medic update 2003 capno

7/29/2019 Medic UPdate 2003 Capno

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End Tidal CO2: Riding the Wave

Harvey Conner, AS,NREMT-P


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Objectives

Review carbon dioxide chemistry, physiology in the

human bodyReview methods for measuring carbon dioxide in

exhaled air

Describe the normal capnogram

Discuss physiological and pathological factors affectingthe capnogram


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Why ETCO2?????

The AHA in their Guidelines 2000 identified

ETCO2as the Gold Standard in confirmationof ET tube placement.

ACEP has followed AHAs lead and also

emphasized ETCO2 as the standard indetermining ET tube placement.

These two combined have provided the EMS

community with a national standard of care

In other words you had better do it!


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Oxygen-> lungs -> alveoli -> blood

muscles + organs

Oxygen

cells

Oxygen

Oxygen

+

Glucose

energy

CO2

blood

lungs

CO2

breath

CO2

Physiology


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Terminology

Capnometry Measurement of CO2 in the airway during

respiration

Capnography

Graphic display of this measurement over time


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Methods for measuring PetCO2


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Methods for reporting PetCO2

Partial pressure (mmHg)

Percentage (%)

1% = 7.6 mmHg


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pH sensitiveIndicator is metacresol purple

Color change yellow-purple

Avoids red-green spectrum

(8% of population is red-green color blind)

Colorimetric method


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A (purple) = < 4 mm Hg

B (tan) = 4-15 mm Hg

C (yellow) = > 15 mm Hg

Colorimetric method


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PetCO2 device types

1.Sidestream

2.Mainstream

For the purposes of this lecture

well look at sidestream devices

only


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Sidestream analysis

Aspirate gas from exhaled air

columnLightweight port

Easy to use on non-intubated

patient

Sample line easily plugged by

secretions2-3 sec delay

Extraneous air leaks


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PetCO2 device types

Sidestream

Quantative = numerical or

sliding bar scale Qualatative= graphic

representation of wave form

along with numerical values


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PetCO2 device types

SidestreamQuantative = numerical or sliding bar scale


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PetCO2 device typesSidestream

Qualatative= graphic representation of wave

form along with numerical values


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Capnographic waveform

Zero baseline (A-B)

Rapid, sharp rise (B-C)

Alveolarplateau (C-D)

End tidal value (D)

Rapid, sharp downstroke (D-E)


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Waveform A-B

Respiratory baseline

Exhalation of CO2 free gas indead space

Value should be zero

Increased value with re-breathing


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Waveform B-C

Sharp rise

Exhalation of mixed dead spaceand alveolar gas from aciniwith the shortest transit times

Less steep upstroke due tomechanical problem,

broncho-spasm, obstruction


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Waveform C-D

Alveolar plateau

Exhalation of mostly alveolargas

Should be nearly flat

Upward slanting due touneven emptying of alveoli(asthma, obstruc-tion,

COPD)


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Point D

End-tidal CO2 value that

is recorded by acapnometer this is

nearly = to PaCO2


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Waveform D-E

Sharp downstroke

Inhalation of CO2

free gas

Nearly vertical drop tobaseline

Slope prolonged with leaky ETcuff or other leaks inexpiratory circuit


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Factors affecting PetCO2

Production (metabolism)

Delivery (blood flow)

Elimination (ventilation)


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Production (metabolism)

Hypothermia

Fever

Hyperthyroidism


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Delivery (blood flow)

Cardiac arrest/CPR Shock

PE

O%

4%

PetCO2

Garnett AR, Ornato JP, Gonzalez ER et al. JAMA 1987; 257:512-4


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Elimination (ventilation) Determination of ET placement

Garnett AR, Gervin CA, Gervin AS. Ann Emerg Med 1989; 18:387-90

In trachea

In esophagus


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Elimination (ventilation)

Hyperventilation (low PetCO2)

Hypoventilation (high PetCO2)


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Respiratory patterns that inhibit completealveolar emptying

Asthma

COPD

Hyperventilation without allowing for complete

exhalation Ventilation with inadequate tidal volumes

High frequency jet ventilation


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ETCO2 Evolving Technology

The Oridion Corp. has

produced sidestreamsampling devices that now

work on nonintubated

patients. This type of

ETCO2

monitoring allows

the device to be used on

breathing patients and

holds great promise for use

in the management of

patients withbronchospastic disease

like Asthma.


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The SHARK FIN

The TOP HAT


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Summary

Reviewed carbon dioxide chemistry, physiology in the

human bodyReviewed methods for measuring carbon dioxide inexhaled air

Described the normal capnogram

Discussed physiological and pathological factors affectingthe capnogram

Acknowledgements:

This presentation was developed through the use ofseveral resources available on the internet. I wish tothank those individuals for their generosity in providingthis information.

H. Conner

medic update 2003 capno

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