CAPNOGRAPHY: THE VENTILATION VITAL SIGN Mazen Kherallah, MD FCCP Critical Care Medicine and Infectious DIsease.
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CAPNOGRAPHY: THE VENTILATION VITAL SIGNMazen Kherallah, MD FCCPCritical Care Medicine and Infectious DIsease
Objectives
Define Capnography Discuss Respiratory Cycle Discuss ways to collect ETCO2
information Discuss Non-intubated vs. intubated
patient uses Discuss different waveforms and
treatments of them.
So what is Capnograhy?
Capnography- Continuous analysis and recording of Carbon Dioxide concentrations in respiratory gases ( I.E. waveforms and numbers)
Capnometry- Analysis only of the gases no waveforms
Respiratory Cycle
Breathing- Process of moving oxygen into the body and CO2 out can be passive or non-passive.
Metabolism-Process by which an organism obtains energy by reacting O2 with glucose to obtain energy. Aerobic- glucose+O2 = water vapor, carbon
dioxide, energy (2380 kJ) Anaerobic- glucose= alcohol, carbon
dioxide, water vapor, energy (118 kJ)
Respiratory Cycle con’t
Ventilation- Rate that gases enters and leaves the lungs Minute ventilation- Total volume of gas
entering lungs per minute Alveolar Ventilation- Volume of gas that
reaches the alveoli Dead Space Ventilation- Volume of gas that
does not reach the respiratory portions ( 150 ml)
Oxygen -> lungs -> alveoli -> blood
muscles + organs
Oxygen
cells
Oxygen
Oxygen +Glucose
energy
CO2
blood
lungs
CO2
breath
CO2
Respiratory Cycle
METABOLISM PERFUSION VENTILATION
ALL THREE ARE IMPORTANT!
Respiratory Cycle
How is ETCO2 Measured?
Semi-quantitative capnometry Quantitative capnometry Wave-form capnography
Semi-Quantitative Capnometry Relies on pH change Paper changes color
Purple to Brown to Yellow
Quantitative Capnometry
Absorption of infra-red
light Gas source
Side Stream In-Line
Factors in choosing device:
Warm up time Cost Portability
Waveform Capnometry
Adds continuous waveform display to the ETCO2 value. Additional information in waveform shape can provide clues about causes of poor oxygenation.
Interpretation of ETCO2
Excellent correlation between ETCO2 and cardiac output when cardiac output is low.
When cardiac output is near normal, then ETCO2 correlates with minute volume.
Only need to ventilate as often as a “load” of CO2 molecules are delivered to the lungs and exchanged for 02 molecules
Hyperventilation Kills
EtCO2 Values
Normal 35 – 45 mmHg Hypoventilation > 45 mmHg Hyperventilation < 35 mmHg
Relationship between CO2 and RR RR CO2 Hyperventilation RR CO2 Hypoventilation
Physiology
Why ETCO2 I Have my Pulse Ox?
Oxygen SaturationReflects OxygenationSpO2 changes lag when patient is hypoventilating or apneicShould be used with Capnography
Carbon Dioxide
Reflects Ventilation
Hypoventilation/Apnea detected immediately
Should be used with pulse Oximetry
Pulse Oximetry Capnography
What does it really do for me?
Bronchospasms: Asthma, COPD, AnaphlyaxisHypoventilation: Drugs, Stroke, CHF, Post-IctalShock & Circulatory compromiseHyperventilation Syndrome: Biofeedback
Verification of ETT placementETT surveillance during transportControl ventilations during CHI and increased ICPCPR: compression efficacy, early signs of ROSC, survival predictor
Non-Intubated Applications Intubated Applications
NORMAL CAPNOGRAM
NORMAL CAPNOGRAM
Phase I is the beginning of exhalation Phase I represents most of the anatomical dead
space Phase II is where the alveolar gas begins to mix
with the dead space gas and the CO2 begins to rapidly rise
The anatomic dead space can be calculated using Phase I and II
Alveolar dead space can be calculated on the basis of : VD = VDanat + VDalv
Significant increase in the alveolar dead space signifies V/Q mismatch
NORMAL CAPNOGRAM
Phase III corresponds to the elimination of CO2 from the alveoli
Phase III usually has a slight increase in the slope as “slow” alveoli empty
The “slow” alveoli have a lower V/Q ratio and therefore have higher CO2 concentrations
In addition, diffusion of CO2 into the alveoli is greater during expiration. More pronounced in infants
ET CO2 is measured at the maximal point of Phase III.
Phase IV is the inspirational phase
ABNORMALITIES
Increased Phase III slope Obstructive lung
disease Phase III dip
Spontaneous resp Horizontal Phase III
with large ET-art CO2 change Pulmonary
embolism cardiac output Hypovolemia
Sudden in ETCO2 to 0 Dislodged tube Vent malfunction ET obstruction
Sudden in ETCO2 Partial obstruction Air leak
Exponential Severe
hyperventilation Cardiopulmonary
event
ABNORMALITIES
Gradual Hyperventilation Decreasing temp Gradual in
volume Sudden increase
in ETCO2 Sodium bicarb
administration Release of limb
tourniquet
Gradual increase Fever Hypoventilation
Increased baseline Rebreathing Exhausted CO2
absorber
PaCO2-PetCO2 gradient
Usually <6mm Hg PetCO2 is usually less Difference depends on the number of
underperfused alveoli Tend to mirror each other if the slope of
Phase III is horizontal or has a minimal slope Decreased cardiac output will increase the
gradient The gradient can be negative when healthy
lungs are ventilated with high TV and low rate Decreased FRC also gives a negative gradient
by increasing the number of slow alveoli
LIMITATIONS
Critically ill patients often have rapidly changing dead space and V/Q mismatch
Higher rates and smaller TV can increase the amount of dead space ventilation
High mean airway pressures and PEEP restrict alveolar perfusion, leading to falsely decreased readings
Low cardiac output will decrease the reading
USES
Metabolic Assess energy expenditure
Cardiovascular Monitor trend in cardiac output Can use as an indirect Fick method, but
actual numbers are hard to quantify Measure of effectiveness in CPR Diagnosis of pulmonary embolism: measure
gradient
PULMONARY USES
Effectiveness of therapy in bronchospasm Monitor PaCO2-PetCO2 gradient Worsening indicated by rising Phase III without
plateau Find optimal PEEP by following the gradient.
Should be lowest at optimal PEEP. Can predict successful extubation.
Dead space ratio to tidal volume ratio of >0.6 predicts failure. Normal is 0.33-0.45
Limited usefulness in weaning the vent when patient is unstable from cardiovascular or pulmonary standpoint
Confirm ET tube placement
Normal Wave Form
Square box waveform
ETCO2 35-45 mm Hg
Management: Monitor Patient
Dislodged ETT
Loss of waveform Loss of ETCO2
reading Management:
Replace ETT
Esophageal Intubation
Absence of waveform Absence of ETCO2 Management: Re-Intubate
CPR
Square box waveform ETCO2 10-15 mm Hg (possibly higher)
with adequate CPR Management: Change Rescuers if ETCO2
falls below 10 mm Hg
Obstructive Airway
Shark fin waveform With or without prolonged expiratory
phase Can be seen before actual attack Indicative of Bronchospasm( asthma,
COPD, allergic reaction)
ROSC (Return of Spontaneous Circulation) During CPR sudden increase of ETCO2
above 10-15 mm Hg Management: Check for pulse
Rising Baseline
Patient is re-breathing CO2 Management: Check equipment for
adequate oxygen flow If patient is intubated allow more time to
exhale
Hypoventilation
Prolonged waveform ETCO2 >45 mm Hg Management: Assist ventilations or
intubate as needed
Hyperventilation
Shortened waveform ETCO2 < 35 mm Hg Management: If conscious gives
biofeedback. If ventilating slow ventilations
Patient breathing around ETT Angled, sloping down stroke on the
waveform In adults may mean ruptured cuff or
tube too small In pediatrics tube too small Management: Assess patient,
Oxygenate, ventilate and possible re-intubation
Curare cleft
Curare Cleft is when a neuromuscular blockade wears off
The patient takes small breaths that causes the cleft
Management: Consider neuromuscular blockade re-administration
CAPNOGRAM #1
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997
CAPNOGRAM #2
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997
CAPNOGRAM #3
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997
CAPNOGRAM #4
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997
CAPNOGRAM #5
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997
CAPNOGRAM #6
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997
CAPNOGRAM #7
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997
CAPNOGRAM #8
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997
Now what does all this mean to me? ETCO2 is a great tool to help monitor the
patients breath to breath status. Can help recognize airway obstructions
before the patient has signs of attacks Helps you control the ETCO2 of head
injuries Can help to identify ROSC in cardiac
arrest
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