70% in patients in cardiac arrest– clogged, no CO2-O2 exchange taking place (cellular metabolism) 5%= 35-37 mmHg Yellow could by gastric acid, drugs
CO2 enters blood, most diffuses into red blood cells, which contain the enzyme CARBONIC ANHYDRASE. The enzyme catalyzes the reaction of carbon dioxide and water to form carbonic acid: Carbonic acid then dissociates. The Bicarbonate ions diffuse out of the red blood cells into the plasma, leaving HYDROGEN IONS (HEMOGLOBIN BUFFERS THE IONS, CL- (CHLORIDE IONS) enter the red blood cell When the blood reaches the lungs, an area of lower PCO2, these reactions are reversed, CO2 is re-formed and diffuses into the alveoli. Eliminated during exhalation
O2 carried by weak bond with hemoglobin (98.5%) each hemoglobin can bind FOUR molecules of O2 (HbO2) oxyhemoglobin 10%= dissolved in blood 20%= HbCO2= carbaminohemoglobin 70%= bicarbonate ions
Stroke volume- amount of blood ejected by the left ventricle with each contraction approximately 60-80ml. Varies with age, sex, health. Tidal volume- amount of air inspired and expired in a normal breath.
Low cardiac output caused by cardiogenic or hypovolemia resulting from hemorrhage wont carry as much co2 back to the lungs, resulting in lower co2. Doesn’t mean the pt is hyperventilating, or their arterial co2 level will be reduced. Reduced perfusion to the lungs alone causes this phenomenon. Lung function is perfectly normal.
Beta angle increases with rebreathing
Hydrogen cyanide byproduct of combustion, plastics in house fires. CO= Leading cause of death from fire. Hemoglobin’s affinity for CO is over 240 times greater than O2. CO forms CARBOXYHEMOGLOBIN (COHb)
Stop compressions for 20 seconds decreased survival by 50%.
A sudden rise in EtCO 2 indicates increased cardiac output. Cardiac output immediately after ROSC is often low and drugs such as epinephrine can produce peripheral vasoconstriction, so palpating a pulse may be very difficult. The presence of an organized rhythm on the monitor accompanied by a sudden increase in EtCO 2 indicates ROSC has occurred and cardiac output has improved despite questionable pulses.
Hypercapnia causes cerebral vasodilation, which causes increased CBF, and further elevates ICP. Hypocapnia causes cerebral vasoconstriction, reduce ICP. Resulting in hypoperfusion. MAP-ICP=CPP
CAPNOGRAPHY presented by: Fred Halazon, NREMT-P Mike Burke, NREMT-P Cunningham Fire
What is Capnography?Noninvasive, continuous measurement ofexhaled carbon dioxide concentration over timeDigital display provides EtCO2 valueProvides a distinct waveform for eachrespiratory cycle
OverviewHistoryAnatomy & PhysiologyCapnographic waveformDiagnosing different waveformsCase studies
RelevanceETT VerificationCardiac ArrestVentilationBronchospastic DiseaseEarly detection of cellular hypoxia
History of capnographyUsed byanesthesiologistssince the 1970sStandard of care inthe OR since 1991
History of Capnography in EMSColormetric- Useful device to confirm ETtube placement in patients not in cardiacarrestTube could be in esophagus or thatcirculation is not bringing CO2 to thelungsProne to contamination, leads to falsenegatives
History of Capnography in EMSPulse oximetry preceded capnographyPulse oximetry measures oxygenationCapnography measures ventilationNew technologies now allow use in EMS
CapnometryProvides only a numerical measurementof carbon dioxide (EtCO2)
CapnogramA waveform display of carbondioxide over time
Definition of CapnographyNumerical value of the EtCO2 ANDWaveform of the concentration present inthe airwayRespiratory rate detected from the actualairflow
DefinitionsPACO2—Partial pressure of CO2 in the alveoliPaCO2—Partial pressure of CO2 in arterialbloodPEtCO2—Partial pressure at the end ofexpirationPvCO2—Partial pressure of CO2 in mixedvenous bloodPCO2—Partial pressure of CO2
DefinitionsPaO2—Partial pressure of O2 in arterial blood(hypoxemia)SPO2—Saturation of arterial blood (POX)percentSaO2—Percentage of arterial hemoglobinsaturated with O2 (POX)PO2—Partial pressure of O2
What is Carbon Dioxide?Capnos comes from the Greek word for“smoke” Smoke from the Fire of metabolism Natural waste product of cellular activityCO2 is a compound molecule 2 elements of oxygen and 1 element of carbon Colorless and heavier than air
Gas Transport in BloodO2 carried in blood Dissolved in blood plasma Bound to hemoglobin with ironCO2 carried in blood Dissolved in plasma (5-10%) Chemically bound to hemoglobin in (RBC’s) (carbaminohemoglobin) (20-30%) Most carried as bicarbonate ions (HCO3-) (60-70%)
Physiology of CO2End of inspiratory cycle, airways filledwith CO2 free gasCO2 is a product of cellular metabolismCO2 is continuously diffused across thecell membrane into the circulating blood
Physiology of CO2Transported to the lungs in the bloodstreamDiffused across cell membrane intoalveoliEliminated during exhalation
Oxygen> lungs> alveoli> blood O2 breathCO2 lungs Muscles + organsCO2 O2 blood energy cells Oxygen + CO2 Glucose
Physiology of CO2The evolution of CO2 from the alveoli tothe mouth during exhalation, andinhalation of CO2 free gases duringinspiration gives the characteristic shapeto the CO2 curve which is identical inall humans with healthy lungs
Capnographic Waveform C D A B EInspiration Expiration Inspiration
Physiology of CO2Alveoli in lower lung is more perfused,but less ventilatedIn the more proximal respiratory tract, theCO2 falls gradually to zero at some point
Physiology of CO2Concentration of CO2 in alveoli isdetermined by: PERFUSION (Q) VENTILATION (V)
Physiology of CO2 Concentration of CO2 in alveoli:Varies INDIRECTLY with ventilation Increase Ventilation: Decrease CO2 in Alveoli Decrease Ventilation: Increase CO2 in AlveoliVaries DIRECTLY with perfusion Decrease Perfusion: Decrease CO2 in Alveoli Increase Perfusion: Increase CO2 in Alveoli
Oxygenation and Ventilation What is the difference?Oxygenation: is the transport of O2 viathe bloodstream to the cells Oxygen is required for metabolismVentilation: is the movement of air intoand out of the lungs exhaling of CO2 via the respiratory tract Carbon dioxide is a byproduct of metabolism
OxygenationMeasured by pulse oximetry (SpO2) Noninvasive measurement Percentage of oxygen in red blood cells Changes in ventilation take several minutes to be detected Affected by motion artifact, poor perfusion, temperature
VentilationMeasured by the end-tidal CO2 Partial pressure (mm Hg) or volume (%) of CO2 in the airway at end of exhalation Breath-to-breath measurement provides information within seconds Not affected by motion artifact, distal circulation, temperature
Distinguishing betweenoxygenation and ventilation
Normal Ventilation/Perfusion RatioThe volume of blood returning to thelungs matches the capacity of the lungsto exchange gasesVentilationCardiac Output
Ventilation-Perfusion (V/Q) MismatchPhenomenon where either perfusion orventilation to an area of lung decreases;results in diminished gas exchange,hypoxemia, and hypercapnia
•If ventilation is held constant, then changes in EtCO2 are due to changes in cardiac output
Value of the Capnographic Waveform Provides valid EtCO2 value Visual assessment of patient airway integrity Verify proper ET tube placement (with pulmonary perfusion) Waveforms have characteristic shape like an ECG
Capnographic Waveform Height shows amount of CO2 Length depicts time450
Phases of Capnogram Expiratory segmentConsists of the following three phases
Phase IPhase I- Represents CO2 free gas fromairways (Dead Space)
Slope of Phase IIICO2 is being continuously excreted intothe alveoliLate emptying of alveoli with lower (V/Q)ratios, produces higher PCO2End-tidal End of the wave of exhalation
Expiratory segment cont…Alpha angle- Angle between phase II andphase III (V/Q status of lung) C D A B E
Phases of Capnogram Inspiratory segmentBeta Angle- Angle between phase III anddescending limb of inspiratory segment C D A B E
Inspiratory segmentPhase 0- Inspiration, fresh gases inhaledand CO2 falls rapidly to zero (DescendingPhase)
Phase 0 C D Descending Phase InhalationA B E 0
End-tidal CO2 (EtCO2)Allows monitoring for changes in Ventilation—Asthma, COPD, airway edema, FBAO, stroke Diffusion—Pulmonary edema, alveolar damage, CO poisoning (COHb), smoke inhalation, hydrogen cyanide Perfusion—shock, pulmonary embolus, cardiac arrest, severe dysrhythmias
Decreased EtCO2Decreased Metabolism Respiratory System Analgesia/ sedation Alveolar hyperventilation Hypothermia Bronchospasm Mucus pluggingCirculatory System Equipment Cardiac arrest Leak in system Embolism Partial obstruction Sudden hypovolemia or ETT in hypopharynx hypotension
Increased EtCO2Increased Metabolism Respiratory System Pain Respiratory insufficiency Hyperthermia Respiratory depression Malignant hyperthermia Obstructive lung disease ShiveringCirculatory System Equipment Increased cardiac output Defective exhalation valve with constant ventilation Exhausted CO2 absorber
Major Benefits in Pre-HospitalVerifying ETT placement and continuousmonitoring of position during transportCardiac Arrest Effectiveness of cardiac compression Predictor of survivalVentilationBronchospastic Disease
Benefits in HospitalVerification of ETT placement andcontinuous monitoringCardiac ArrestVentilationProcedural sedation
ETT Displacement Most likely occurs when patient is moved
CPRPositive pressure ventilationIncreased intrathoracic pressurePressure on Vena Cava, decreasedpreloadIncreased RR does not allow forexhalation
CPRIncreased intrathoracic pressure leads toDecrease in cardiac output, coronaryartery perfusion, and CPP
Optimize VentilationTitrate carbon dioxide levels in patientssensitive to fluctuations Head Injuries Stroke Brain tumors Brain infections
Optimize VentilationCarbon dioxide affects cerebral bloodflow (CBF) Influencing intracranial pressure Hypercapnia causes vasodilationHyperoxygenate, NOT hyperventilate Hyperventilation does not improve oxygenation Maintain CO2 of 35-40 mm Hg
HyperventilationHypocapnia < 35 mmHgNormal range is 35-45 mm Hg (5% vol)How would hyperventilation change thewaveform? (26-30) Frequency Duration Height Shape
What is up coming and how Capnography will assistThe newest phase in CPR Protocols. How it will effect our decisions to work a patient or not. The CPR first protocols. Therapeutic Hypothermia.
What is Therapeutic HypothermiaIs an evidence based change in CardiacArrest patientsThis change effects treatment of thepatient with a return to spontaneouspulses.The studies show good stats that backup this method of treating patients
The European Study This study was conducted in Nine hospitals and 5 countries. The Study was performed completely random. The patients were accepted into the study based on speed of response to V- fib arrest.
The Australian studyLess involved study.This study took place in Melbourne andinvolved four hospitalsThis study was done Pseudo randomformat with patients selected based onan odd or even day.
CriteriaThe patient to be accepted into the study hadto be a persistent V-fib arrest and still in comastate u/a to hospital.The patient must have Resuscitation effortsperformed by trained personnel within 5-15minutes of collapse.The patient must also have ROSC in undersixty minutes.The patient must also be intubated andventilated.
European Study ProceduresThe patient was cooled to 32 to 34degrees Celsius.This temp was reached in the first fourhours of the resuscitation.Pt was held at this temp for twenty fourhours and then passively re-warmed.
Australian StudyPt. Accepted on the same criteriahowever it was based on if it was an oddor even day.The pt were cooled to 33 degreesCelsius and kept there for 12 hours andthe actively re-warmed after 18 hours.
The Results and they were impressive!In the European Study 75 of 136patients(55%) had a favorableneurological outcome.In the normothermic patients the resultswere still good but not great at 39%The Australian Study showed a 49%save rate in the hypothermic pt and a26% in the normothermic pt.
Why do this work?The proof is in the pudding for itsbenefits.However the actions is slightly moretheoretical. Fist is hypothermia lowers the cerebral metabolic rate for oxygen by 6% for every 1 degree C Second hypothermia suppresses chemical reactions.
If this so great why don’t we use it!Simple LogisticsThe patient once taken to thehypothermic state must remain there tohave benefit. A Rolla coaster approach isnot going to work.The equipment to do this efficiently andcontrolled is expensive but is expected tofall in price as it becomes more widelyspread.
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