Intro Unit 6

What are the 2 types of electrochemical oxygen analyzers

Polarographic

Galvanic Fuel Cell

Which electrochemical oxygen analyzers is used for continuous O2 monitoring

polarographic

Which electrochemical oxygen analyzers is reusable

polarographic

Which electrochemical oxygen analyzers senses PO2 but displays FIO2

polarographic

Which electrochemical oxygen analyzers displays FIO2 but senses PO2

Galvanic

Which electrochemical oxygen analyzers have a limited shelf life

Galvanic

Which electrochemical oxygen analyzers has a lesser reaction time to changes in FiO2 when compared to the other?

Galvanic

polarographic has the fastest analysis time

How do we calibrate an O2 analyzer when we want to use >60% O2

high calibration --> turn calibrate control to 100%

How do we calibrate an O2 analyzer when we want to use

low calibration --> turn calibrate control to 21%

If we cannot calibrate the O2 analyzer to 21%, what may be some possible causes?

-H2O condensation on cell membrane

-Bad Cell

-cell not fully exposed to 21% O2

If we cannot calibrate the O2 analyzer to 100%, what may be some possible causes?

-low battery

-H2O condensation

- cell not fully exposed to 100% O2

If the measured O2% on an O2 analyzer is much different than expected, what could be some possible causes?

-low battery

-analyzer not calibrated

-Error in O2 delivery device

-bad cell

If the O2 analyzer is reading 0 O2, what are some causes?

-low battery

-cell not plugged into analyzer

-dead cell

what 2 things does the pulse oximeter measure?

spectrophotometry

photoplethysmography

Spectrophotometry

uses light to determine the proportion of Hb that is saturated w O2

Photoplethysmography

a measure of volumetric changes associated with pulsatile arterial blood flow.

how do we confirm accuracy on a pulse ox

the O2 waveform must match the pulse wave

for the pulse ox, saturation is based on the ratio of....

light absorption between 2 or more wavelengths and baseline phases

baseline component--> represents stable absorbance of the tissue bed (venous and capillary blood)

pulsatile component --> intermittent arterial flow through tissues

Capnometry is the measure of...

end tidal CO2

how well CO2 is being moved throughout the system

Vd/VT (dead space / tidal volume)

A capnograph displays the....

PETCO2

what is the normal rand for capnometry

0.33-0.45

what are the two types of capnometry

Side Stream

Main Stream

Mainstream capnometer

CO2 sensor located between endotracheal tube and breathing circuit (in the airway)

measures right in line & measures the fastest (less dead space!

What are the advantages of Mainstream Capnometry

-sensor @ patient airway

-fast response (crisp waveform)

- short lag time

- no sample flow to reduce TV

What are the disadvantages of Mainstream Capnometry

-secretions & humidity block sensor

-frequent calibration

-bulky sensor @ airway (can cause ET Tube to come out

-hard to use w nonintubated patients

-reusable adapters require cleaning and sterilization

Sidestream capnometer

uses small-bore tubing to aspirate gas from or adjacent to the airway

which capnometer (mainstream v sidestream) creates more deadspace

sidestream

this will have lower gas exchange so CO2 will increase in the blood

this is useful for people who have a low TV

Advantages of Sidestream Capnometer

-no bulky sensor in airway

-can measure N2O

-Disposable sample line

-Ability to use nonintubated patients

Disdvantages of Sidestream Capnometer

-secretions block sample

-trap required to remove water from sample

-frequent calibration

-slow response to CO2 changes

-lag time between CO2 change and measurement

-sample flow may decrease TV

What is described by phase 1 of this normal capnogram

exhaled gas from conducting airways

REMEMBER: the anatomic deadspace is always exhaled first

What is described by phase 2 of this normal capnogram

a mixture of conducting airways and alveolar air (expiratory upstroke)

What is described by phase 3 of this normal capnogram

alveolar plateau

What is described by phase 4 of this normal capnogram

inspired air (0.3% CO2) (inspiratory upstroke)

Describe a low ventilation/perfusion relationship

caused by a shunt that reduces ventilation --> leads to no gas exchange

(pulmonary embolism, cardiogenic shock)

Describe a high ventilation/perfusion relationship

caused by functional deadspace that reduced perfusion

(airway obstruction, pneumonia)

Describe this abnormal capnograph (fig 10-7)

obstruction (bronchospasm/asthma)

it's taking longer to get the gas out

Describe this abnormal capnograph (fig 10-8)

weak effort

typical for someone coming out of anesthesia (pt is mechanically ventilated)

Describe this abnormal capnograph (fig 10-9)

sign of pneumothorax

air is evacuating elsewhere

unequal and incomplete emptying of lungs

Describe this abnormal capnograph (fig 10-10)

cardiogenic oscillations may be seen in patients with long expiratory times and slow respiratory rates

which type of monitoring uses miniature clark and severinghaus electrodes to measure transcutaneous PCO2

Transcutaneous PO2 and PCO2 monitoring

how does transcutaneous PO2 and PCO2 monitoring work

transcutaneous monitors heat the electrode to 44C which dissolves the lipid structure of the epidermal layer making it more permeable to gases

https://www.youtube.com/watch?v=4I4Cj0TmMxc

What are the indications for using capnometry

-to assess pulmonary circulation

-verification of artificial airway

-optimize mechanical ventilation

Why is a neonate's skin more permeable to to O2 and CO2

bc as we age, the human skin forms an impermeable barrier

factors that affect the relationship between PaO2 and PtcO2

-capillary blood flow

-skin blood flow

-metabolic oxygen consumption

what are the 4 problems associated with pulse oximetry

-No signal; SpO2 of zero

-Erratic signal

-SpO2 much different from measured HbO2

-Heart rate on pulse oximeter much different from actual HR

When the pulse ox is showing no signal, or an SpO2 of zero, what are the possible options

-probe not plugged into unit

-probe not properly placed

-light transmission blocked (nail polish color)

When the pulse ox has an erratic signal, what are the possible causes?

-poor perfusion

-motion artifact

-unstable hemodynamics

When the pulse ox SpO2 is much diff from measured HbO2, what could be the causes?

-dyshemoglobinemia

-exogenous or endogenous dyes or pigments

When the pulse ox is measuring a HR that is much different from actual HR, what is the cause?

poor perfusion -- choose another site!

What are possible problems that can arise while using capnometry

-PetCO2 zero with absent capnogram

-High/ Low PetCO2

-Increased slope of phase III of the capnogram

-Capnogram does not return to zero during inspiration

-Dampened capnogram

When the capnometer produces a low PetCO2, what could be the cause

-dead space producing disease

-decreased pulmonary perfusion

What are the possible problems that can arise while using a transcutaneous monitor

-unable to calibrate

-High/Low PtCO2

-High/ Low PtCCO2

-Skin Burns

-skin tears and irritation

If the Transcutaneous monitor is displaying a low PtcCO2 and a high PtCO2, what could the issue be?

not secured to the skin

If the Transcutaneous monitor is displaying a high PtcCO2 and a low PtCO2, what could the issue be?

poor perfusion to the tissue

Which monitors discussed in class are non invasive

pulse ox

end tidal CO2 monitor

transcutaneous monitoring

what is the equation to calculate the ratio between dead space and TV

VD/VT= PACO2-PECO2/PaCO2

PETCO2

partial pressure of end-tidal carbon dioxide

What are causes of sudden change in PETCO2

High

-↑ CO

-release of tourniquet

-injection of sodium bicarb

Low

-hyperventilation

-↓ CO

-pulmonary embolism

-air embolism

-disconnected from vent

-obstruction of ET

-leak In circuit

What are causes of gradual change in PETCO2

High

-hypoventilation

-↑ CO2 production

Low

-hyperventilation

-↓O2 consumption

-↓ pulmonary perfusion

List the flow measuring devices

-Fleish type Pneumotachometers

-Modified Fleisch type Pneumotachometers

-Thermistors

-Turbinometers

A pneumotachometer measures

air flow

-expiration creates small flow of pressure

-inspiration crates a decrease of pressure

A pneumothacter is based on which law?

Poiseulle's law of laminar flow

what physiological factors can impact the accuracy of a pneumotachometer

-viscocity (temp of gas effects viscosity)

-radius

-length

which pneumotachometer sets the standard for all other flow measuring devices

Fleisch Pneumotachometer

how does a Fleisch Pneumotachometer work

resistance is created by a bundle of brass capillary tubes

what happens if condensation clogs the capillary tube in a Fleisch Pneumotachometer

causes increase in resistance

do we use Fleisch Pneumotachometer for mechanical ventilation? Why?

No we don't

they can become occluded

which modification of the Fleisch Pneumotachometer replaced the capillary tubes with stainless steel heated screens? what is the purpose of these screens?

Metal Screen Pneumotachometer

middle screen --> creates resistance

outer screen --> prevents particulate matter from reaching middle screen & makes airflow more laminar

how does temp affect the Metal Screen Pneumotachometer

screens are heated to 37C

when they are heated, it prevents condensation

it can cause a discrepancy bc gases are not always measured @ body temp--> must use correction factor (BTPS)

Which pneumothacter is not used for diagnostic testing, but instead is used for screening

Fiber Screen Pneumothacter

How were the Fiber Screen Pneumothacter altered

metal screens replaced with single layer of fibrous material

fibrous material absorbs water vapor

what is a disadvantage of Fiber Screen Pneumothacter

the fiborous material absorbs water vapor so we must dispose after a few exhalations--> otherwise can lead to inaccurate results

How is a ceramic pneumothacter used?

uses a ceramic resistance element in place of the brass capillary tubes

what are the advantages of using a ceramic pneumothacter

-excellent heat conduction to the gases

-it is porous so water is absorbed

which pneumothacter is larger and heavier than the Fleish

ceramic pneumothacter

which pneumothacter is best for diagnostic

ceramic

What are the 2 types of orifice pneumotachometers?

Fixed

Variable

Which type of orifice pneumotachometer is not effected by humidity or temp & has minimal effect of varying O2 concentrations

fixed orifice pneumotachometer

thermistor

measures the temp change created by gas flowing through it

the higher the gas flow --> the greater the heat transfer

thermistors perform best when...

flow is laminar

what is the best way to place the flow sensor for a thermistor?

place it several feet away from mouth using smooth, large diameter tubing

this will

-minimize turbulent flow

-eliminate need for protective screen

-temp of gas being measured has less of an effect

how are turbinometers used

they use a windmill effect to measure airflow

What is the Indication for use of turbinometer

used for:

-measurement of exhaled TV

-evaluate spontaneous volumes before extubation

-evaluate inhaled or exhaled TV during mechanical ventilation

What are the two types of principle's used by Sonic Devices

ultrasonic and vortex

what is the ideal use for the Sonic Device

Monitor TV and minute volume during mechanical ventilation

Ultrasonic principles

ultrasonic signal is transmitted downstream or in the direction of the flow while another signal is transmitted upstream.

the differential time is used to calculate the velocity of the liquid that velocity is then used to calculate the volumetric flow through the pipe.

https://www.youtube.com/watch?v=h2veNh2I4IY

Vortex principles

-measures vortices

-essentially a sensor tab will Bend and flex from side to side as the vortex passes the bend and flex action will then produce an output frequency that is proportional to volumetric flow.

Why are vortex devices not suited for measuring FVS

due to upper flow rate limit of 250 L/min

peak flow meter

a handheld device often used to test those with asthma to measure how quickly the patient can expel air

https://www.youtube.com/watch?v=055fSYXgNKU

What are factors that may affect the performance of peak flow meters

- position

-gas density

-age of device

-any change to resistance of the device (secretions)

what is the purpose of the peak flow meter

designed for patient self assessment

make sure the patient uses the same flow meter --> diff devices give diff readings

List the instructions for using a peakflow meter

1. move marker to bottom of numbered scale

2. stand/sit up straight

3. take full inspiration

4. place mouthpiece into mouth and between teeth. Close lips. Do not put tongue inside mouth piece

5. blow out hard

6. write down peak flow

7. repeat 2 more times& record highest number

8. check to see which peak flow zone you are In

at what time of day should the peak flow measurement be taken?

every morning BEFORE taking asthma medication

also important to use when having symptoms & after taking medicine for asthma attack

which value is the highest peak flow?

the highest peak flow recorded

What are the 3 zones involved in a peak flow reading

green--> healthy, safe zone

yellow --> may need med adjustment

red--> get immediate medical attention

what are the 3 categories of devices used to measure pressure

-gravity dependent fluid manometers (barometers)

-mechanica aneroid manometer (pressure gauge on tanks

electromechanical transducers

gravity dependent fluid manometers (barometers)

AKA mercury barometer

used to measure atmospheric pressure

how does a mercury barometer relate to ABGs

used to calibrate blood gas analyzers

mechanical aneroid manometer are used for...

monitor pressure during mechanical ventilation

measure static and dynamic pressures

ventilators, disconnect alarms, resuscitation equipment

Strain gauge transducer

A pressure sensing and measuring device consisting of a group of wires that stretch when pressure is applied, creating resistance, thereby changing the process pressure into an electronic signal