E & T I: Unit 2: Humidity and Aerosol Therapy

Given the water vapor content of inspired air, calculate the body humidity deficit.

For Example: A patient is breathing room air at a temperature of 21*C and that same volume of air contains 18 mg/L of water vapor. The %BH is then calculated by comparing 18 mg/L/44 mg/L = 41%. Using the above example of a volume of gas at 21*C containing 18 mg/L of water vapor, the Humidity deficit would be 44 mg/L - 18 mg/L = 26 mg/L. In other words, the body would have to add 26 mg/L of water vapor to inspired gas to make it 100%saturated at body temperature.

Depth of Aerosol Penetration (related to particle size)

Aerosol droplets with a Mean Mass Aerodynamic Diameter (MMAD) < 5 microns are optimal for deposition in the smaller airways and lungs. As you view the graph, aerosol particles with an average MMAD of 3 microns offers the best size for deposition into the smaller airways. Particles > 5 microns deposit in the upper airway, with aerosol particles greater than 10 microns being deposited in the mouth and nose. Particles between 0.8 and 2 microns may deposit in the lung parenchyma, whereas particles less than 1 micron are less likely to be deposited and more likely to be exhaled.

Discuss how aerosol physical properties (size, motion, stability, ventilatory pattern, etc) will affect aerosol deposition and penetration.

Aerosol particles must overcome certain obstacles in order to penetrate the lower airways: upper airway anatomy.jpgWhether inhaled by mouth or nose, aerosol particles must make an almost 90 degree turn in order to traverse from the oropharynx or nasopharynx into the trachea. Many aerosol particles will impact the back of the throat and deposit there. Next the aerosol particles must enter through the narrow opening of the vocal cords as seen here.eppiglottis.jpg bronchial tree.jpg Finally, aerosol particles must take many turns in order to deposit in the smaller airways. This should be very easy to see why typically less than 20% of an aerosol dose of medication actually deposits in the intended site of the lower airways.

body humidity

Amount of water vapor required to saturate alveolar air at body temperature ( 44 mg/L)

Passover (wick) humidifier

The heated wick humidifier is a type of passover humidifier. The wick part of the humidifier becomes wet from sitting in water and gas passes through the wick which is placed inside an aluminum cannister and picks up heat and water vapor before going to the patient. The amount of heat is controlled by a servo-controlled heating unit. Because it is heated, the wick humidifier is capable of delivering 100% body humidity. It is primarily used for patients with artificial airways who are on mechanical ventilation. Employs a cylinder-shaped absorbent paper or sponge that draws water from a reservoir using capillary action. The absorbent paper provides a larger surface area for evaporation of water into the gas. The cylinder is heated which allows the device to deliver up to 100% Body Humidity. Used primarily for patients on mechical ventilation. Condensation of water vapor occurs in the tubing as it travels to the patient. Heater is servo-controlled.

Adaptive Aerosol Deliver (AAD)

The newest technology in aerosolized medication is the adaptive aerosol delivery system. This system has been available in Europe for a few years and has now been approved for use in the US (I-Neb). The system is a breath actuated nebulizer that is battery operated and creates aerosol through a vibrating mesh technology. It will deliver a precise dose of medication according to the patient's inspiratory flow and inspiratory time. Once the dose has been reached, the treatment is stopped and any medication left in the nebulizer is discarded. It can work with a smaller fill volume than standard nebulizers and treatments will last less than with conventional nebulizers.

Describe the design and function of devices that can be used in the administration of bland aerosol therapy

- Large Volume Nebulizer: - Ultrasonic Nebulizer -Misty-Ox Gas Injection Nebulizer (GIN):

The advantages of using a small volume nebulizers include:

-ability to aerosolize many drug solutions -minimal coordination is required for inhalation -useful in very young or very old, debilitated patients or those in acute distress -effective with low inspiratory flows or volumes -a breath hold is not required for efficacy

Advantages of the Ultrasonic Medication Nebulizer include:

-does not require patient coordination -High doses of medication can be given, and less medication is lost during exhalation -Delivery is much faster than with a small volume nebulizer.

List the advantages of aerosol delivery of medication.

ADVANTAGES Aerosol doses of medication are smaller than those used for systemic treatment The onset of the drug action is rapid Drug delivery is targeted to the respiratory system for a local pulmonary effect Systemic side effects are fewer and less severe than with oral or parenteral therapy Inhaled drug therapy is painless and relatively convenient

Inertial Impaction:

Particles tend to travel in a straight path. When there is a directional change, the aerosol continues in a straight path and therefore collides or impacts with the wall of the airway. The larger the aerosol particle size, the greater the inertia. Higher inspiratory flows, turbulence, and the convolutions of the airway cause greater inertia.

Define the terms penetration and deposition of aerosols.

Penetration: the maximum depth a particle can be carried into the tracheobronchial tree. Deposition: when a particle falls out or rains out on a surface.

Breath-Actuated Nebulizers (BAN)

The BAN nebulizer reduces medication waste by only nebulizing when the patient inhales, and not on exhalation. On the top of the nebulizer is a spring-loaded one-way valve that opens when the patient inhales and allows the jet to drop down to the capillary tube to commence nebulization. When the patient is finished inhaling, the one-way valve and jet move back to the closed position. This nebulizer will increase the amount of drug inhaled and the treatment time by a factor of four.

List and describe several effects of delivering improperly humidified gas to the airway.

When dry cold gases are inhaled, ciliary function and mucus production are compromised. The lower gas temperature farther down the airways reduces ciliary function within 10 minutes. Once compromised, ciliary function can take several weeks to recover. Without enough water vapor, respiratory secretions become thicker, contributing to mucus plugging, atelectasis, and pneumonia.

Dry Powdered Inhalers

With dry powdered inhalers (DPI) aerosol is created by drawing air through a dose of powdered medication. The powder contains micronized drug particles less than 5 MMAD with larger lactose or glucose particles greater than 30 microns. Adding the larger particles to the medication diminishes the cohesive forces in the micronized drug powder so that separation into individual respirable particles occurs better. The larger particles act like carriers of the smaller drug particles. In order for these fine powdered aerosol particles to enter into the smaller airways, inspiratory flows greater than 40 - 50 L/m are required. For this reason, DPIs are not recommended for children under the age of 6, or those who are elderly and weak or have altered mental status who normally cannot generate the necessary flow to operate the DPI. The magnitude and duration of the patient's inspiratory effort influences aerosol generation from the DPI. Breath coordination is also important during use of the DPI since the device is breath actuated. As with the MDI, the effectiveness of the DPI is dependent upon good patient instruction and technique. Because there is more than one type of DPI device, click on the links below to view a brief film about instructional technique. Humidity can affect the device and cause clumping of the powdered particles, causing less deposition into the smaller airways. Patients should be instructed not to store their DPI device in rooms such as the bathroom where humidity levels are high. Also, exhaling into the mouthpiece will cause exhaled moisture to be trapped within the device causing clumping of the powdered medication.

Gravitational Sedimentation:

particlesize.jpgOccurs when particles slow and settle out of suspension. The larger the particle, the more the influences of gravity will cause it to settle. Smaller particles (1 - 5 microns) are aided in gravitational sedimentation by the breath hold maneuver.

Recognize and discuss the hazards or complications that may occur during the administration of bland aerosol therapy

-Because bland aerosols are dense and contain a large quantity of aerosol particles, bronchoconstriction, airway irritation, wheezing and bronchospasm are possible. This is especially true when an ultrasonic nebulizer is used to deliver the bland aerosol. -Aerosol particles offer an ideal vehicle for the transmission of airborne pathogens from one person to another. Microscpopic aersol particles are similar in size to bacteria and bacteria love warm, moist environments. The caregiver can also be exposed to these airborne contagions as well. -A potential for overhydration but this is primarily in infants who are receiving dense aerosol delivery from equipment such as ultrasonic nebulizers -Infection/cross contamination #1 -aerosols of pneumonia may travel to a aerosol of a postoperative aerosol. -Bronchoconstriction, wheezing, airway irritation are possible- If somebody already have hyperreaactive airway disease (asthma) receiving cold aerosol may cause them to wheeze -over hydration: Primarily in infants (Extremely rare: 1 in a billion)

List and describe clinical situations that would indicate the need for bland aerosol therapy

-Heated aerosol is used to minimize humidity deficit when upper airway has been bypassed -Cool aerosol is used to reduce swelling of large upper airway in laryngeal edema, subglottic edema -People with laryngeal will have stridor -To stimulate a cough for sputum production -Heated -thins secretions -Use primarily for the purpose of humidification to patients with artificial airways (ET and tracheostomy tubes). Usually the bland aerosol is also administered with oxygen. -To reduce swelling of the large upper airway in cases such as laryngeal edema, or croup (cool bland aerosols) -To stimulate a cough for sputum production. Aersols which are hypertonic or even hypotonic can irritate the mucosal lining of the airway and stimulate coughing. This coughing may then move secretions up into the tracheobronchial tree for expectoration. . Special Note: Many believe that bland aerosol delivery thins down thick secretions due to the delivery of liquid particles. But this is not true. What aerosols may due is simply make the surface of the airway wet which may help secretions move with less friction. In order for secretions to be thinned down, they must absorb humidity (water vapor). Systemic hydration with fluids is the best way to thin down thick secretions. A humidifier with heat or a nebulizer with heat may provide the extra humidity required to re-hydrate and thin mucus.

Advantages of DPI include:

-Less patient coordination than MDI without spacer. -Propellant is not required. -Portable and convenient

Disadvantages of DPI include:

-Requires moderate to high inspiratory flow rates -High pharyngeal deposition is possible -High doses are difficult to deliver.

The depth and effectiveness of an aerosol delivered to the lungs depends upon multiple factors, including:

-Size and physical characteristics -Anatomy and geometry of the airways -Patient's ventilatory pattern

Disadvantages of using a small volume nebulizer include:

-equipment required for use is expensive and cumbersome -treatment times are more lengthy as compared to MDI and DPI -variability in performance characteristics among different brands -contamination is possible with inadequate cleaning

Advantages of the metered dose inhaler include:

-portability -convenience -inexpensive -If using a spacer, less coordination is required and less pharyngeal deposition occurs.

Disadvantages of the Ultrasonic medication nebulizer include:

-the device is very expensive and the system is prone to malfunction -Not all medications can be delivered with the USN -the device requires considerable preparation prior to its use.

Disadvantages of the metered dose inhaler include:

-without a spacer, patient coordination is required -There may be a high percentage of pharyngeal deposition -Difficult to deliver high doses

Misty-Ox Gas Injection Nebulizer (GIN):

A specially designed large volume nebulizer that can provide high FiO2 levels and high flow rates (over 100 L/m). Unlike the traditional large volume nebulizer (LVN), the Misty-Ox GIN is NOT an air entrainment device. It is a closed system device which requires two gas sources (oxygen and air). One gas source powers the nebulizer and a second gas is njected via an attached titration tube to achieve any FiO2 at any total flow. Being a closed system, the nebulizer can provide a positive pressure as well as hydration and variable oxygen concentrations. To achieve oxygen concentrations from 0.21 to 0.50, the device should be connected to an air flowmeter (driving primary jet) and titrate oxygen to blend specific concentrations. To achieve oxygen concentrations between 0.50 to 1.0, the device should be connected to an oxygen flowmeter (driving primary jet) and titrate air to blend specific concentrations.

Define the term bland aerosol and list the types of liquids that constitute bland aerosols

By definition, the word bland means not irritating, stimulating, or invigorating. And the word aerosol means a suspension of fine solid or liquid particles in gas <smoke, fog, and mist are aerosols>. Thus, putting them together describes a suspension of non irritating, stimulating or invigorating liquid particles in a gas. In respiratory care, these bland aerosols can be derived from sterile water, normal saline, or hypertonic saline. In other words, bland aerosols do not involve any prescribed medications. -Bland aerosols consist of liquid particles suspended in gas -Sterile water- objective is humidity -Normal saline (0.9% NaCl0)-same as our body -Hypotonic saline(less than 0.95 NaCl) -Hypertonic saline (Greater than .9%( -No prescribed medication humidity thins thick secretions NOT aerosols -Pg 835- Bland aerosol administration ( Indications....) -Presence of bypassed upper airway -Need for sputum specimens or mobilization of secretion

Ventilatory Pattern of the Patient:

Can be one of the most important factor influencing aerosol deposition to the airways. For Small Volume Nebulization of medication, patient should be instructed to breath slow at normal tidal volumes. For MDI administration, the patient should be instructed to take a deep breath using slow to moderate inspiratory flowrates. Optimally, a 10 second breath hold should follow the deep breath, but a 3 to 5 second breath hold is satisfactory. Passive exhalation. Encourage coughing. For DPI administration, the patient should be instructed to empty lungs first so that a deep inhalation with sufficient inspiratory air flows can be achieved: take a forceful deep breath, followed by passive exhalation. In most cases, a breath hold is not necessary.

List and explain the hazards associated with aerosol drug delivery

DISADVANTAGES There are a number of variables affecting the dose of aerosol drug that is delivered to the airways It is difficult to determine how much of a drug (dose) the patient has received and it will vary from patient to patient It is difficult for some patients to coordinate hand action and breathing with metered dose inhalers Lack of physician, nurse and therapist knowledge of device use and administration protocols Lack of standardized technical information for practitioners on aerosol producing devices Number of device types and variability of use is confusing to patients and practitioners There are virtually no hazards associated with the use of the aerosol devices such as small volume nebulizers, metered dose inhalers, or dry powdered inhalers. The complications that do occur are almost always associated with the medication being nebulized. Without going into specific drug complications, (refer to pharmacology course), the drug complications can be summarized in the following chart: Drug Class Complication Bronchodilator Drugs Bronchodilators may cause cardiovascular side effects (such as tachycardia and hypertension), nervousness, and muscle tremors. Mucolytics (Acetylcystein) Mucolytics can cause bronchospasm, or nausea Antiobiotics Antiobiotics may cause airway mucosal irritation and nausea All Aerosolized Drugs Drug reconcentration may increase any drug side effects. Drug reconcentration occurs when a portion of the medication is not nebulized and is allowed to stay in the nebulizer for the next several treatments.

Heat and Moisture exchanger

Heat and moisture exchangers or HME's come in a variety of shapes and sizes but all of them function relatively the same. Their nickname......Artificial Nose......... is derived from the way they function. That is, they function much like our own noses to heat and humidify inspired gas. These devices are mainly used for patients with artificial airways who are receiving mechanical ventilation. The HME device is placed between the patient's artificial airway and the circuit wye. This way, both inhaled and exhaled gas must travel through the HME. On exhalation, heat and moisture are trapped in the HME hygroscopic material and are re-applied to the inspired gas. So heat and moisture from exhalation is "exchanged" into the dry inspired gas. HMEs can provide about 85-93% (average 90%) of body humidity. The amount of humidity provided by the HME depends on several factors: the size of the patient's tidal volume. The bigger the tidal volume, the less effective and vice versa the inspiratory flowrate of gas. Faster flows tend to make the HME less effective the FiO2 of the gas. The higher the FiO2, the less HME effectiveness Patient minute volume. Since minute volume is a product of respiratory rate and tidal volume, as minute volume increases, HME effectiveness decreases. Ideally, patients should have a minute volume less than 10 L/m for optimum HME effectiveness. Because HME do not provide 100% body humidity, they may often be ineffective as a humidification device for patients who already have thick secretions. Or patient's may develop thick secretions after an HME has been in use. For patient's with an abundance of thick secretions, or for patients whose secretions become thick while using an HME, the HME should be removed and a humdifier capable of providing 100% body humidity should be used. Becaue HMEs do not provide much heat, they should not be used for humidification purposes on patients who are hypothermic such as those who may require mechanical ventilation from cold water drowning or those who have been through cardiovascular surgery where the body temperature is intentionally lowered during the procedure. Because of their location within the breathing circuit, HME should be removed when administering aerosolized medications. Otherwise, the HME will trap the aerosol particles. The AARC Clinical Practice Guideline for humdification during mechanical ventilation has great information on HME and their use. Best suited for patients undergoing short-term mechanical ventilation (96 hours or less) with minute volumes less than 10 L/min, limited secretions, and normal body temperature. The HME must be placed in-line in the ventilator circuit between the patient's artificial airway and the "wye" connector of the ventilator circuit. Efficiency of humidification is influenced by the size of the patient's tidal volume, inspiratory gas flow rate, and FiO2. As each of these factors increases, the efficiency of humidification decreases. Do not use on patients who have a large volume of secretions, or thick dehydrated secretions, hypothermia, during aerosol therapy, with other heated humidification devices, or for patient's with large leaks around the artificial airway.

Describe how temperature affects humidity and water vapor pressure.

The air we breath always contains a certain amount of water vapor depending on the temperature. When water sources are available and the temperature is warm, the humidity is great. Higher temperatures increase the capacity of a gas to carry water vapor. Likewise, when temperatures are cold, the amount of water vapor in the air is less. Many people often complain of dry skin and mucus membranes during winter months due to the dryness ( or lack of humidity) in the air. Nevertheless, humidity is important for normal lung function and is often an integral part of respiratory care to patients.

Ultrasonic Nebulizer

The basic principle of the ultrasonic nebulizer is that electric current produces sound waves which are used to break up fluid into aerosol particles. The electric current is transmitted to a piezoelectric transducer that vibrates at a frequency of 1.35 megahertz beneath a surface of tap water. The vibration creates sound waves that form a column of water and from this water column comes the aerosol. The amplitude controls the amount of aerosol output from the machine. Particle size range is from 1 to 10 microns, with a mean size of 3 microns. Fluid output averages are higher than those from a typical large volume nebulizer (up to 7 ml/min or 420 ml/hr). A fan creates gas flow that delivers the aerosol to the patient. Large Ultrasonic nebulizers are mainly used to aid in sputum induction. Some manufacturers have made small volume nebulizers that use the ultrasonic principle to nebulize bronchoactive medications at home. In addition, ultrasonic room humidifiers are available.

Breath-Enhanced Nebulizer

The breath enhanced nebulizer also reduces medication waste but is not as efficient as the BAN nebulizer. Nebulization is continuous with the breath-enhanced nebulizer, but aerosol will not be delivered to the patient except upon inhalation. A small rubber flap on top of the nebulizer opens when the patient inhales and creates a flow of gas sufficient to carry the aerosol particles to the patient's airways during inspiration. The flap closes at end inspiration. During exhalation, a small one-way flap below the mouthpiece will open allowing exhaled gas to exit the system instead of being returned to the nebulizer.

Heated wire circuit

The heated wire circuit is also a heated passover humidifier. The wires are attached to the humidifier and are threaded through the ventilator circuit. Sterile water is placed inside the reservior which has an aluminum plate located on the bottom. This aluminum plate sits atop of a heating unit. The heater warms the water in the reservior to the temperature set by the practitioner (usually close to 37 C). As gas exits the humidifier and travels the length of circuit hose, the wires in the circuit keep the gas the same temperature. Since the temperature is held constant through the entire length of the patient circuit, the condensation in the tubing is minimal (a real advantage). The heated wire circuit system is very capable of providing 100% body humidity. Usually employs a wick or Passover design but has the addition of wire-like structures threaded through the circuit which maintain desired gas temperature throughout the length of the circuit. Temperature is regulated with a dual servo-controller. Has many alarms built in such as low temperature, high temperature, and probe disconnect. Since the temperature is held constant through the entire length of the patient circuit, the condensation in the tubing in minimal (a real advantage). Gas temperature is maintained at or near body temperature. It is important to maintain an adequate water supply, keeping the water at the proper level, and ensuring tight ffittings of the temperature probe connections.

Large Volume Nebulizer:

The large volume nebulizer (LVN) is the most common piece of equipment used to deliver aerosol over long periods of time. They utililize high-pressure gas source (usually 50 psi oxygen) to produce an aerosol via the Bernoulli principle. It also incorporates air entrainment ports to entrain air and mix with oxygen in the same manner as an Air-Entrainment mask. This air-entrainment principle is to allow a large enough flow to carry the aerosol, not necessarily for specific FiO2. The result is a high flow of gas that when exiting the jet breaks the liquid into particles which are directed to a baffle which breaks larger aerosol particles into smaller ones. The FiO2 can be altered by adjusting the size of the entrainment ports. Heating attachments can be added to increase the water content of gas. Particles range from about 1 to 40 microns and so deposition usually occurs in the large and upper airways. Liquid particle aerosols are generated by passing gas at a high velocity through a small "jet" oriface. The resulting low pressure at the jet draws fluid from the reservoir up to the top of a siphon tube, where it is sheared off and shattered into liquid particles. As stated previously, the larger water particles are baffled and broken into smaller particles. The variable air entrainment ports allow air mixing to increase flow rates and alter FiO2. These air to oxygen entrainment ratios are the same as for an air entrainment mask. If heat is required, a heating element or hot plate can be attached to the reservoir to heat the water. When heated, these LVNs may provide about close to body humidity. Without heat, these devices may only produce about 45-60% body humidity. The nebulizer flow rate should always be run at 10 L/m or more. A large volume nebulizer is usually used with one of the following oxygen adminstration devices attached to a large bore hose: (see previous picture under Indications) Aerosol Mask Face Tent Trach mask T-Piece

Metered Dose Inhalers

The metered dose inhaler is the most widely used form of aerosol device. These inhalers have a variety of dispersal agents that are used to improve drug delivery and keep the drug in suspension. These dispersal agents may be Soya Lecithin, sorbitan trioleate, oleic acid or some other agent. As a result, some patients may develop severe cough or wheezing caused by the propellant or surfactant. Particles produces from the flashing of propellants are initially 35 microns and rapidly decrease in size due to evaporation as the particle moves away from the nozzle. Due to the velocity of the jet, approximately 80% of the drug impacts and deposits in the oropharynx (and possibly more when the cannister is placed in the mouth). Alcohol may be present in some MDIs as a co solvent. Concentrations of alcohol can be over 35% in some products. This can be a respiratory irritant for some patients. MMAD is between 3 and 6 microns with deposition in the lung of about 10%. The actual amount of the drug that is delivered to the patient is unpredictable. The use of a chamber device may result in less impaction of the medication on the walls of the circuit tubing or airway . The artificial airway generally reduces the amount of medication that deposits in the airway. Therefore, the dosage that is written is usually doubled when administering to intubated patients. Good patient technique is the most important variable affecting the delivered dose to the patient and therefore affecting the effectiveness of the drug. For a review of the proper click on the link and watch the brief video: How to Administer a Metered Dose Inhaler

Small Volume Nebulizer

The standard small volume nebulizer (aka medneb, or handheld nebulizer or updraft nebulizer) is a gas powered aerosol generator. Gas from a flowmeter is driven through a restricted orifice across the top of a capillary tube which is submerged in the medication solution. When the jet stream of gas meets the fluid from the capillary tube, an aerosol is produced and baffled to reduce particle size. Smaller particles exit and are breathed in by the patient, larger aerosol particles are returned to the reservoir. Although they are simple to use, several factors must be considered when using this device. Gas nebulizers do not aersolize below a minimal volume known as the dead volume. This volume varies with the brand of nebulizer but usually ranges between 0.5 and 1.0 ml. This is one of the main reasons why a diluent, such as normal saline, must be added with the drug. A dose of 0.5 ml of a drug would not get to the patient. With the diluent and the drug, only about 40-52% of the total dose will be delivered from the nebulizer. If the nebulizer is placed in a positive pressure ventilator circuit, only about 30% of the total dose will be delivered. These values do NOT, however, represent what will be deposited in the patients lungs. This amount will be considerably less! The average amount of drug that gets deposited into a patient's lungs is only about 12% of the dose. For optimum performance, small volume nebulizers should be run at flowrates between 6-8 L/m. This usually takes 10 minutes or less to deliver the medication.

Ultrasonic Medication Nebulizer

The ultrasonic medication nebulizer works with the same principle as the large ultrasonic nebulizer discussed in Bland aerosol therapy. That is, it uses a piezoelectric crystal that vibrates at a high frequency to convert electricity to sound waves, creating standing waves in the liquid immediately above the transducer, forming a geyser of droplets, which are dispersed as aerosol. This device uses a battery-powered source so it is considered portable. These smaller medication USN have a smaller dead volume than standard nebulizers (most all of the medication is nebulized) and in an optimum particle range of 3-5 microns.handheld_ultrasonic.jpg The device can be used with a mouthpiece or aerosol mask and requires only normal tidal volume breathing as does a standard medication nebulizer.

Simple bubble diffusion humidifier

Unheated Bubble Humidifier: Gas exits the flowmeter and bubbles through water in the reservoir bottle. The bubbles created when gas flows through the water create a larger surface area for the evaporization of water into the gas. Since it is not heated, though, it is not a very efficient humidifier and may, at best, provide about 25-30% of body humidity. Non-heated bubble humidifiers are typically used to humidify oxygen when delivered by a nasal cannula or simple mask delivery devices They should not be used to humidify gases to patients with artificial airways. In many hospitals, the use of these types of humidifiers is decreasing since they add an amount of equipment cost to the patient's bill and since they don't really add much humidity to the inspired gas. In fact, many people will not use them unless oxygen is being delivered at or above 4 L/m. Most commonly used to humidify dry therapeutic gases in simple oxygen administration devices. Comes equipped with a pressure-relief valve in case of obstruction to gas flow. The more smaller and frequent the bubbles, the greater the surface area for evaporation of water into gas.

List and explain the factors which influence the effectiveness of any humidifier.

· Temperature of the water and gas: This is the MOST IMPORTANT factor in determining the humidity output of a humidifier. Heating the water and gas increases the capacity of the gas to carry water vapor. · Contact Time: The longer the time a gas is in contact with water, the greater the water vapor content of the gas. If the flow rate of the gas through the water is too fast, this may not allow enough time for saturation of the gas. · Surface Area: The greater the gas/liquid interface, the greater the chance of the water molecules pushing into the gas mixture. Increasing the gas/liquid surface area can be accomplished by generating small bubbles below the surface of the liquid.

List and describe the indications or goals of humidity therapy.

Goal 1: To provide adequate heat and humidity to the inspired gas (especially dry therapeutic gases such as oxygen). This is especially important to those patients who have artificial airways.

Humidity deficit

Humidity Deficit: this is the difference between the water vapor content of inspired gas and the water vapor content at body humidity.

Humidity

Humidity can alter the delivery of aerosolized medications causing a reduction in the amount of aerosol delivered to the lungs. High humidity cause aerosol particles to coalesce and grow in size thus reducing their deposition into the smaller airways.

humidity

Invisible moisture or water vapor that is contained in our inspired gas

Kinetic Activity (Brownian Movement):

Kinetic activity primarily affects aerosol particles less than 2 microns. These small particles behave like gas molecules and stay in motion. They collide with other aerosol particles, and this increased motion causes them to coalesce and impact with the airway. (think of bumper cars bumping into each other)