"Humidity and Aerosol Therapy - DOC - DOC"
Humidity and Aerosol RsCr 220 INTRODUCTION TO HUMIDITY AND AEROSOL THERAPY The body’s systems require a certain amount of hydration in order to maintain homeostasis. The best way is through drinking plenty of fluids and administration of IV fluids. Signs of dehydration are chapped lips, flaky skin, dry cracked elbows and heels. The respiratory signs include crusty nasal cavities, nosebleeds, dry mouth, scratchy throat and a dry hacking cough. Many of our patients have bypassed normal airway and an important part of our job is to provide for their special needs. Under normal conditions, body water loss through respiration is approximately 200 – 500 mL / day. Respiratory therapists deliver oxygen that needs to humidified and often heated to adequately meet the needs of their patients. Humidity Terms Vapor Content – is the amount of water present in the air. Measured in mg/L. Water vapor content at body temperature is 43.9 mg/L, at room temperature it is less. Vapor pressure – water as a vapor exerts a pressure (Dalton’s Law) and is part of the total atmospheric pressure. Water vapor pressure in the lungs exert 47 mmHg Absolute Humidity – the actual amount of water vapor in the atmosphere Relative Humidity – the percent of water vapor in the air as compared to the amount necessary to cause saturation at the same temperature. Body Humidity – the relative humidity at 37 degrees Celsius Humidity Deficit – the amount of water vapor needed to achieve full saturation that temperature. Isothermic Saturation Boundary – At or just below carina (end of trachea) The point at which inspired gases are fully 100% saturated and warmed to body temperature (44 mg/L at 37oC) Uses of Humidity therapy 1. Humidification of inspired gases 2. Thinning of bronchial secretions 3. Sputum induction Solutions Used - Bland Aerosols i.e. Sterile water (Hypotonic) - (Normal) Isotonic saline (.9% Na) with (Aerosol / Medicine) Treatments - Hypertonic saline (10%) 1 Humidity and Aerosol RsCr 220 Indications for Humidity Therapy 1. Relieve Upper Airway Swelling (inflammation) Examples Croup/Epiglotitis Requires differential diagnosis to determine illness Both illnesses have similar symptoms Post extubation stridor Always use cool gas with sterile water (DECREASES inflammation) 2. Overcome humidity deficit - thins secretions and prevents further drying of secretions - Used in patients with bypassed upper airway Trach patients Patients with ET tubes -Always use warm gas - Increased ability to hold water (increased MAH) - Solutions used should always be sterile water - Also used to provide specific FIO2 3. Sputum induction (production) Uses hypertonic solutions via aerosol (greater than 0.9% Na) 5-10% normal saline solution Mucomyst-breaks down thick mucous (breaks disulfide bonds) The hypertonic saline draws out water from the tissues of the throat and trachea to help liquefy secretions for expectoration Used mainly in cases where samples are needed to test for type of bacteria growing in lungs (sensitivity and gram stain) Also can be used to test for T.B. (Acid-fast Bacilli) Goals of Humidity Therapy Provide adequate heat and humidity to the inspired gas Reduce airway swelling To aid in the removal of thick secretions To prevent airway response to cold air AMERICAN NATIONAL STANDARD INSTITUTE STATES MINIMUM STANDARDS FOR HUMIDIFICATION UPPER AIRWAY OUTPUT OF 10 MG/L FOR UNHEATED 50% RH AT ROOM TEMPERATURE (22OC) LOWER AIRWAY AT LEAST 30 MG/L HEATED (100% AT 30OC) Hazards of Humidity Therapy Bronchospasm from cool mist (watch out for asthmatics) 2 Humidity and Aerosol RsCr 220 Infection risk – ‘change out’ regularly Over hydration in patients with CHF and in infants TYPES OF HUMIDIFIERS Low Flow Bubble Diffusers for nasal cannula Relative Humidity – 30-40% @ body temp used when O2 flow is greater then 4 l/m High Flow Large Volume Jet Nebulizers (Aerosol Mist setup) Has lower FIO2 28-50% capabilities Need to run nebs at flush (limits to 12-15 LPM) For higher FIO2 may have to use double nebulizers - High flow flowmeters help too Special Point: Always place drain bag inline to collect excessive water accumulations. If water buildup causes a restriction, the entrainment ports will be compromised and unit will produce higher then expected oxygen concentrations. Nebulizer for Mist Tent (Croup Tent) produces a high-density output ideal for producing a moisture-rich enclosed environment such as a croup tent (Also can use Babington Hydroshere) Ventilator Humidifiers Heat and Moisture Exchangers (HME’s) referred to as artificial noses inhibits the growth of bacteria can be plugged with excessive secretions produces an rh of 80% at 26-30c should be replaced each 24 hours (72hr max) Take out of line when nebulizing treatment Wick type humidifier heated, capable of high flow rates very efficient, produces 100% humidity at body temperature can be used for up to 1 week before needing to be replaced are thermostatically controlled with alarms a. Fisher Paykel b. Concha therm Cascade type humidifier changed every 3-4 days not used any longer due to the fact that they produced an increased risk of infections. 3 Humidity and Aerosol RsCr 220 AEROSOL THERAPY Is the administration of a suspension (aerosol) of either a solid or a liquid in a gas. A force equal to the weight of the fluid displaced buoys up dependent upon Archimedes Principle, which states that a body located in any fluid. Similar to Brownian movement. Measurement of Aerosol Particles They are measured in microns in a range of 0.5 to 100 microns. Generally the smaller the particle, the deeper the penetration into the respiratory tract. Nose and mouth 20 – 100 microns Upper airways 5 – 20 microns Lower airways 2 – 5 microns Alveoli 1 – 3 microns Particle size is measured by calculating their average or mean size. MMAD refers to Mass Median Aerodynamic Diameter where half the volume is in a particular size range. Count median diameter (CMD) divides the sample into equal portions by number i.e. half above and half below. Particles follow mathematical rules of a normal distribution curve called GSD. Volume Output The amount of water that is produced as an aerosol from the liquid reservoir can be computed. Aerosol and Humidity Density The concentration of the particles is important. If the mist is really thick and a large amount for the volume that is being produce it is considered dense. The formula for density is mass / volume. The mass is usually in milligrams and the volume in liters. A common density is 44 mg/L of water particles to saturate the air in the lungs at 37oC. Always place the nebulizer as close to the patient as possible. This will prevent losing most of the medicine to the inside of the tubing. Factors Influencing Penetration and Deposition 1. Inertial Impaction a. A particle carried in an air stream tends to continue in a straight direction even when the direction of the air stream changes. Also known as sideways slip. Affects particles >3 microns. 2. Gravity a. Stokes Law of Sedimentation – The settling rate of an aerosol is related to the diameter and density of the particle i.e. density x diameter2 3. Physical Nature of the Particle a. Shape of the particle b. Electric charge c. Hygroscopic Properties 4 Humidity and Aerosol RsCr 220 4. Breathing pattern a. A deep slow inspiration through an open mouth, with a breath-hold, is the ideal pattern TYPES OF NEBULIZERS Atomizer Hand-bulb or nasal spray pump Used to produce and aerosol with large varied particles Targets the upper airway (nasal passages, pharynx and larynx) (Obviously no baffle) Small Volume Nebulizer (acorn, nebs, SVN, HHN, med neb, updraft neb) Powered by air or oxygen connected to flowmeter /compressor. Uses a baffle to reduce the size of the particles into the respiratory size (i.e. 2 to 5 microns) for deposition into the smaller airways. Types of medications 1. bronchodilators – adrenergics 2. bronchodilators - anticholinergics 3. corticosteroids 4. mast cell inhibitors 5. mucokinetics 6. antibiotics Specialized Nebulizers A. Circulaire – reservoir bag/filter on exhale port (morphine) B. Respigaard – for delivery of anti-infectives (pentamadine) C. Heart and HOPE nebulizers for continuous (1 hour) therapy in ER D. New Generation – AERx, Aeroneb, Respirmat, AeroEclipse (and others) E. Small Particle Aerosol Generator (SPAG) - used to deliver medicine (Virazole) to neonates F. Ultrasonic Nebulizers (not used much anymore – in hospital setting) - Electrically powered to deliver meds with high output of moisture - uses high frequency sound waves to create high density aerosols - Now more popular as a portable machine for nebulizing treatments for children away from home METERED DOSE INHALERS (MDI’S) Equivalent doses of medications delivered w/o diluent Good for those who are not tachypnic Should always be used with a spacer to improve aerosol deposition. Also it makes it easier to administer. Less oral deposition leads to fewer side effects. DRY POWDERED INHALORS (DPI’S) 5 Humidity and Aerosol RsCr 220 - made of organic materials to lessen side effects - used to deliver dry aerosol medication - does not use cfc’s. (flourocarbons) propellants - easier for adults to use who have good inspiratory flows CONTROLLING ENVIRONMENTAL CONTAMINATION Negative Pressure Rooms Needed for Respiratory Isolation Chicken Pox or TB Private Room with a set of double doors with and entry way. Air exchanged at least 6 times an hour Vented to the outside Booths and Stations Provides for containment of aerosol during therapy Used for sputum inductions with suspected TB patients Used for pentamidine administration with HIV patients Personal Protection Equipment Airborne Precautions implemented Wear a reusable HEPA filter mask over and above gloves and gown Need to be personally fitted for mask, inserviced on it’s use and have annual compliance re-training. Students – do NOT qualify 6