Using Capnography to Improve
Patient Safety
Kim Kraft BSN RN CPAN
ASPAN President 2010 - 2011
The Big Picture
• With recent emphasis on treating
pain aggressively, there is substantial
concern of opioid-induced respiratory
depression resulting in hypoxia
The Big Concern
• When patients are using opioids for pain relief,
there’s always a risk for respiratory depression
• The amount of opioid required by a patient is
variable; it depends on patient’s physiology and
ability to use and metabolize the medication
• Intermittent nurse monitoring of postoperative
patients may not pick up ventilatory depression
that might occur during unattended periods
Another Concern…
• Standard measures for assessing patients for
sedation (hourly RR and sedation score) fail to
account for the fact that overly sedated patients
can be aroused and respond to questions
• The respiratory status may improve with
stimulation, but will revert to lower levels when
stimulation stops
Also...
• 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
Pulse Oximetry
• Continuous pulse oximetry can alert us to the
hypoxic postoperative patient but does not give
adequate forewarning of impending hypoxia due
to ventilatory depression. Absence of
forewarning can delay deployment of corrective
measures
Is there a better
way to monitor our
patients?
Basic Physiology of the Lungs
• The lungs have two
main functions
▫ to inhale oxygen into
the body
▫ 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
Respiratory Cycle
• Oxygen is inhaled into the lungs and carried into
the bloodstream to the cells
• Carbon dioxide is 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 vs. Ventilation
• Oxygenation is measured by monitoring arterial
oxygen saturation (SpO2) in a patient’s blood
▫ Pulse oximetry measures oxygenation
▫ Affected by motion, artifact, distal circulation,
temperature, supplemental oxygen use
• Ventilation is measured by monitoring alveolar
carbon dioxide (EtCO2) in a patient’s exhaled
breath
▫ Capnography measures ventilation
▫ Not affected by motion, artifact, distal circulation,
temperature, supplemental oxygen use
Capnography vs. Pulse Oximetry
Capnography
• Carbon dioxide
• Reflects ventilation
• Hypoventilation & apnea
detected immediately
• Reflects change in
ventilation within 10
seconds
• Should be used with
pulse oximetry
Pulse Oximetry
• Oxygen saturation
• Reflects oxygenation
• SpO2 changes lag when
patient is hypoventilating
• Reflects change in
oxygenation within 5
minutes
• Should be used with
capnography
Why Use Capnography?
• Facilitates patient management by:
▫ Providing continuous and non-invasive monitoring of
ventilation
▫ Providing early detection of clinically significant or
catastrophic events by:
 Displaying changes in the amount of carbon dioxide detected
 Displaying abnormal waveforms
Mainstream or Sidestream
• Mainstream: CO2 sensors are located directly in
the patient’s breathing circuit
• Sidestream: remote from the patient as part of
CO2 monitoring system
Microstream CO2 Sampling
®
Microstream CO2 Sampling
®
• Only system providing
accurate EtCO2 readings for
non-intubated patients that
receive supplemental oxygen
and switch between oral
and/or nasal breathing
• Maximum oxygen flow rate of
5l/min
• Unique delivery method
reduces CO2 sampling dilution
• Works effectively under
oxygen delivery mask as well
Definitions
• Capnogram – a waveform
display of carbon dioxide
over time
• Capnometer – a numerical
display of carbon dioxide
• Capnography - the
continuous measurement and
graphic display of the carbon
dioxide level in exhaled
breath.
The Capnogram
•
•
•
•
Visual assessment of patient airway integrity
Height shows amount of exhaled carbon dioxide
Length depicts time
The shape of a capnogram is identical in all humans with
healthy lungs.
• Any deviations in shape must be investigated to determine a
cause of the abnormality
Normal Ventilation Waveform
• Waveforms have a characteristic shape like an ECG
• The evolution of CO2 from the alveoli to the mouth
during exhalation, and inhalation of CO2 free gases
during inspiration gives the characteristic shape to the
CO2 curve
• Normal CO2 waveforms must have all of these
components:
A.
B.
C.
D.
E.
A zero baseline
A rapid, sharp uprise
An alveolar plateau
A well-defined end-tidal point
A rapid, sharp downstroke
Normal Values
• Normal PaCO2 from an ABG sample is 35 – 45 mmHg
• Normal End-tidal CO2 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 24
• Pediatric respiratory rate – 12 to 60 (age dependent)
Hypoventilation
• Clinical findings:
▫ Slow breathing, high EtCO2
• Possible causes:
▫ Increased sedation, overmedication
▫ Snoring or possible obstruction
• Possible responses:
▫
▫
▫
▫
▫
Follow hospital protocol
Assess Airway, Breathing and Circulation (ABC’s)
Assess sedation level
Stimulate patient
Notify prescribing physician
• Call the rapid response team if no improvement is noted
Hypoventilation
Hypoventilation #2
• Clinical findings:
▫ Slow breathing, low EtCO2
▫ Followed by deep breath
• Possible causes:
▫ Increased sedation
▫ Low tidal volume
• Possible responses:
▫
▫
▫
▫
▫
Follow hospital protocol
Assess ABC’s
Maintain patent airway
Stimulate patient, encourage deep breaths
Notify prescribing physician
• Call the rapid response team if no improvement is noted
Hypoventilation #2
Hyperventilation
• Clinical findings:
▫ Rapid breathing, low EtCO2
• Possible causes:
▫ Increase in pain level or splinting
▫ Increase in anxiety or fear
▫ Respiratory distress or shortness of breath
• Possible responses:
▫
▫
▫
▫
▫
Follow hospital protocol
Assess ABC’s
Treat cause of increased RR
Decrease pain stimulus
Notify prescribing physician
• Call the rapid response team if no improvement is noted
Hyperventilation
Partial Obstruction
• Clinical findings:
▫ Irregular breathing, possible snoring or audible
breathing
▫ EtCO2 may be above or below baseline
• Possible causes:
▫ Poor head or neck alignment
▫ Overmedication or sedation
• Possible responses:
▫
▫
▫
▫
▫
▫
Follow hospital protocol
Assess ABC’s
Perform head-tilt/chin lift
Encourage deep breaths
Check position of cannula
Notify prescribing physician
• Call the rapid response team if no improvement is noted
Partial Obstruction
No Breath
• Clinical findings:
▫ Very shallow or no respiratory rate pattern
▫ Sudden loss of EtCO2 reading
• Possible causes:
▫
▫
▫
▫
No breath or apnea
Very shallow breathing
Overmedication or sedation
Displaced cannula
▫
▫
▫
▫
▫
Follow hospital protocol
Assess ABC’s
Stimulate patient
Open airway
Notify prescribing physician
• Possible responses:
• Call the rapid response team if no improvement is noted
No Breath
EtCO2 Alarms
• Low EtCO2 Alarm
▫ Possible causes: true measurement, disposable not correctly
attached to patient
• High EtCO2 Alarm
▫ Possible causes: true measurement, fever or hypermetabolic
state, disposable not correctly attached to patient
• High FiCO2 Alarm
▫ Possible causes: pt. 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: patient is not breathing, disposable not correctly
attached to patient and/or device, disposable not detecting
exhaled breath (shallow breath)
Signs & Symptoms Of Hypoventilation
•
•
•
•
•
•
•
•
•
•
Decreased LOC, confusion, anxiety or agitation
Shallow breathing (rate may be normal)
Dyspnea or shortness of breath…eventual apnea
May look like tachypnea with very shallow breaths
Cyanosis
Pallor
Diaphoresis
Tachycardia…eventual bradycardia
Decreased O2 Sats (late sign)
Increased CO2 capnography
Treatment Guidelines
• Assess Airway, Breathing and Circulation
• Follow PCA orders to treat or reverse the cause
(naloxone, romazicon)
• Decrease opioids and/or benzodiazepines
• Stimulate the patient, encourage to take deep
breaths
• Notify prescribing physician
• Call the rapid response team if no improvement
is noted.
Case Study # 1
• A 69 year-old healthy patient with a BMI of 25 is
admitted to your unit following a total knee replacement.
• He received a femoral nerve block prior to OR.
• He is on a Morphine PCA postop: 2 mg dose, 6 minute
lockout with a dose limit of 12 mg/hr.
• Two hours after initiating the PCA, his respiratory rate
decreases to 8 breaths per minute and his EtCO2
increases from 35 to 50 mmHg and he is slow to respond
to verbal stimuli.
Discussion
• What treatments or interventions would be
appropriate for this patient?
• What is the most likely cause of the observed
distress?
Case Study # 1
(cont.)
• The PCA was restarted two hours later at 1 mg dose with
a 6 minute lockout. The nurse noted his respiratory rate
was 10 breaths/minute, EtCO2 was 25 mmHg and he had
minimal chest excursion. When he took a deep breath,
the EtCO2 increased to 58 mmHg. He was arousable to
verbal stimuli and denied pain.
Discussion
• What treatments or interventions would be
appropriate for this patient?
• What is the most likely cause of the observed
distress?
Case Study # 2
• A 16 year-old trauma patient is experiencing shortness of
breath.
• Blood pressure 160/85 – 138 – 36 – 99%; his EtCO2
dropped from 35 to 25.
• Pneumothorax, pulmonary embolism and pneumonia
were all ruled out.
• He has been on a Fentanyl PCA dose of 15 mcg with a 15
minute lockout and a 90 mcg hourly dose.
Discussion
• What treatments or interventions would be
appropriate for this patient?
• What is the most likely cause of the observed
distress?
Case Study # 3
• 60 year-old female admitted with back pain due to
metastasis of breast cancer. PCA Morphine for pain control
was started. After 2 hours, her pain score was 9/10. The
PCA dose was increased to 2 mg with a lockout of 6 minutes
and a continuous rate of 2 mg/hr was added.
• An hour later she was lethargic, respirations were shallow
and irregular at a rate of 6, oxygen saturation was 68% and
EtCO2 was 72.
Discussion
• What treatments or interventions would be
appropriate for this patient?
• What is the most likely cause of the observed
distress?
Why Use Continuous Monitoring and PCA
Therapy?
The following patient conditions and alarm states can be
observed using continuous EtCO2 and SpO2 monitoring and
PCA therapy:
1.
2.
3.
4.
5.
Opioid - induced apnea: detected by no breath alarm
Undiagnosed sleep apnea: detected by no breath alarm
Post-op pneumonia: detected by low oxygen saturation alarm
Congestive hearth failure: detected by low oxygen saturation alarm
Respiratory depression secondary to opioid overdose: detected by all of the
following:
 Low oxygen saturation alarm
 High EtCO2 alarm
 Low respiratory rate alarm
 No breath alarm
For more information…
• http://www.capnographyeducation.com
References
1.
2.
3.
4.
Bhavani-Shankar, K., MD. http://capnography.com/
Capnography in the Management of the Critically Ill
Patient, EducationPAK for Critical Care and
Procedural Sedation - A Guide to Capnography, CDROM - Needham, MA, Oridion Medical, 2003.
AACN Procedure Manual for Critical Care 5th Ed.
(2005). Ed. Lynn-McHale Wiegand, D.J. & Carlson
K.K.. American Association of Critical-Care Nurses.
Thalan’s Critical Care Nursing Diagnosis and
Management 4th Ed.(2001) Ed. Urden, L.D., Stacy,
K.M. & Lough, M.E.. C.V. Mosby