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I & E Gas Monitoring
SIUE-Nicole's Ins. and Exp. Gas Monitoring
| Question | Answer |
|---|---|
| Where are the oxygen sensors located on the anesthesia machine? | Inspiratory limb |
| When does the Oxygen sensor alarm? | When it drops below 30%. |
| What are the three different types of O2 Analyzers? | Paramagnetic oxygen analysis, Galvanic cell analyzer, polarographic oxygen analyzer. |
| In this oxygen analyzer the O2 is attracted to magnetic energy b/c of unpaired electrons in their outer shell? | Paramagnetic O2 Analysis |
| In a paramagnetic O2 analysis what does the sensor consist of? | Sensor consists of a cylindrical shaped container inside of which is placed a small glass dumbell that is filled eith an inert gas (usually nitrogen) and suspended on a plat. wire within a nonuniform magnetic field. |
| What happens when O2 is processed through the sensor of a paramagnetic O2 analyzer? | The O2 molecules are attracted to the stronger of the 2 magnetic fields, that causes a displacement of the dumbbell and results in it rotating. |
| In a P.O.A (paramagnetic O2 analyzer) the current or rotation required to maintain the dumbbell in its normal state is proportional to? | Partial pressure of oxygen. |
| What is used to measure the degree of rotation of the dumbbell in a P.O.A.? | Optical system consisting of a light source, photodiode, and amplifier curcuit. |
| The degree of rotation or current required to maintain the dumbbell in its normal state is represented electronically in what? | Percent Oxygen |
| A higher O2 reading using a P.O.A. would indicate what about the displacement of the dumbbell? | More displacement of the dumbbell, and more deflection of light onto photocell. |
| This type of O2 analyzer uses an electrochemical sensor? | Galvanic Cell Analyzer (G.C.A.) |
| A G.C.A. contain two electrodes immersed in an aqueous electrolyte that is commonly what? | Potassium Hydroxide |
| When O2 is analyzed by a G.C.A. what happens? | O2 molecules diffuse through a semi-permeable membrane, on one side of the sensor where they are reduced at the cathode to + Hydroxyl ion, which then goes to the sensor anode where oxidation rxn takes place |
| The resultant reduction/oxidation rxn using a G.C.A. generates an electrical current proportional to? | The oxygen concentration. |
| The current that is generated from the G.C.A. is measured with external electronics and displayed on what? | Digital panel meter in percent oxygen. |
| Polographic Oxygen Analyzers (P.G.O.A.)are components of what other analyzers? | Gas machine analyzers, blood gas analyzers, and transcutaneous oxygen analyzers. |
| In a P.G.O.A both the anode and cathode are immersed in an aqueous electrolyte of what? | Potassium Chloride |
| In a P.G.O.A. once the molecular O2 is consumed electrochemically with an accompanying flow of electrical current that is directly proportional to? | O2 concentration is generated from the sensor and is measured and amplifies electronically to provide a percent measurement. |
| Where do we monitor expired gases? | Sampled near the endotracheal tube-gas delivery interface, the Y piece or elbow. |
| What are the three ways in which you can measure expired gases? | Infrared absorbtion spectrophotometry (IRAS), Mass spectrometry systems, Raman scattering techniques. |
| IRAS uses what to measure expired gases? | Asymmetric molecules that absorb infrared light at specific wavelengths- allows us to see how much of each gas is absorbed. |
| IRAS devices can detect which types of gases? | CO2,N2O and inhalational anesthetic agents. |
| What is the downfall of IRAS and inhalational anesthetic agents? | All of the anesthetic vapors absorb infrared light at the same wavelength so we are unable to detect the concentration of the specific anesthetic agents. |
| What are the five components of IRAS devices? | Infrared light source, gas sampler, optical path, detection system, and signal processor. |
| Measures the unique energy absorbed by gases and vapors placed into the optical path of an infrared beam. | IRAS |
| What does the signal processing section of an IRAS instrument have? | Memory section that correlated the absorbed energy with a predicted concentration. Predicted by the Beer-Lambert Law. |
| This system bombards the gas mixture with electrons? | Mass Spectrometry systems |
| In a mass spectrometry system what happens when the gas mixture is bombarded with electrons? | Ions are fragmented of a predictable mass and charge, and accelerated into a vacuum, and then the sample enters a measurement chamber. |
| In a mass spectrometry system the fragment stream is subjected to a high magnetic field in which? | Separates the ion fragments by mass and charge and are deflected onto a detector plate. |
| Mass spectrometry deflects fragments onto a detector plate in which has a specific landing site, what does this measure? | Ion impacts are proportional to the concentration of each gas or vapor. |
| Raman scattering operates by? | By using photons generated by a high intensity argon laser collide with gas molecules. |
| What gases can be measured using a raman scattering system? | O2, NO2, N2, CO2, H2O vapor. NO helium! |
| Using this system does not require a scavenging system. | Raman scattering allows for the return of sampled gas to pt. |
| Expired CO2 can be useful for detecting alterations in what? | Ventilation, cardiac output, distribution of pulmonary blood flow, and metabolic activity, correct ET tube placement. |
| What three things are involved with Carbon dioxide monitoring? | Capnometry, Capnogram, Capnography |
| Measurement and numeric representation of the CO2 concentration during inspiration and expiration? | Capnometry-hooked into expiratory limb |
| Capnogram is what? | continuous concentration time display of the CO2 concentration during ventilation. Displays # and waveform. |
| Capnography | The continuous monitorying of a patients capnogram. |
| By using capnography we have the ability to? | Identify changes related to pt. physiologic status, dx. of M.H., identification of equipment problems, GOLD standard of ETT verification, predicts PaCO2. |
| Capnometry is determined useing infrared light. What are the two different wavelengths? | 2600nm and 4300nm. Control gas is compared to sample from circuit and the calculation is displayed as a number. |
| The A-B stage on a capnogram represents what? | It is the first stage of exhalation, gas sampled occupies the anatomic dead space and therefor contains no CO2. |
| B on capnogram | CO2-containing gas presents itself |
| B-C on capnogram | Shown by a sharp upstoke that is determined by the evenness of ventilation and alveolar emptying. |
| C-D on capnogram | Alverolar or expiratory plateau and is normally horizontal. |
| D on capnogram | Highest CO2 value, ETCO2, best reflection of alveolar CO2. |
| D-E on capnogram | Patient is beginning to inspire, fresh gas entrained, steep down stroke, and should return back to baseline, unless retaining CO2. |
| EtCO2 is typically __mmHg lower than the PaCO2. | 5-10mmHg |
| Factors in which would decrease the accuracy of capnography are? | V/Q mismatch, problems in gas sampling, shallow tidal breaths, prolongation of the expiratory phase of ventilation, uneven alveolar emptying. |
| What is the extreme example of V/Q mismatch? | Dead space ventilation |
| Non-perfused alveoli have a PaCO2 of__? | 0- and would give a lower EtCO2 reading and increase the PaCO2-EtCO2 gradient. |
| What are some examples that could cause a V/Q mismatch? | Embolic phenomena, hypoperfusion states with reduced pulmonary blood flow, COPD. |
| If a blood clot is blocking alveoli in which are being ventilated, what would the V/Q be? | V/Q would be 1/0 because the alveoli are being ventilated but they are not being perfused. |
| If the R mainstem was intubated and there was adequate blood flow to the alveoli what would the V/Q be? | V/Q would be 0/1 because the R mainstem is being ventilated and not the alveoli, but there is adequate perfusion to the alveoli. |
| Capnography helps determine tracheal vs. esophageal placement of the ETT, but not.. | Correct placement in the trachea. |
| Three consecutive breaths are needed for a __ EtCO2 reading. | Stable |
| Increases in EtCO2 can be expected when? | CO2 production exceeds ventilation. |
| A decreased EtCO2 can indicate? | decreased perfusion, decreased gas exchange, and indicate decreased C.O. or decrease B.P. |
| Factors that may increase EtCO2 during anesthesia are... | Increase muscular activity (shivering), M.H., ^ C.O. (resuscitation), Bicarb infusion, tourniquet release, effective drug therapy for bronchospasm, decreased minute ventilation. |
| Factors that may decrease EtCO2 during anesthesia are... | Decreased muscular activity (muscle relaxants), hypothermia, decreased C.O. (arrest), pulmonary embolus, bronchospasm, increased minute ventilation. |
| When studying waveforms what should you look at first and what does that determine? | Y-axis determines the magnitude of CO2, is it normal or abnormal? |
| What is the next thing you should look at after the y-axis? | X-axis to determine if it returns to baseline, which indicates if the patient is retaining CO2. |
| After looking at the Y and X axis of the capnogram, what else should you look at? | The expiratory limb B-D, and ALWAYS R.R. |
| Pulse oximetry measures? | Pulse rate, and O2 saturation of Hgb. |
| Pulse oximetry accurately detects__ while predicting__? | Accurately detects SaO2, and may predict PaO2. |
| Where is O2 most accurately measured on your pt? | The right ear |
| What does a decrease tone indicate? | Decrease in O2. |
| The color of blood is a function of what? And if there is a change in color it results from what? | Oxygen saturation, interaction of hgb with O2. |
| Absorbtion spectrophotometry can determine what? | The ratio of oxyhgb and reduced hgb. |
| The combined technology of plethysmography and spectrophotometry. | Pulse oximetry. Plethysmography produces a pulse trace that is helpful in tracking circulation, and O2 saturation is determined by spectrophotometry. |
| Spectrophotometry is described using the Beer Lambert Law which states.. | There is a logarithmic dependence b/t the transmission of light through a substance, the product of the absorption coefficient of the substance, and the distance the light travels through the material. |
| How is the Beer-Lambert Law applied to Pulse Oximetry? | As a constant light intensity and Hgb concentration, the intensity of light transmitted through a tissue is a logarithmic function of the O2 saturation of the Hgb. |
| Clinical accuracy of pulse oximetry is +/- 2-3% from __% saturation, and +/- 3% from __ % saturation? | +/- 2-3% from 70-100% O2 saturation, and +/- 3% from 50-70% saturation. |
| Some factors that may have an effect on the Reliability of Pulse Oximetry are.... | Dyshemoglobins- (Methemoglobin, Carboxyhemoglobin), low C.O., anemia, vital dyes-(methylene blue,indigocarmine, false lows), nail polish, ambient light, light emitting diode varibility, motion artifact, background noise(electrocautery) |
| Methemoglobin effects pulse oximetry in what way? | Methemoglobin absorbs red and infrared equally and results in sat of 85%, gives a false low if sat is >85%. |
| How does Carboxyhemoglobin affect pulse oximetry? | Gives a false high reading because it absorbs light at same wavelength. |
| If a smoker is hooked up to a pulse oximetry and it is reading 96%, what is their real O2 saturation? | 7 points less, because differential b/t deoxyhemoglobin. SpO2 will not distinguish between O2 hgb and carboxyhemoglobin. |
| Infrared light 940 nm is absorbed by__, Red light 660 nm is absorbed by__? | oxyhemoglobin, deoxyhemoglobin |
| Defines the relationship of hemoglobin saturation and oxygen tension. | Oxyhemoglobin Dissociation Curve |
| Shifts in the curve to the right or left defines what? | Changes in the affinity of hgb for oxygen. |
| Shift to the left on the Oxyhemoglobin dissociation curve can be altered by? | Decrease in PaCO2, decrease in temp, and increase in Ph. Shift to the left indicates a greater attachment of O2 to Hgb. |
| Shift to the right on the oxyhemoglobin dissociation curve can be altered by? | Increase in PaCO2, Increase in temp, decrease in pH. Shift to the right indicates a more readily release of O2 from Hgb. |
| SpO2 of 97%=PaO2 of__, SpO2 of 90%=PaO2 of__, SpO2 of 80%=PaO2 of__,SpO2 of 70%=PaO2 of__. | 1)97% 2)60% 3)50% 4)40% Difference of 30. |
Created by:
ngawlik
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