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CO2 Physiology

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What is Carbon Dioxide?

• Capnos comes from the Greek word for “smoke”– smoke from the fire of metabolism– a natural waste product of cellular activity

• CO2 is a compound molecule

– 1 element of carbon and 2 elements of oxygen

– colorless and heavier than air

– green plants clean up after our exhaled CO2

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Physiology of CO2

• CO2 produced by cellular metabolism diffuses across the cell membrane into the circulating blood.

• The blood transports the CO2 to the lungs.• Then it diffuses from the blood into the lungs.• CO2 is eliminated with alveolar ventilation on

exhalation.

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Physiology of CO2

• Carbon Dioxide is transported in the blood in three (3) principle forms:– 5 to 10% as gas & reflected by the PCO2

– 20 to 30% is bound to blood proteins, the major one being hemoglobin

– 60 to 70% is carried as bicarbonate (HCO3)

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Physiology of CO2

• About 5-10% of CO2 is eliminate through exhalation only.

• The rest is recycled in the body through the circulatory and renal systems.

• The heart and lungs would have to increase their work 10 times if they were required to eliminate all the CO2 the body produces!

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Ventilation & EtCO2 Monitoring

• Endtidal CO2 (EtCO2) is the CO2 measured at the end of expiration.

• EtCO2 concentration provides a clinical estimate of the PaCO2, if ventilation and perfusion are appropriately matched.

• EtCO2 monitoring allows for a breath by breath assessment of ventilation.

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Capnography—

The continuous measurement and graphic display (waveform) of the CO2 concentration in the patient’s airway during the respiratory cycle.

Normal waveform:

Respiratory Cycle

O2 CO2

CO2 O2

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Respiratory Cycle

• Oxygenation = oxygen → lungs→ alveoli→ blood

Monitored by a Pulseoximeter

• Metabolism = oxygen is converted to energy + CO2

Monitored by a Metabolic Computer

• Hymodynamic Parameter

• Monitored by ECG, IPB, NIBP, Temperature

• Ventilation = CO2 → blood→ lungs→ exhalation

Monitored by a Capnograph

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Normal conditions: • EtCO2 is between 35 – 45 mmHg

• PaCO2 & EtCO2 will be very close

• EtCO2 is most 2 - 5 mmHg less with normal physiology

Widening of this difference can be caused by:• Incomplete alveolar emptying• Ventilation-perfusion abnormalities• Poor sampling

Capnography monitoring of Critically ill patient may alert clinicians to underlying conditions

The relationship – EtCO2 and PaCO2

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PaCO2 vs. EtCO2

PaCO2 – Partial pressure of CO2 present in arteries (similar to concentration)

Invasive ABG analysis

EtCO2 – concentration of CO2

exhaled in each breath

Non-invasive measurement at airway

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A-B: Baseline = no CO2 in breath

B-C: Rapid rise in CO2

D-E: Inhalation

C-D: Alveolar plateau

D

D: End expiration (EtCO2)

Normal waveform

D

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Normal waveform - 35-45 mmHg

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Hypoventilation

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Hypoventilation with shallow breathing

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Relationship between EtCO2 and RR

Breath-to-breath measure of ventilatory status

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Hyperventilation

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Some Definitions

• Capnometer• Capnography

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Capnometer

A Capnometer provides only a numerical measurement of carbon dioxide in mmHg or kPa or Vol.-%

Capnograpy

Capnography provides the CO2 value and the waveform of carbon dioxide over time

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Capnography—The Ventilation Vital Sign™

• Earliest sign that something is going wrong

• Breath by breath assessment of ventilation

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CapnographyCapnography

An EtCO2 value of e.g. 38 mm/Hg

without a

Time

5040302010

0

it´s like a heart rate of e.g. 80 without an

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CO2 Measurement Technology

General:

• CO2 measurement technologyInfrared absorption

• Technique of airway gas sampling

Main stream vs. side stream vs. Microstream

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Sampling Technology

• Mainstream sampling - CO2 analysis chamber is in-line between the patient airway and the ventilator circuit

• Sidestream sampling - CO2 analysis chamber is within the device. The patient’s expired gas is sucked from the airway and drawn to that chamber through a sampling line.

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Conventional main stream technology

Monitor

Fresh gas

InspirationExpiration

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Conventional side stream technology

Sample line

(Monitor)

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Unique solutions for Capnography= Microstream®

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Microstream® CO2

• A combination of a unique CO2 sidestream measurement technology and;

• FilterLine (proprietary sampling lines) - for single patient use

• Only system providing accurate EtCO2 readings for non-intubated patients that receive supplemental O2 and switch between oral and/or nasal breathing

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Microstream® CO2— Major benefits

• Ease of Use

• Reliable Technology

• Flexible for all patient types

• Versatile for all environments

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Microstream® advantages

• Superior moisture handling of liquids, secretions and humidity

• CO2 specificity – no cross-sensitivity to anesthetic gases

• Rugged – no moving parts in sensor

• Long-term monitoring

Reliable technology

• 50 ml/min flow rate supports entire patient population – including neonates (Competition at 3 – 5 times the flow rate)

• Does not compete for Neonate tidal volume

• The lower the flow, the less moisture to be handled

Flexible for all patient populations – solution for monitoring Neonates

Microstream® advantages

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Microstream® advantages

• No expensive sensors to replace• Yearly calibration – done in 5 minutes• Warm up time –

45 seconds from ON until first waveform and number appears

• One-piece Plug & Play consumables

Ease of use

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Light source Micro sample cell 15 µL

Light source housing

1 Eurocent

Microstream® advantages

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Microstream® Core Technology

Sensor Housing

I.R Source

Optic Block

(Micro Sample Cell)

I.R Detectors

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Microstream® advantages

• Fast response time

• 1 mm micro bore tubing reduces delay time

• Crisp waveform – longitudinal filter maintains laminar flow

• Build-in water trap – don't clean and re-use any FilterLine – it destroys the inline filter

Reliable Technology

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Microstream® advantages

Flexible

• Both intubated and nonintubated applications

• Alternating mouth and nose breathing

• Oxygen delivery (low flow O2 solution; solution for high flow O2 delivery)

• Adult, pediatric, and neonates

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Microstream® advantages

Versatile

All clinical environments:

• Critical Care

• Sedation Procedures

• EMS/ED

• Operating Room

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Unique solutions for CapnographyFilterLine® patient interfaces

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FilterLine® solutions for all applications

FilterLine®

Sets

IntubatedNon-Intubated

Smart Solutions NIV-Line

CapnoLine H

Smart CapnoLine / Smart CapnoLine O2

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Smart Solutions for nonintubated patients

• Continuous sampling from both

mouth and nose

• Special oral-piece design optimally

samples from mouth - Increased surface area provides greater sampling accuracy in the presence of low tidal volume (adult/intermediate size)

“Microstream® technology allows the accurate measurement of EtCO2 in the absence of an endotracheal tube.”*

*ASA 2001 Jay Brodsky, MD Professor of Anesthesia, Stanford University Medical Center, CA USA

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Smart Solutions for nonintubated patients

Smart CapnoLine™ Plus /Smart CapnoLine™ Plus O2

nasal cannula for CO2 measurement and O2 delivery

• Uni-junction sampling method ensures optimal waveform and ultra-fast response time

• Unique O2 delivery method reduces CO2 sampling dilution (up to 5l/min)

• Solution for high flow O2 delivery (works effectively under oxygen delivery mask)

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Solutions for non-intubated patientsSolutions for non-intubated patients

CapnoLine H*™ / CapnoLine H O2

• Enables continuous EtCO2 monitoring in high humidity environments (i.e. ICU)

• Can be used up to 72 hours

* = Humidity

Piece of Nafion

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Small pin holes deliver pillow of oxygen around both nose and mouth

Nasal and Oral Sampling

Microstream®—A Unique Solution For Non-intubated PatientsCO2 sampling / O2 delivery for non-intubated patients (up to 5 L/min.)

Uni-junction™ of sampling ports prevents dilution from non-breathing source

Increased surface area provides greater sampling accuracy in the presence of low tidal volume

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• Easily handles moisture and secretions without water traps

• Able to measure in any position

• Nafion® tubing allows for long-term monitoring without moisture build up

• Easily switches to non-intubated monitoring without re-calibration of monitor

• Low add. dead space (0,4 cc) to use on neonates

FilterLine® Sets - Solutions for intubated patients

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FilterLine® recommendations: Sedation Areas; GI Lab, Cath Lab, EP Lab

Is the Patient on Oxygen?

YES NO

Smart CapnoLine Plus O2 Smart CapnoLine Plus

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Do not try to dry the FilterLine® - this will damage the filter

Ensure there are no kinks in the sampling line

Do not cut the oral flange on the Smart CapnoLine

Do not cover the Nafion®

Do not instill medications through the airway adapter

Never pass a suction catheter or stylus through the airway adapter

Change the FilterLine® or the Set if a “Blockage” message appears on the monitor screen or if the readings become extremely erratic

FilterLine® information to avoid problems

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Latex free

Single-patient use

Not sterile

FilterLine® answers for the most FAQ´s:

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Sedation Procedures

“Monitoring of exhaled carbon dioxide should be considered for all patients receiving deep sedation and for patients whose ventilation cannot be directly observed during moderate sedation.”*

*Practice Guidelines for Sedation and Analgesia by Non-Anesthesiologists, Developed by the American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non Anesthesiologists: Anesthesiology 2002; 96:1004

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• Assesses -

patent airway (airway obstruction)

protective reflexes

response to verbal/physical stimuli

• Respiratory changes can immediately be assessed

• Microstream® allows for continuous respiratory monitoring with no nuisance alarms in procedural sedation environments where currently there is minimal usage of monitoring

Microstream® solutions during Sedation Procedures

Benefits and Uses

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Microstream® solutions during Sedation Procedures

• Cardiac Cath. Lab

• GI lab

• Pulmonary lab

• Emergency Department

• Hyperbaric medicine

• Dental Clinics

• Radiology

Applications

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Moderate – procedural sedation

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How can capnography make a difference in how you care for the sedated patient?

• What you do will not change

• When you do it will!

Capnography and sedation

Early detection of potential patient compromise

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Protocol during procedural sedation

• E.g. after 12 hours NPO (nothing by mouth) = EtCO2• Know the respiratory rate, waveform, and EtCO2 numeric

value before drug administration

Baseline Ventilatory Assessment

• RR, ETCO2 value…changes from baseline (trends)

• Changes in the Waveform…Earliest indicator of potential problems. (size, shape)

Continuous monitoring throughout case and recovery

Early intervention

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Changes from baseline

• Change in EtCO2 value > 10 mmHg

• Significant waveform change

Becomes erratic

Flatlines

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• Remember the ABC’s (airway, breathing, circulation)

• Assess the patient

• Follow your normal protocol, which may include:

Changes from baseline - action

Ensure open airway

Stimulate patient if necessary

Check the cannula positioning

Stop drug delivery

Inform M.D. / pause procedure if necessary

Administer reversal agents as prescribed

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• Requires higher vigilance in ventilatory monitoring

• Maintain patent airway

• Potential dead space ventilation

• Chest moves up and down

Deep sedation

• Inadequate respiratory effort to clear dead space

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Assessing for changes from baseline

Hypoventilation with shallow respirations

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Nursing interventions

• Continue to monitor

• Ask patient to take a deep breath

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Abnormal waveforms

Possible causes

• Partial airway obstruction caused by:

• Tongue

• Position of head

Absent alveolar plateau indicates incomplete alveolar emptying or loss of airway integrity

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Assessing for changes from baseline

• Poor head and neck alignment

• Draping near the airway

• Shallow breathing – not clearing

dead space

Rebreathing often results from:

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Assessing for changes from baseline

• Chest movement

• Little – to no air movement in and

out of lungs

Dead space ventilation

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Abnormal waveforms

Possible causes

• Partial airway obstruction caused by:

– Tongue

– Position of head

Absent alveolar plateau indicates incomplete alveolar emptying or loss of airway integrity

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Nursing interventions

• Assess patient

• Ask patient to take a deep breath

• Adjust patient’s head position, if

necessary

• Adjust cannula position, if

necessary

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Putting it all together

• The transition from conscious sedation to unconscious/anesthesia is very subtle and can be undetected until oxygenation is impaired

• You must be prepared to monitor a patient at a level deeper than intended

• “Respiratory frequency and adequacy of pulmonary ventilation are continually monitored”

• Only capnography provides an immediate notification of a ventilatory event