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Home , Carbaminohemoglobin, Carboxyhemoglobin

Non-Invasive Respiratory Gas Monitoring Module

Endorsements This educational module has been Non-Invasive Respiratory endorsed by the following professional organizations: Gas Monitoring Bryan E. Bledsoe, DO, FACEP The George Washington University Medical Center

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Review Board

Roy Alson, MD, PhD, FACEP James Augustine, MD, FACEP Edward Dickinson, MD, FACEP Marc Eckstein, MD, FACEP RESPIRATORY GAS Steven Katz, MD, FACEP Mike McEvoy, PhD, RN, EMT-P PHYSIOLOGY Joe A. Nelson, DO, MS, FACOEP, FACEP Ed Racht, MD Mike Richards, MD, FACEP Keith Wesley, MD, FACEP Paula Willoughby-DeJesus, DO, MHPE, FACOEP 3

Respiratory Gasses Respiratory Gasses

Normal Atmospheric Most important Gasses: respiratory gasses:

Oxygen (O2) (O2)

Carbon Dioxide (CO2) (CO2)

Nitrogen (N2)

Water Vapor (H2O) Trace gasses: Argon (Ar) Neon (Ne) Helium (He) Non-Invasive Respiratory Gas Monitoring Module

Respiratory Gasses Respiratory Gasses

Respiratory gasses often represented Determining partial pressures:

based upon their partial pressures. PA = XA × P Dalton’s Law: Where: PA = pressure of the gas X = mole fraction of the gas “The total pressure in a container is the A P = total pressure of the mixture sum of partial pressures of all gasses in PO = 0.2095 × 760 mm Hg the container.” 2 PO2 = 159.22 mm Hg Partial pressure of oxygen in atmosphere at sea level = 159 mm Hg

Atmospheric Gasses Respiratory Gasses

GAS† PRESSURE PERCENTAGE Atmospheric Humidified Alveolar Expired Air Air Air Air (mm Hg) (%) GAS (mm Hg) (mm Hg) % % (mm Hg) % (mm Hg) % Nitrogen (N2) 593.408 78.08 78.6 74.0 74.9 74.5 N2 597.0 563.4 569.0 566.0

Oxygen (O2) 159.220 20.95 20.8 19.7 13.6 15.7 O2 159.0 149.3 104.0 120.0 Argon (Ar) 7.144 0.94

CO 0.3 0.04 0.3 0.04 40.0 5.3 27.0 3.6 Carbon Dioxide (CO2) 0.288 0.03 2

Neon (Ne) 0.013 0.0018 0.50 6.20 6.2 6.2 H2O 3.7 47.0 47.0 47.0 Helium (He) 0.003 0.0005 TOTAL 760 100 760 100 760 100 760 100 TOTAL 760 100

† = dry air at sea level.

Oxygen Oxygen

Odorless. Derived from plant Tasteless. photosynthesis: Colorless. Algae (75%). Terrestrial Plants Supports combustion. (25%). Present in the Oxygen atom must atmosphere as a share electrons for diatomic gas (O2). stability. Necessary for animal life. Non-Invasive Respiratory Gas Monitoring Module

Carbon Dioxide Carbon Dioxide

Colorless. Waste product of animal Sour taste at high life (carbohydrate and concentrations. fat metabolism). Found in very low Contains 2 atoms of concentrations in oxygen and 1 atom of fresh air. carbon. Asphyxiant.

Abnormal Respiratory Gasses

Carbon monoxide Colorless (CO) Odorless Tasteless Results from incomplete combustion of carbon-containing compounds. Heavier than air.

Respiratory Gas Transport

Oxygen Carbon Dioxide - Complex. 97% reversibly bound 70% as Transports oxygen to - to hemoglobin. (HCO3 ). peripheral tissues. 3% dissolved in 23% reversibly bound Removes a limited plasma. to hemoglobin. amount of carbon 7% dissolved in plasma. dioxide from the peripheral tissues. Non-Invasive Respiratory Gas Monitoring Module

Hemoglobin Hemoglobin Binding Sites

Human hemoglobin is made of various sub- units: 2 α sub-units 2 β sub-units 4 iron-containing structures.

Deoxyhemoglobin Oxyhemoglobin Heme is in Fe2+ state and Heme is in Fe3+ state and domed. Can bind oxygen. planar. Oxygen bound. Also called the “T” state. Also called the “R” state.

Hemoglobin Binding Sites Hemoglobin

The binding of oxygen changes the conformation (shape) of the hemoglobin molecule. Deoxyhemoglobin is converted to oxyhemoglobin.

Abnormal Hemoglobin States (COHb)

Carboxyhemoglobin Results from the binding of CO to hemoglobin following CO exposure. Some always present in smokers. Non-Invasive Respiratory Gas Monitoring Module

Carboxyhemoglobin (COHb) Methemoglobin

CO has 250 times the Heme must be in the affinity for hemoglobin ferrous (Fe2+) state to bind O2. as does O2. Methemoglobin is CO displaces O2 from hemoglobin in the ferric hemoglobin. (Fe3+) state and cannot CO can be displaced bind O2. by high-concentration Normally < 1% of O . hemoglobin is 2 methemoglobin. Half-life is 4-6 hours. High levels lead to hypoxemia.

Methemoglobin Oxygen Saturation

Hereditary: Hemoglobin oxygen Hemoglobin M saturation is directly Enzyme deficiency related to the partial Acquired: pressure of oxygen in Nitrates the (PO2). Nitrites Venous blood Dyes saturation. Sulfonamides Lidocaine Arterial blood Benzocaine saturation.

Factors Affecting Saturation 2,3-biphosphoglycerate

Decreased saturation. Aids in oxygen Decreased pH (). release in the Increased CO . 2 peripheral tissues. Increased temperature. Increased BPG (2,3- Higher levels found in biphosphoglycerate) people who live at Increased saturation. high altitudes. Increased pH (alkalosis) Helps mitigate the Decreased CO2. Decreased temperature. effects of . Decreased BPG (2,3- biphosphoglycerate) Non-Invasive Respiratory Gas Monitoring Module

Carbon Dioxide Transport Carbon Dioxide Transport

Some CO is Majority of CO2 transported in the form of 2 bicarbonate ion (HCO -). transported on 3 hemoglobin. Binds to a different CO + H O → H CO → H+ + HCO - site than O2 (binds to 2 2 2 3 3 an amino acid). Resultant compound is called increases speed of reaction 5,000 fold. (CO2Hb).

Bohr Effect

Increases in CO2 Binding of oxygen to hemoglobin tends to levels in the blood displace CO2. cause oxygen to be displaced from Oxyhemoglobin is more acidic than hemoglobin. deoxyhemoglobin: Increases oxygen Promotes removal of CO2 in the alveoli. transport. Promotes release of hydrogen ions which

combine with bicarbonate ions to form H2O and CO2 which are eliminated.

Haldane Effect Respiratory Gas Measurement

Arterial Blood Gas Sampling Capnography

Transcutaneous CO2 Monitoring Non-Invasive Respiratory Gas Monitoring Module

Arterial Blood Gasses Arterial Blood Gasses

Gold standard for Excellent diagnostic Parameter Normal respiratory gas tool. pH 7.35-7.45 monitoring. Impractical in the PO2 80-100 mm Hg Invasive prehospital setting. Expensive PCO2 35-45 mm Hg

Painful - HCO3 22-26 mmol/L Difficult BE -2 - +2

SaO2 > 95%

Pulse Oximetry

Introduced in early 1980s. Non-invasive OXYGEN measurement of oxygen saturation. Safe Inexpensive

Pulse Oximetry Pulse Oximetry

How it works: Some light is Probe is placed over a absorbed by: vascular bed (finger, Arterial blood earlobe). Venous blood Light-emitting diodes Tissues (LEDs) emit light of two different Light that passes wavelengths: through the tissues is Red = 660 nm detected by a Infrared = 940 nm photodetector.

© Brook Wainwright Non-Invasive Respiratory Gas Monitoring Module

Pulse Oximetry

Only inflow of blood is used to determine

SpO2. Hence the name “Pulse Oximetry”

Hb and HbO2 absorb light and different rates due to color and conformation.

Pulsatile Flow Oximetry Probe Placement Finger Earlobe Heel (neonates)

This is the band used to measure

SpO2.

Oximetry Probe Placement Pulse Oximetry

Accuracy falls when LEDs and Some manufacturers use reflective oximetry for photoreceptors poorly aligned. monitoring. Accuracy decreases with lower pulse LEDs and photodetectors in same electrode. oximetry readings. Light reflected from the tissues and detected by photodetectors and findings interpreted by the software in the oximeter. Can be used on forehead or back. Non-Invasive Respiratory Gas Monitoring Module

Pulse Oximetry Perfusion Index

HbO2 absorbs more Reflects the pulse infrared light than Hb. strength at the Hb absorbs more red light monitoring site. than HbO . 2 Ranges from 0.02% Difference in absorption is measured. (very weak pulse Ratio of absorbance strength) to 20% (very strong pulse matched with SpO2 levels stored in the strength). microprocessor. Helps determine best site to place probe.

Pulse Oximetry Pulse Oximetry

Pulse oximetry tells you: SpO SaO or SpO ? 2 2 2 Pulse rate

SaO2 used for oxygen saturation readings Pulse oximetry cannot tell you: derived from arterial blood gas analysis. O2 content of the blood SpO used for oxygen saturation readings 2 Amount of O dissolved in blood from pulse oximetry. 2 Respiratory rate or tidal volume (ventilation) SpO and SaO are normally very close. 2 2 Cardiac output or blood pressure.

Who Should Use? Prehospital Indications

Any level of 1. Monitor the adequacy of prehospital care arterial oxyhemoglobin saturation (SpO2) provider who 2. To quantify the SpO2 administers O2. response to an First Responders intervention. EMTs 3. To detect blood flow in EMT-Intermediates endangered body regions (e.g., Paramedics extremities) Non-Invasive Respiratory Gas Monitoring Module

Limitations First-Generation Oximeter Problems

Oximetry is NOT a measure of ventilation False Readings: Hypotension. (EtCO2 a better measure of ventilation). Hypothermia. Vasoconstriction. Oximetry may lag behind hypoxic events. Dyes/pigments (e.g., nail polish). Oximetry is not a substitute for physical Movement may cause false reading in absence of pulse. Abnormal hemoglobin: examination. COHb. Very low saturation states may be METHb. Oximeter can’t perform: inaccurate due to absence of measured Bright ambient lighting. SpO2 levels in the database. Shivering. Helicopter transport.

First-Generation Oximeter Problems Second-Generation Technology

Motion, noise, and Newer technology low perfusion states uses signal can cause artifacts processing to and false oximetry minimize artifacts and false readings. readings: These have been Adaptive Filters eliminated or Signal Processing minimized in second- Algorithms generation oximeters. Improved Sensors

Second-Generation Technology Myths

Technology prevents: Age affects SpO2 Motion artifact. Gender affects SpO2 False readings during low-flow states. Anemia affects SpO2 False bradycardias. SpO2 inaccurate in False hypoxemias. dark-skinned Missed desaturations. individuals. Missed bradycardias. Jaundice affects Data dropouts. SpO2. Effects of dyshemoglobins. Non-Invasive Respiratory Gas Monitoring Module

Prehospital Usage

Assure scene safety. Initial assessment. ABCs Apply oxygen when appropriate (either with or after oximetry). Secondary Assessment Ongoing monitoring.

Reading the Oximeter What Does it Mean?

SpO2 (%) SpO2 READING (%) INTERPRETATION

PI (%) 95 – 100 Normal Signal Strength Pulse Rate (bpm) 91 – 94 Mild Hypoxemia

86 – 90 Moderate Hypoxemia

< 85 Severe Hypoxemia

Interventions Oximetry to Assess Circulation

SpO2 INTERPRETATION INTERVENTION READING Oximeter probe can (%) be placed onto tissue distal to an injury to 95 – 100 Normal Change FiO2 to maintain saturation. detect circulation. Oximeter can monitor 91 – 94 Mild Hypoxemia Increase FiO2 to increase saturation. distal circulation with fractures and crush 86 – 90 Moderate Increase FiO to increase saturation. 2 injuries. Hypoxemia Assess and increase ventilation. Clinical correlation < 85 Severe Hypoxemia Increase FiO to increase saturation. 2 always needed. Increase ventilation. Non-Invasive Respiratory Gas Monitoring Module

End-Tidal CO2 Monitoring

CO2 cannot be measured with the same technology used in oximetry.

CO2 binds to a different site on hemoglobin compared to O . CARBON DIOXIDE 2 No hemoglobin color change. No hemoglobin conformation change. Carbaminohemoglobin cannot be distinguished from deoxyhemoglobin via oximetry.

End-Tidal CO2 Monitoring End-Tidal CO2 Monitoring

Expired CO detected CO2 can be non- 2 invasively monitored with pH sensitive paper or through measurement infrared spectography. of exhaled air. Respiratory cycle results in a capnogram. Sensors available for End-tidal CO2 (EtCO2) is endotracheal tubes the maximum amount of

and for non-intubated exhaled CO2 at the end of patients. respiration.

End-Tidal CO2 Monitoring End-Tidal CO2 Monitoring

Capnography provides Indications: information about Endotracheal tube ventilation. placement.

Normal EtCO2: To determine the adequacy ~ 5% of ventilation. ~ 35-37 mm Hg Continuous monitoring of a A → End of inhalation critical patient where ABGs Gradient (PaCO2 and may not be available. EtCO2): 5-6 mm Hg B → Beginning of exhalation EtCO can be used to To maintain a specific 2 B-D → Exhalation of alveolar gasses estimate PaCO in carbon dioxide level (e.g., 2 brain injury). patients with normal D → EtCO2 . D-E → Inhalation Non-Invasive Respiratory Gas Monitoring Module

End-Tidal CO2 Monitoring End-Tidal CO2 Monitoring

Elevated or continually rising: Lowered of continually diminishing: Decreased CO production (e.g., Increased CO2 production (e.g., fever, 2 seizures). hypothermia, cardiac arrest, pulmonary Decreased alveolar ventilation (e.g., embolism). Increased alveolar ventilation (e.g., CNS depression, ↓ Vmin, muscular disorder). tachypnea, hyperpnea, ↑Vmin). Equipment malfunction (e.g., bad Equipment malfunction (e.g., obstruction of sensor). ventilation system, misplaced ET tube, bad sampling head).

Transcutaneous CO2 Monitoring Technology available for almost 30 years. Primarily used in neonates. Transcutaneous O often 2 CARBON MONOXIDE available.

Correlates to PCO2. Probe is heated and must be moved often. Measurements based upon pH.

Carbon Monoxide Carbon Monoxide

Carbon monoxide CO results from the (CO) is the leading incomplete combustion cause of poisoning of carbon-based fuels. deaths in industrialized It is odorless, colorless countries. and tasteless. ~ 3,800 people in the CO is heavier than air US die annually from and tends to CO poisoning. accumulate in the lower aspect of structures. Non-Invasive Respiratory Gas Monitoring Module

Cherry red Carbon Monoxide Signsskin andcolor notSymptoms always

CO displaces O2 from the SeveritypresentCOHb and, Signs & Symptoms COHb levels hemoglobin molecule whenLevel forming carboxyhemoglobin do not always Mildpresent,< 15 - 20%is Headache, nausea, vomiting, dizziness, blurred (COHb). vision. correlate with CO affinity for hemoglobin often a late ~250 times greater than O . Moderate 21 - 40% Confusion, syncope,symptoms chest pain, dyspnea, nor 2 finding. weakness, tachycardia, tachypnea, CO-Hb has a bright red rhabdomyolysis. predict color. Severe 41 - 59% Palpitations, dysrhythmias,sequelae. hypotension, Patients become myocardial ischemia, cardiac arrest, respiratory progressively hypoxemic. arrest, pulmonary edema, seizures, coma. Fatal > 60% Death

Carbon Monoxide Carbon Monoxide

CO detection New generation previously required oximeter/CO-oximeter hospital-based ABGs can detect 4 different hemoglobin forms. to measure COHb. Uses 8 different Technology now wavelengths of light. available to detect Provides:

COHb levels in the SpO2 prehospital and ED SpCO setting. SpMET Pulse rate

CO-Oximetry

• CO evaluation should be routine at Missed CO all levels of EMS and poisoning is a the fire service. significant legal • All field personnel should be educated risk for EMS and in use of the fire service oximeter and CO- personnel. oximeter. Non-Invasive Respiratory Gas Monitoring Module

CO-Hb Levels in Persons 3-74 Years Treatment

Smoking Status % COHb % COHb Treatment is based on the severity of symptoms. (mean ±σ) (98th percentile) Treatment generally indicated with SpCO > Nonsmokers 0.83 ± 0.67 < 2.50 12-15%.

High-concentration O2 should be administered to Current Smokers 4.30 ± 2.55 ≤ 10.00 displace CO from hemoglobin. Be prepared to treat complications (e.g., All persons 1.94 ± 2.24 ≤ 9.00 seizures, cardiac combined ischemia).

Treatment Treatment Prehospital CPAP can Efficacy of hyperbaric maximally saturate oxygen therapy hemoglobin and (HBO) is a matter of increase oxygen conjecture although solubility. still commonly practiced. Strongly suggested for Generally reserved moderate to severe for severe poisonings. poisonings. May aid in alleviating tissue hypoxia.

Treatment Algorithm CO Poisoning Considerations

Significant and evolving body of literature now suggests that there are numerous long- term and permanent sequelae from CO poisoning.

89 Non-Invasive Respiratory Gas Monitoring Module

CO Poisoning Considerations CO Poisoning A simple has Remember, CO COHb reading a much greater poisoning is the great can save a affinity for CO than imitator. adult hemoglobin. Missed CO exposure life and Pregnant mothers may exhibit mild to often leads to death prevent long- moderate symptoms, and disability. term yet the may CO is a particular risk . have devastating for firefighters. problems outcomes.

Methemoglobin

METHb is hemoglobin with heme in the Fe3+ state.

Cannot bind O2. SpMET levels usually < METHEMOGLOBIN 1% (Range 1-3%) Reflects hemoglobin at the end of its functional life. Results in dark reddish- brown blood. Most frequently seen in children < 4 months (blue baby).

Methemoglobinemia Causes As SpMET levels increase, a functional Inherited: Acquired: anemia occurs (total Hb normal but Hemoglobin Nitrites significant percentage of Hb non- disorder (HgM). Nitrates functional). Enzyme disorders Sulfonamides Cyanosis begins (usually around lips) (e.g., G6PD Lidocaine deficiency). when SpMET >10 - 15%. Benzocaine

Organs with high O2 demands (e.g., CNS, Certain aromatic cardiovascular system) manifest toxicity hydrocarbons first. Dyes Non-Invasive Respiratory Gas Monitoring Module

Symptoms Prehospital Treatment

SpMET Symptom High-concentration O2. 1-3% Normal, asymptomatic Remove offending agents. Methylene blue (accelerates the enzymatic 3-15% Slight grayish blue skin discoloration degradation of METHb) is . 15-20% Asymptomatic, but cyanotic.

25-50% Headache, dyspnea, confusion, weakness, chest pain. 50-70% Altered mental status, delirium.

CO and Cyanide Poisoning Financial Disclosure Hydroxocobalamin Parts of cyanide antidote kit (amylis the nitrite, cyanide sodium This program was nitrite) induce methemoglobinemia.antidote of choice prepared with an Cyanide and CO poisoning can lead to unrestricted grant elevated COHb and METHbfor significantly mixed cyanide from . Masimo reducing O2 capacity of blood. and CO Sodium nitrite should be avoidedpoisonings. for did not control combination cyanide/CO poisonings when SpCO content. >10%. Hydroxocobalamin converts cyanide to cyanocobalamin (Vitamin B12) which is renally- cleared.

Credits Credits This is a product of Cielo Azul Publishing. Content: Bryan Bledsoe, DO, FACEP Art: Robyn Dickson (Wolfblue Productions) Power Point Template: Code 3 Visual Designs The following companies allowed use of their images for this presentation: Brady/Pearson Education Scripps/University of California/San Diego JEMS/Brook Wainwright Bryan Bledsoe, DO, FACEP Masimo, Inc. 102