NON-INVASIVE CAPNOGRAPHY
ALS Blue In-Service
Part III
Oxygenation and Ventilation
What is the difference?
Oxygenation and Ventilation
Ventilation
(capnography)
CO2
O2
Oxygenation
(oximetry)
Cellular
Metabolism
Oximetry and Capnography
• Pulse oximetry measures oxygenation
• Capnography measures ventilation and
provides a graphical waveform available
for interpretation
Oxygenation
• Measured by pulse oximetry (SpO2)
– Noninvasive measurement
– Percentage of oxygen in red blood cells
– Changes in ventilation take minutes
to be detected
– Affected by motion artifact, poor perfusion
and some dysrhythmias
Oxygenation
Pulse Oximetry
Sensors
Pulse Oximetry Waveform
Ventilation
• Measured by the end-tidal CO2
– Partial pressure (mmHg) or volume (% vol) of
CO2 in the airway at the end of exhalation
– Breath-to-breath measurement provides
information within seconds
– Not affected by motion artifact, poor perfusion
or dysrhythmias
Ventilation
Capnography
Lines
Capnography waveform
Oxygenation and Ventilation
• Oxygenation
– Oxygen for
metabolism
– SpO2 measures
% of O2 in RBC
– Reflects change in
oxygenation within
5 minutes
• Ventilation
– Carbon dioxide
from metabolism
– EtCO2 measures
exhaled CO2 at
point of exit
– Reflects change in
ventilation within
10 seconds
Oxygenation versus Ventilation
• Monitor your own
SpO2 and EtCO2
• SpO2 waveform is in
the second channel
• EtCO2 waveform is
in the third channel
Oxygenation versus Ventilation
• Now hold your breath
• Note what happens to
the two waveforms
SpO2
EtCO2
How long did it take the EtCO2 waveform to go flat line?
How long did it take the SpO2 to drop below 90%?
• Numeric reading: HR 100
• Waveform:
• Numeric reading: HR 100
• Waveform:
Capnography in EMS
Capnography in EMS
Low-flow sidestream technology
Using Capnography
• Immediate information via
breath-to-breath monitoring
• Information on the ABCs
– Airway
– Breathing
– Circulation
• Documentation
Using Capnography
Airway
• Airway
– Verification of ET tube
placement
– Continuous monitoring of
ET tube position
• Circulation
Circulation
– Check effectiveness of
cardiac compressions
– First indicator of ROSC
– Monitor low perfusion states
Using Capnography
• Breathing
– Hyperventilation
– Hypoventilation
– Asthma
– COPD
Using Capnography
Waveforms
Trends
• Documentation
– Waveforms
• Initial assessment
• Changes with treatment
– EtCO2 values
• Trends over time
Why Measure Ventilation—
Intubated Patients
•
•
•
•
•
Verify and document ET tube placement
Immediately detect changes in ET tube position
Assess effectiveness of chest compressions
Earliest indication of ROSC
Indicator of probability of successful
resuscitation
• Optimally adjust manual ventilations in patients
sensitive to changes in CO2
• A 2005 study comparing field intubations
that used capnography to confirm ETT
placement vs. non-capnography use
showed a 0% unrecognized misplaced
ETT and 23% in the non-EtCO2 monitored
group
• Confirm ETI with waveform capnography!!
Why Measure Ventilation—
Non-Intubated Patients
• Objectively assess acute
respiratory disorders
– Asthma
– COPD
• Possibly gauge response to treatment
Why Measure Ventilation—
Non-intubated Patients
• Gauge severity of hypoventilation states
–
–
–
–
–
Drug and ETOH intoxication
Congestive heart failure
Sedation and analgesia
Stroke
Head injury
• Assess perfusion status
• Noninvasive monitoring of patients in DKA
End-tidal CO2 (EtCO2)
Pulmonary Blood Flow
Ventilation
Right
Ventricle
Artery
Vein
Oxygen
CO2
O2
O2
Perfusion
Left
Atrium
a-A Gradient
arterial to Alveolar Difference for CO2
Ventilation
Right
Ventricle
Alveolus
Artery
EtCO2
PaCO2
Perfusion
Vein
Left
Atrium
End-tidal CO2 (EtCO2)
• Normal a-A gradient
– 2-5mmHg difference between the EtCO2
and PaCO2 in a patient with healthy lungs
– Wider differences found
• In abnormal perfusion and ventilation
• Incomplete alveolar emptying
• Poor sampling
End-tidal CO2 (EtCO2)
• Reflects changes in
– Ventilation - movement of air in and
out of the lungs
– Diffusion - exchange of gases between
the air-filled alveoli and the pulmonary
circulation
– Perfusion - circulation of blood
End-tidal CO2 (EtCO2)
• Monitors changes in
– Ventilation - asthma, COPD, airway
edema, foreign body, stroke
– Diffusion - pulmonary edema,
alveolar damage, CO poisoning,
smoke inhalation
– Perfusion - shock, pulmonary
embolus, cardiac arrest,
severe dysrhythmias
Physiological Factors Affecting ETCO2
Levels
Interpreting EtCO2 and the
Capnography Waveform
• Interpreting EtCO2
– Measuring
– Physiology
• Capnography waveform
Capnographic Waveform
• Normal waveform of one respiratory cycle
• Similar to ECG
– Height shows amount of CO2
– Length depicts time
Phase 1
• First Upstroke of the capnogram
waveform
• Represents of gas exhaled from upper
airways (I.e. anatomical dead space)
Phase 2
• Transitional Phase from upper to lower
airway ventilation, and tends to depict
changes in perfusion
Phase 3
• Represents alveolar gas exchange, which
indicates changes in gas distribution
• All increases of the slope of Phase 3
indicates increased maldistribution of gas
delivery
Capnographic Waveform
• Waveforms on screen and printout
may differ in duration
– On-screen capnography waveform is
condensed to provide adequate information
the in 4-second view
– Printouts are in real-time
– Observe RR on device
Capnographic Waveform
• Capnograph detects only CO2
from ventilation
• No CO2 present during inspiration
– Baseline is normally zero
C
A
B
D
E
Baseline
Capnogram Phase I
Dead Space Ventilation
• Beginning of exhalation
• No CO2 present
• Air from trachea,
posterior pharynx,
mouth and nose
– No gas exchange
occurs there
– Called “dead space”
Deadspace
Capnogram Phase I
Baseline
B
A
I
Baseline
Beginning of exhalation
Capnogram Phase II
Ascending Phase
• CO2 from the alveoli
begins to reach the upper
airway and mix with the
dead space air
– Causes a rapid rise in the
amount of CO2
• CO2 now present and
detected in exhaled air
Alveoli
Capnogram Phase II
Ascending Phase
C
Ascending Phase
Early Exhalation
A
II
B
CO2 present and increasing in exhaled air
Capnogram Phase III
Alveolar Plateau
• CO2 rich alveolar gas
now constitutes the
majority of the
exhaled air
• Uniform concentration
of CO2 from alveoli to
nose/mouth
Capnogram Phase III
Alveolar Plateau
Alveolar Plateau
C
D
III
A
B
CO2 exhalation wave plateaus
Capnogram Phase III
End-Tidal
• End of exhalation contains the highest
concentration of CO2
– The “end-tidal CO2”
– The number seen on your monitor
• Normal EtCO2 is 35-45mmHg
Capnogram Phase III
End-Tidal
C
A
D
End-tidal
B
End of the the wave of exhalation
Capnogram Phase IV
Descending Phase
• Inhalation begins
• Oxygen fills airway
• CO2 level quickly
drops to zero
Alveoli
Capnogram Phase IV
Descending Phase
C
A
B
D
IV
Descending Phase
Inhalation
E
Inspiratory downstroke returns to baseline
Capnography Waveform
Normal Waveform
45
0
Normal range is 35-45mm Hg (5% vol)
Capnography Waveform Question
• How would your capnogram change
if you intentionally started to breathe
at a rate of 30?
–
–
–
–
Frequency
Duration
Height
Shape
Hyperventilation
RR
: EtCO2
Normal
45
0
Hyperventilation
45
0
Waveform:
Regular Shape, Plateau Below Normal
• Indicates CO2 deficiency
 Hyperventilation
 Decreased pulmonary perfusion
 Hypothermia
 Decreased metabolism
• Interventions
 Adjust ventilation rate
 Evaluate for adequate sedation
 Evaluate anxiety
 Conserve body heat
Capnography Waveform Question
• How would your capnogram change
if you intentionally decreased your
respiratory rate to 8?
–
–
–
–
Frequency
Duration
Height
Shape
Hypoventilation
RR
: EtCO2
Normal
45
0
Hypoventilation
45
0
Waveform:
Regular Shape, Plateau Above Normal
• Indicates increase in ETCO2
 Hypoventilation
 Respiratory depressant drugs
 Increased metabolism
• Interventions
 Adjust ventilation rate
 Decrease respiratory depressant drug dosages
 Maintain normal body temperature
Capnography Waveform Patterns
Normal
45
0
Hyperventilation
45
0
Hypoventilation
45
0
Capnography Waveform Question
How would the waveform
shape change during an
asthma attack?
Bronchospasm Waveform Pattern
• Bronchospasm hampers ventilation
– Alveoli unevenly filled on inspiration
– Empty asynchronously during expiration
– Asynchronous air flow on exhalation dilutes
exhaled CO2
• Alters the ascending phase and plateau
– Slower rise in CO2 concentration
– Characteristic pattern for bronchospasm
– “Shark Fin” shape to waveform
Capnography Waveform Patterns
Normal
45
0
Bronchospasm
45
0
Capnography Waveform Patterns
Normal
45
0
Hyperventilation
45
0
Hypoventilation
45
0
Bronchospasm
45
0
The Intubated Patient
Confirm ET Tube Placement
45
0
Detect ET Tube Displacement
• Capnography
– Immediately detects
ET tube displacement
45
0
Hypopharyngeal Dislodgement
Source: Murray I. P. et. al. 1983. Early detection of endotracheal tube accidents
by monitoring CO2 concentration in respiratory gas. Anesthesiology 344-346
Detect ET Tube Displacement
• Only capnography provides
– Continuous numerical value of EtCO2 with
apnea alarm after 30 seconds
– Continuous graphic waveform for immediate
visual recognition
Esophageal Dislodgement
45
0
Source: Linko K. et. al. 1983. Capnography for detection of accidental
oesophageal intubation. Acta Anesthesiol Scand 27: 199-202
Confirm ET Tube Placement
• Capnography provides
– Documentation of
correct placement
– Ongoing documentation
over time through the
trending printout
– Documentation of
correct position at
ED arrival
Capnography in
Cardiopulmonary Resuscitation
• Assess chest compressions
• Early detection
of ROSC
• Objective data for decision
to cease resuscitation
CPR: Assess Chest Compressions
• Use feedback from
EtCO2 to depth/rate/
force of chest
compressions
during CPR
45
0
CPR: Detect ROSC
• Briefly stop CPR and
check for organized
rhythm on ECG monitor
45
0
ETCO2 & Cardiac Resuscitation
• Non-survivors
– Average ETCO2:
4-10 mmHg
• Survivors (to discharge)
– Average ETCO2:
>30 mmHg
Optimize Ventilation
• Use capnography to titrate EtCO2 levels
in patients sensitive to fluctuations
• Patients with suspected increased
intracranial pressure (ICP)
–
–
–
–
Head trauma
Stroke
Brain tumors
Brain infections
Optimize Ventilation
• High CO2 levels induce
cerebral vasodilatation
– Positive: Increases CBF to
counter cerebral hypoxia
CO2
– Negative: Increased CBF,
increases ICP and may increase
brain edema
• Hypoventilation retains CO2
which increases levels
Optimize Ventilation
• Low CO2 levels lead to cerebral
vasoconstriction
– Positive: EtCO2 of 25-30mmHG
causes a mild cerebral
vasoconstriction which may
decrease ICP
– Negative: Decreased ICP but
may cause or increase in
cerebral hypoxia
• Hyperventilation decreases
CO2 levels
CO2
Optimize Ventilation
• Treatment goals
• Avoid cerebral hypoxia
– Monitor blood oxygen
levels with pulse oximetry
– Maintain adequate CBF
• Target EtCO2 of 35 mmHg
The Non-intubated Patient
CC:
“trouble breathing”
The Non-intubated Patient
CC: “trouble breathing”
Bronchitis?
The Non-intubated Patient
Capnography Applications
• Identify and monitor bronchospasm
– Asthma
– COPD
• Assess and monitor
– Hypoventilation states
– Hyperventilation
– Low-perfusion states
Capnography in
Bronchospastic Conditions
• Air trapped due to
irregularities in airways
• Uneven emptying of
alveolar gas
– Dilutes exhaled CO2
– Slower rise in CO2
concentration during
exhalation
Alveoli
Capnography in
Bronchospastic Diseases
• Uneven emptying of
alveolar gas alters
emptying on exhalation
A
• Produces changes in
ascending phase (II)
with loss of the sharp
upslope
• Alters alveolar plateau
(III) producing a “shark fin”
C
B
D
II
E
III
Capnography in Bronchospastic Conditions
Capnogram of Asthma
Normal
Bronchospasm
Changes in dCO2/dt seen with increasing bronchospasm
Source: Krauss B., et al. 2003. FEV1 in Restrictive Lung Disease Does Not Predict
the Shape of the Capnogram. Oral presentation. Annual Meeting, American Thoracic
Society, May, Seattle, WA
Capnography in Bronchospastic Conditions
Asthma Case Scenario
Initial
After therapy
Capnography in Bronchospastic Conditions
Pathology of COPD
• Progressive
• Partially reversible
• Airways obstructed
– Hyperplasia of mucous glands
and smooth muscle
– Excess mucous production
– Some hyper-responsiveness
Capnography in Bronchospastic Conditions
Capnography in COPD
• Arterial CO2 in COPD
– PaCO2 increases as disease progresses
– Requires frequent arterial punctures for ABGs
• Correlating capnograph to patient status
– Ascending phase and plateau are altered by
uneven emptying of gases
Capnography in Bronchospastic Conditions
COPD Case Scenario
45
Initial Capnogram A
0
Initial Capnogram B
45
0
Capnography in CHF
Case Scenario
•
•
•
•
88 year old male
C/O: Short of breath
H/O: MI X 2, on oxygen at 2 L/m
Pulse 66, BP 164/86, RR 36 labored and
shallow, skin cool and diaphoretic,
2+ pedal edema
• Initial SpO2 69%; EtCO2 17mmHG
Capnography in CHF
Case Scenario
• Placed on non-rebreather mask with 100%
oxygen at 15 L/m and aggressive SL nitroglycerin
as per protocol
• Ten minutes after treatment:
SpO2 69%
EtCO2 17mmHG
99%
35 mmHG
45
35
25
0
Time condensed
to show changes
Capnography in
Hypoventilation States
• Altered mental status
–
–
–
–
–
–
Sedation
Alcohol intoxication
Drug Ingestion
Stroke
CNS infections
Head injury
• Abnormal breathing
• CO2 retention
– EtCO2 >50mmHg
Capnography in
Hypoventilation States
45
0
Time condensed; actual rate is slower
• EtCO2 is above 50mmHG
• Box-like waveform shape is unchanged
Capnography in Hypoventilation States
Hypoventilation
65
55
45
35
25
0
Time condensed; actual rate is slower
Capnography in Hypoventilation States
Hypoventilation
45
0
Hypoventilation in shallow
breathing
Capnography in Low Perfusion
• Capnography reflects changes in
• Perfusion
– Pulmonary blood flow
– Systemic perfusion
– Cardiac output
Capnography in Low Perfusion
Case Scenario
•
•
•
•
•
•
57 year old male
Motor vehicle crash with injury to chest
History of atrial fib, anticoagulant
Unresponsive
Pulse 100 irregular, BP 88/p
Intubated on scene
Capnography in Low Perfusion
Case Scenario
45
35
25
0
Low EtCO2 seen in
low cardiac output
Ventilation controlled
Capnography in Pulmonary Embolus
Case Scenario
45
35
25
0
Strong radial pulse
Low EtCO2 seen in
decreased alveolar perfusion
Capnography in Rebreathing Circumstances
Elevated Baseline
45
0
Baseline elevation
• Oxygen mask
• Poor head and neck alignment
• Shallow breathing – not clearing deadspace
Capnography in DKA
Case Scenario
45
0
Rapid rate, normal waveform
and elevated EtCO2 seen
in early respiratory
compensation in DKA
Source: Flanagan, J.F., et al. 1995. Noninvasive monitoring of end-tidal
carbon dioxide tension via nasal cannulas in spontaneously breathing children with
profound hypocarbia. Critical Care Medicine. June; 23 (6): 1140-1142
Capnography Applications
on Non-intubated Patients
• New applications now being reported
–
–
–
–
–
Pulmonary emboli
CHF
DKA
Bioterrorism
Others?
A rt e ry
O xy g e n
O2
V e in
Quiz Time!
Sudden Loss of Waveform
 Apnea
 Airway Obstruction
 Dislodged airway (esophageal)
 Airway disconnection
 Ventilator malfunction
 Cardiac Arrest
Increase in ETCO2
• Possible causes:




Decrease in respiratory rate (Hypoventilation)
Decrease in tidal volume
Increase in metabolic rate
Rapid rise in body temperature (hyperthermia)
Esophageal Tube
• A normal capnogram is the best evidence that the
ETT is correctly positioned
• With an esophageal tube little or no CO2 is
present
Rebreathing
• Possible causes:
 Faulty expiratory valve
 Inadequate inspiratory flow
 Insufficient expiratory flow
Inadequate Seal Around ETT
• Possible causes:
 Leaky or deflated endotracheal or
tracheostomy cuff
 Artificial airway too small for the patient
Decrease in ETCO2
• Possible causes:




Increase in respiratory rate (Hyperventilation)
Increase in tidal volume
Decrease in metabolic rate
Fall in body temperature (hypothermia)
Obstruction
• Possible causes:




Partially kinked or occluded artificial airway
Presence of foreign body in the airway
Obstruction in expiratory limb of the breathing circuit
Bronchospasm
Muscle Relaxants
• “Curare Cleft”:
 Appears when muscle relaxants begin to subside
 Depth of cleft is inversely proportional to degree of drug
activity
You Survived!
Thanks!
Questions to me via groupwise:
jcushman@co.ho.md.us