Humidity and Aerosol Therapy Flashcards
Complications associated with dry medical gases
Administration at flows greater than 4 L/min to the upper airway causes immediate heat and water loss, and if prolonged can cause structural damage. Ciliary motility is reduced, airways become irritable, mucus production increases, and pulmonary secretions because inspissated (thickened due to dehydration). As long as humidity is 60% of BTPS conditions, no injury occurs.
Clinical signs and symptoms
-Atelectasis, dry nonproductive cough, increased airway resistance, increased incident of infection, increased WOB, substernal pain and airway dryness, thick dehydrated secretions.
Indications for Humidity Therapy
Humidifying dry medical gases, overcoming humidity deficit created when airway is bypassed, managing hypothermia, treating bronchospasm caused by cold air.
Recommended gas heat and humidity delivered to the…
Nose, Hypopharynx, and trachea
Nose- 20-22 degrees C, 50% rel. humidity, 10 mg/L abs. h.
Hypopharynx- 29-32 degrees C, 95% rel. humidity, 28-34 mg/L abs. h.
Trachea- 32-55 degrees, 100% rel. hum., 36-40 mg/L abs. h.
Principles governing humidifier function (4)
- Temperature (increase temp=increase capacity)
- Surface area (increase S.A.=more evaporation)
- time of contact (“ “)
- thermal mass (increased T.M. = increased capacity to hold and transfer heat.
Bubble Humidifier
Absolute humidity ~15-20mg/L
increase in gas flow is a decrease in efficiency
Pressure release valve (2psi)
Passover humidifiers
Simple- gas directed over surface of water, typically used with heated fluids for MV, but can be used with room temp. solution for nasal CPP or bilevel ventilation
Wick- increases surface area of air to water interface. No aerosol produced because there is no bubbling.
Membrane-type-hydrophobic membrane only allows water vapor molecules to pass through but not water.
Types of HME’s
HME’s passively humidify by absorbing exhaled humidity of patient and returning it to them on the next inhalation. Returns up to 70% humidity
Simple condenser HME- condenser element with high thermal conductivity consisting of metallic gauze, corrugated metal, or parallel metal tubes, recapture ~50% efficient
Hygroscopic HME- low thermal conductivity, paper, wool, foam, impregnated with hygroscopic salt, ~70% efficient
Hydrophobic HME- water repellent element, low thermal conductivity, temp. increases on exhalation, ~70% efficiency, may increase artificial airway occlusion.
Contraindications to HME use
-Patients with thick, copious or blood secretions, expired Vt less that 70% of the delivered Vt (patients with large bronchopleural fistulas or incompetent or absent endotracheal tube cuffs), body temp. lower than 32 C, patients with Ve greater than 10 L/m, for patients receiving in-line aerosol drugs.
Types of heating elements used (5 types)
- Hot-plate element at base of humidifier
- fischer-paykal, vapor humidifiers - a wrap-around type that surrounds the humidifier chamber
- pneumotac - a yolk, or collar, element that sits between the reservoir and the gas
- bubble humidifier - an immersion-type heater with the element placed in the water reservoir
- passover humidifier - a heated-wire in the insp. limb warming a saturated wick
- incubators and radiant warmers, MV
Indications, contraindication, and hazards of humidity therapy during MV.
Indications- humidity therapy is mandatory during MV
Contraindications- Same as HME contraindications.
Hazards/Complications- high flows may aerosolize contaminated condensate, underhydration and mucous impaction, increased WOB, hyppovent. caused by Vd, elevated airway pressures caused by condensation, ineffective low pressure alarm during disconnection, improper ventilator function caused by condensation, gas trapping or hypovent. caused by mucous plugging, hypothermia, potential burns, potential electric shock, airway burns, inadvertent over filling, tracheal lavage from pooled condensate.
Monitoring patients on MV
HH should be set to 33C plus or minus 2, and should provide at least 30mg/L of wv. Monitor inspired gas temp, airway temp. should never exceed 37C, probe placed outside of incubator or away from radiant warmer, water level monitored, secretion characteristics noted, remove HME and substitute HH if secretions become copious.
Factors that influence condensation
- temp. difference across the system
- the ambient temperature
- the gas flow
- set airway temperature
- the length, diameter, and thermal mass of the breathing circuit
Indications, contraindications of bland aerosol therapy
Indications- presence of upper airway edema (cool bland aerosol), laryngotracheobronchitis, subglottic edema, postextubation edema, postoperative management of the upper airway, presence of a bypassed upper airway, need for sputum specimens or mobilizations of secretions.
Contraindications- bronchoconstriction, history of airway hyperresponsiveness
Assessment of need/outcomes of aerosol therapy
Need- stridor, croup like cough (brassy), hoarseness after extubation, history of upper airway irritation, and increased WOB, patient discomfort associated with airway instrumentation, bypassed upper airway
Outcome- decreased WOB, improved vitals, decreased stridor, decreased dyspnea, improved ABG, improved sats,
Sputum induction
Gather supplies, check chart, wash hands, introduction, position the patient upright, have patient rinse mouth and clear excess saliva, perform pretreatment (vitals, muscle tone, ability to cough and auscultation), assemble neb, fill med chamber with 3% sterile saline, adjust output of unit, place mask on pt, assess patients condition, end treatment after 15-30 minutes, encourage patient to cough, observe volume, color, consistency, odor, and presence or absence of blood.
