Capnography for the intensivist - PowerPoint Presentation

Slide1

Capnography for the intensivist

Sarah

Philipson

Slide2

THE END.

Slide3

THE END.

Questions?

Slide4

Questions?

CO

2

physiology

What is

capnography

?

Slide5

Questions?

What is

capnography

?

CO

2

physiology

Slide6

Questions?

What is

capnography

?

CO

2

physiology

How is it used?

Slide7

Questions?

What is

capnography

?

CO

2

physiology

How is it used?

Do I care? What are the problems with it?

Slide8

Capnography

Measurement of CO

2

vs timeInfrared spectroscopy measures the fraction of energy absorbed and converts this to a percentage of CO2 exhaledNormal capnogram

I –

inspiratory

baseline

II – expiratory upstroke

III – alveolar plateau

IV – inspiratory downstroke

Slide9

Capnography

Measurement of CO

2

vs timeInfrared spectroscopy measures the fraction of energy absorbed and converts this to a percentage of CO2 exhaledNormal capnogram

I –

inspiratory

baseline

II – expiratory upstroke

III – alveolar plateau

IV –

inspiratory

downstroke

Slide10

Normal EtCO2

= 38-40mmHg

Capnography

Measurement of CO

2

vs

time

Infrared spectroscopy measures the fraction of energy absorbed and converts this to a percentage of CO

2 exhaledNormal capnogram

I –

inspiratory

baseline

II – expiratory upstroke

III – alveolar plateau

IV –

inspiratory

downstroke

Slide11

A-B: Dead space

B-C: Dead space + alveoli

C-D: Alveoli

D: ETCO

2

D-E: Inspiration

Slide12

How we measure CO2

Slide13

Physiology – “ICU is easy!”

Slide14

Carbon Dioxide

PRODUCTION AT TISSUES

Slide15

Carbon Dioxide

PRODUCTION AT TISSUES

TRANSPORT IN BLOOD

Slide16

Carbon Dioxide

PRODUCTION AT TISSUES

TRANSPORT IN BLOOD

REMOVAL VIA VENTILATION

Slide17

Carbon Dioxide

PRODUCTION AT TISSUES

TRANSPORT IN BLOOD

REMOVAL VIA VENTILATION

Slide18

Carbon Dioxide

PRODUCTION AT TISSUES

TRANSPORT IN BLOOD

REMOVAL VIA VENTILATION

Slide19

Carbon Dioxide

PRODUCTION AT TISSUES

TRANSPORT IN BLOOD

REMOVAL VIA VENTILATION

Slide20

CO2 production

Produced in tissues through cellular respiration –

glycolysis

, Krebs cycle,

phosphorylation

Slide21

CO

2

up

CO

2 downIncreased metabolic rateSepsis

Hyperthermia

Burns

Trauma

HyperthyroidismShiveringMalignant hyperthermia

Neuroleptic malignant syndromeDecreased metabolic rateHypothermiaStarvationDrugs for hyperthyroidism

Metabolic acidosisCO2 production

Slide22

CO2 transport

Diffuses across capillary membranes and is transported to lungs through the venous system

~7% transported dissolved in blood

~20% as

carbaminohaemoglobin (reaction between carbon dioxide and the amine radicals of the haemoglobin molecule)~70% as bicarbonate and hydrogen ions from dissociation of carbonic acid

Slide23

CO

2

transport i.e. cardiac output

Diffuses across capillary membranes and is transported to lungs through the venous system

~7% transported dissolved in blood

~20% as carbaminohaemoglobin (reaction between carbon dioxide and the amine radicals of the haemoglobin molecule)

~70% as bicarbonate and hydrogen ions from dissociation of carbonic acid

CO = SV x HR

Slide24

CO2 transport

CO

2

up

CO

2

down

Tourniquet release

Arrest

ShockDrugs- Carbonic anhydrase inhibitor (acetazolamide) – prevents CO

2 transportShunting eg. PE

Slide25

CO2 removal i.e. ventilation

Ventilation = rate, volume, diffusion

Slide26

CO2 removal i.e. ventilation

CO

2

up

CO

2

down

Low

RR Drugs – sedatives, opiates

Neurological causesHigh RRAcidoticPsychologicalVentilator settings

Diffusion impaired Chronic lung diseaseInflammation – infection/inflammatory processImpaired ventilation

APO

Intrapulmonary shunt:

atelectasis

, collapse,

haemo

/

pneumothorax

, effusion

Low volumes

Ventilator settings

Poor compliance

Equipment –

leak, tube placement

High volumes

- Ventilator

settings

eg

. PS too high

Slide27

ETCO2 - Why is it useful?

Reflects changes in:

Ventilation

Can predict impending respiratory failure

Provides early warning of airway compromiseTransport

Can be used as a predictor of fluid responsiveness – found to be proportional to CI in measuring response to passive leg raise in patients with stable metabolic and respiratory conditions

Production

Metabolism

Slide28

Have I convinced you?

Slide29

Slide30

Slide31

Slide32

Slide33

Slide34

Slide35

Slide36

Slide37

Slide38

Slide39

Slide40

Slide41

Slide42

Slide43

Slide44

Slide45

Slide46

Problems with capnography

Only reliable(?) in patients with stable metabolic and respiratory states

Abnormal

Aa

gradients make EtCO2 not a good predictor of PaCO2, but can still use trend

Needs to be a trend, not a one-off measure

Detects, does not diagnose – more tests!

Difficulty with equipment – easily clogged with water droplets

Normal capnogram can occur with

glottic intubation – still need an XR

Slide47

Convinced?

Capnography

CO

2

physiologyProductionTransportVentilationThe capnography curve and what it can tell usProblems with

capnography

Slide48

KEEP CALM

AND

WATCH THE

CO

2