1. Capnography in the PACU: Theory and Clinical Applications
of end tidal C02 Monitoring
Perianesthesia Nurses Association of British Columbia Cathy Hanley, RN, BSN November 6, 2010

2. Objectives 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

3. Brief History of Capnography
Used in anesthesia since the 1970s
Canadian Anesthesiologists’ Society requires it in the OR
New recommendations and standards expanding utilization
Ventilatory monitoring has been used in the OR for over 30 years.
The American Society of of Anesthesiology made continuous ventilatory monitoring of anesthetized patients a standard of care in the 1990s
With the expansion of the use of procedures requiring sedation outside of the OR, the Joint Commission has looked at the safety of these patients undergoing procedural sedation and added a new standard.
Source: Practice Guidelines for Sedation and Analgesia by Non-anesthesiologists (Approved by the House of Delegates on October 25, 1995, and last amended on October 17, 2001) Anesthesiology 96: , 2002

4. Capnography outside of the OR
Capnography = Solutions for all Intubated and Non-Intubated patients
Capnography can be used in all areas of the hospital
Peds. GI
MRI
Med-
Surg
EP/ Cath
Pain Mgmt OR
PACU
ICU
Capnography has traditionally been used in the OR and ICU’s. With the changes in clinical practice and the evolvement technology has taken, capnography can be used in many areas within the clinical setting.
Microstream is the latest (3rd generation) technology and has a solution for both intubated and non-intubated patients….in all clinical areas
Let’s start with a few common terms that you will hear.

5. Overview of Capnography
Capnography is the non-invasive, continuous measurement of CO2 concentration at the airway
Capnography provides three important parameters:
Respiratory rate detected from the actual airflow
Numeric etCO2 value
Normal range mmHg
Waveform tracing for every breath
Capnography is simply a measurement of exhaled carbon dioxide, referred to as End Tidal Carbon Dioxide or etCO2. The etCO2 numeric value typically ranges between millimeters of mercury.
Capnography provides 3 important tools: 1) a respiratory rate, 2) an etCO2 numeric value, and 3) a waveform tracing for every breath.
((etCO2 value also measured less frequently in volume percent in kilo Pascal))
((only counts adequate breaths containing minimum of 7.5 mmHg))

6. Obtaining an Accurate Respiratory Rate
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)
Attempt to breathe
Chest movement
Based on measuring respiratory effort or any other sufficient movement of the chest
etCO2
Actual exhaled breath at airway
Hypoventilation and No Breath detected immediately!
Most accurate RR, even when you are not in the room!
The first tool that capnography provides is an accurate RR
Traditional respiratory monitoring requires us to place a stethoscope on the pt to listen to breath sounds and observe the patient’s chest rise and fall.
Large body types, blankets, or patient position may limit visualization of chest movement, and rapid breathers or crying kids can refer sounds further limiting our assessment. Lastly, there is no automated documentation or alarm if your patient fails to breathe when you are not in the room.  
ECG leads provide a respiratory rate based on chest movement or respiratory effort ...burping, coughing, or the attempt to breath may cause sufficient movement of the chest to generate a RR.  (Impedance Pneumography or measuring RR with ECG)
Capnography measures every effective breath at the airway. Therefore, capnography provides the most accurate respiratory rate…and it does this even when you’re not in the room!

7. Respiratory Cycle = Oxygenation and Ventilation
Two separate physiologic processes
The process of getting O2 into the body
Oxygenation
The process of eliminating CO2 from the body
Ventilation

8. Important Measurements
Capnography
Measures etCO2
Reflects ventilation
Hypoventilation & apnea detected immediately
Pulse Oximetry
Measures SpO2
Reflects oxygenation
Values lag with hypoventilation & apnea, several to many minutes
Important Measurements
Both pulse oximetry & etCO2 are important measurements
The problem is: pulse oximetry lags behind when a patient hypoventilates or stops breathing – plus, if the patient is on supplemental oxygen the lag time may be extended because of the body’s ability to hold on to oxygen
Since capnography provides breath-by-breath information regarding airway status – the clinician is notified immediately when the pt stops breathing.

9. The Relationship between PaCO2 and etCO2
etCO2 normal range is mmHg
Under normal ventilation and perfusion conditions, the PaCO2 & etCO2 will be very close
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

10. Ventilation-Perfusion Mismatch
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 CO2)
Unventilated areas of lung are being perfused (“Shunt”)
Effect on etCO2 may be small but oxygenation may decrease greatly

11. Dead Space Ventilation
Physiologic
conducting airways and unperfused alveoli
Mechanical
breathing circuits
Disease states leading to this include:
Severe hypotension
Pulmonary embolism
Emphysema
Bronchopulmonary dysplasia
Cardiac arrest
Teaching Tip:
Physiologic dead space is a normal phenomena. First, the conducting airways do not exchange gas and participate in the exhaled gasses. Second, there are always a few alveoli which are atelactatic or unventilated, even in the normal lung.
When you connect a breathing circuit to a patient, the circuit acts as an extension of the airways, adding additional dead space.
Several diseases lead to an increase in dead space. With pulmonary emboli, a section of lung has its perfusion blocked so the entire section become “dead space.” Emphysema increases dead space through destruction of lung tissue and hyperinflation of areas of lung restricting perfusion in those areas.
It should be remembered that the greater the difference between the Paco2 and the Petco2 levels, the more severe the disruption between pulmonary ventilation and pulmonary perfusion.

12. Ventilation-perfusion mismatch
Bronchial intubation
Increased secretions
Mucus plugging
Bronchospasm
Atelectasis
Some conditions that result in shunt perfusion are:
Bronchial intubation, increased bronchial & alveolar secretions causing mucus plugging, bronchospasm, and severe atelectasis.  
The effect on End Tidal CO2 may be small, although it will still be lower than PaCO2; however, the effect on Oxygenation can be substantial.

13. Summary - EtCO2 vs. PaCO2
End tidal CO2 (EtCO2) = noninvasive measurement of CO2 at the end of expiration
EtCO2 allows trending of PaCO2 - a clinical estimate of the PaCO2, when ventilation and perfusion are appropriately matched
Wide gradient is diagnostic of a ventilation-perfusion mismatch
EtCO2 monitoring allows for a breath by breath assessment of ventilation.
To summarize,
When monitoring intubated patients – usually mechanically ventilated – remember:
EtCO2 is a noninvasive measurement of CO2 at the end of expiration
EtCO2 provides a clinical estimate of PaCO2 when ventilation and perfusion are appropriately matched – EtCO2 will be about 2 – 5 mmHg lower than PaCO2
When you are presented with abnormal values, waveforms and/or V/Q Mismatch, Consult Respiratory Care Services . They can assess ventilator settings, patient’s response to treatments, and other possible factors.
EtCO2 allows for a breath by breath assessment of ventilation

14. Why use etC02 in the PACU ?
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
Improving patient safety
Airway monitoring, using EtCO2 provides the most dependable respiratory rate – called an airway respiratory rate because the value is taken directly from measuring air movement in and out of the airway. EtCO2 monitoring provides early warning of hypoventilation, or a total absence of breathing.
Alarms tell the Clinician to check the patient’s breathing, and remind the patient to breathe.
Smart Technology is unique to Microstream, and provides accurate measurements because it samples only the patient’s exhaled breath. This is important when patients switch from nose to mouth breathing.
Continuous EtCO2 monitoring offers an additional level of patient safety and provide the caregiver with vital information to make accurate assessments and timely interventions for the patient.

15. Why use etC02 in the PACU? 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)

16. 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 salpingo-oophorectomy 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.

17. Case Study in PACU 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

18. 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%.

19. Discussion   The continuous monitoring of EtCO2 and SpO2 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 CO2. The probability of a PE in this case was low with a measured EtCO2 of 62 mmHg and a correlating PaCO2 of 64.9 mmHg. One would expect a wider gradient in the presence of significant dead space ventilation.

20. PACU, Post-op PCA, Med/Surg Floors
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

21. Compelling Recent Research
“During analgesia and anesthesia, cases of respiratory depression were 28 times as likely to be detected if they were monitored by capnography as those that were not”
Resp depression is 28 times more likely to be detected when monitoring CO2 (resp depression often defined as: EtCO2 of 50mmHg or 10mmHg change from baseline)
So what can follow resp depression? Hypoxia, decreased LOC, resp failure, lack of oxygen to vital organs, heart arrhythmia, ACLS, intubation, higher level of care, extended stay, increased costs, litigation…
It can all be avoided by early intervention
University of Alabama – Birmingham, Waugh, Epps, Khodneva - meta-analysis presented at the Society of Technology in Anesthesia International Congress, January, 2008

22. Capnography monitoring in patients receiving patient controlled analgesia (PCA)

24. Patient safety with Patient Controlled Analgesia (PCA)
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: pdf/patientSafety/qr pdf.

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

26. Currently, no monitoring during PCA therapy at most hospitals
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

27. Opioids Depress the Brain’s signals to the Respiratory Muscles
How Ventilation Deteriorates when Administering Opioids
Opioids Depress the Brain’s signals to the Respiratory Muscles
Respiratory Depression and Eventual Failure
CO2 Build-up
Decreased LOC
Hypoventilation
Decreased RR And Depth
CO2 accumulates
Pts at risk of respiratory failure include those who’re resting in a nice quiet, warm environment after noxious manipulation. The meds they received to tolerate the noxious procedure may negatively impact the brain’s respiratory center
Pain medications (Opiods) cause the brain to become unaware of accumulating levels of blood CO2 and subsequently under stimulate the lung musculature (diaphragm and intercostal muscles)
This causes hypoventilation:
•A decrease in respiratory rate
•Or a decrease in respiratory depth
•Or a combination of both
CO2 removal then falls behind production
Leading to increased blood CO2 levels above normal limits
Patient’s LOC decreases, along with a decreased response to stimulus
Finally, toxic levels and Respiratory Failure if adequate ventilation is not restored
CO2 production must equal CO2 removal
CO2 Production
CO2 Removal

28. Case scenario
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.

29. Case scenario
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

30. Obstructive Sleep Apnea
Sleep apnea is the most widely known sleep disorder besides insomnia
Believed to be under-reported
18-40 million people have sleep apnea
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
Practice Guidelines for the Perioperative Management of Patients with Obstructive Sleep Apnea, Anesthesiology 2006; 104:1081–93
Sleep Diagnosis and Therapy ♦ Vol 3 No 5 September-October 2008

31. Mechanism of OSA…a vicious pattern
Muscles of the pharynx relax during deep sleep
Airway obstruction
Hypoxemia & Hypercarbia
Acidosis activates respiratory centers in the CNS
Stimulates and arouses patient to ventilate
Survival Mechanism

32. A more vicious pattern…with sedation
Muscles of the pharynx relax during deep sleep
Airway obstruction
Hypoxemia & Hypercarbia
Acidosis activates respiratory centers in the CNS
Does not ventilate
Respiratory Arrest Without Intervention
Opiates & sedatives inhibit arousal mechanisms

33. PCA Case Scenario #2
60 year old female with morbid obesity and history of intractable low back pain
X-rays demonstrated severe bone-on-bone changes in both knee and hip areas
Placed on PCA continuous infusion with PCA demand dose
Placed on continuous SpO2 and EtCO2 monitoring

34. PCA Case Scenario #2 cont.
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

35. PCA Case Study #2 cont.
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 = mmHg

36. Normal Waveform

37. Anatomy of a Waveform
A-B: Baseline = no CO2 in breath, end of inhalation
C-D: Alveolar plateau D
B-C: Rapid rise in CO2
D: End point of exhalation (EtCO2)
D-E: Inhalation
There is only one normal waveform:
A to B shows the waveform baseline. There should be little or no CO2
B to C shows the rise in CO2 as the dead space ventilation mixes with alveolar gas. This part of ventilation involves the trachea, main stem bronchus and airways.
 At C to D the waveform levels off representing the alveolar plateau. This part of ventilation involves mostly alveolar gas.
 D is the point at the end of expiration, and just before inspiration, where ETCO2 is measured.
The end of the waveform is segment D to E, a rapid, sharp down stroke indicating a drop in CO2 back to zero, and the beginning of inspiration.

38. Abnormal waveforms – No Breath loss of waveform
Sudden loss of waveform and EtCO2 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
In the intubated patient, a sudden loss of waveform indicates that “no breath” is detected. ”
Other clinical causes may be:
Kinked or misplaced ET Tube
Total airway obstruction
Total ventilator disconnection
Defective ventilator
Defective CO2 analyzer,or other technical disturbance where the patient is not necessarily in danger

39. 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
With the intubated patient, an absent alveolar plateau indicates incomplete alveolar emptying or loss of airway integrity. Some possible causes are:
Bronchospasm
Secretions causing partial airway obstruction
A leak around the ET Tube
Partial disconnection from the ventilator
Or a misplaced ET Tube
    

40. Classic Hypoventilation

41. Classic Hyperventilation

42. Abnormal waveforms - decreased etCO2
Gradual decrease in etCO2 with normal waveform indicates a decreasing CO2 production, or decreasing systemic or pulmonary perfusion
Hypothermia (decrease in metabolism)
Hyperventilation
Hypovolemia
Decreasing cardiac output
This waveform shows a gradual lowering of the ETCO2 waveform where the curve retains its normal shape, but the height of the plateau becomes gradually lower. In an artificially ventilated patient this phenomenon can be caused by:
Hypothermia due to a decrease in metabolism
Gradual hyperventilation
Hypovolemia
Decreased Cardiac Output

43. Capnography in Obstructive Lung Disease
Waveform shape detects presence of bronchospasm
etCO2 trends assess disease severity (e.g., asthma, emphysema)
etCO2 trends gauge response to treatment (e.g., asthma, emphysema
In obstructive lung disease, the CO2 waveform can be used to detect the presence of bronchospasm, and EtCO2 trends can be used to assess disease severity and response to treatment.
In patients with asthma, EtCO2 trends can be used to gauge the severity of an asthma attack as well as to assess the patient’s response to treatment.
In COPD, EtCO2 trends can be used to gauge response to treatment as these patients have chronic partial airway obstruction..

44. Abnormal waveforms – rebreathing intubated and non-intubated
Rise in baseline CO2 indicates rebreathing of CO2
Intubated patient
Addition of mechanical dead space to ventilator circuit
Technical errors in CO2 analyzer
Non-intubated patient
Poor head & neck alignment
Draping at the airway
Insufficient flow to O2 mask
Shallow breathing that does not clear anatomical dead space
When the EtCO2 waveform, does not return to baseline, this indicates rebreathing of CO2. Some causes may be:
Additional ventilator circuit, or mechanical dead space
Technical errors in the CO2 analyzer
 In non-intubated patients, causes may include:
Poor head & neck alignment
Draping at the airway
Insufficient flow to an oxygen mask
Very shallow breathing that does not clear anatomical dead space

45. Abnormal Waveforms – What to do
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 airway protocol

46. Movers and Shakers / Clinical Compass

47. ‘The monitoring used in the PACU should be appropriate to the patient’s condition and a full range of monitoring devices should be available’. Canadian Anesthesiologists’ Society, R. Merchant, et al Revised edition 2010

48. 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

49. ASA (American Society of Anesthesiologists)
Practice guidelines for the perioperative management of patients with obstructive sleep apnea
CO2 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):

50. Conclusion
Capnography for sedation/analgesia/postoperative monitoring:
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

51. Be Prepared. Be Proactive

52. Continuing Capnography Education
Oridion Knowledge Center:
Three capnography courses available:
A Guide to Capnography during Procedural Sedation
A Guide to Capnography in the Management of the Critically Ill
A Guide to Monitoring etCO2 during Opioid Delivery