Capnography - Indication and Procedure

Introduction:

Capnography is essential in medical settings, particularly during anesthesia and sedation. To ensure a patient's safety, it measures the amount of carbon dioxide in their breath. It assists doctors in preventing a deadly condition known as hypoxia, which occurs when the body does not receive enough oxygen. Capnography is employed in emergency departments, x-ray rooms, other medical settings, and operating rooms. It has become a common aspect of monitoring patients during anesthesia and sedation to avoid brain damage caused by a lack of oxygen.

What Is Capnography?

Capnography is a noninvasive way of measuring the amount of carbon dioxide (CO2) in exhaled breath over time. This information is shown as a graph called a capnogram. Changes in the capnogram can indicate certain health conditions, while the maximum CO2 concentration at the end of each breath can tell us how severe a disease is and how well the treatment is working. Capnography helps doctors assess two important things: ventilation (how well the body is getting rid of CO2) and oxygenation (how well the body is getting enough). It has become a standard part of anesthesia care in hospitals and is used to monitor patients before and during medical treatment.

How Does Capnography Assist Doctors in Different Medical Scenarios?

Capnography is a medical tool that helps doctors in various ways:

• Checking if a breathing tube is correctly placed in the windpipe.

• Ensure that a breathing tube or a surgically made hole in the windpipe is clear and in the right position.

• Monitoring if a patient is receiving enough support from a ventilator (breathing machine).

• Assisting during the placement of a tube in the windpipe for breathing.

• Keeping an eye on patients with increased pressure inside the head.

• Monitoring how effective the treatment is for bronchospasm, a condition that affects the airways in the lungs.

• Estimating how well the heart is pumping blood.

• Using it during cardiac arrest (heart stoppage) situations.

• Measuring how well the body gets rid of carbon dioxide with each breath tells us about a person's breathing efficiency.

How Can You Identify a Normal Capnography Waveform?

Capnography waveform interpretation is a way to understand the information provided by the CO2 graph produced during breathing. The normal capnogram has four phases:

Phase I: This represents the beginning of each breath, where the air you inhale has minimal CO2.

Phase II: This marks the transition between the air that doesn't exchange gasses and air from the deeper parts of the lungs that do exchange gasses.

Phase III: Here, the CO2 level stabilizes, representing the CO2 from the deepest parts of the lungs.

Phase 0: This marks the beginning of the next breath.

Some important features to consider in capnography waveform interpretation include:

• Normal end-tidal CO2 (ETCO2) is around 38 mmHg or 5%.

• The alpha angle is the transition point between Phase II and Phase III.

• The beta angle is the transition point between Phase III and Phase I (the next breath).

• In pregnancy, an additional Phase IV may be seen.

Different patterns in the capnography waveform can indicate various conditions and issues:

• A flat ETCO2 trace could suggest ventilator disconnection, respiratory/cardiac arrest, or apparatus malfunction.

• An increased ETCO2 level might be due to factors like fever, cardiac output, or hyperventilation.

• A sudden drop in ETCO2 to zero could indicate problems like a kinked endotracheal tube or ventilator defects.

• Issues like CO2 rebreathing or water condensation can cause certain changes in the baseline.

• Recognizing certain patterns in the capnogram can help identify conditions such as esophageal intubation, right main bronchus intubation, or partial paralysis in mechanically ventilated patients.

Capnography waveform interpretation helps doctors understand breathing and diagnose various medical conditions by analyzing the CO2 levels in the breath. Different patterns can indicate different problems, making it a valuable tool for monitoring patients and troubleshooting ventilators.

What Are the Indications for Capnography?

• Capnography is a helpful technique used to monitor breathing, blood flow, and metabolism in a noninvasive way.

• It provides valuable information about the levels of carbon dioxide in the breath.

• This helps ensure the accuracy of oxygen saturation measurements from pulse oximeters.

• Doctors can gain insights into various hidden health conditions and ongoing disease processes by analyzing the capnography waveform.

• Capnometry is a quick and reliable method to understand how well a person is breathing, blood circulation, and metabolic activity.

• It is instrumental in diagnosing and monitoring patients before they reach the hospital, especially in emergencies.

• Certain conditions affecting blood flow in the lungs don't change the shape of the capnography curve but can alter the relationship between exhaled CO2 and the CO2 levels in the blood.

• Capnography can also measure carbon dioxide production, which increases during fever and shivering but decreases during anesthesia and hypothermia.

How Does Capnography Work?

Capnography is a monitoring technique that helps healthcare providers assess how well a patient breathes and how efficiently their body handles carbon dioxide. It is a method that uses special waves called infrared waves to measure the level of carbon dioxide at the end of each breath and provides real-time information through graphical waveforms and numerical readings. Infrared waves are not visible to our eyes, and they have a lower frequency compared to light. Capnography devices can be either sidestream (CO2 sensor away from the patient) or mainstream (CO2 sensor near the patient's airway). They are used in various medical settings, including anesthesia, emergency rooms, intensive care units, and during patient transport.

The reason we can use infrared waves to measure carbon dioxide is that gases with at least two different atoms can absorb these waves. Since oxygen in the air has two similar atoms, it cannot absorb infrared waves. Capnography not only measures carbon dioxide but can also measure other gasses like isoflurane and nitrous oxide. Using capnography, healthcare providers can quickly identify potential breathing problems like airway obstruction, hyperventilation, or insufficient breathing. This allows them to take timely action, such as providing supplemental oxygen or adjusting treatment, to prevent serious complications.

Capnography is crucial during anesthesia and sedation, as it helps prevent adverse events like respiratory depression and hypoxia. It's also used during cardiopulmonary resuscitation (CPR) to monitor the effectiveness of lifesaving measures. Recent technological advances have expanded the use of capnography beyond anesthesia, and it's now applied in various medical situations to improve patient safety and outcomes. Capnography can work quickly and accurately, even in premature babies with fast breathing and small breaths. The carbon dioxide levels are shown as a partial pressure value, helping healthcare providers monitor a patient's breathing and make sure everything is going well.

Conclusion:

Capnography monitors breathing and how well the body handles carbon dioxide. It gives real-time data through waveforms and numbers. There are two types of devices: sidestream (away from the patient) and mainstream (near the airway). It's used in anesthesia, emergencies, and patient transport. Capnography helps spot breathing issues quickly, so doctors can act fast to prevent complications. It's crucial during anesthesia, sedation, and CPR to ensure safety. New technology expands its use in various medical settings to improve patient outcomes.