessness) - HR - BP - RR - Sputum production (color, consistency, odor, amount) - skin color - breath sounds - pulse ox - spirometry (if adverse reaction is a concern)

what do you the RT need to monitor during a bland aerosol treatment?

it monitors temperature at or near the patient's airway using a thermistor probe

what does a servo- controlled heating system monitor?

something (in this case, secretions) becomes thickened due to dehydration

what does inspissated mean?

there will be visual condensation in the flex tube between the airway and HME

what is a bedside indication that the HME is performing well?

to place water traps at low points in the circuit

what is a common method to minimize problems with condensate?

HH

what is indicated for long-term (HME or HH)

HME

what is indicated for short-term (HME or HH)

they exert no traction on the airway and allow secretions and condensate to escape from the airway, reducing airway resistance

what is the benefit for the tracheostomy mask?

invasive- humidification is mandatory when an endotracheal or a tracheostomy tube is present noninvasive- humidification is optional when an endotracheal or tracheostomy tube is present

what is the indication for humidification with an invasive and noninvasive mechanical ventilation

maintaining heat in the circuit with a heating wire element

what is the most common method used to prevent condensation?

the primary goal of humidification is to maintain normal physiologic conditions in the lower airways.

what is the primary goal of humidification?

they waste a lot of water, and disrupts or occludes the gas flow through the circuit, potentially altering ventilator function

what is the problem with condensation when dealing with humidification?

it requires manually refilled so it increased the risk for cross contamination

what is the problem with manual reservoir systems

to always treat breathing circuit condensation as infectious waste, and to always use standard precautions: (including wearing gloves and googles, draining the tubing away from the patient's airway into an infectious waste container and disposing of the waste accordingly)

what is the rule of thumb for treating breathing circuits?

infants and small children

what patients are enclosures (mist tents and hoods) used on?

70%

what percentage of heat does the HME capture, to return it back to the patient on their next inspiration?

high inspiratory flows and high FiO2 levels

what two things can decrease HME efficiency?

-for patients with thick, copious, or bloody secretions -for patients with an expired tidal volume of less than 70% of the delivered tidal volume (e.g. pts with large bronchoneural fistulas or incompetent or absent endotracheal tube cuffs) -for pts whose body temperature is less than 32 degrees c -for pts with high spontaneous minute volumes (>10 L/m) -for pts receiving in-line aerosol drug treatments (an HME must be removed from the patient circuit during treatments)

when is an HME contraindicated? (5)

if secretions have contaminated the filter and/or if the flow resistance has increased causing an increase in the work of breathing

when should HMEs be replaced?

only to spot check parameters to ensure the patients receiving gas at the expected temperature and humidity level on a vent.

when should a hygrometer be used?

mainly ambulatory settings (room humidifiers)

when would we use a vaporizer humidifier?

for patients receiving ventilatory support via endotracheal or tracheostomy tubes

when would you the RT use an HME?

when a patient cannot tolerate the aerosol mask (e.g post-op facial surgery patients)

when would you want to use the face tent?

in the isothermic saturation boundary (ISB). About 5 cm below the carina

where is the BTPS normally found?

at or near the patient's airway openings

where should inspired gas temperatures be monitored for a patient on a heated humidifier?

at the airways

where should you place the HME for the best results?

large volume jet nebulizer

which device is the most common for the delivery of bland aerosol?

by using an element with low thermal conductivity, hygroscopic condenser HME can retain more heat than simple condensers

why does the hygroscopic condenser benefit from using low thermal conductivity

to either: - decrease WOB - improve vital signs - decrease stridor - decrease dyspnea - improve arterial blood gas values - improve O2 saturation, as indicated by pulse ox - sputum sample

why would you the RT even give bland aerosol? (7)