12leadecg,transcutaneousmonitoring, andpulseoximetry · 3 indicaons"for"ecg" •...
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12 Lead ECG, Transcutaneous Monitoring, and Pulse Oximetry
Craig Black, PhD, RRT-‐NPS, FAARC
9. Perform Procedures a. 12 lead ECG b. Transcutaneous monitoring c. Pulse oximetry and capnography
10. Interpret procedure results a. 12-‐lead ECG b. Transcutaneous monitoring c. Pulse oximetry and capnography
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IntroducNon • The 12-‐lead ECG, transcutaneous monitoring, pulse oximetry, and capnography all yield informaNon which directly applies to the paNent’s respiratory status.
• Must always be placed in the context of the paNent’s clinical condiNon.
• No subsNtute for direct observaNon of paNent. • Always treat the paNent, not the “numbers.”
12-‐lead ECG • Extremely useful non-‐invasive diagnosNc tool • Recording on the skin of the electrical acNvity from heart’s conducNon system
• PaTern of the trace used to determine abnormaliNes in heart’s conducNon system
• Abnormal paTerns in traces correlated to specific clinical condiNons
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IndicaNons for ECG • History of significant heart disease, especially with certain signs and symptoms: • Chest pain, especially radiaNng to arms or up into neck • Shortness of breath • Dyspnea (esp. with palpitaNons) • Diaphoresis • Syncope • Weakness or lethargy
• Used to screen paNents prior to surgery or medically strenuous or risky procedures.
Performing the ECG • Wire leads from ECG machine will be
labeled to designate their placement on the body—criNcal that leads be placed in correct posiNons on the body • RA-‐right arm, LA-‐le^ arm, RL-‐right leg, LL-‐
le^ leg (usually on ankles) • Leads V1—V6 called precordial and are
placed on chest
• PaNent seated or lying flat
• Eliminate electrical interference
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ECG InterpretaNon • ECG printed on graph paper with small squares (1mm) and large squares (5mm)
• ECG has number of waves corresponding to movement of the impulse through heart’s conducNon system.
• P wave • QRS complex • T wave P T
QRS
Analyzing the ECG Trace 1. Determine the heart rate (beats/minute) 2. Examine PR interval (number of small boxes between start of P and start of QRS)—
should be <5 small boxes (0.2 sec) 3. Examine QRS complex; should be <2-‐3 small boxes (0.12 sec) 4. Examine T wave; should be upright—inverted suggests ischemia 5. Examine ST segment (base line between end of S and beginning of T wave)—should
be flat and no more than 1mm above or below base line 6. Report any abnormaliNes idenNfied to physician
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Sinus Bradycardia
• Normal sinus rhythm except for rate of <60/min • May be a result of intense athleNc condiNoning • Only a problem if it results in clinical symptoms
• Low blood pressure • FaNgue • Syncope
Atrial Fibrilla2on • Atrial muscle “quivers” in irregular paTern • Baseline electrical acNvity is erraNc—no true P waves present • Clinically
• May cause decreased cardiac output • StagnaNon of flow in atria may result in thrombi—risk of pulmonary embolism
• Treatment
• Drugs to stabilize atrial acNvity (e.g. digoxin, beta-‐blockers)
• Cardioversion if drugs do not work
• AnNcoagulant drugs (e.g. coumadin, lovenox)
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Atrial Flu4er • Ectopic focus causes rapid atrial depolarizaNon (250-‐350/min) • Extra P-‐waves present for every QRS • QRS complex normal • Not considered as serious as atrial fibrillaNon since it normally does not cause
thrombi due to stagnant atrial blood flow • Treatment
• Same as atrial fibrillaNon except anNcoagulants normally not used
Ventricular Tachycardia • Characterized by wide, bizarre QRS complexes • No P-‐wave • Ventricular rate of 100-‐250/min • Is considered sustained V-‐tach if last >30sec • Especially serious because may lead to ventricular fibrillaNon • Treatment
• Cardioversion • Long-‐term anN-‐arrhythmic drugs • Implanted automaNc, internal cardioverter/defibrillator if necessary
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Ventricular Fibrilla2on • Totally erraNc, disorganized rhythm paTern • Most serious of all arrhythmias • Ventricular muscle only “quivers” resulNng in no cardiac output • Fatal if more normal rhythm is not restored quickly • Treatment
• ACLS protocol for cardiac arrest—combinaNon of drugs and defibrillaNon • Survivors
• Long-‐term anN-‐arrhythmic drugs • Implanted automaNc, internal cardioverter/defibrillator • Cardiac catheterizaNon with placement of stents or coronary artery bypass
surgery
Transcutaneous Monitoring • Provides conNnuous non-‐invasive es4mates of arterial pO2/pCO2 via sensor held on
skin by adhesive • Sensor enclosed in heaNng element that warms skin
• Heat “arterializes” capillary blood beneath sensor • Increases skin permeability to O2/CO2 diffusion • Sensor measures transcutaneous O2/CO2 (PtcO2/PtcCO2)
• Works well only in neonates although PtcCO2 monitoring is more accurate than end-‐Ndal CO2 in intubated adults
• Readings may diverge significantly from actual PaO2/PaCO2 and must be correlated with arterial or capillary blood gases
• Most useful as a way to “trend” changes in PaO2/PaCO2
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IndicaNons for Transcutaneous Monitoring
• Need for conNnuous, non-‐invasive monitoring of oxygenaNon and venNlaNon (especially criNcally ill infants)
• Need to quanNfy in real-‐Nme the responses to diagnosNc procedures and therapeuNc intervenNons (e.g. venNlator senng changes)
• Monitoring PaCO2 levels in adult paNents undergoing general anesthesia (more accurate than end-‐Ndal)
ContraindicaNons
• Very fragile skin (extreme prematurity) • Poor peripheral circulaNon (e.g. shock) • Skin allergy to adhesive
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Performing Transcutaneous Monitoring
• Sensor is calibrated per machine instrucNons • HeaNng element temperature set (41oC for combined PtcO2/PtcCO2 monitoring)
• Sensor with heaNng element applied to skin • Sensor site must be changed every 2-‐3 hours • A^er sensor is moved, new readings should be correlated with blood gases
InterpretaNon of PtcO2/PtcCO2 Readings
• Readings must be allowed to stabilize (10-‐20min) before considered valid
• If a reliable esNmate of PaO2/PaCO2 is desired, PtcO2/PtcCO2 values must be correlated with blood gas values
• Changes in readings may be useful for trending changes in PaO2/PaCO2 even without correlaNon
• Trending can be helpful in determining appropriate Nming for blood draws
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Pulse Oximetry • UNlizes light transmission through living Nssue to determine the percent
oxidized hemoglobin (saturaNon) and pulse rate • Two wavelengths (660 and 940nm) • Changes in light transmission occurring with changes in Nssue blood flow measured to determine pulse rate
IndicaNons for Pulse Oximetry • Need to monitor arterial oxyhemoglobin saturaNon levels
• Need to determine the response of arterial oxyhemoglobin saturaNon to various diagnosNc (e.g. bronchoscopy) or therapeuNc intervenNons (e.g. applicaNon of O2 delivery device to paNent)
• Need to comply with regulaNons of regulatory agencies (e.g. TJC or CMS)
• Is considered “Standard of Care”
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ContraindicaNons
• Presence of significant levels of CO in blood • Presence of significant levels of MetHb in blood
Performing Pulse Oximetry • Note date, Nme, and paNent posiNon and acNvity
• Apply sensor probe to paNent
• Note O2 status (room air, O2 delivery device, flow/FIO2)
• Alarm senngs important
• Low alarm
• 88-‐92% for term infants, children, adults
• Use insNtuNonal protocol for premature infants
• High alarm
• Unnecessary for term infants, children, adults
• Use insNtuNonal protocol for premature infants
• Note paNent appearance (e.g. cyanosis, capillary refill)
• Note reading (value, stability, correlaNon with heart rate by ECG or palpaNon)
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InterpretaNon of Pulse Oximetry Results Certain factors affect the validity and accuracy of pulse
oximetry results Factor Effect Presence of CO in blood Falsely high %HbO2
Presence of metHb Falsely low %HbO2 if SaO2<85%
Severe anemia (Hct<10%) High %HbO2 , but low CaO2 Dark skin pigmentaNon Falsely high %HbO2 (3-‐5%) Poor perfusion Poor signal, unpredictable (correlate heart
rate with ECG) MoNon arNfact Poor signal, unpredictable (correlate heart
rate with ECG) MRI Falsely low %HbO2
Capnography • Graphic representaNon of the levels of CO2 in gases as measured by a capnograph
• Usually applied to air being breathed • Modern capnographs can display changes in pCO2 throughout individual breaths
• Most common use is to monitor changes in levels of CO2 in paNent on mechanical venNlaNon
• Most commonly used sensor technology is infrared absorpNon
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IndicaNons for Capnography • EvaluaNon of exhaled CO2 especially end-‐Ndal levels (PETCO2) • Monitoring severity of pulmonary disease and response to
therapeuNc intervenNons • Determining ETT placement in trachea (not esophagus) • Monitoring integrity of venNlator circuit including arNficial airway • Monitoring effecNveness of mechanical venNlaNon • Monitoring inspired CO2 when it is being therapeuNcally
administered • Measurement of metabolic rate and/or alveolar venNlaNon
Performing Capnography • Two types of capnographs—both measure PCO2 • sidestream • mainstream
• Calibrate analyzer • Apply to paNent venNlator circuit • Note all mechanical venNlaNon senngs • Note paNent respiratory/cardiovascular status
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InterpretaNon of Capnography Results • Normal capnogram
• PCO2 is 0 during inspiraNon • PCO2 near 0 during very early
exhalaNon (A on diagram—Phase I) represenNng emptying of dead space
• PCO2 increases (A to B—Phase II) as alveolar gas mixes with dead space gas
• PCO2 level plateaus (B to C—Phase III) as exhaled gas is nearly all from alveoli
• PCO2 at highest level at end of Phase III (Point C—end exhalaNon) represenNng alveolar gas, the end-‐Ndal value (PETCO2)
• PETCO2 normally 3-‐5mm Hg less than PaCO2
Time
40
30
20
10A
BC
pCO
2 (m
m H
g)
Certain abnormal capnogram traces are indicaNve of specific pulmonary disease processes
Abnormality Pa4ern seen on trace
Rapid increase in cardiac output Elevated PETCO2
Rapid decrease in cardiac output Decreased PETCO2
HypervenNlaNon Decreased PETCO2
HypovenNlaNon Elevated PETCO2 Massive pulmonary embolism Decreased PETCO2
Circuit disconnect Trace disappears
V/Q mismatch Point B not clearly defined and Phase III shows increased slope