END TIDAL CO2 MEASUREMENTS
JULY 2012
Originally developed by Lauren Walker BSN, RN, CCRN and Julia Burgess MSN, RN, ACNSBC, CCRN-CMC Clinical Nurse Specialist
Objectives:
1. Recognize key definitions
2. Demonstrate understanding of end tidal CO2 (EtCO2) measurement
3. Identify appropriate patient population requiring EtCO2 Measurement
4. Correlate changes in waveforms according to patient condition
5. Review equipment for EtCO2 monitoring
Time for completion: 30 minutes.
Test due date (return to educator): August 15, 2012
developed 07/0/12 developed in collaboration with Corporate Education and Training
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Table of Contents
Instructions ........................................................................................................................................... 3
I.
Capnography Review
A. Definitions………..………………………………………………………………………………………….……………………4
B. Basic Pathology of the lungs……………………………………………………..…………………………………..5
C. Capnography….......………………………………………………………………………………………………………..……5
D. Clinical applications of EtCO2 in the ICU…………………………………..……………………………… 7
E. Applicable patients for EtCO2……………………………………………………………………………………….8
F. Normal Values…...……………………………………………………………………………………….……………………..8
G. Waveform Interpretation……………....……………………………………………………………………………9
H. Equipment………
I. Alarms……………………………………………………………………………………………………….……………………...16
II. Patient Education………………………...…………………………………………….………………………………………..16
III Post Test…………………..…………..…………………………………………………………………………………………………17
IV: References……………………………………………………………………………………………………………..………………..18
V: Evaluation……………………..……………………………………………………………………….……………………………………19
developed 07/0/12 developed in collaboration with Corporate Education and Training
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Instructions
This activity is designed for Registered Nurses in the acute care setting who care for
patients recommended for EtCO2 monitoring. It serves to heighten awareness of the
purpose of EtCO2 monitoring and the skill review for the nurse in interpreting waveform
results. This packet serves as education in preparation for the roll out of EtCO2
monitoring in the Critical Care Unit.
The approximate time for completion of this packet should be 30 minutes.
This Self Learning Activity will refresh your knowledge of key definitions for
oxygenation and ventilation, provide a review of the basic physiology of the lungs and
capnography, include waveform interpretation and identify patients who could benefit
from EtCO2 monitoring.
This Self Learning Activity consists of three parts:
(1) Educational Information
(2) Post Test
(3) Evaluation
Please read the educational information and answer the post test.
Document completion of this SLA on your annual continuing education record and give
the post test to your manager or clinical educator.
Your feedback regarding this activity is important to us. You will find an evaluation form
at the end of this activity. When you complete this form, please forward it to your
Nursing Educator or Nursing Education Office. We will use your feedback when the time
comes to make revisions to this activity.
Thank you and we hope you find this activity helpful.
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Definitions
End Tidal CO2 (EtCO2) – Peak concentration of carbon dioxide occurring at the
end of expiration. Normal EtCO2 value: 30 – 45 mmHg.
Capngram: A graphical
waveform display of
carbon dioxide
concentration over time.
Capnometry: Continuous
and non-invasive
measurement and
graphical display of
EtCO2. There is a sample
chamber/sensor placed
for optimum evaluation
of ventilation with a
numeric display of
carbon dioxide.
Pulse Oximetry: The amount of oxygen on the hemoglobin molecule reflecting
oxygenation. Normal value 93-100%.

Can alert the care provider to the hypoxic patient but does not give
adequate forewarning of impending hypoxia due to ventilatory depression.
When the patient slows or stops their breathing, the pulse oximeter will
not detect the change until the number of oxygen molecules on the
hemoglobin has dropped. This takes more time, especially if the patient is
receiving supplemental oxygen.
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Capnography
Basic Physiology of the Lungs:
The lungs have two main functions:
o to inhale oxygen into the body
o to exhale carbon dioxide from the body
In normal lungs, the amount of carbon dioxide exhaled is very close to the level of
carbon dioxide in the blood. Oxygen is inhaled into the lungs and carried into the
bloodstream to the cells. Carbon dioxide is then transported back from the cells via the
bloodstream to the lungs and exhaled. The transport of O2 via the bloodstream to the
cells is called oxygenation. The movement of air into and out of the lungs and exhaling
of CO2 via the respiratory tract is called ventilation.

Oxygenation is measured by monitoring arterial oxygen saturation (SpO2) in a
patient’s blood. Pulse oximetry measures oxygenation and it is affected by
motion, artifact, distal circulation, temperature, and supplemental oxygen use.

Ventilation is measured by monitoring alveolar carbon dioxide (EtCO2) in a
patient’s exhaled breath. Capnography measures ventilation and it is not affected
by motion, artifact, distal circulation, temperature, or supplemental oxygen use.
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In the last ten years ETCO2 monitoring, or capnography, has become the standard
of care for anesthesia administration. The American Society of Anesthesiologists (ASA)
has recently recommended that any patients receiving moderate or procedural sedation
also be provided with ETCO2 monitoring. The practice of ETCO2 monitoring has been
less widely used in the critical care setting, but has many useful applications.
Capnography is a tool for non-invasively measuring the partial pressure of carbon
dioxide at the end of exhalation and directly measures ventilatory performance of the
lungs. Carbon dioxide, produced during aerobic metabolism, builds up in the tissues. It
diffuses out of the cells, into the circulation and across the alveolar membrane during
respiration. It is then excreted by exhalation. Poor ventilation, as a result of sedation,
results in a build-up of CO2, which is recognized by the monitor.
Patients have the ability to maintain adequate SpO2 levels for prolonged periods
in the presence of hypoventilation and apnea, especially during the administration of
supplemental oxygen. A decrease in oxygen saturation, as reflected in a drop in the
SpO2 displayed by the monitor, is a late indicator of hypoventilation and apnea. EtCO2
monitoring gives an accurate picture of the patient’s ventilatory status. A normal value
is 35 - 45 mmHg and provides breath-to-breath information. Recent studies have shown
that the use of capnography improves patient outcomes by providing early warning signs
of hypoventilation, apnea, and airway obstruction, thus preventing hypoxic events.
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Clinical Applications for the use of EtCO2 in the Intensive Care Unit
 To confirm proper placement of an advanced airway
 Monitor the quality of compressions during CPR
o EtCO2 drops during cardiac arrest
o A sudden rise in EtCO2 during CPR indicates a return of spontaneous
circulation
o EtCO2 of 20 mmHg should be maintained during CPR.
o A drop may indicate fatigue by the person performing compressions and a
need to change rescuers.
 Monitor the respirations in patients at risk for respiratory depression due to recent
sedation, narcotics, or respiratory compromise
o The amount of sedation required by a patient is variable; it depends on
patient’s physiology and ability to use and metabolize the medication
o Intermittent nurse monitoring of postoperative patients may not pick up on
ventilatory depression
 Monitor respirations in patients with sleep apnea
 Assist with successful ventilator weaning
 Identify loss of advanced airway during long-term mechanical ventilation in the
inpatient setting
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Intensive Care Unit Patient’s who could benefit from the use of EtCO2
Non-Intubated:

High risk for respiratory depression either from recent anesthesia or sedation

Receiving IV opiates or narcotics for pain control such as those on PCA pump

Respiratory conditions that are at a higher risk for compromise such as COPD or
asthma
Obstructive Sleep Apnea

Intubated:

Weaning from mechanical ventilation

Sedation management

Confirmation of ETT placement

Predicting survival in cardiopulmonary resuscitation
Trends in EtCO2 correlate with changes in the PaCO2 and can provide an early
warning of metabolic or cardiorespiratory problems such as shunting, dead space,
bronchoconstriction or pulmonary embolism.
Normal Values

Normal PaCO2 from an ABG sample is 35 – 45 mmHg

Normal EtCO2 is between 30 – 45 mmHg

EtCO2 under normal conditions can be 2 to 5 mmHg lower than an arterial PaCO2
on an arterial blood gas sample.

Fractional Inspired Carbon Dioxide (FiCO2) is 0 mmHg; This is the “0” baseline on
the capnogram

Adult respiratory rate – 8 to 18
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EtCO2 Waveform Interpretation
The capnographer displays each breath as a waveform in millimeters of mercury
(mmHg) of CO2 as a function of time, and provides a continuous reading for the carbon
dioxide level. It also displays a numeric value for the CO2 level at the end of expiration.
The capnogram, or EtCO2 waveform, is a visual assessment of the patient airway
integrity. Waveforms have characteristic shape like an ECG. The evolution of CO2
from the alveoli to the mouth during exhalation, and inhalation of O2 free gases during
inspiration gives the characteristic shape to the CO2 curve.
On the EtCO2 waveform:




Height shows the amount of exhaled carbon dioxide
Length depicts time
Shape of a capnogram is identical in all patients with healthy lungs
Any deviations in shape must be investigated to determine a cause of the
abnormality.
Capnography Waveforms:
Wave
Wave
Wave
Wave
1: Exhalation begins; air from the anatomic dead space has cleared
2: Alveolar air mixes with atmospheric air and ETCO2 rises rapidly
3: A exhalation proceeds, the CO2 waveform levels, air is primarily alveolar
4: As inspiration occurs, atmospheric air rushes in, CO2 levels fall to zero
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Normal ETCO2 Waveform:
The normal waveform values are 30-45
Hyperventilation Waveform:
In hyperventilation the waveforms starts out normal and then as the rate of
respirations increases the waves become closer together and value of the CO2
decreases.
Clinical findings:
Rapid breathing, low EtCO2
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Hypoventilation Waveform:
The waveform looks normal but the value of the CO2 begins to rise as the patient’s
breathing becomes less effective, usually due to a narcotic overdose, CNS depression,
or heavy sedation, and they are not exhaling all of their CO2.
Clinical findings:
Slow breathing, high EtCO2
Bronchoconstriction Waveform:
The shark fin appearance of the waveform indicates a possible airway constriction as
seen in poor head and neck alignment, asthma, COPD exacerbation or partial airway
obstruction.
Clinical Findings:
Possible irregular breathing, snoring or audible breathing
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Apnea or loss of the waveform:
In the spontaneously breathing patient this could be a sign of respiratory arrest. If the
patient is breathing it could indicate a equipment defect. If the patient is intubated it
could indicate an obstruction. Always assess the patient.
Clinical findings:
Very shallow of no respiratory rate pattern, sudden loss of EtCo2 reading
Esophageal Intubation Waveform:
When the ETT is incorrectly placed in esophagus the waveforms are either small and
transient or completely flat
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EtCO2 Waveform during CPR:
Waveform capnography allows providers to monitor CPR quality, optimize chest
compressions and detect a return of spontaneous circulation during chest compressions.
If the EtCO2 is less than 10 mmHg, attempt to improve quality of compressions
A sudden increase in EtCO2 during CPR indicates a return of spontaneous circulation
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EtCO2 Equipment and Devices
Mainstream: CO2 sensors are located directly in the patient’s breathing circuit.
Sidestream: Remote from the patient as part of CO2 monitoring system
Inline adaptor for patients on mechanical intubation:
Microstream CapnoLine that has a nasal cannula with CO2 detector:
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Adaptor that attaches to central monitor. The EtCO2 cord will attach to the
adaptor and display a waveform on the central monitor:
EtCO2 waveform on central monitor:
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EtCO2 Alarms
Low EtCO2 Alarm: possible causes include a true measurement, disposable not correctly
attached to a patient
High EtCO2 Alarm: Possible causes include a true measurement, fever or hypermetabolic
state, disposable not currently attached to patient
High FiCO2 Alarm: Possible causes include the patient is inspiring exhaled CO2,
disposable not correctly attached to patient, oxygen flow to mask may have stopped,
covers may be over patient’s face
No Breath Detected Alarm: Possible causes include patient is not breathing, disposable
not correctly attached to patient and/or device, disposable not detecting exhaled
breath (shallow breath)
Patient Education:
As with every intervention, patients must be educated to the purpose, potential side
effects of whatever intervention that is prescribed for the patient.
Patients and family should be educated about the following:



Purpose of monitoring CO2
Importance of monitor alarm
Activity restriction, if any
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EtCO2 Post Test
1. Which patient would be a good candidate for EtCO2 monitoring?
A. 25 year old female s/p central venous line placement with two doses of lidocaine
B. 59 year old mechanically vented male on sedation s/p bronchosopy
C. 78 year old male on bipap with orders for comfort measures
D. 66 year old female with obstructive sleep apnea s/p cardiac cath
2. Identify the waveform below:
A. Normal
B. Hypoventilation
C. Hyperventilation
D. Apnea
3. Your patient is in cardiac arrest and CPR is initiated. EtCO 2 is also being monitored during chest
compressions. The team leader tells you that the EtCO 2 is 12 mmHg. What is your next action?
A. Continue chest compressions at the same rate, an EtCO2 above 10 mmHg indicates good quality
chest compressions.
B. Increase the quality of chest compressions, EtCO2 below 30 mmHg indicates poor quality
compressions.
C. Decrease the intensity of the chest compressions, EtCO 2 below 10 mmHg indicates chest
compressions that are too intense in quality.
D. Stop chest compressions, the patient has a ROSC.
4. Capnography or ETCO2 measures:
A. Oxygenation
B. Ventilation
C. Perfusion
D. AA Gradient
5. True or False. EtCO2 can be used on intubated and non-intubated patients.
A. True
B. False
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References
American Heart Association. (2012). Waveform capnography. Retrieved June 28, 2012,
from http://acls-algorithms.com/waveform-capnography
Good, V., & Luehrs, P. (2010). Continuous end-tidal carbon dioxide monitoring. AACN
procedure manual for critical care (5th ed., pp. 105-111). St Louis: Saunders.
Kraft, K. (2011). Using capnography to improve patient safety. Unpublished manuscript.
Marini, J., & Wheeler, A. (2010). Critical care medicine, the essentials. Philadelphia:
Lippincott Williams & Wilkins.
Marino, P. (2009). The little ICU book. Philadelphia: Lippincott Williams & Wilkins.
Nikolova-Todorova, Z. (2008). Clinical applicaitons to capnography. SIGNA VITAE, 3(1),
S44-S45.
St. John, R. (2003). End-tidal carbon dioxide monitoring: Protocols for practice. Critical
Care Nurse, 23(4): 83-88.
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Test Answers: D,B, A, B, A
EVALUATION
Title of Activity:
ETCO2 MONITORING
Date:
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Self-directed learning activity objectives were met.
1. The following individual objectives were met:
Demonstrate understanding of EtCO2 monitoring.
Enhance ability to communicate patients at risk for respiratory
depression and would benefit from EtCO2 monitoring
Demonstrate assessment of patients based on scope of practice.
Discuss the normal ETCO2 waveform
1. Materials and Methods
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(Please comment if you selected “Disagree” or “Strongly Disagree” for any of the above sections.)
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Please return this form via interoffice mail addressed to CCU CCNS
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