Respiratory Care Procedures | unit 5 a & b

unit 5 a& b -humidity therapy

Absolute Humidity

The actually mass or content of water in a measured volume of air, usually expressed in grams per cubic meter or pounds. (AKA the actual content of water in the air)

what is the formula to calculate absolute humidity

relative humidity x capacity

Relative Humidity

The amount of moisture in the air compared with the maximum amount that the air could contain at the same temperature

what is the formula to calculate relative humidity

(absolute humidity / capacity) x 100

What instrument is used to measure Humidity

Hygrometer

Hygrometer

an instrument that directly measures the relative humidity of a mixture or gas

how many thermometers does a hygrometer have

2; one with a wet wick surrounding the bulb and one with a dry bulb

how does a hygrometer work

use a transducing element with electrical properties that change with water content. Once saturated, _____________are not reliable for reporting changes in humidity over time

body Humidity

Absolute humidity in a volume of gas saturated at body temperature of 30C, equivalent to 44mg/L of water in the air

Coalescence

The process where 2 or more droplets merge to form a single larger droplet

Dewpoint

The temperature at which water vapor condenses back to its liquid form

Diffusion

Movement of molecules from areas of higher concentration to areas of lower concentration

what does BTPS stand for

Body temperature and pressure saturated

body temperature and pressure saturated

volume of gas expressed as if it was saturated with water vapor at body temperature(32C) and at the ambient barometric presssure(44mg/L, 47 torr or 47 mmHg).

what is the measurement of relative humidity at BTPS

100% at 37C

what does ISB stand for

isothermic saturation boundary

isothermic saturation boundary

The point at which inspired air becomes full saturated to 100% relative humidity at body temp to BTPS. Air moves through the upper respiratory tract and becomes humidified by the time it hits the ISB.

what is ISB’s significance

it indicates when the airways are no longer exchanging heat and moisture, and the temperature and humidity remain constant.

where is ISB located

5cm below the carina

what can change the ISB

person breathes cold/dry air

airway is bypassed

minute ventilation is higher than normal.

potential humidity

The maximum amount of moisture (AKA water vapor) that air can contain at a given temperature.

how does temperature change affect potential humidity

as the ambient temperature increases, so does the potential humidity (and vice versa)

What are the four types of Heat transfer

conduction

convection

radiation

evaporation/ condensation

conduction

main method of heat transfer in solids; via direct contact between molecules

convection

mixing of fluid molecules at different temperatures; transfers heat in liquids and gases

radiation

occurs without direct contact between two substances

evaporation/ condensation

form of vaporization, change of state from liquid to gas, or gas to liquid.

give an example of conduction

Ex: pan on a hot stove, heat from burner transfers directly to pan

give an example of convection

Ex: convection oven/ airfryer.

give an example of radiation

Ex: microwave, warmth of sun on your skin, radiant lamp, warmer.

give an example of evaporation

Ex: sweat evaporating from your skin, hanging clothes to dry

What part of the respiratory system is mainly responsible for humidification of inspired gases

concha/turbinates

concha/turbinates

3 shelflike bones projecting from lateral walls.

what is the function of the concha/turbinates

increases surface area for filtering, warming, and humidifying inhaled gases

laminar flow

fluid moving in discrete cylindrical layers or streamlines

turbulent flow

loss of regular streamlines; fluid molecules form irregular whirlpools in chaotic
pattern is predicted by using reynolds number

transitional flow

a mixture of the laminar and turbulent flow

reynolds number

a dimensionless numer used to determine whether a flow is laminar or turbulent

what is the reynolds number for turbulent flow

0-2000

wat is the reynolds number for turbulent flow

2000-5000

humidity deficit

a condition associated with a body humidity(BH) less than 100% that represents the amount of water vapor the body must add to the inspired gas to achieve saturation at body temperature.

when does humidity deficit occur

when the inspired gas is not fully saturated at body
temperature.

what is the calculation for humidity deficit

44mg/L - absolute humidity

Where does sensible water loss occur

urination and defecation

Where does insensible water loss occur

the skin and lungs

what are the major indications for humidity therapy

primary and secondary goals

what are the primary goals for humidity therapy

Humidifying dry medical gases

overcoming humidity deficit created when the upper airway is bypassed

what are the secondary goals for humidity therapy

thick, copious, or bloody secretions

Expired Vt< 70% of delivered Vt

Body temp < 32C

High spontaneous minute volumes(>10 L/min)

What are the significant risks/hazards for humidity therapy

Cross-contamination and infection

Inadequate humidity production

Overhydration

Swelling of dried (inspissated) secretions

Bronchospasms

inspissated

thickened in consistency, or made or having become thick, heavy, or intense. the process of increasing the viscosity of a fluid

what does HME stand for

heat-moisture humidifier

what is an HME reffered to as

an artificial nose

when is an HME indicated

when patients are receiving ventilator support, laryngectomy patients, and short-term usage.

when is an HME contradicted

potential electric shock

potential thermal injury

underhydration during hypoventilation

increase in deadspace

unintentional tracheal lavage

elevated airway pressures

poetntial airway burns

what is a HME

a device that humidifies and filters the air you breathe

manual systems

simple (large) reservoir systems are manually opened and refillled with sterile or distilled water; cross contamination ca occur. Small inlet can be attached to gravity-fed intravenous bag and line allows refilling without interruption

automatic systems

avoid the need for constant checking and manual refilling; has level compensated reservoir and floatation valve controls

What are the benefits of a heated wire circuit

Can be utilized to maintain a set temperature in the entire circuit(from ventilator to patient)

what is a bubble humidifier

type of humidifier that breaks underwater gas stream into small bubbles

when is the bubble humidifier indicated

when using unheated with oxygen delivery systems to raise water vapor content of gas to ambient levels or delivering approximately 20 – 40% relative humidity at BTPS.

when is the bubble humidifier contradicted

for patients with an endotracheal tube, a tracheostomy, or tenacious secretions

what events can affect the action of a bubble humidifier

gasket connections

condensation

a form of vaporization, change of state from liquid to gas, or gas to liquid

what are the hazards associated with condensation

the growth of mold and
bacteria

What are the current AARC recommendations for humidity therapy

34-41C at the circuit wye with a minimum of 30mg/L water vapor for intubated pts. heat inhaled gas to maintain airway temperatures near 35-37C

wick humidifier

a type of humidifier that uses a wick to absorb water from a reservoir and release it into the air.

how does a wick humidifier work

Absorbent material increases surface area for dry air to interface with heated water->

Typically an upright wick with gravity dependent end in heated water reservoir->

heated by elements below or surrounding the wick->

capillary action draws water from the reservoir->

dry air enters the chamber, flows around the wick.

passover humidiier

humdifier that directs gas over a surface containg water.

how does a passover humidifier work

Simple reservoir->

directs gas over the surface volume of fluid->

surface area for gas-fluid interface is limited
(heated for invasive mechanical ventilation) (room temperature fluid for home CPAP)