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Humidity Therapy and Humidifiers

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Lack of condensate may be a clue that humidification is less than adequate and that alternative systems may be appropriate for use with that particular patient. – PowerPoint PPT presentation

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Title: Humidity Therapy and Humidifiers


1
Humidity Therapy and Humidifiers
  • RET 2274
  • Respiratory Care Theory 1
  • Module 5.0

2
Humidity Therapy and Humidifiers
  • Humidity
  • Water that exists as individual molecules in the
    vaporous or gaseous state and is present in the
    air we breathe often described as water vapor

3
Humidity Therapy and Humidifiers
  • Humidity Therapy
  • Involves adding water vapor and (sometimes) heat
    to an inspired gas
  • Primary goal of humidification is to maintain
    normal physiological conditions in the lower
    airways or treat abnormal conditions

4
Humidity Therapy and Humidifiers
  • Humidity Therapy
  • Administration of dry medical gases at flows
    greater than 4 L/min to the upper airway causes
    immediate heat and water loss, and if prolonged,
    causes structural damage

5
Humidity Therapy and Humidifiers
  • Absolute Humidity
  • Is the actual content or weight of water present
    in a given volume of gas
  • Expressed as
  • Grams per cubic meter (g/m3)
  • Milligrams per liter (mg/L)
  • Also know as water content

6
Humidity Therapy and Humidifiers
  • Relative Humidity (RH)
  • Is the ratio of actual content or weight or the
    water present in a gas relative to the samples
    capacity to hold water at that temperature
  • Expressed as a percentage
  • RH measured humidity (content) X 100
  • water capacity
  • When the amount of water that a gas contains at a
    given temperature is equal to the gass capacity,
    the RH is 100 - described as saturated

7
Humidity Therapy and Humidifiers
  • Relative Humidity (RH)
  • Increasing the temperature of a gas, increases
    its capacity to hold water
  • If absolute humidity is held constant, increasing
    the temperature of the gas will decrease the RH
  • If absolute humidity is held constant, decreasing
    the temperature of the gas will increase the RH
    or it will remain at 100

8
Humidity Therapy and Humidifiers
  • Relative Humidity (RH)
  • ?Temp ?RH
  • ?Temp ?RH

9
Humidity Therapy and Humidifiers
  • Condensation
  • Cooling a gas that has an RH of 100 decreases
    its capacity to hold water, which results in
    water being squeezed out of the gas
  • ?Temp ?RH

10
Condensation
11
Humidity Therapy and Humidifiers
  • Evaporation
  • The process of water moving from a liquid to a
    gaseous state at temperatures lower than its
    boiling point
  • The warmer the air contacting the water surface,
    the faster the rate of evaporation
  • Heating water will increase the rate of
    evaporation

12
Humidity Therapy and Humidifiers
  • Humidity
  • Partial Pressure
  • The random motion of water molecules exerts a
    pressure (water vapor pressure) in a way similar
    to gas exerting pressure
  • As the temperature of a gas increases, kinetic
    activity increases, so the pressure also
    increases

13
Humidity Therapy and Humidifiers
  • Humidity
  • Partial Pressure
  • Its magnitude is solely dependent upon
    temperature and relative humidity not upon
    barometric pressure
  • The partial pressure of water vapor must always
    be accounted for (subtracted) when calculating
    the partial pressure of other gases in a mixture

14
Humidity Therapy and Humidifiers
  • Humidity
  • Partial Pressure
  • Alveolar Air Equation
  • FiO2 (PB Water Vapor Pressure) PaCO2
  • 0.8
  • .40 (760mm Hg 47 mm Hg) 40 mm Hg
  • 0.8

15
Humidity Therapy and Humidifiers
  • Physiological Control of Heat and Moisture
    Exchange
  • Primary function of the upper respiratory tract
  • Nose (primary)
  • Heats and humidifies gas on inspiration and cools
    and reclaims water from the gas that is exhaled
  • Sinuses, Trachea, and Bronchi
  • Also aid in heating and humidifying the inspired
    gases

16
Humidity Therapy and Humidifiers
  • Physiological Control of Heat Moisture Exchange
  • As inspired gas moves into the lungs, it achieves
    BTPS (body temperature, 37? C barometric
    pressure saturated with water vapor 100
    relative humidity at 37? C)
  • Isothermic Saturation Boundary (ISB)
  • The point in the respiratory tract at which
    incoming gas reaches BTPS
  • Below the ISB, temperature and relative humidity
    remain the same

17
Humidity Therapy and Humidifiers
  • Indications for Humidification
  • Primary goal of humidification is to maintain
    normal physiological conditions in the lower
    airways or treat abnormal conditions

18
Humidity Therapy and Humidifiers
  • Indications for Humidification
  • Administration of dry medical gases at flows
    greater than 4 L/min to the upper airway causes
    immediate heat and water loss, and if prolonged,
    causes structural damage
  • Ciliary motility is reduced
  • Airways become irritable
  • Mucous production increases
  • Pulmonary secretions become thick and inspissated

19
Humidity Therapy and Humidifiers
  • Indications for Humidification
  • Prolonged breathing of improperly conditioned
    gases through a tracheal airway can result in the
    following
  • Hypothermia
  • Inspissation of airway secretions
  • Mucociliary dysfunction
  • Destruction of airway epithelium
  • Atelectasis
  • As long as inspired humidity is at least 60 of
    BTPS conditions, no injury occurs in normal lungs

20
Humidity Therapy and Humidifiers
  • Indications for Humidification
  • Humidified gas delivered to an artificial airway
    (endotracheal or tracheostomy tube) must be
    between 31? and 35? C with a minimum of 30 mg/L
    of absolute humidity
  • To maintain the appropriate temperature and
    humidity levels, monitoring at the interface of
    the patient and humidifying device is necessary

21
Humidity Therapy and Humidifiers
  • Equipment
  • Humidifier is a device that adds molecular water
    to gas

22
Humidity Therapy and Humidifiers
  • Physical Principles Governing Humidifiers
  • Temperature
  • The greater the temperature of a gas, the more
    water it can hold
  • The cooler the water in a humidifier the less
    efficient they are

23
Humidity Therapy and Humidifiers
  • Physical Principles Governing Humidifiers
  • Surface Area
  • The greater the area of contact between water and
    gas, the more opportunity for evaporation to
    occur
  • Passover humidifiers pass gas over a large
    surface area of water

24
Humidity Therapy and Humidifiers
  • Physical Principles Governing Humidifiers
  • Surface Area
  • Bubble-diffuser type humidifiers

25
Humidity Therapy and Humidifiers
  • Physical Principles Governing Humidifiers
  • Surface Area
  • Wick technologies use porous water-absorbent
    materials to increase surface area

26
Humidity Therapy and Humidifiers
  • Physical Principles Governing Humidifiers
  • Contact Time
  • The longer gas remains in contact with water, the
    greater the opportunity for evaporation to occur
  • Depth of water column (bubble type)
  • ? depth of water ? evaporation
  • ? depth of water ? evaporation
  • Flow rate of gas (passover and wick)
  • ? flow rate ? evaporation
  • ? flow rate ? evaporation

27
Humidity Therapy and Humidifiers
  • Types of Humidifiers
  • Active
  • Actively adds heat and/or water to the
    device/patient interface
  • Bubble
  • Passover
  • Membrane
  • Passive
  • Recycling exhaled heat and humidity from the
    patient
  • HME

28
Humidity Therapy and Humidifiers
  • Types of Humidifiers
  • Bubble Humidifier (Active)
  • Breaks an underwater gas stream into small
    bubbles
  • Unheated commonly used oronasal O2 delivery
    systems (e.g., cannula)
  • Goal to raise the water vapor content of the gas
    to ambient levels
  • Can generate aerosols at high flows
  • Equipped with pressure-relief valve pop-off

29
Humidity Therapy and Humidifiers
  • Types of Humidifiers
  • Passover Humidifier (Active)
  • Directs gas over a water surface
  • Two types
  • Wick
  • Membrane

30
Humidity Therapy and Humidifiers
  • Types of Humidifiers
  • Passover Humidifier
  • Wick type
  • A cylinder of absorbent material (wick) is placed
    upright in a reservoir of water and surrounded by
    a heating element
  • Dry gas enters the chamber, flows around the
    wick, picks up moisture, and leaves the chamber
    saturated with water vapor

31
Humidity Therapy and Humidifiers
  • Types of Humidifiers
  • Passover Humidifier
  • Membrane type
  • Separates the water from the gas stream by means
    of a hydrophobic membrane
  • Water vapor molecules pass through the membrane
    (liquid cannot)
  • Dry gas enters the chamber, flows across the
    membrane, picks up moisture, and leaves the
    chamber saturated with water vapor

32
Humidity Therapy and Humidifiers
  • Types of Humidifiers
  • Heat and Moisture Exchangers (HME)
  • Passive humidifier
  • Functions similar to the upper airway
  • Captures exhaled heat and moisture during a
    patients exhalation and returns it to the
    patient during the next inspiration

33
Humidity Therapy and Humidifiers
  • Types of Humidifiers
  • HME (Passive)
  • Best Suited for
  • Short-term mechanical ventilation ( 96 hours)
  • Minute ventilation lt 10 L/min
  • Limited secretions
  • Normal body temperature

34
Humidity Therapy and Humidifiers
  • Types of Humidifiers
  • HME (Passive)
  • Rule of Thumb
  • You can estimate if an HME is performing well at
    the bedside by visually confirming condensation
    in the flex tube. Lack of condensate may be a
    clue that humidification is less than adequate
    and that alternative systems may be appropriate
    for use with that particular patient.

35
Humidity Therapy and Humidifiers
  • Heaters, Reservoirs, and Feed Systems
  • Heat improves the water output of bubble and
    passover humidifiers
  • Heated humidifiers are used mainly for patients
    with bypassed upper airways and/or for those
    receiving mechanical ventilatory support

36
Humidity Therapy and Humidifiers
  • Heaters, Reservoir, and Feed Systems

37
Humidity Therapy and Humidifiers
  • Heaters, Reservoir, and Feed Systems

38
Humidity Therapy and Humidifiers
  • Heaters, Reservoir, and Feed Systems
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