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Capnography/Oxymetry
| Question | Answer |
|---|---|
| What are the 4 steps of monitoring? | 1. Check Intrumentation 2. Observation and vigilance 3. Interpretation of data 4. Initiation of corrective therapy |
| Why is monitoring imortant in anesthesia? | Note the baselin so that you can be aware of changes during anesthesia delivery and correct the changes. |
| Standard I of anesthesia Monitoring | Qualified personel continuously present to monitor the patient and make necessary modifications |
| Standard II of anesthesia Monitoring | Continuously evaluate the patient's O2, ventilation, circulation, and temperature |
| Monitoring sounds | Alarm annunciations using unique sounds and visual prompts that are incorporated into anesthesia equipment |
| High pitch oxymetry sounds =? | high oyxgenation |
| What is the purpose of Oxygen analyzers? | Determines the FiO2, oxygenation in the circuit, does not gaurentee adequate arterial oxygenation, protects against hyoxic mixtures |
| Where are O2 analyzers located | On the inspiratory limb of the circuit. |
| When does an O2 analyzer alarm? | When the FiO2 is detected below 30-40% |
| What are the 3 types of O2 analyzers? | Paramagnetic, Gavanic Cell Analyzer, Polarographic Analyzer |
| How does the paramagnetic O2 analyzer work? | A glass dumb bell filled with N2 is suspended by a platinum wire within a non-uniform magnetic field. When O2 is passed through the sensor it causes the dumb bell to rotate. The speed of the rotation is proportionate to FiO2. |
| How does a paramagnetic O2 analyzer with a current work? | A current is applied to keep the dumb bell from displacing as a result of the magnetic field. The amount of current required is proportionate to the FiO2 |
| How does a Galvanic Cell Analyzer Work? | An anode and a cathode are immersed in a KOH aqueous solution. O2 passes throught a semi-permeable membrane and is reduced @ the cathode to OH+ and creates a current between the cathode and anode. Current is directly proportionate to FiO2 |
| How does a Polarographic O2 Analyzer Work? | An anode and a cathode are immersed in KCl. Molecular O2 is consumed electromagnetically with accompanying flow of electrical current that is directly proportional to FiO2 |
| What type of O2 analyzer is most common on anesthesia machines? | Polarographic. It is part of the gas machine analyzer, blood gas analyzer, and transcutaneous O2 analyzers. |
| Where are expired gases monitored? | Near the ETT |
| 3 ways to monitor expired gas | Infrared absorption spectrophotometry, mass spectrometry, Raman scattering techniques |
| IRAS | Because molecules are all different shapes they absorb light differently. The amount of light absorbed determines the type of gas it is |
| What is a drawback of IRAS? | Anesthetic gases cannot be differentiated because the all absorb close to the same amount of infrared light. |
| 5 Components of IRAS | Infrared light source, gas sampler, optical path, detection system, signal processor |
| Mass Spectrometry | Particals are charged and accelerated out of a vaccum. The particles leave the container at same speed in presence of a mag. The dist that particals travel and the number of particals that land determine which gases are present and their concentration |
| Raman Scattering Technique | Photons from an Argon laserbeam collide with gas molecules. Different molecules scatter to different degrees. Can determine all anesthetic gases present and their concentrations |
| Why is CO2 monitoring Important? | Detects alterations in ventilation, CO, distibution of pulmonary blood flow and metabolic activity, determines correct tube placement |
| Capnometry | Numeric representation of CO2 during inhalation and exhalation |
| How is Capnometry determined? | Using 2 wavelengths of infrared light (2600nm & 4300nm. Control gas is compared to sample from anesthesia circuit and it is displayed as a number |
| Capnogram | Waveform representing concentration of CO2 during ventilation |
| Capnography | Monitoring of patient's capnogram |
| Importance of Capnography (5) | Identify changes related to patient's phyiological status; Diagnosis of MH, ID equipment problems; Gold standard for ETT placement; Predicts PaCO2. |
| A-B on Capnogram | 1st stage, baseline should be zero |
| B-C on Capnogram | Expiration is initiated (exspiratory upstroke) |
| C-D on Capnogram | Expiratroy plateau |
| D on Capnogram | ETCO2, Highest Co2 level; best reflexion of alveolar CO2 |
| D-E on Capnogram | Inhalation (inspiratory downstroke); return to baseline |
| How do you measure ETCO2 | Capnogram |
| Where do you measure PaCO2 | ABG |
| Where do you measure PACO2 | Alveoli |
| What is PACO2 | Alveolar CO2 |
| How does ETCO2 compare to PaCO2? | ETCO2 is about 5-10mmHg less than PaCO2 |
| Types of V/Q mismatch | Shunt and Dead Space |
| What is dead space | Ventilation occurs, but there is no perfusion ex. PE |
| What is a shunt? | Ventilation does not occur, but perfusion continues. Ex.) Left lung is shunted during Right mainstem intubation. |
| How do you ensure proper ETT placement using a capnogram? | Stable ETCO2 for 3 consecutive breaths |
| When will ETCO2 be high? | Whenn CO2 production exceeds ventilation |
| Factors that increase ETCO2 | Shivering, MH, Increased CO, HCO3 infusion, Turniquet release, decreased minute ventilation, bronchodilation |
| Factors that decrease ETCO2 | Muscle relaxant, hypothermia, decreased CO, PE, bronchospasm, increased minute ventilation |
| What are risk factors for MH? | SUX, Anesthetic Gases |
| Steps to read a capnogram | 1. Use y-axis to determin if CO2 is normal 2. Examine x-axis to make sure CO2 returns to normal of zero 3. Examine expiratory limb (B-D) 4. Examine RR |
| What does no ETCO2 mean on a capnogram? | Esophogeal Intubation |
| What does normal upstroke, normal downstroke, but no return to base line mean on a capnogram? | The patient is rebreathin CO2, so the CO2 scrubber may need to be changed |
| How should you correct CO2 rebreathing in the middle of a case | Do NOT change scrubber, increase fresh gas flows to at least 5 L/min |
| what should you check if there is a change in the upstroke on a capnogram | Expiratory valve on the circuit |
| What should you check if there is a change in the downstroke on a capnogram? | Inspiratory valve on circuit |
| What causes increased RR and decreased CO2 on a capnogram and how do you fix it? | Pain can induce hyperventilation, so you should give more narcotics. |
| What causes decreased RR and increased CO2 on a capnogram? | Hypoventilation |
| What causes curare cleft and where is it located, and how do you fix it | Cause-Diaphragm movement from patient trying to breath on their own; Location-Expiratory plateau; How To Fix-Paralytics |
| What are cardiac Oscelations | Rhythmic movement on downstroke seen when trying to let the patient breath on their own |
| What causes a slanted plateau and progressively higher CO2 | MH |
| What causes a slanted plateau and decreased CO2 | PE; No gas exchange so CO2 is decreased |
| What is the purpose of oxygenation monitoring? | Early detection and propt intervention can prevent complications. |
| What does a pulse oximeter measure? | Pulse Rate and O2 saturation of hemoglobin. |
| Where is the pulse ox most accurate? | Right Ear |
| What is the pulse ox a good predictor of? | PaO2 |
| What does the pleth tell you? | Perfusion. (increased pleth = increased perfusion and vice versa) |
| How does the pulse ox work? | 2 light diodes with different wavelengths separately measure the amount of light that is absorbed by oxyhemoglobin and deoxyhemoglobin. The ratio of absorption is expressed as a perccentage. |
| What wavelength is absorbed by oxyhemoglobin? | 940nm |
| What wavelength is absorbed by deoxyhemoglobin? | 660nm |
| What are some limitations to Pulse oximetry? | It does not distinguish oxyhemoglobin from carboxyhemoglobin or methemoglobin which can lead to false results |
| Methemoglobin in the blood can result in... | a displayed O2 sat of 85% no matter what the actual saturation is. This is because methemoglobin absorbs both wavelenghths equally. |
| Carboxyhemoglobin in the blood can result in... | Falsely high O2 saturations, because carboxyhemoglobin absorbs the same wavelength as oxyhemoglobin (940nm) |
| Considerations for pulse-ox on a smoker | The actual SpO2 is about 7% less than what is displayed on the monitor due to circulating carboxyhemoglobin. |
| Things that can effect pulse-ox reliability | dyshemoglobin, low CO, anemia, methylene blue, nail polish, ambient light, diode variability, motion artifact, electrocautery |
| How to Trouble shoot a malfunctioning pulse-ox | Is the red light on; Is the sensor on thick skin, Is the extremity cold/vasoconstricted, Movement?, Cautery?, Ambient Light?, Nail Polish? IS THE PATIENT ALIVE?!? |
| Left shif Oxyhemoglobin shift | decreased CO2, Decreased Temp, Increased pH |
| Right Shift Oxyhemoglobin Shift | Increased CO2, Increased Temp, Decreased pH |
| SpO2 comparison to PaO2 | 97=97; 90=60; 80=50; 70=40 |
Created by:
SRNA84
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