Capnography Detailed

Question 1

Why is capnography considered a standard monitor for patients under anesthesia?

Answer 1

Recommended by AANA/ASA to provide essential information on ventilation, metabolism, and cardiovascular function.

Question 2

How does hypercarbia impact the body?

Answer 2

Elevated CO2 levels resulting in respiratory acidosis can lead to effects like increased CBF, elevated ICP, and potassium shifts.

Question 3

What effects can hypocarbia have on the body?

Answer 3

Decreased CO2 levels causing respiratory alkalosis can lead to reduced CBF, decreased pulmonary resistance, and potassium shifts.

Question 4

What aspects of physiology and monitoring does capnography provide insights into?

Answer 4

Capnography evaluates ventilation, pulmonary blood flow, aerobic metabolism, tube placement, breathing circuit integrity, and cardiac output adequacy.

Question 5

What equation is utilized in capnography to calculate physiological dead space?

Answer 5

Capnography uses the Bohr Equation to determine the physiological dead space during monitoring.

Question 6

What is dead space in respiratory physiology?

Answer 6

Volume of each inhaled breath that does not participate in gas exchange.

Question 7

Differentiate between anatomic dead space and physiologic dead space.

Answer 7

Anatomic dead space is in the conducting airways, while physiologic dead space includes airway and alveolar dead space.

Question 8

What is alveolar dead space?

Answer 8

Portion of physiologic dead space within alveoli not involved in gas exchange.

Question 9

List conditions increasing alveolar dead space.

Answer 9

Hypovolemia, pulmonary hypotension, pulmonary embolus, V/Q mismatch, alveolar overdistension.

Question 10

What is capnometry and how is it measured?

Answer 10

Measurement and quantification of inhaled or exhaled CO2 concentrations using a capnometer.

Question 11

Explain capnography and its significance.

Answer 11

Method of CO2 measurement with a graphical display over time, essential for confirming endotracheal intubation.

Question 12

Describe time capnography and its representation.

Answer 12

Pressure vs time plot showing CO2 concentrations digitally as inspired and end tidal, aiding quick breath interpretation.

Question 13

Differentiate between high-speed and slow-speed time capnography.

Answer 13

High-speed allows quick breath information interpretation, while slow-speed offers trend appreciation of expired and inspired CO2.

Question 14

What are the key features of side-stream capnography?

Answer 14

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.

Question 15

Explain main-stream capnography and its advantages.

Answer 15

Directly analyzes gas in the breathing circuit, faster rise time with no delay, providing real-time measurements.

Question 16

Where is Tidal CO2 typically measured?

Answer 16

Tidal CO2 is measured at the end-point of Phase III, just before inspiration.

Question 17

What is the significance of the Tidal CO2 value recorded just before inspiration?

Answer 17

The Tidal CO2 value recorded just before inspiration is typically the largest value observed at that specific time.

Question 18

What does the average Tidal CO2 value represent?

Answer 18

The average Tidal CO2 value represents the CO2 concentration at a specific time during respiration.

Question 19

What is the approximate difference between Arterial CO2 and ETCO2?

Answer 19

There is an approximate 5 mm Hg difference between PaCO2 and ETCO2, with ETCO2 typically lower than PaCO2.

Question 20

How do factors like V/Q mismatching impact the Arterial CO2 / ETCO2 difference?

Answer 20

V/Q mismatching can exacerbate the difference between PaCO2 and ETCO2, leading to discrepancies in CO2 readings.

Question 21

How do breathing patterns influence the Arterial CO2 / ETCO2 difference?

Answer 21

Breathing patterns affecting gas delivery can increase the difference between PaCO2 and true ETCO2 levels.

Question 22

In what situations do issues with the capnograph contribute to the Arterial CO2 / ETCO2 difference?

Answer 22

Issues like sampling catheter leaks, calibration errors, and slow response time can augment the difference in CO2 readings.

Question 23

What is the primary method used for clinical measurement of CO2 levels?

Answer 23

Clinical measurement primarily relies on IR light absorption techniques to assess CO2 concentrations.

Question 24

Describe the relationship between CO2 levels and IR light absorption in clinical monitoring.

Answer 24

There is an inverse relationship between CO2 levels and IR light reaching the detector in respiratory monitoring.

Question 25

How is the presence of CO2 indicated using chemical indicators in monitoring?

Answer 25

Chemical indicators utilize color change, with yellow indicating the presence of CO2 and purple indicating its absence.

Question 26

Why is verification of endotracheal tube (ETT) placement necessary through alternative methods in clinical practice?

Answer 26

Verification of ETT placement through alternative methods is required due to the limitations of CO2 measurement techniques.

Question 27

What is the acceptable range for maintaining CO2 reading accuracy in capnography?

Answer 27

Maintain CO2 reading within +/- 12% of the actual value.

Question 28

Which substances should manufacturers disclose for potential interference in capnography readings?

Answer 28

Manufacturers should disclose any interference caused by ethanol, acetone, and halogenated volatiles.

Question 29

Why is a high CO2 alarm required in capnography monitoring?

Answer 29

A high CO2 alarm is necessary for monitoring inhaled and exhaled CO2 levels and for detecting low exhaled CO2 levels.

Question 30

What parameters can be understood from CO2 values in the interpretation of a time capnogram?

Answer 30

CO2 values can help approximate blood CO2 levels, pulmonary blood flow, and alveolar ventilation.

Question 31

What are the potential differential diagnoses for loss of exhaled CO2 in capnography?

Answer 31

Differential diagnoses may include esophageal intubation, accidental extubation, disconnection of sampling line/device, apnea, bronchospasm, or cardiac arrest.

Question 32

What do the inspiratory and expiratory segments in capnography refer to?

Answer 32

Inspiratory phase 0 and Expiratory Phases I, II, and III.

Question 33

What does Phase I of a capnogram indicate?

Answer 33

Phase I indicates the baseline phase showing exhalation of anatomic dead space with essentially no CO2.

Question 34

Describe Phase II of a capnogram.

Answer 34

Phase II marks the expiratory upstroke starting with CO2-rich alveolar gas and sampling of alveolar gases.

Question 35

What does Phase III of a capnogram represent?

Answer 35

Phase III is the plateau phase reflecting CO2 in the alveolus, showing ventilation heterogeneity with a slight increasing slope.

Question 36

Under what circumstances can Phase IV (Occasional Phase IV) occur in capnography?

Answer 36

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.

Question 37

What is the significance of the Alpha Angle in capnography?

Answer 37

The Alpha Angle separates phase II and phase III, ranging between 100 to 110 degrees, increasing with conditions like COPD or bronchospasm.

Question 38

How does the Alpha Angle change in case of expiratory airflow obstruction?

Answer 38

The Alpha Angle increases in conditions such as expiratory airflow obstruction, kinked endotracheal tube, COPD, or bronchospasm.

Question 39

Describe the Beta Angle in capnography.

Answer 39

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.

Question 40

What factors can lead to an increase in the Beta Angle?

Answer 40

An increase in the Beta Angle can result from malfunctioning inspiratory unidirectional valves, rebreathing, or low tidal volume with rapid respiratory rate.