1. Capnography Mike McEvoy, PhD, NRP, RN, CCRN
EMS Coordinator – Saratoga County, NY
EMS Editor – Fire Engineering magazine
Cardiac Surgical ICU RN & Chair Resuscitation Committee – Albany Medical Center

2. Mike McEvoy: www.mikemcevoy.com

3. Outline: Carbon dioxide Capnography – what, where, why? Oxygenation
Ventilation
EtCO2 equipment
Waveforms
Uses
Cases

4. Carbon Dioxide = CO2 2 oxygen atoms + 1 carbon atom
Trace gas on earth ( %)
CO2 produced by:
Coal combustion (hydrocarbons)
Fermentation of beer
Respiration of living organisms
Plants: sunlight + CO2 + water  O2
Plants scavenge CO2 and, in the presence of sunlight, convert CO2 into oxygen.

5. Carbon Dioxide = CO2 Human body produces 2.3 # per day
Solid form = dry ice
Gas = fire extinguishers, carbonated drinks…

6. CO2 (Carbon Dioxide) Greenhouse gas (heavier than air) Global warming
Ocean acidification (carbonic acid)
CO2 is a well known Greenhouse gas that is considered responsible for global warming and acid rain which results in acifidication of large bodies of water.

7. Physiology of Metabolism
Oxygen  Lungs  alveoli  blood
Oxygen
Breath
CO2
Muscles + Organs
Lungs
Oxygen
CO2
Cells
The body uses oxygen, glucose and water to produce energy. The byproduct of this process (metabolism) is CO2. The more energy produced, the more CO2. The less metabolism (less energy produced), the less CO2.
ENERGY
Blood
Oxygen +
Glucose
CO2 7

8. Carbon Dioxide
Oxygen (O2) enters the body through the lungs and is used to produce energy
This process is called metabolism
Carbon Dioxide (CO2) is the waste product of metabolism

9. Typical Gas Percentages
Atmospheric
Exhaled
Nitrogen (N2)
78%
74%
Oxygen (O2)
21%
16%
Carbon Dioxide (CO2)
0.04% 4%
Water (H2O)
0.5% 6%
Atmospheric air is mostly nitrogen with some oxygen, trace amounts of CO2 and water. Exhaled air contains 4% CO2.
Normal Exhaled CO2 = 35 – 45 mmHg

10. CO2 In the Blood CO2 is your drive to breathe  CO2 causes air hunger
Goal is to maintain PaCO2 at 40
Body adjusts respiratory rate & depth
Oxygen does not affect respirations
CO2 is the gas that produces the respiratory drive. When CO2 levels increase, people experience air hunger. The body responds to increased CO2 in the blood by increasing respiratory rate and depth. Oxygen levels in the blood do not affect respirations in the vast majority of people.

11. Question:
What would happen if you injected CO2 into the blood? Respiratory rate and depth would 

12. Question:
Why do swimmers who hyperventilate loose consciousness underwater?  CO2 eliminates the drive to breathe
Swimmers who deliberately hyperventilate in order to hold their breath underwater for longer periods of time sometimes loose consciousness. The mechanism for this phenomena is marked reduction of CO2 induced by hyperventilation, resulting in loss of drive to breathe and elimination of air hunger. When the oxygen level in the blood drops below that needed to maintain consciousness, the swimmer passes out. The usual warning that s/he should surface to breathe is bypassed by hyperventilating before diving into the water.

13. Turns yellow when CO2 is detected
Measuring Exhaled CO2
Colorimetric
Capnometry
Capnography
In the 1970’s colorimetric devices were used to measure CO2. These devices use a piece of pH paper positioned in the airway to indicate the presence of CO2 by changing from purple to yellow.
Turns yellow when CO2 is detected

14. Colorimetric Pros Cons Accurate Secretions Cheap (~$10-15)
Changes color when CO2 present
Work for 2+ hours
Disposable
Cons
Secretions
Not quantitative
Adds dead space
False positives
Hard to read at night
Colorimetric devices are inexpensive, disposable and usually last for at least 2 hours (sometimes as long as 24 hours). They can be damaged when the pH paper gets wet from secretions resulting in false positive CO2 readings. It is difficult to quantify the amount of CO2 using a colorimetric device, although the degree of color change can suggest various levels of CO2. In small patients, the dead space added to the airway by placing a CO2 detector can be excessive.

15. Measuring Exhaled CO2 Capnometry Colorimetric Capnography
Second generation CO2 measuring devices were capnometers. These provide a respiratory rate and digital measurement of CO2 as well as a bar graph with each breath.

16. Capnometry Pros Cons Numeric value + RR Portable
Cheaper than waveform capnography
Cons
No waveform
Does not trend
Bulky adapter/unit
Capnometers are portable, provide more information than colorimetric devices but lack a waveform which would be helpful for visualizing trends and tend to be somewhat bulky (which means they may add additional weight to an advanced airway, potentially dislodging an endotracheal tube). In 2012, the EMMA Capnometer (Masimo Corp., Irvine CA) was redesigned to include a waveform which transformed the capnometer into a waveform capnography device.
PHASEIN
EMMA™ (Masimo)

17. Measuring Exhaled CO2 Capnography Colorimetric Capnometry
Waveform capnography is the third and current generation of devices used to measure exhaled CO2.

18. Capnography Pros Cons Numeric value + RR Waveform Trending
Very accurate
Cons
Expensive
Fragile
Warm-up time (some units)
Secretions
Temperature sensitive (some)
Waveform capnography is extremely accurate but expensive, fragile, prone to clogging from respiratory secretions and, in some cases, require time to warm up prior to use and/or are affected by environmental or patient temperature extremes.

19. Infrared Spectroscopy
CO2 absorbs 4.26 µm wavelength
Infrared light aimed at sample
Infrared sensors detect absorption and calculate CO2
CO2 in gas form absorbs light at the 4.26 micrometer spectrum.

20. Capnography Technologies
Sidestream (1st generation)
Sensor in remote location
Samples gas from circuit ( mL/min)
Mainstream (2nd generation)
Sensor in the airway
First generation CO2 technologies were sidestream devices. The sensor was in a remote location and sampled large amounts of gas from the respiratory circuit in order to make measurements. This large volume sampling mandated that sidestream analyzers have moisture traps. Second generation devices moved the sensor into the airway itself.

21. Capnography Technologies
Microstream® (next generation)
Sensor in remote location
Samples only 50 mL/min from circuit
Third generation devices (Microstream) work in a similar fashion to sidestream devices but sample significantly less air from the line, eliminating the need for a large moisture trap and allowing use in very small patients and in spontaneously breathing patients. Moisture is trapped by a filter placed in the Microstream connector.

22. SpO2 versus EtCO2
The is a significant difference between pulse oximetry and capnography.

23. Oxygenation and Ventilation
Oxygenation (Pulse Ox)
O2 for metabolism
SpO2 measures % of O2 in RBCs
Reflects changes in oxygenation within 5 minutes
Ventilation (Capnography)
CO2 from metabolism
EtCO2 measures exhaled CO2 at point of exit
Reflects changes in ventilation within 10 seconds
A quick summary of the two physiological processes. They require different monitoring modalities which are complimentary measures of your patient’s status.

24. Physiology of Metabolism
Oxygen  Lungs  alveoli  blood
Oxygen
Breath
CO2
Muscles + Organs
Lungs
Oxygen
CO2
Cells
In summary, pulse oximetry measures oxygen going IN to the body; capnography measures CO2 coming OUT of the body.
ENERGY
Blood
Oxygen +
Glucose
CO2 24

25. Pulse Oximetry Problems: Accuracy Motion & artifact Dyshemoglobins
Perfusion
Pulse oximetry has some problems.

26. Pulse Oximetry
First generation pulse oximetry has been known to produce a reading and a waveform even when not connected to patient.

27. Pulse Oximetry
First generation pulse oximetry sometimes produces “weird” readings. Seemingly healthy patients may exhibit very low saturations. When a blood gas is drawn, the actual oxygen saturation is found to be normal.

28. Model of Light Absorption At Measurement Site Without Motion
AC Variable light absorption due pulsatile volume of arterial blood
DC Constant light absorption due to non-pulsatile arterial blood.
DC Constant light absorption due to venous blood.
DC Constant light absorption due to tissue, bone, ...
Absorption
Time
IMPORTANT POINTS on the original design of pulse oximetry:
AC (alternating current) represents the arterial blood that is moving inside the body.
DC (direct current) represents the blood and other components that are not moving inside the body.
This is the Aoyagi model that assumed the only component that moves inside the body is the pulsating arterial blood.
One of the reasons for many false alarms for this model is that it does not accurately predict what is occurring inside the body. Aoyagi assumed that the only thing that moves in the body is pulsating arterial blood. So, when he uses the pulse for his in vivo calibration, if other components move, the reading will be in error.

29. Model of Light Absorption At Measurement Site With Motion
AC Variable light absorption due pulsatile volume of arterial blood
DC Constant light absorption due to non-pulsatile arterial blood.
AC Variable light absorption due to moving venous blood
DC Constant light absorption due to venous blood.
DC Constant light absorption due to tissue, bone ...
Time
Absorption
IMPORTANT POINTS
Moving (AC) venous blood is the main contributor to motion artifact.
This was not predicted by the Aoyagi design.
This effect is significant in monitored patients and causes erroneous values.
Aoyagi’s model was correct as long as the patient did not move. But as soon as the patient proceeded with even normal daily activity the above moving venous blood (AC) was introduced and affected the reading.

30. Influence of Perfusion on Accuracy of Conventional Pulse Oximetry During Motion
Good Perfusion (Conventional PO)
SpaO2=98
SpO2=93
SpvO2=88
Poor Perfusion (Conventional PO)
IMPORTANT POINTS
Venous averaging is a significant clinical problem.
When the perfusion is good the effect is only slightly observed.
When perfusion is very poor, the effect can be dramatic and cause an inappropriate clinical response.
Common Cause of a False Alarm:
This effect can be demonstrated with a motion low perfusion ice water demonstration. By cooling the hand using a glass of ice water and then moving the cold hand with a conventional sensor attached, poor peripheral perfusion (the second example above) can be simulated. The moving venous blood causes a conventional oximeter to average the arterial and venous values together and report a value between arterial and venous. This erroneous value will set off alarms, bring the clinician to the bedside, and potentially waste caregiver time responding to the situation. If this situation persists, the caregiver may silence or turn off the alarms and put the patient at risk for a true desaturation event later.
SpaO2=98
SpO2=74
SpvO2=50

31. Conventional Pulse Oximetry Algorithm
Digitized, Filtered & Normalized
R/IR
Post Processor
% Saturation
R & IR
MEASUREMENTT
CONFIDENCE
3 options during motion or low perfusion:
Freeze last good value
Lengthen averaging cycle
Zero out
In conventional pulse oximetry, the incoming red and infrared signals are received from the photodetector. In many of the newer oximeters, the signals are digitized. The signals then pass through band filters to remove much of the unwanted artifact above and below the signal bandwidth. These filters address external noise sources like electrical devices or mechanical artifact. After the signals have been filtered, a red to infrared ratio is calculated. This calculated ratio is compared to a “look up” table that converts the red to infrared ratio to a corresponding SpO2%.
Once the SpO2 is calculated, the oximeter’s decision matrix must decide if the data is reportable or not.
If the decision is “Yes, it looks good” the SpO2 and pulse rate are reported. If the decision is ‘No, this looks questionable” , there are a few paths the oximeter can take depending on what the oximeter manufacturer has programmed into the system. Some oximeters might “lie” and freeze or continue to display the last valid SpO2 and pulse rate value it recorded for one minute or longer, regardless of the patient’s changing clinical status. Others might go into a longer averaging cycle “hoping” that whatever was interfering with the signal will just go away or self resolve. Some device will just “zero out” and give up. Regardless of whether the oximeter chooses to “lie, hope or give up” the clinician no longer has reliable pulse oximetry data, often in situations when it is needed the most..

32. Next Generation Pulse Oximetry
Each manufacturer has designed confidence based algorithms to improve the accuracy of their pulse oximetry. Nellcor (now Covidien) uses an algorithm that focuses on the accuracy of the pulse rate being detected by the oximeter.

33. Next Generation Pulse Oximetry
Philips also uses a confidence based algorithm.

34. Masimo SET: Signal Extraction Technology
R/IR (Conventional Pulse Oximetry)
Confidence Based Arbitrator
% % 97% 100%
SpO2%
Post Processor
Digitized, Filtered & Normalized
% Saturation
SSTTM
Proprietary Algorithm 4
DST
SET – 97%
DSTTM
FSTTM
MEASUREMENT
CONFIDENCE
R & IR
IMPORTANT POINTS
1) Signal Extraction Technology uses a variety of algorithms or engines. Each is designed for a different type of signal noise.
2) The confidence based arbitrator determines which engines are providing the most accurate saturation value and displays that value.
3) Discrete Saturation Transform is the most powerful engine and can remove the noise caused by moving venous blood which is the number one cause of motion artifact.
While this slide may look complicated, focus on the R/IR, DST engines and the Confidence based Arbitrator. The R/IR engine is the same as other conventional pulse oximeters and reads accurately about 50% of the time. When patients are healthy, well perfused and without motion artifact, most pulse oximeters can determine the saturation.
As was discussed earlier, DST can remove the number one cause of motion artifact which is moving venous blood. It is used about 25 % of the time and eliminates the false reading associated with venous blood artifact.
Finally, the confidence based arbitrator gives SET the ability to change as patient conditions change. It can select from any one or a combination of the engines and accurately determine the saturation in spite of challenging conditions.
SET “Parallel Engines”

35. Averaging - inaccurate Measure Through Motion Pulse Oximetry
Discrete Saturation Transform (DST)
SET separates the venous and arterial saturation values (conventional oximetry averages the values to produce a reading)
Variable
Constant
% % % % 100%
SpO2%
Averaging - inaccurate
% % % % %
SpO2%
Measure Through Motion Pulse Oximetry
Separating - accurate
Masimo actually identifies both the arterial and venous signals and displays only the arterial oxygen saturation value.
Conventional Pulse Oximetry

36. Carbon Monoxide (CO) Gas: Physical Properties: Colorless Odorless
Tasteless
Nonirritating
Physical Properties:
Vapor Density = 0.97
LEL/UEL = 12.5 – 74%
IDLH = 1200 ppm
Physical properties of carbon monoxide (a dyshemoglobin): Vapor Density is just about equal to that of the ambient air. This means that rather than rising to the highest point (lighter than air) or sinking to the low lying areas, CO acts like the ambient air and travels through the entire occupancy, following natural air flow. This translates to poisonous gasses presenting themselves across the occupancy, rather than lingering near the offending source, and exposure should never be ruled out because the occupants’ report that they were not near fuel fired appliances. The flammability range, expressed as the range between the Upper Explosive Limits (UEL) and the Lower Explosive Limits (LEL) is rather wide, therefore efforts to control ignition sources should be undertaken. The Immediately Dangerous to Life and Health is expressed as the IDLH in parts per million. While this number may seem a bit on the high side, EMS providers should take caution as they typically do not respond with self-contained breathing apparatus (SCBA) and atmospheric levels in an enclosed environment can climb rather quickly. The bond length is pm.

37. Limitations of Pulse Oximetry
Conventional pulse oximetry can not distinguish between COHb and O2Hb
From Conventional Pulse Oximeter
SpCO-SpO2 Gap:
The fractional difference between actual SaO2 and display of SpO (2 wavelength oximetry) in presence of carboxyhemoglobin
From invasive CO-Oximeter Blood Sample
IMPORTANT POINTS
The arterial oxygen saturation (SpO2) from conventional two-wavelength pulse oximetry is inaccurate (often significantly inaccurate) in the presence of CO poisoning.
Two-wavelength pulse oximeters actually count carboxyhemoglobin as oxyhemoglobin
The reported functional value often lends a false sense of security that the patients oxygenation status is good, as SpO2 may read normal even when significant COHb is poisoning the patient.
A standard 2 wavelength oximeter adds to the problem. They only read 2 parameters, which result in a ratio of the oxyhemoglobin to the hemoglobin that is available for binding . This is called the Functional value and does not decrease
to any significant degree, as shown by the graph above, even when exposed to high levels of CO. In this experiment a dog is exposed to CO and the pulse oximeter only decreases slightly to 90% when the actual oxyhemoglobin saturation is 30%. This actual saturation value is called the fractional saturation. Fractional saturation is not subjected to this false reading and would have read 30% in this situation.
Barker SJ, Tremper KK. The Effect of Carbon Monoxide Inhalation on Pulse Oximetry and Transcutaneous PO2. Anesthesiology 1987; 66:

38. Pulse CO-oximetry
The RAD-57 is a pulse CO-oximeter. It is able to measure both oxygen (oxyhemoglobin) and carbon monoxide (carboxyhemoglobin) in the blood.

39. Pulse CO-oximetry Uses multiple wavelengths of light
Differentiates CO from O2
This is accomplished by using multiple (8+) wavelengths of light, some visible and some invisible spectra.

40. Hgb Signatures: Physics of O2 Pathways
Extinction coefficients comparable to Absorption wavelengths of each analyte (in mm-1). Invisible spectrum range 660 to 940 nm.

41. Protect from ambient light
SpCO User Concerns
Multiple wavelengths of light (8+) =
Probe Placement:
Probe fits the finger
Centered over nail bed
Visible spectrum light =
Protect from ambient light
Sunlight, strobes, etc.
The fact that CO is measured in a visible spectrum of light means that it is particularly susceptible to interference from visible light. Because the technology is using multiple wavelengths of light, probe positioning and probe size is much more important than a conventional pulse oximeter (which uses only 2 beams of light). If the probe is misplaced (or too large for the finger), light will pass around the finger (instead of passing through the finger). This may result in false CO readings.

42. Know Your Equipment
It is important to know your equipment.

43. Back to CO2… What does exhaled CO2 tell us? Ventilation Perfusion
Metabolism
Back to CO2 – exhaled CO2 provides information about ventilation, perfusion, and metabolism.

44. Endotracheal Intubation
Endotracheal intubation is a high risk procedure.

45. What Should Happen Lungs (Good) $tomach (Bad, Very Bad)
A missed esophageal intubation can be catastrophic.
$tomach (Bad, Very Bad)

46. Anesthesia Litigation
Anesthesiologists in the 1960’s and 1970’s had the highest malpractice rates of any medical profession, largely due to lawsuits for unrecognized esophageal intubations. 46

47. Respiratory Damaging Events
Capnography Introduced
Beginning in the 1980’s, anesthesiologists using end tidal CO2 were able to reduce their claims for respiratory damaging events. Today, malpractice insurance premiums for anesthesiology providers are among the lowest in the medical community.
American Society for Anesthesiologists: Closed Claims Project Database, 2010 47

48. #1 Capnography Use for EMS:
Paramedics have the same risks as anesthesiologists. This is the number one use of end tidal CO2 monitoring.

49. Guidelines 2005 EtCO2 recommended to confirm ET tube placement
Capnography was first recommended in the AHA Guidelines 2005.

50. Intubated Patient Airway adapter plugs into LifePak®
Be sure adapter is tightly attached
If not seated, waveform may flatten
An important consideration in using capnography is to assure that the connector is tightly screwed into the monitor. If the connector is not firmly seated, atmospheric air will be pulled into the monitor from around the connector, resulting in poor or no end-tidal CO readings.

51. Capnography Information
Respiratory Rate
End Tidal Carbon Dioxide
Waveform capnography provides three pieces of information.
Capnography Waveform

52. Capnography Waveforms
The higher the waveform, the more CO2
Normal EtCO2 is 35 – 45 mmHg (usually the same as arterial CO2) 45
The height of the waveform equates to the amount of CO2.

53. Capnography Waveforms
The length of the waveform corresponds to respiratory rate
Hyperventilation 45
The length of the waveform corresponds to the respiratory rate. The shorted the waveform, the faster the rate. 45
Hypoventilation

54. Inspiration or manual ventilation with a bag-valve-mask or ventilator
Capnography Waveform
Inspiration or manual ventilation with a bag-valve-mask or ventilator 54

55. Capnography Waveform
Exhalation 55

56. Capnography Waveform End-tidal
End-tidal (EtCO2) is the end point of expiration. This is the point on the waveform that produces the numeric CO2 value. 56

57. Capnogram Parts
Start of exhalation
No CO2 (dead space)
Phase I 57

58. Capnogram Parts Phase II Exhalation continues Rapid rise in CO2
Mixing dead space & alveolar gases 58

59. Capnogram Parts Phase III also called the Alveolar Plateau
End exhalation
All alveolar gas 59

60. Capnogram Parts
Phase IV
Rapid drop in CO2
Start of inhalation 60

61. Capnogram Angles  (beta angle)  (alpha angle)  normal = 90°
Rebreathing will 
 normal = 100 – 110°
Airway obstruction will  61

62. Capnography Waveforms
Normal 45
Hyperventilation 45
Hypoventilation 45

63. Intubation
You have intubated a 36 year old motorcyclist laying in the roadway
HR 128, RR 14 by BVM, SpO2 99%
Esophageal intubation
6 breaths to evacuate gastric CO2
The standard practice for “washing out” gastric CO2 is to provide 6 breaths and then measure CO2. If the tube is in the esophagus, 6 breaths will wash out any gastric CO2.

64. SpO2 will not drop for several minutes (5+ minutes)
What about the Pulse Ox?
Sp02 98
Pulse oximetry takes considerably longer to drop once breathing ceases.
SpO2 will not drop for several minutes (5+ minutes)

65. Intubation You re-intubate the motorcyclist
This is the capnography waveform:
Is the tube in?
Is the ventilation rate and depth appropriate?
mmHg
Yes, the tube is now appropriately located in the trachea. The respiratory rate of 16 and depth (size of breaths) is adequate as the exhaled CO2 is 39, midway between the target of mmHg.

66. During Transport
Enroute to the trauma center, you observe this on the capnography:
What happened?
When is this most likely to occur?
Tubes most commonly displace during patient movement
The tube came out. This most commonly occurs with patient movement, often at the moment the patient is transferred to the ED stretcher. This is a major reason for documenting the presence of a good capnography waveform following endotracheal intubation and during transport.

67. Ventilator Transport
You are moving a 23 yo GSW to the head from a community ED to a neurosurgical ICU
He is intubated and sedated:
EtCO2 = 35, RR = 24
“Curare Cleft” = diaphragmatic movement (breathing over drugs)

68. Ventilator Transport You don’t make any changes
The patient appears to awaken:
EtCO2 = 30, RR = 38
“Curare Cleft” = diaphragmatic movement (breathing over drugs)
“Bucking” ventilation needs drug tx

69. Ventilator Transport You are moving a ventilated patient
The patient appears short of breath
Waveform does not return to zero
Baseline gradually increasing
This is called “rebreathing”
Rebreathing is more often seen in patients on mechanical ventilation and is often association either with excessive respiratory rates or faulty ventilator equipment. It is sometimes referred to as “breath stacking”

70. Ventilator Transport
You’re cardiac arrest reversal is unresponsive, on BVM ventilation
BP 110/58, HR 90, RR 22, SpO2 97
Is the patient ventilating?
Causes: cuff leak, ETT displaced…
NOT WELL

71. Cardiac Arrest

72. Carbon Dioxide (CO2) Production
Oxygen Circulation Respiration
Carbon Dioxide

73. Carbon Dioxide (CO2) Production
Cardiac Arrest
In cardiac arrest, CO2 production stops.
Oxygen Circulation Respiration
Carbon Dioxide

74. AHA Guidelines 2010
Continuous quantitative waveform capnography recommended for intubated patients throughout peri-arrest period. In adults:
Confirm ETT placement
Monitor CPR quality
Detect ROSC with EtCO2 values

75. 1. Confirm ET placement
When is an advanced airway most likely to become dislodged?
During patient movement

76. 2. Monitor the quality of CPR
Try to maintain a minimum EtCO2 of 10 mmHg
Push
HARD (> 2” or 5 cm)
FAST (at least 100)
Change rescuer
Every 2 minutes
In actuality, high quality CPR should produce near normal end-tidal values.

77. CPR in progress: Compression depth Compression rate Compressor
Extreme acidosis
Futility
Other?
Reasons for low EtCO2 during CPR can be related to any of these.

78. High-Quality CPR =  CO2
High quality CPR will produce near normal EtCO2 values. 78

79. 3. EtCO2 to detect ROSC (Return Of Spontaneous Circulation)
90 pre-hospital intubated arrest patients
16 survivors
13 survivors: rapid rise in exhaled CO2 was the earliest indicator of ROSC
Before pulse or blood pressure were palpable
Using an EtCO2 of 10 mmHg or less as a theoretical threshold to predict death in the field successfully discriminated between the 16 survivors to hospital admission (those that achieved return of spontaneous circulation) and 75 prehospital deaths. Of the 16 survivors to hospital admission, 9 died in the hospital, and 7 were discharged from the hospital alive. In 13 of the 16 survivors, the first evidence of return of spontaneous circulation, before a palpable pulse or blood pressure, was a rising ETCO2.
Wayne MA, Levine RL, Miller CC. “Use of End-tidal Carbon Dioxide to Predict Outcome in Prehospital Cardiac Arrest” . Annals of Emergency Medicine. 1995; 25(6):
Levine RL., Wayne MA., Miller CC. “End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest.” New England Journal of Medicine. 1997;337(5):

80. 3. EtCO2 to detect ROSC Question: Would bicarbonate  EtCO2?
ROSC is associated with significantly increases EtCO2. Administering bicarb will transiently elevate CO2 as acids buffered by the bicarbonate in the blood are eliminated as CO2.
Question: Would bicarbonate  EtCO2?
Answer: Yes

81. CPR – What Causes This? Notice the small “ripples” ?
Compressions generate air movement – this expels CO2

82. Spontaneously Breathing
Capnography helps assess:
Accurate respiratory rate
Airway patency (bronchospasm, air trapping, obstruction)
Shock states
Response to treatment

83. Bronchospasm Asthma, COPD…
Elevation of  angle, loss of alveolar plateau (“shark-fin” appearance)
Degree of angle = severity

84. Effects of Treatments
This is a patient with significant SOB. With nebulizer treatment, the waveform demonstrates resolution of the bronchospasm.

85. Air Trapping Emphysema is results in prolonged expiration
Increases  angle:
Emphysema results in air trapping (difficulty inhaling). Hence, the beta angle increases and the alveolar plateau dips downward.

86. Unconscious
16 yo found unresponsive in high school locker room – unknown hx
Hypoventilation (? pharmaceutical)
Use capnography on EVERY patient you treat with narcotics!
The best way to observe respiratory effort and rate is with capnography. Every patient given narcotics should have continuous waveform capnography monitored.

87. Difficulty Breathing 14 yo asthmatic – severely SOB Hyperventilation
No evidence of airway obstruction or air trapping
Fast respiratory rates are difficult for the capnography equipment to accurately track. Waveforms then, loose their crisp appearance in pediatric and neonatal patients as well as in adults with high respiratory rates.

88. Difficulty Breathing 81 yo with COPD and heart failure
Acutely short of breath
Capnogram favors pulmonary edema (no evidence acute COPD exacerbation)

89. Same Patient – Diff Breather
81 yo with COPD and heart failure
Acutely short of breath
Capnogram favors COPD exacerbation

90. Chest Pain 51 yo with substernal chest pain No distress, STEMI work up
“Cardiac oscillations” – cardiac pressures being transmitted to airway (ripple effect)

91. Perfusion and pH Cardiac arrest = no CO2
Capnography reflects perfusion
 cardiac output =  EtCO2
CO2 is transported in the blood as bicarbonate (HCO3)
In severe acidosis,  HCO3 =  EtCO2
In cardiac arrest, no CO2 is produced. In profound metabolic acidosis, CO2 is used in the blood to combine with the acids and is not exhaled. The lower the bicarb level in the blood (i.e., the more acidotic the patient) the lower the exhaled CO2 will be.

92. Post Cardiac Arrest Patient
You have resuscitated a 47 yo pt. found in v-fib on a city bus
The patient is unresponsive, ventilated by BVM; pulses are weak
Suspect falling cardiac output!

93. 17 yo pt. in DKA
You are called to a physician office to transport a patient in DKA
The patient is alert and oriented; blood sugar is reportedly 880
This is another waveform tracing from a 17-year-old in diabetic ketoacidosis. Note here again the extremely low cardiac arrest level EtCO2 of 6 millimeters of mercury, and a corresponsive pH of This waveform tracing illustrates how sensitive and accurate capnography is in detecting conditions of metabolic acidosis.

94. General Weakness Patient
You are called to see a 75 yo heart failure pt. with general weakness
She is cool, BP 80/50, HR 128 afib
What does the capnography say?
Low perfusion associated with lactic acidosis will produce a low EtCO2!
Cardiogenic Shock!

95. Rounded Waveforms Be suspicious of rounded waveforms:
These often imply low perfusion, acidosis, sepsis, poisoning or other metabolic derangements

96. Review

97. Label Inhalation & Exhalation
Expiration
Inhalation 97

98. Where is EtCO2 Measured?
End-tidal CO2
Normal EtCO2 is
35 – 45 mmHg 98

99. AHA Guidelines 2010
What are the three reasons for use of continuous quantitative waveform capnography during cardiac arrest?
Confirm ETT placement
Monitor CPR quality
Detect ROSC with EtCO2 values

100. Goals During Cardiac Arrest
Try to maintain a minimum EtCO2 of ?
10 mmHg
Push
HARD (> 2” or 5 cm)
FAST (at least 100)
Change rescuer
Every 2 minutes

101. Review 14 yo patient, SOB, asthma hx Clutching her albuterol inhaler
Slow upstroke = bronchospasm

102. Review 67 yo COPD patient, acute SOB SpO2 97%, HR 88, BP 138/86
Normal waveform, hyperventilation

103. Review 74 yo ROSC post v-fib arrest, unconscious, on ventilator, VSS
Cleft (“curare cleft”) suggests non-compliance with vent

104. Review
45 yo auto-pedestrian, bilateral tib-fib fractures, BP 120/60, HR 90, RR 16, SpO2 97%, EtCO2 45
Normal waveform

105. Review Elderly cancer pt., unresponsive at home in bed
Normal waveform – hypoventilation
RR 4, EtCO2 75 (> than 70 in without COPD = respiratory failure)

106. Review
60 yo COPD patient fever, chest pain, denies SOB, using accessory muscles to breathe
Prolonged expiration (  angle); air trapping – normal capnogram in emphysema

107. Review
90 year old cardiac arrest, immediately after endotracheal intubation:
Esophageal intubation
6 breaths to evacuate gastric CO2

108. Review 55 yo COPD patient with flu like s/s
Cardiac oscillations – normal EtCO2

109. Review
18 yo GSW to chest
Profound hypoperfusion – arrest imminent

110. Thanks for your attention! Slides posted at: www.mikemcevoy.com
Questions?
Thanks for your attention! Slides posted at:
Mike McEvoy
Slides available at -> choose “Open Bar” tab