Perianesthesia Nurses Association of British
Columbia
Cathy Hanley, RN, BSN
November 6, 2010

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Review of physiology, ventilation vs oxygenation
Identify normal and abnormal etC02 values and waveforms and appropriate clinical interventions
Discuss current applications of capnography in the PACU and beyond
Discuss current standards and recommendations
Review of capnography case studies

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Used in anesthesia since the 1970s
Canadian
Anesthesiologists’
Society requires it in the OR
New recommendations and standards expanding utilization

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
Capnography = Solutions for all Intubated and
Non-Intubated patients
Capnography can be used in all areas of the hospital
ICU PACU
OR
EP/
Cath
Pain
Mgmt
Med-
Surg
Peds
.
MRI
GI

Overview of Capnography
 Capnography is the non-invasive, continuous measurement of CO
2
concentration at the airway
 Capnography provides three important parameters:
•
Respiratory rate detected from the actual airflow
•
Numeric etCO
2
• value
Normal range 35-45 mmHg
•
Waveform tracing for every breath

Manual Counting
• Measures:
• Chest or air movement
• Based on observation or auscultation that may be restricted by patient movement, draping or technique
Impedance (ECG Leads)
• Measures:
• Attempt to breathe
• Chest movement etCO
2
• Measures:
• Actual exhaled breath at airway
• Based on measuring respiratory effort or any other sufficient movement of the chest
• Hypoventilation and No
Breath detected immediately!
• Most accurate RR, even when you are not in the room!

Respiratory Cycle =
Oxygenation and Ventilation
Two separate physiologic processes
Oxygenation
• The process of getting O the body
2 into
• The process of eliminating CO
2 from the body
Ventilation

Important Measurements
• Measures etCO
2
• Reflects ventilation
• Hypoventilation
& apnea detected immediately http://www.covidien.com
• Measures SpO
2
• Reflects oxygenation
• Values lag with hypoventilation
& apnea, several to many minutes

2
2

 etCO
2 normal range is
35 - 45 mmHg
Under normal ventilation and perfusion conditions, the PaCO
2
& etCO be very close
2 will
– 2 – 5 mmHg with normal physiology
Ideally, every alveolus is involved in air exchange (ventilation) and has blood flowing past it (perfusion), but in reality, ventilation and perfusion are never fully matched, even in the normal lung

 There is inappropriate matching of ventilation and perfusion when:
–
–
“Dead space” is being ventilated with no perfusion
• Since no gas exchange occurs, air coming out is the same as air going in (no CO
2
)
Unventilated areas of lung are being perfused (“Shunt”)
• Effect on etCO
2 may be small but oxygenation may decrease greatly

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Physiologic
– conducting airways and unperfused alveoli
Mechanical
– breathing circuits
Disease states leading to this include:
–
–
–
–
–
Severe hypotension
Pulmonary embolism
Emphysema
Bronchopulmonary dysplasia
Cardiac arrest

Ventilation-perfusion mismatch

 Bronchial intubation
Increased secretions
 Mucus plugging
 Bronchospasm
 Atelectasis

2
2
 End tidal CO
2
CO
2
(EtCO
2
) = noninvasive measurement of at the end of expiration
 EtCO
2 allows trending of PaCO
2 of the PaCO
2 appropriately matched
- a clinical estimate
, when ventilation and perfusion are
 Wide gradient is diagnostic of a ventilation-perfusion mismatch
 EtCO
2 monitoring allows for a breath by breath assessment of ventilation.

 Accurately monitors effective ventilation, giving a true airway respiratory rate
• Early warning of :
 Hypoventilation
 Apnea
 Obstruction
Provides easy and accurate airway monitoring for intubated or non-intubated patients
– Promotes better ventilation assessment resulting in timely interventions
– Titrate sedation and pain medication

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Indicator of Malignant Hyperthermia
Use with patient with history of respiratory compromise, such as asthma or COPD to monitor trend and need for breathing treatments and response to treatment
Endotracheal tube placement
Monitoring during weaning
Decrease frequency of arterial blood gases
Use with non-invasive ventilation (NIV)

Case Study: Microstream
Capnography in the PACU:
Submitted by: Larry
Myers RRT
Cottonwood Hospital
Murray, Utah

 Profile
A 31-year-old female s/p abdominal hysterectomy 6 months prior to admission is admitted with right lower quadrant pain. The patient underwent a bilateral salpingooophorectomy and lysis of adhesions on this admission. On post-op day one she became hypotensive and had a substantial decrease in her hematocrit. The patient was returned to the OR for an exploratory laparotomy.

Clinical Situation:
When the patient was returned to the PACU, she was extubated and became acutely hypoxic on a non-rebreather mask. The patient was in profound distress, drowsy, lethargic, but arousable and able to converse with c/o severe abdominal and chest pain.
Sp02: 82% pH: 7.22
PaC02: 64.9mmHg
HCO3: 25.5mEq/L
Pa02: 53mmHg
Sa02: 81%
RR: 40bpm
HR: 130bpm
BP: 107/48

Clinical Situation
At this point anesthesia was preparing to reintubate. A suggestion was made to use etC02 with an oral/nasal cannula and place the patient on a high flow 02 delivery system with an Fi02 of 1.0 and monitor the patient closely.
The patient was rushed to the Radiology Department for a
CT angiogram where a pulmonary embolus was ruled out.
Initial values: etC02: 62mmHg
Sp02: High 80’s
Over the next 2 hours, etC02 fell to 44mmHg and Sp02 increased to 98%.

The continuous monitoring of E t
CO
2 and SpO
2 when measured in concert but evaluated independently allowed this patient to be safely observed and avoid reintubation and mechanical ventilation. It is also interesting to note, retrospectively, an expensive procedure to rule out PE may have been avoided with a better understanding of the relationship between arterial and end-tidal CO
2
. The probability of a PE in this case was low with a measured
E t
CO
2 of 62 mmHg and a correlating PaCO
2 of 64.9 mmHg.
One would expect a wider gradient in the presence of significant dead space ventilation.

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Post operative patients on Patient Controlled Analgesia (PCA)
- often starts in PACU
Bariatric Patients/Obstructive Sleep Apnea(OSA) high risk patients
Awareness building regarding the need for monitoring ventilation/breathing on general floors
–
–
Patient sentinel events/deaths
Recent professional statements (APSF, ISMP)
Great need for more education on Oxygenation vs.
Ventilation for nurses in non-acute areas

University of Alabama – Birmingham, Waugh, Epps, Khodneva - meta-analysis presented at the
Society of Technology in Anesthesia International Congress, January, 2008

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Patient Controlled Analgesia (PCA) aids patients in balancing effective pain control with sedation
The risk of patient harm due to medication errors with
PCA pumps is 3.5-times the risk of harm to a patient from any other type of medication administration error
 2004 more deaths with PCA than with all other IV infusions combined
 Due to oversedation and respiratory depression with PCA delivery
Sullivan M, Phillips MS, Schneider P. Patient-controlled analgesia pumps. USP
Quality Review 2004;81:1-3. Available on the web at: http://www.usp.org/ pdf/patientSafety/qr812004-09-01.pdf.

 PCA by proxy
 Drug product mix-ups
 Device design flaws
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 Inadequate patient/family education
 Practice issues including pump misprogramming
Inadequate monitoring
ISMP Medication Safety Newsletter, July 10, 2003 Vol 8, no.14

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 Post operative surgical units where there is no centralized monitoring
Large units making proximity to patient impossible
Vital signs are typically every 4 hours
Sometimes spot checking with pulse oximetry
Nurse to patient ratio can be 1:6 – 1:10

How Ventilation Deteriorates when Administering Opioids
Opioids Depress the
Brain’s signals to the
Respiratory Muscles
CO
2
Production CO
2
Removal

 16 yr-old Billy falls off his skateboard and sustains a left femur fracture. He is now post-op from ORIF and is in the PACU extubated. He rates his pain at a 10 on 0-10 scale and has been given multiple doses of IV Morphine and is now on a PCA pump for pain.

 Later that evening on the med-surg floor, after hours of poor pain control, Billy falls asleep
 Afraid Billy will soon wake up and again be in severe pain, Billy’s mother repeatedly presses his morphine PCA button while he is asleep
 He subsequently stops breathing and is resuscitated, but suffers hypoxic brain injury

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 Sleep apnea is the most widely known sleep disorder besides insomnia
Believed to be under-reported
18-40 million people have sleep apnea
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Effects 2% of middle-aged females
Effects 4% of middle-aged males
More common in men
It is estimated that nearly 80% of men and 93% of women with moderate to severe sleep apnea are undiagnosed
Sleep Apnea, Anesthesiology 2006; 104:1081
–93
Sleep Diagnosis and Therapy
♦ Vol 3 No 5 September-October 2008

Muscles of the pharynx relax during deep sleep
Survival
Mechanism
Stimulates and arouses patient to ventilate
Acidosis activates respiratory centers in the CNS
Airway obstruction
Hypoxemia
&
Hypercarbia

Does not ventilate
Muscles of the pharynx relax during deep sleep
Respiratory Arrest
Without Intervention
Opiates & sedatives inhibit arousal mechanisms
Acidosis activates respiratory centers in the CNS
Hypoxemia
&
Hypercarbia
Airway obstruction

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60 year old female with morbid obesity and history of intractable low back pain
X-rays demonstrated severe bone-onbone changes in both knee and hip areas
Placed on PCA continuous infusion with PCA demand dose
Placed on continuous SpO2 and EtCO2 monitoring

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Soon after starting PCA, patient desaturated to SpO2 = 85%
Patient placed on 60% O2 aerosol mask and
EtCO2 monitoring discontinued
PCA continuous discontinued, PCA demand dose continued

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Following morning, patient appeared very lethargic and difficult to arouse
SpO2 in high 90s
EtCO2 monitor reapplied on patient with readings of 74 mmHg* indicating elevated CO2 level
Patient was transferred to ICU with diagnosis of obstructive sleep apnea complicated by obesity and PCA
*Normal EtCO2 = 35-45 mmHg

D
A-B: Baseline = no CO
2 in breath, end of inhalation
B-C: Rapid rise in CO
2
C-D: Alveolar plateau
D: End point of exhalation (EtCO
2
)
D-E: Inhalation

Abnormal waveforms – No Breath loss of waveform
Sudden loss of waveform and
EtCO
2 to zero or near zero / no respiration detected
– Possible causes
• Intubated:
• Kinked or dislodged
ETT
 Total airway obstruction
 Complete disconnect from ventilator
 Non-intubated:
 Apnea
 Dislodged Capnoline

Abnormal waveforms
Loss of alveolar plateau
Absent alveolar plateau indicates incomplete alveolar emptying or loss of airway integrity
– Possible causes
 Intubated:
 Partial airway obstruction caused by secretions
 Leak in the airway system
 Bronchospasm
 Endotracheal tube in the hypopharynx
 Non-intubated:
 Head and neck position
 secretions

Abnormal waveforms decreased etCO
2
Gradual decrease in etCO
2 with normal waveform indicates a decreasing CO
2 production, or decreasing systemic or pulmonary perfusion
 Hypothermia (decrease in metabolism)
 Hyperventilation
 Hypovolemia
 Decreasing cardiac output

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Waveform shape detects presence of bronchospasm etCO
2 trends assess disease severity (e.g., asthma, emphysema) etCO
2 trends gauge response to treatment
(e.g., asthma, emphysema

Abnormal waveforms – rebreathing intubated and non-intubated
Rise in baseline CO
2 rebreathing of CO
2 indicates
 Intubated patient
– Addition of mechanical dead space to ventilator circuit
– Technical errors in CO
2 analyzer
 Non-intubated patient
Poor head & neck alignment
Draping at the airway
Insufficient flow to O
2 mask
Shallow breathing that does not clear anatomical dead space

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Assess patient
Check sample line position – reposition or check ET tube position
Check head/neck alignment, and open airway, suction if needed
Instruct patient to take a deep breath
If patient is not breathing and not responding, follow

Canadian Anesthesiologists’ Society, R. Merchant, et al
Revised edition 2010

Institute for Safe Medication Practices (ISMP)
 “Do not rely on pulse oximetry readings alone to detect opiate toxicity. Use capnography to detect respiratory changes caused by opiates, especially for patients who are at high risk (e.g., patients with sleep apnea, obese patients).”
– Establish guidelines for appropriate monitoring of patients who are receiving opiates, including frequent assessment of the quality of respirations (not just respiratory rate) and specific signs of oversedation.
ISMP Medication Safety Alert, February 22, 2007, Vol.
12, Issue 4

ASA (American Society of Anesthesiologists)
 Practice guidelines for the perioperative management of patients with obstructive sleep apnea
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CO
2 monitoring should be used during moderate or deep sedation for patients with OSA. If moderate sedation is used, ventilation should be continuously monitored by capnography or another automated method if feasible because of the increased risk of undetected airway obstruction in these patients.
Postoperative Management:
OSA patients should be monitored for a median of 3 hours longer than the non-OSA counterparts before discharge. Monitoring of OSA patients should continue for a median of 7 hours after the last episode of airway obstruction or hypoxemia.
Practice guidelines for the perioperative management of patients with obstructive sleep apnea: a report by the
American Society of Anesthesiologists Task Force on Perioperative Management of Patients with Obstructive Sleep
Apnea. Anesthesiology 2006 May;104(5):1081-93

 Capnography for sedation/analgesia/postoperative monitoring:
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Accurately monitors RR
Monitors adequate ventilation
Monitors hypoventilation due to over-sedation more effectively than pulse oximetry
Earliest indicator of apnea and obstruction
Adds additional level of safety providing caregiver with objective information to make accurate assessments and timely interventions

Continuing Capnography Education
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Oridion Knowledge Center: www.capnographyeducation.com
Three capnography courses available:
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A Guide to Capnography during Procedural Sedation
A Guide to Capnography in the Management of the
Critically Ill
A Guide to Monitoring etCO
2 during Opioid Delivery