End Tidal CO 2 (EtCO 2 ) Monitoring

END TIDAL CO2

(ETCO2) MONITORING

EtCO2 Monitoring

“Snapshot in time” Assists with patient assessment BUT:

–Do NOT replace eyes-on/hands-on care–Are just one piece of clinical judgment–ALL have pitfalls/malfunctions/limitations–Is more complex than ever

EtCO2 Monitoring

Non-invasive method of determining Carbon Dioxide levels in

intubated and non-intubated patients

Uses infra-red technology, to monitor exhaled breath to determine CO2 levels numerically and by

waveform (capnogram).

EtCO2 Monitoring

EtCO2 is directly related to the ventilation status of the patient (as opposed to SAo2, which relates oxygenation of the patient)

Capnography can be used to verifyendotracheal tube/Combi-Tube & King Airway placement and monitor its position, assess ventilation and treatments, and to evaluate resuscitative efforts during CPR

EtCO2 Monitoring Review of Pulmonary

Anatomy & Physiology

The primary function of therespiratory system is toexchange carbon dioxide foroxygen.

During inspiration, air enters theupper airway via the

nose where it is warmed, filtered, and humidified

The inspired air flows throughthe trachea and bronchial

tree to enter the pulmonary alveoli where the oxygen diffuses across the alveolar capillary membrane into the blood.

Nasal Passages

Roof of the Mouth

Epiglottis

Trachea (windpipe)Esophagus (food tube)

Alveoli

BronchiPulmonary VeinBronchiole

Cellular Ventilation

EtCO2 Monitoring

EtCO2 Monitoring

Alveolar Ventilation

EtCO2 Monitoring

Measurement methods Single, one-point-in-time (Easy-Cap).

Electronic devices Continuous information Utilize infrared (IR) spectroscopy to measure the

CO2 molecules’ absorption of IR light as the light passes through a gas sample.

EtCO2 Monitoring Electronic Devices:

Mainstream Located directly on the patient’s endotracheal tube

Sidestream Remote from the patient.

Mainstream sampling Occurs at the airway of an intubated patient Was not originally intended for use on non-intubated

patients. Heavy and bulky adapter and sensor assemblies may

make this method uncomfortable for non-intubated patients.

EtCO2 Monitoring Sidestream sampling

Exhaled CO2 is aspirated (at 50ml/min) via ETT, cannula, or mask through a 5–10 foot long

sampling tube connected to the instrument for analysis

Both mainstream and sidestream technologies calculate the CO2 value and waveform.

EtCO2 Monitoring A new technology, Microstream, utilizes a

modified sidestream sampling method, and employs a microbeam IR sensor that

specifically isolates the CO2 waveform.

Microstream can be used on both intubatedand non-intubated patients.

EtCO2 Monitoring• Continuous EtCO2 monitoring = changes are immediately seen

(CO2 diffuses across the capillary-alveolar membrane <½ second)• Sa02 monitoring is also continuous, but relies on trending.

- and -• The oxygen content in blood can maintain for

several minutes after apnea (especially w/ pre-oxygenation)

EtCO2 Monitoring Definitions

Tachypnea Abnormally rapid respiration

Hyperventilation Increased minute volume that results in lowered CO2

levels (hypocapnia)

Hypoventilation Reduced rate & depth of breathing that causes an

increase in carbon dioxide (hypercapnia)

EtCO2 Monitoring EtCO2 Numerical Values

(Ventilatory Assessment)

Normal = 35-45mmHg

< 35mmHg = Hyperventilation Respiratory alkalosis

> 45mmHg = Hypoventilation Respiratory acidosis

EtCO2 Monitoring EtCO2 Numerical Values

(Metabolic Assessment)

Normal = 35-45mmHg < 35mmHg = Metabolic Acidosis > 45mmHg = Metabolic Alkalosis

Dependant on 3 variables CO2 production Delivery of blood to lungs Alveolar ventilation

EtCO2 Monitoring Increased EtCO2

Decreased CO2 clearance Decreased central drive Muscle weakness Diffusion problems

Increased CO2 Production Fever Burns Hyperthyroidism Seizure Bicarbonate Rx ROSC Release of tourniquet/Reperfusion

EtCO2 Monitoring Decreased EtCO2

Increased CO2 Clearance Hyperventilation Acidosis ( ↓ HCO3 levels 2° to ↑ Hydrogen) Decreased CO2 production

Hypothermia Sedation Paralysis

Decreased Delivery to Lungs Decreased cardiac output

V/Q Mismatch Ventilating non-perfused lungs (pulmonary

edema)

EtCO2 Monitoring

Ventilation/Perfusion Ratio (V/Q)• Effective pulmonary gas exchange depends on

balanced V/Q ratio• Alveolar Dead Space (atelectasis/pneumonia)

(V > Q = CO2 content)• Shunting (blood bypasses alveoli w/o picking up o2)

(V < Q = CO2 content)• 2 types of shunting:

• Anatomical – blood moves from right to left heart w/o passing through lungs (congenital)

• Physiological – blood shunts past alveoli w/o picking up o2

EtCO2 Monitoring

EtCO2 Monitoring Ventilation/Perfusion Ratio (V/Q)

V/Q Mismatch Inadequate ventilation, perfusion or both 3 types

Physiological Shunt (V<Q) Blood passes alveoli Severe hypoxia w/ > 20% bypassed blood Pneumonia, atalectasis, tumor, mucous plug

Alveolar Dead Space (V>Q) Inadequate perfusion exists Pulmonary Embolus, Cardiogenic shock, mechanical ventilation w/

tidal volumes Silent Unit ( V & Q)

Both ventilation & perfusion are decreased Pneumothorax & ARDS

EtCO2 Monitoring

More Air Less BloodV > Q

Equal Air and BloodV = Q

More Blood Less Air

V < Q

EtCO2 Monitoring

EtCO2 Monitoring Components of the normal

capnogram

EtCO2 Monitoring

A - B =respiratory baseline CO2-free gas in the deadspace of the

airways

EtCO2 Monitoring

B-C (expiratory upstroke) Alveolar air mixes with dead space air

EtCO2 Monitoring

C-D (expiratory plateau) Exhalation of mostly alveolar gas

(should be straight) Point D = measurement point

(35-45mmHg)

EtCO2 Monitoring

D-E =inspiration Inhalation of CO2-free gas

EtCO2 Monitoring

EtCO2 Monitoring

Changes in the capnogram or EtCO2 levels: Changes in ventilation Changes in metabolism Changes in circulation Equipment failure

EtCO2 Monitoring

EtCO2 in specific settings

Non-Intubated patients Asthma & COPD CHF/Pulmonary Edema Pulmonary Embolus Head Injury Metabolic Illnesses

EtCO2 Monitoring

Asthma and COPD Provides information on the ventilatory status of the

patient Combined with other assessments, can guide treatment

EtCO2 Monitoring

Asthma and COPD (Cont’d) Shark fin waveform

EtCO2 Monitoring

Asthma and COPD (Cont’d) Ventilatory assistance and/or intubation

may be considered with severe dyspneaand respiratory acidosis (EtCO2 >50mmHg)

18% of ventilated asthma patients suffer atension pneumothorax

New ACLS standards recommend ETI forasthma patients who deteriorate despiteaggressive treatment.

EtCO2 Monitoring

Emphysema

EtCO2 Monitoring

EtCO2 & CHF/Pulmonary Edema Wave forms will be normal (there is no

bronchospasm) Values may be increased (hypoventilation) or

decreased (hyperventilation)

EtCO2 Monitoring

Pulmonary Embolus

“Normal” waveform but low numerical value(why?)

Look for other signs and symptoms

EtCO2 Monitoring Pulmonary Embolus Note near “normal” waveform, but angled C-

D section (indicates alveolar dead space)

EtCO2 Monitoring

EtC02 is very useful in monitoring intubated head- injured patients.

Hyperventilation = Hypocapnia = Cerebral Ischemia

Target EtC02 value of 35-38 mmHg

Head Injury

EtCO2 Monitoring

Hypothermia

EtCO2 Monitoring

Hyperventilation

EtCO2 Monitoring

Hypoventilation

EtCO2 Monitoring

EtCO2 in the Intubated Patient

Identifies esophageal intubations & accidental extubations (head/neck motion can cause ETT movement of 5 cm)

Waveforms/numerical values are absentor greatly diminished

Do not rely on capnography alone to assureintubation!

EtCO2 Monitoring

Tracheal –vs- Esophageal Intubation

EtCO2 Monitoring

Esophageal Intubation

EtCO2 Monitoring Esophageal Intubation w/carbonated

beverages

EtCO2 Monitoring EtCO2 and cardiac output

Values <20mmHg = unsuccessful resuscitation Low (20-30mmHg) = good CPR or recovering heart

EtCO2 Monitoring• EtCO2 and cardiac output• Sudden increase in value = ROSC

Cardiac arrest survivors had an average ETCO2 of 18mmHg, 20 minutes into an arrest while non survivors averaged 6. In another study, survivors averaged 19, and non-survivors 5.

EtCO2 MonitoringEtCO2 and cardiac output

Successful defibrillation = pulses & EtcO2

EtCO2 MonitoringEtCO2 and cardiac outputBecause ETCO2 measures cardiac output, rescuer fatigue during CPR will show up as decreasing ETCO2.

Change in rescuers – Note values w/ non-fatigued compressor

EtCO2 Monitoring

Right Mainstem Bronchus Intubation

Numerical Values and Waveforms may/may notchange, but SAo2 will drop

EtCO2 Monitoring

Kinked ET Tube

No alveolar plateau – very limited gas exchange

EtCO2 Monitoring Spontaneous Respirations in the

paralyzed patient (Curare Cleft)

Metabolic States Diabetes/Dehydration

EtCO2 tracks serum HCO3 & degree ofacidosis ( EtcO2 = metabolic

acidosis) Helps to distinguish DKA from NKHHC and

dehydration

EtCO2 Monitoring

Metabolic StatesEtCO2 Monitoring

EtCO2 monitoring will show you thecorrect respiratory rate, too.

Define “Synypnea”

EtCO2 Monitoring

Synypnea is seen across the country and is defined as when emergency

department waiting room patients have the same respiratory rate.

EtCO2 Monitoring

EtCO2 MonitoringTroubleshooting

Sudden increase in EtCO2

Malignant HyperthermiaVentilation of previously unventilated lung

Increase of blood pressureRelease of tourniquet

Bicarb causes a temporary <2 minute rise in ETCO2

EtCO2 Monitoring

EtCO2 values 0

Extubation/Movement into hypopharynxVentilator disconnection or failure

EtCO2 defectETT kink

Troubleshooting

EtCO2 Monitoring

Sudden decrease EtCO2 (not to 0)

Leak or obstruction in systemPartial disconnect

Partial airway obstruction (secretions)High-dose epi can cause a decrease (unk why)

Troubleshooting

EtCO2 Monitoring

Change in Baseline

Calibration errorMechanical failureWater in system

Troubleshooting

EtCO2 Monitoring

Continual, exponential decrease in EtCO2

Pulmonary EmbolismCardiac Arrest

Sudden hypotension/hypovolemiaSevere hyperventilation

Troubleshooting

EtCO2 Monitoring

Gradual increase in EtCO2

Rising body temperatureHypoventilation

Partial airway obstruction (foreign body)Reactive airway disease

Troubleshooting

Many special thanks to: JEMS Magazine (http://www.jems.com/) Peter Canning, EMT-P (http://emscapnography.blogspot.com/) Dr. Baruch Krauss (baruch.krauss@tch.harvard.edu) Bhavani-Shankar Kodali MD (http://www.capnography.com/) Bob Page, AAS, NREMT-P, CCEMT-P Steve Berry (https://www.iamnotanambulancedriver.com/mm5/merchant.mvc?) Dr. Reuben Strayer (reuben.strayer@mail.mcgill.ca) UTSW/BIOTEL EMS SYSTEM (http://www.utsouthwestern.edu/) Oridion Medical Systems (http://www.oridion.com/global/english/home.html) Blogborgymi (http://blogborygmi.blogspot.com/) University of Adelaide, South Australia

(http://www.health.adelaide.edu.au/paed-anaes/talks/CO2/capnography.html)