Transcript
Page 1: 09 pre hospital capnography

Pre-Hospital Capnography

Dr Nick Foster EMICS

Page 2: 09 pre hospital capnography

Early Warning: When do you want the patient’s parachute to open?

Capnography 4-10 minutes

Pulse Oximetry

Pulse Oximetry 30-60 seconds

ECG

ECG 10 seconds

No monitor = free fall!

Page 3: 09 pre hospital capnography

Physiology

Carbon dioxide

A Capnograph will show you second by second where you are with the patient by showing you

The CO2 readingThe CO2 waveformThe Respiratory rateThe Oxygen saturationThe pulse rate

Metabolism/Perfusion/Ventilation

Page 4: 09 pre hospital capnography

CapnographyCapnography

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

with a trace

Time

5040302010

0

is as diagnostic as an ECG

Page 5: 09 pre hospital capnography

► Application in clinical practice

Objectives

► How it works

► The physiology involved

Page 6: 09 pre hospital capnography

►How it works

Page 7: 09 pre hospital capnography

►CO2 monitoring technology

Capnometry: the measurement and numerical display of the CO2 level appearing in the airway

Capnograpahy: the measurement and graphical display of the CO2 level appearing in the airway

Page 8: 09 pre hospital capnography

►CO2 monitoring technology

Compares the amount of infrared light absorbed by a sample of expired CO2 to a chamber with no CO2

Infrared spectroscopy

Page 9: 09 pre hospital capnography

►CO2 monitoring technology Respiratory gases are continuously aspirated by a side port tube connection from the patients airwaySidestream sampling

Advantages

•Able to monitor intubated and non-intubated patients

•Uses thin tubing therefore less dead space

•Less likely to become contaminated with moisture because it is away from the airway

•Uses a zero reference to keep the monitoring calibration

Page 10: 09 pre hospital capnography

►CO2 monitoring technology

Sidestream sampling

Disadvantages

•There is a lag time between sampling and measurement Advances: faster response time

•If the patient is breathing rapidly, there may be contamination of the inhaled and exhaled gases and give a falsely low CO2 reading. Advances: Lower sample rates now used

•The tubing can get obstructed by water and mucus

•Pre-hospital use is in its infancy

Page 11: 09 pre hospital capnography

► The physiology involved

Physiology of RespirationPhysiology of Metabolism

Page 12: 09 pre hospital capnography

Physiology of metabolism

An acidoisis makes the pH more acidic than usualAn alkalosis makes the pH more alkaline than usual

Metabolism

Homeostasis. The body tries to maintain a state of equilibrium despite everything we throw at it.

Body pH range 71.-7.8, homeostasis is about 7.3 -7.4

A body pH of 7.2 called acidaemiaA body pH of 7.5 called alkalaemia

Page 13: 09 pre hospital capnography

Physiology of metabolism

There are a number of acids in the body• CO2• Lactic acid from cell activity if starved of oxygen.

Complex chemical interactions that keep these in balance.

These dangerous acids need to be removed

• Buffers: immediate• CO2 production: minutes• Renal excretion/Liver breakdown: days

Page 14: 09 pre hospital capnography

Physiology of metabolism

A balance exists

ACID CO2Tissues Lungs

By looking at what goes into the body via the lungs (Oxygen) and what comes out (Carbon dioxide) you get a picture as to how damaged or ill the body is

Page 15: 09 pre hospital capnography

Physiology of respiration

a natural waste product of cellular activity

Carbon dioxide

Page 16: 09 pre hospital capnography

OxygenOxygen -> lungs -> alveoli -> blood

muscles + organs

OxygenOxygen

cells

OxygenOxygen

OxygOxygenen ++GlucoGlucosese

energy

COCO22

blood

lungs

COCO22

breath

COCO22

Physiology of respiration

Oxygen/Carbon dioxide interaction: Metabolism

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

5-10% carried in solution

20-30% bound to haemoglobin

60-70% carried as bicarbonate in the red blood cell

Page 17: 09 pre hospital capnography

O2

CO2 O2

CO2

CO2

Physiology of respiration

Oxygen/Carbon dioxide interaction: Perfusion and Ventilation

Ventilation

Perfusion

Page 18: 09 pre hospital capnography

• Oxygenation = oxygen → lungs→ alveoli→ blood

• Metabolism = oxygen is converted to energy + CO2

• CO2 elimination = CO2 → blood→ lungs→ exhalation

Physiology of respiration

Ventilation

Perfusion

Page 19: 09 pre hospital capnography

METABOLISM PERFUSION VENTILATION

So CO2 levels provide evidence of three parameters going on the body

Physiology

What's happening at the cellular level How well the circulation is

performingHow well the lungs are working

Page 20: 09 pre hospital capnography

METABOLISM PERFUSION VENTILATION

Physiology

If metabolism fails, acid forms (metabolic acid).

With severe shock, the patient becomes very “acidic” and very ill

Metabolic acidosisThis may be tolerated if circulation and oxygenation are maintained. The acid is converted to CO2 and this is blown off by the lungs

Page 21: 09 pre hospital capnography

METABOLISM PERFUSION VENTILATION

Physiology

If the circulation is failing, this “acid” cannot be transported to the lungs and the patient becomes iller

Metabolic acidosisCO2 cannot be removed from the lungs as it cannot get there. Your only hope is to get the circulation working more effectively

Page 22: 09 pre hospital capnography

METABOLISM PERFUSION VENTILATION

Physiology

Carbon dioxide

If the breathing is inadequate, CO2 accumulates in the blood and is converted to acid

Respiratory acidosisBy ventilating the patient, we can get rid of the excessive CO2 and thereby reduce the damage the “acid” in the blood is doing to the tissues

Page 23: 09 pre hospital capnography

Physiology

Metabolic acidosisAcid builds up (anaerobic metabolism)•Tissue hypoxia (anaemia, shock, severe infection, diabetic ketoacidosis)•Renal failure•Loss of body salts (severe diarrhoea)

Respiratory acidosisHypoventilation: CO2 builds up•Airway obstruction•Central neuro: brain injury, stroke, opiates•Periph neuro: spinal cord, MND•Chest wall disease (muscle, flail chest, trauma, pneumothorax•COPD•Pneumonia,

Respiratory alkalosisHyperventilation: CO2 blown off•Anxiety states•Asthma - low O2, low CO2•PE - low O2, low CO2BUT as exhaustion sets in -low O2 with rising CO2

Metabolic alkalosisAcid is lost•Severe vomiting (acid lost from stomach)

Page 24: 09 pre hospital capnography

Capnography measurements

Page 25: 09 pre hospital capnography

Normal waveform:

Capnography measurements

The waveform

I just want you to look at the display first for a minute and then I will break the wave down into its constituent parts

Page 26: 09 pre hospital capnography

Capnography measurements

The waveform

The lungs are composed of tissue involved in gas exchange (alveoli) and tubes connecting them to the outside world (bronchi, trachea). These tubes ARE NOT involved in gas exchange and is called dead space.

Page 27: 09 pre hospital capnography

Capnography measurements

The waveform

Phase IRepresents the CO2-free gas from the airways (anatomical and apparatus dead space).

Page 28: 09 pre hospital capnography

Capnography measurements

The waveform

Phase IIConsists of a rapid upswing on the tracing (due to mixing of dead space gas with alveolar gas).

Page 29: 09 pre hospital capnography

Capnography measurements

The waveform

Phase IIIConsists of an alveolar plateau representing CO2-rich gas from the alveoli. It almost always has a positive slope, indicating a rising PCO2

Page 30: 09 pre hospital capnography

Capnography measurements

The waveform

Phase 0Is the inspiratory phase where normal air is breathed in. There is only 0.36mmHg of CO2 in the air compared to 40mmHg in expired air

Page 31: 09 pre hospital capnography

Capnography measurements

The waveform

Page 32: 09 pre hospital capnography

Normal waveform:

Capnography measurements

The waveform

Page 33: 09 pre hospital capnography

Causes for a rise in end tidal CO2

Increased CO2 output

Increased Pulmonary perfusion

Reduced Alveolar Ventilation

Technical errors Machine faults

Fever Hypercatabolic states

Increased cardiac output Increased blood pressure

Hypoventilation by patientBronchial intubation (reduces the dead space)Rebreathing

Inadequate fresh gas flowsPoor ventilation by DrFaulty valves

Page 34: 09 pre hospital capnography

Causes for a fall in end tidal CO2

Reduced CO2 output

Reduced Pulmonary perfusion

Increased Alveolar Ventilation

Technical errors Machine faults

HypothermiaHypocatabolic state (eg gross myxoedema)

Reduced cardiac output •Hypotension•Hypovolaemia•Pulmonary embolism•Cardiac arrest

Hyperventilation ApnoeaAirway blocked: obstruction, ET tube extubated

Circuit disconnection Sampling tube leak

Page 35: 09 pre hospital capnography

Look for five characteristics of the waves, Height (normal = 38mmHg. Tall = high CO2,

small = low CO2) Rate Rhythm (regular, getting bigger (or smaller) Base line (how wide it is) Shape of the wave

Waveform analysis

Page 36: 09 pre hospital capnography

Waveform analysis

Hyperventilation Baseline at zero, but height is reduced gradually

Hypoventilation Base line at zero, but height is increased gradually

Page 37: 09 pre hospital capnography

Clinical applications

Page 38: 09 pre hospital capnography

Intubated patients

Applications

Page 39: 09 pre hospital capnography

ApplicationsIntubated patients

Intubation

Verification of tube placement and monitoring ET placement during transport AND its dynamic (cf to a CO2 disc)

5-20% of tubes are misplaced either at the time of intubation or during transfer.

Page 40: 09 pre hospital capnography

ApplicationsIntubated patients

Cardiac arrest

CO2 is a a measure of cardiac output. Because CO2 tracks cardiac output, capnography can show you how effective CPR is.

It is the earliest sign of a returning circulation. It is even more effective than a pulse check

PEA – an ECG with no endtidal CO2.

Page 41: 09 pre hospital capnography

ApplicationsIntubated patients

Cardiac arrest and CPR

Page 42: 09 pre hospital capnography

Non-intubated patients

Applications

Page 43: 09 pre hospital capnography

ApplicationsNon-intubated patients

Chest pain: MI or not an MI

Chest pain + tachyarrhythmia with normal capnogrpahy: Pt stable

Chest pain + tachyarrhytmia with CO2 at 10mmHg is about to have a cardiac arrest on you

Page 44: 09 pre hospital capnography

Applications

3 patients who are short of breathWho has asthma, who has COPD

and who has CCF?

Page 45: 09 pre hospital capnography

Applications3 patients short of breath

Waveform diagnostic of asthma/COPD. It indicates bronchospasm/airway obstruction

Asthma

NormalBronchospasm/Airway

Obstruction

The reason for the shark fin shape is due to the increased dead space present

Page 46: 09 pre hospital capnography

Applications

AsthmaThe shape is a shark fin

Width of the shape gets smaller as the patient gets worse

Page 47: 09 pre hospital capnography

Applications

Worsening asthma

This patient needs ventilatory assistance

Note the narrow base and tachypnoea and rising CO2

3 patients short of breathAsthma

Page 48: 09 pre hospital capnography

Applications

Response to treatment with Terbutaline. Indices return to normal.This patient has asthma: Diagnosis.

3 patients short of breathAsthma

Page 49: 09 pre hospital capnography

Applications COPD

Shark fin shaped waveform appearance showing airway obstruction.Wide base (cf asthma which was narrow)Elevated ETCO2 level 50mmHgPt has COPD

In contrast with asthma

3 patients short of breath

Page 50: 09 pre hospital capnography

Applications CCF

•The low waveform height shows a low CO2 level. •It is not shark fin in shape so not COPD/asthma. •The low CO2 level indicates poor perfusion. •This is a poor circulation that could go with CCF. The heart is not pumping as well as it should

3 patients short of breath

Page 51: 09 pre hospital capnography

Applications

Chest infection

Page 52: 09 pre hospital capnography

Applications

Chest infectionFever causes the CO2 level to go up

and the pulse rate to go upThe pneumonia causes the SpO2

level to go down

Page 53: 09 pre hospital capnography

Applications

Another patient with a chest infection

Endtidal CO2 27%SpO2 91RR 30Pulse 120

Seen by GP 5 days before and diagnosed flu. Fever for 6 days.Temp 104F, Left side chest sign, creps ++, increased breathsounds, Whisp pect, Diagnosis left pneumonia in fact Legionella developed empyema 4 days later.

Page 54: 09 pre hospital capnography

Applications

Patient with pleuritic chest pain

Endtidal CO2 38SpO2 99 on airRR 14Pulse 80

Chest pain, pleuritic. 4 hours. ECG normal. Chest examination normal, normal percussion, normal breath sounds. Tender chest wall. Calves normal and no tenderness

Page 55: 09 pre hospital capnography

ApplicationsRTA – M1 Car fire following RTA

Endtidal CO2 22SpO2 – on 99% oxygenRR 23Pulse 98

24 year old male, driver RTA car fire. Had to be pulled from the car by passers by. Airway open, no carbonaceous material around mouth, nares clear. Breathing spontaneous, good A/E. Cap refill <2 radial pulse 110/80 GCS 14/15. No focal neurology. No obvious fracture

Page 56: 09 pre hospital capnography

Applications

The unconscious patient

Page 57: 09 pre hospital capnography

ApplicationsThe unconscious patient

Look for hypoventilation i.e. a high endtidal CO2 readingAnd a low respiratory rate

Page 58: 09 pre hospital capnography

ApplicationsThe unconscious patient

• Sedation:• Alcohol: a drunk with a normal CO2 is stable. A drunk who is hypoventilating is at risk• Drug ingestion:

Page 59: 09 pre hospital capnography

Applications

Metabolic states

Page 60: 09 pre hospital capnography

ApplicationsMetabolic states

With acidosis, the respiratory rate increases (e.g. diabetic ketoacidosis)

Page 61: 09 pre hospital capnography

METABOLISM PERFUSION VENTILATION

Physiology reminder

If the circulation is failing, this “acid” cannot be transported to the lungs and the patient becomes iller

Metabolic acidosisCO2 cannot be removed from the lungs as it cannot get there. Your only hope is to get the circulation working more effectively

Page 62: 09 pre hospital capnography

ApplicationsMetabolic states: a tale of two patient both with diabetic ketoacidosis

Who is the sickest of the two?

Patient AEndtidal CO2 30mmHgSpO2 100RR 30Pulse 120

Patient BEndtidal CO2 30mmHgSpO2 99RR 10Pulse 120

Page 63: 09 pre hospital capnography

ApplicationsMetabolic states

A diabetic with a normal ETCO2 is not sickA diabetic with a low ETCO2 is a sick person. An ETCO2 of 6mmHg is bordering on a cardiac arrest

Page 64: 09 pre hospital capnography

ApplicationsMetabolic states

55 year old male collapsed at home

Endtidal CO2 24SpO2 92RR 10Pulse 80

Alcoholic, Myxoedema ( had not taken thyroxine for two years) very pale (Hb 2.4) BP 80/-, hepatic encephalopathy, jaundice, hypotensive. He died 3 days later

This patient is very ill.

Page 65: 09 pre hospital capnography

Applications

The head injured patient

Page 66: 09 pre hospital capnography

Applications

The head injured patient

Midazolam light anaesthesiacapnography and assisted ventilation to maintain homeostasis

Page 67: 09 pre hospital capnography

Why is Pre-Hospital Capnography important

Page 68: 09 pre hospital capnography

Why is Pre-Hospital Capnography important

We cannot do anything about those who are going to die whatever we do. (Triage)

However we should be able to recognise and prevent those who would otherwise die needlessly

Page 69: 09 pre hospital capnography

Why is Pre-Hospital Capnography important

Preventable needless deaths occur • Immediately at the time of injury

Hypoxia and Airway obstruction

• Later following their injuryHypercarbia (too much CO2 )

AcidaemiaCerebral vasodilation

Hypoxia (not enough O2 )Hypoxic encephalopathyCardiac arrest

Page 70: 09 pre hospital capnography

Why is Pre-Hospital Capnography important

Time is important. For every minute of “no pre-hospital resuscitation”, the risk of dying increases by 4.3%

Page 71: 09 pre hospital capnography

Why is Pre-Hospital Capnography important

Airway

Breathing

Circulation

Scene Management

The only thing about ABC is that it occurs at the beginning of the alphabet but it ain’t very practical and doesn't really help

Page 72: 09 pre hospital capnography

ApplicationsReal life incidents

Ilkeston 2330hrs head on RTA – four casualties three unconscious, one conscious but with a fractured L3 spine

female• GCS 7• SpO2 100 • Pulse 120

•RR 10•End tidal CO2 72mmHg

The ABC had been followed

But as I arrived, she had her first fit

capnography

Page 73: 09 pre hospital capnography

Why is Pre-Hospital Capnography important

Airway

Breathing

Circulation

Scene Management

Just because they are BREATHING, does NOT mean they are oxygenating and ventilating properly

Page 74: 09 pre hospital capnography

Why is Pre-Hospital Capnography important

Airway

Breathing

Circulation

Scene Management

and just because they have a CIRCULATION doesn’t mean the blood’s going to the right places or may even be going in the wrong direction.

Page 75: 09 pre hospital capnography

Why is Pre-Hospital Capnography important

Airway

Breathing

Circulation

Scene Management

So having caused you all to have sleepless nights, I would like to suggest an alternative concept

Page 76: 09 pre hospital capnography

Why is Pre-Hospital Capnography important

Airway

Breathing

Circulation

Scene Management

Ventilation

Perfusion

Capnography

Page 77: 09 pre hospital capnography

Why is Pre-Hospital Capnography important

Airway

Ventilation

Haemorrhage control

Assisting the circulation

Procedural sedationTo facilitate extrication

To facilitate manipulation

Pre-hospital anaesthesia

Severe trauma management is not ABC

Perfusion

Ventilation

Airway

Page 78: 09 pre hospital capnography

Beware………………..The patient with the low

CO2 and the low respiratory rate

They could be about to die on you

Take home tip

Page 79: 09 pre hospital capnography

When do you want the parachute to open?

Capnography 4-10 minutes

Pulse Oximetry

Pulse Oximetry 30-60 seconds

ECG

ECG 10 seconds

No monitor = free fall!


Top Related