Capnography

 

What is Capnography?

• Capnography is an objective measurement of exhaled CO2 levels.
• It measures ventilation and provides insights into metabolic activity.

Why is Capnography used?

• Confirmation of Intubation: Assists in confirming correct placement of an endotracheal tube (ET tube).
• Continuous Monitoring: Monitors ET tube placement during transport.
• Ventilation Status: Assesses the adequacy of ventilation.
• Perfusion Assessment: Helps in assessing perfusion status.
• CPR Effectiveness: Evaluates the effectiveness of CPR efforts.
• Predicting Outcomes: Can predict critical patient outcomes.

What are the components of Capnography?

• Definition: Derived from the Greek word "kapnos," meaning smoke.
• Anesthesia Context: In anesthesia, measures gases at the Y connector or mask/nasal cannula.
• Insight: Provides insight into ventilation alterations, cardiac output, pulmonary blood flow, and metabolic activity.

How does Capnography differ from Pulse Oximetry?

• Immediate Insight: Capnography provides immediate feedback on patient condition.
• Apnea Detection: Capnography shows immediate apnea, whereas pulse oximetry shows a delayed drop in saturation.

What are the phases of a Capnographic waveform?

1. Phase I (Baseline): Represents dead space ventilation.
2. Phase II (Ascending): Indicates the beginning of exhalation and initial CO2 from alveoli.
3. Phase III (Alveolar Plateau): Shows uniform CO2 concentration from alveoli.
4. Phase IV (Descending): Marks the beginning of inhalation and a rapid decrease in CO2 levels.

How is Capnography interpreted?

• Numerical Value: Typically 35-45 mm Hg for normal CO2 levels.
• Clinical Indications: High CO2 levels indicate hypoventilation and potential respiratory acidosis; low levels indicate hyperventilation and possible respiratory alkalosis.

What are common uses and considerations for Capnography in EMS?

• ET Tube Confirmation: Provides objective confirmation of correct tube placement.
• Monitoring: Continuously monitors ventilation status during patient transport.
• Detecting Complications: Immediate detection of complications like esophageal intubation or tube displacement.

What are the techniques for monitoring ETCO2?

• Mainstream: Samples gas directly from the airway without removing it, using an adapter in the breathing circuit.
• Sidestream: Aspirates gas from the airway to a remote CO2 analyzer, allowing use in non-intubated patients but with a potential for leaks.

What are the potential complications and troubleshooting methods in Capnography?

• Increasing ETCO2: Due to hypoventilation, metabolic rate increase, or equipment issues.
• Decreasing ETCO2: Due to hyperventilation, decreased metabolic rate, or critical conditions like embolism.
• Waveform Abnormalities: Can be caused by airway obstructions, equipment malfunctions, or patient conditions affecting gas exchange.

How does ETCO2 measurement work?

• ETCO2 monitoring uses a photo detector to measure infrared light absorption by exhaled gases, correlating with CO2 concentration and generating a capnogram waveform.

What are considerations for sensor placement in Capnography?

• Location Importance: Placement affects accuracy; closer placement to the alveoli provides more accurate readings.

This structured format breaks down the content into clear questions and answers with bullet points for easier understanding and reference.

Capnography in Clinical Practice: Question and Answer Format

What are cardiogenic oscillations?

• Cardiogenic oscillations are caused by the beating of the heart against the lungs.

Why is capnography useful in decision-making during resuscitation?

• Capnography provides another objective data point to assess ventilation status, which is crucial in making difficult resuscitation decisions.

How does capnography assist in managing non-intubated patients?

• Capnography helps identify and monitor conditions like bronchospasm (e.g., asthma, COPD), hypoventilation states, hyperventilation, and low-perfusion states.

What are some applications of capnography in bronchospastic conditions?

• Capnography helps identify and monitor conditions such as asthma and COPD by reflecting changes in ventilation, diffusion, and perfusion.

How does capnography differ in bronchospastic diseases like asthma?

• In asthma, capnography shows uneven emptying of alveolar gas, which alters the typical capnogram shape, often with a slower rise in CO2 concentration during exhalation.

What role does capnography play in COPD management?

• Capnography in COPD reflects altered gas emptying due to air trapping and impaired gas exchange, which can be monitored to assess disease progression.

When is capnography particularly useful in hypoventilation states?

• Capnography is crucial in hypoventilation states such as sedation, alcohol intoxication, and stroke, where it helps detect elevated EtCO2 levels indicating CO2 retention.

How does capnography reflect changes in perfusion?

• Capnography reflects changes in pulmonary and systemic perfusion, providing insights into cardiac output and pulmonary blood flow.

What clinical scenarios benefit from capnography monitoring?

• Capnography is beneficial in various scenarios including during seizures, diabetic ketoacidosis (DKA), head injury management, and in identifying tracheal intubation.

Why is capnography recommended over pulse oximetry in certain cases?

• Capnography provides a more direct assessment of ventilation status compared to pulse oximetry, which primarily assesses oxygenation.

What are some myths associated with capnography?

• Capnography does not detect right main stem intubation and may not provide readings in conditions where CO2 production is compromised (e.g., extreme hypothermia).

How should capnography readings be interpreted in cardiac arrest scenarios?

• In cardiac arrest scenarios, a low EtCO2 reading suggests inadequate cardiac output or poor pulmonary blood flow, requiring adjustments in resuscitation efforts.