Capnography Detailed Flashcards
Why is capnography considered a standard monitor for patients under anesthesia?
Recommended by AANA/ASA to provide essential information on ventilation, metabolism, and cardiovascular function.
How does hypercarbia impact the body?
Elevated CO2 levels resulting in respiratory acidosis can lead to effects like increased CBF, elevated ICP, and potassium shifts.
What effects can hypocarbia have on the body?
Decreased CO2 levels causing respiratory alkalosis can lead to reduced CBF, decreased pulmonary resistance, and potassium shifts.
What aspects of physiology and monitoring does capnography provide insights into?
Capnography evaluates ventilation, pulmonary blood flow, aerobic metabolism, tube placement, breathing circuit integrity, and cardiac output adequacy.
What equation is utilized in capnography to calculate physiological dead space?
Capnography uses the Bohr Equation to determine the physiological dead space during monitoring.
What is dead space in respiratory physiology?
Volume of each inhaled breath that does not participate in gas exchange.
Differentiate between anatomic dead space and physiologic dead space.
Anatomic dead space is in the conducting airways, while physiologic dead space includes airway and alveolar dead space.
What is alveolar dead space?
Portion of physiologic dead space within alveoli not involved in gas exchange.
List conditions increasing alveolar dead space.
Hypovolemia, pulmonary hypotension, pulmonary embolus, V/Q mismatch, alveolar overdistension.
What is capnometry and how is it measured?
Measurement and quantification of inhaled or exhaled CO2 concentrations using a capnometer.
Explain capnography and its significance.
Method of CO2 measurement with a graphical display over time, essential for confirming endotracheal intubation.
Describe time capnography and its representation.
Pressure vs time plot showing CO2 concentrations digitally as inspired and end tidal, aiding quick breath interpretation.
Differentiate between high-speed and slow-speed time capnography.
High-speed allows quick breath information interpretation, while slow-speed offers trend appreciation of expired and inspired CO2.
What are the key features of side-stream capnography?
It aspirates gas away from the airway for analysis, with a 50 to 200 mL/min flow rate, involving transport time delay and rise time.
Explain main-stream capnography and its advantages.
Directly analyzes gas in the breathing circuit, faster rise time with no delay, providing real-time measurements.
Where is Tidal CO2 typically measured?
Tidal CO2 is measured at the end-point of Phase III, just before inspiration.
What is the significance of the Tidal CO2 value recorded just before inspiration?
The Tidal CO2 value recorded just before inspiration is typically the largest value observed at that specific time.
What does the average Tidal CO2 value represent?
The average Tidal CO2 value represents the CO2 concentration at a specific time during respiration.
What is the approximate difference between Arterial CO2 and ETCO2?
There is an approximate 5 mm Hg difference between PaCO2 and ETCO2, with ETCO2 typically lower than PaCO2.
How do factors like V/Q mismatching impact the Arterial CO2 / ETCO2 difference?
V/Q mismatching can exacerbate the difference between PaCO2 and ETCO2, leading to discrepancies in CO2 readings.
How do breathing patterns influence the Arterial CO2 / ETCO2 difference?
Breathing patterns affecting gas delivery can increase the difference between PaCO2 and true ETCO2 levels.
In what situations do issues with the capnograph contribute to the Arterial CO2 / ETCO2 difference?
Issues like sampling catheter leaks, calibration errors, and slow response time can augment the difference in CO2 readings.
What is the primary method used for clinical measurement of CO2 levels?
Clinical measurement primarily relies on IR light absorption techniques to assess CO2 concentrations.
Describe the relationship between CO2 levels and IR light absorption in clinical monitoring.
There is an inverse relationship between CO2 levels and IR light reaching the detector in respiratory monitoring.
How is the presence of CO2 indicated using chemical indicators in monitoring?
Chemical indicators utilize color change, with yellow indicating the presence of CO2 and purple indicating its absence.
Why is verification of endotracheal tube (ETT) placement necessary through alternative methods in clinical practice?
Verification of ETT placement through alternative methods is required due to the limitations of CO2 measurement techniques.
What is the acceptable range for maintaining CO2 reading accuracy in capnography?
Maintain CO2 reading within +/- 12% of the actual value.
Which substances should manufacturers disclose for potential interference in capnography readings?
Manufacturers should disclose any interference caused by ethanol, acetone, and halogenated volatiles.
Why is a high CO2 alarm required in capnography monitoring?
A high CO2 alarm is necessary for monitoring inhaled and exhaled CO2 levels and for detecting low exhaled CO2 levels.
What parameters can be understood from CO2 values in the interpretation of a time capnogram?
CO2 values can help approximate blood CO2 levels, pulmonary blood flow, and alveolar ventilation.
What are the potential differential diagnoses for loss of exhaled CO2 in capnography?
Differential diagnoses may include esophageal intubation, accidental extubation, disconnection of sampling line/device, apnea, bronchospasm, or cardiac arrest.
What do the inspiratory and expiratory segments in capnography refer to?
Inspiratory phase 0 and Expiratory Phases I, II, and III.
What does Phase I of a capnogram indicate?
Phase I indicates the baseline phase showing exhalation of anatomic dead space with essentially no CO2.
Describe Phase II of a capnogram.
Phase II marks the expiratory upstroke starting with CO2-rich alveolar gas and sampling of alveolar gases.
What does Phase III of a capnogram represent?
Phase III is the plateau phase reflecting CO2 in the alveolus, showing ventilation heterogeneity with a slight increasing slope.
Under what circumstances can Phase IV (Occasional Phase IV) occur in capnography?
Phase IV occurs as a sharp upstroke in PCO2 due to closure of lung units with lower PCO2, seen in patients with decreased Functional Residual Capacity and lung capacity.
What is the significance of the Alpha Angle in capnography?
The Alpha Angle separates phase II and phase III, ranging between 100 to 110 degrees, increasing with conditions like COPD or bronchospasm.
How does the Alpha Angle change in case of expiratory airflow obstruction?
The Alpha Angle increases in conditions such as expiratory airflow obstruction, kinked endotracheal tube, COPD, or bronchospasm.
Describe the Beta Angle in capnography.
The Beta Angle separates phase III and phase 0, typically at 90 degrees, increasing due to issues like malfunctioning unidirectional valves or low tidal volume.
What factors can lead to an increase in the Beta Angle?
An increase in the Beta Angle can result from malfunctioning inspiratory unidirectional valves, rebreathing, or low tidal volume with rapid respiratory rate.
