How Is CO2 Monitored? Your Complete Carbon Dioxide Guide

How Is CO2 Monitored? Your Complete Carbon Dioxide Guide

How is CO2 Monitored: Your complete carbon dioxide guide

In 2011, a study found that 82% of critical care incidents that led to brain injury and death could have been prevented using one method of carbon dioxide monitoring.

Carbon dioxide monitoring a noninvasive, inexpensive, and often underused way to monitor patient status.   

That’s why we’ve put together your complete guide on CO2 monitoring and how it can improve your patient outcomes. Keep reading to learn what carbon dioxide monitoring is, why you should use it, and what your top industry equipment options are. 

What is CO2 Monitoring?

CO2 monitoring, or capnography, monitors the amount of carbon dioxide a patient exhales. This gives health care providers an overall assessment of the patient’s ventilation. 

 In order to produce a healthy level of CO2, the patient’s breathing has to be healthy. They have to be taking air into the lungs, and have good alveolar respiration within the lung space. They must have good circulation to return waste CO2 to the lungs from body tissues, and have good cellular respiration within the tissue. A healthy CO2 level means that the patient is breathing well overall. 

Carbon dioxide monitoring is usually done with an endotracheal tube. However, it can also be done using nasal cannula. This means it doesn’t have to be invasive. 

How CO2 Monitors Work

CO2 monitors work by shining infrared light across the patient’s breathing tube. Carbon dioxide absorbs infrared light, so the more CO2 is present, the less light is picked up by the sensor. This allows the sensor to determine how much carbon dioxide a patient exhales. 

The sensor sends its data to a monitor, where it is displayed in two ways. First, it is depicted visually, showing the rise and fall of CO2 levels as the patient exhales, producing a waveform graph. This is called capnography. 

Second, it displays the end-tidal CO2, which is normally 30-45 mm Hg. This is called capnometry. (Read more on these two types of data below.)

A good capnography monitor will show both of these data together so that health care providers can get the whole picture of a patient’s status at once. 

CO2 Monitoring vs Oxygen Monitoring

Critical care settings often use pulse oximetry to monitor patients’ breathing and circulation. However, carbon dioxide monitoring is a more sensitive and comprehensive way to measure breathing and circulation problems. Here are a few advantages of CO2 monitoring over pulse oximetry.

Shows Hypoventilation More Quickly

Oxygen is monitored using pulse oximetry. Similar to CO2 monitoring, it uses infrared light to measure how much-oxygenated blood is circulating to peripheral tissues. The pulse oximeter is usually placed on a finger or toe to read the oxygen circulation in the extremities.

However, if a patient begins to have breathing problems, the pulse oximeter does not pick it up right away. It can take several minutes for the blood oxygen saturation to drop enough to register on the pulse oximeter. 

Instead, CO2 monitoring takes a measurement directly from the patient’s breath. If there are any changes in breathing, carbon dioxide monitoring will register them immediately. This gives health care workers the advantage of catching breathing problems early.

Higher Specificity

Pulse oximetry readings can be confused by other factors. If a patient has hypothermia, blood will be shunted away from the extremities, leading to a falsely low oxygen reading. Similarly, in patients with poor distal perfusion, it will be impossible to get a true assessment of oxygen saturation. 

Pulse oximetry is useful for many clinical situations. However, CO2 monitoring is the fastest and most specific way to monitor a patient’s respiratory status. 

Clinical Uses for Carbon Dioxide Monitoring

In the past, CO2 monitoring has been reserved for intensive care settings. However, clinicians are discovering a whole range of clinical uses for it. Here are some of the most beneficial ways to use CO2 monitoring 

Confirming Endotracheal Tube Placement

Confirming that an endotracheal tube is properly placed is a constant challenge for health care providers. When a health care team inserts an endotracheal tube, there is always a risk that it will slip into the esophagus instead of going into the lungs. Clinicians use many techniques to check the placement of the ET tube. Some of the most common ones are listening for breathing sounds in the lungs and using a laryngoscope to see the tube placement.

Instead, the American College of Emergency Physicians recommends CO2 monitoring as the most reliable means of making sure the endotracheal tube is properly placed in the lungs. Because the stomach doesn’t produce carbon dioxide, seeing a significant amount of CO2 being returned through the ET tube means that the tube is properly placed. 

Monitoring Mechanical Ventilation and CPR

Carbon dioxide monitoring is also an effective way to monitor artificial respiration. Steady CO2 levels show that the patient is taking in oxygen and releasing carbon dioxide. This makes capnography a good indicator that mechanical ventilation is working properly.

It also monitors CPR. If the capnography monitor shows a steady, strong exhale of CO2, it means that the compressions are working well and the patient is releasing carbon dioxide.  

Monitoring Spontaneous Ventilation

Since patients don’t need to be intubated to use carbon dioxide monitoring, it’s also useful for patients who are breathing on their own. In critical care contexts, such as the ICU and ED, capnography is a non-intrusive way to monitor the effectiveness of a patient’s breathing. 

Procedural Sedation

Post-procedural patients are vulnerable to respiratory insufficiency. As they come out of anesthesia, their breathing can be unsteady, so it’s essential to monitor their breathing status. It is especially important to monitor post-procedure breathing for patients who have compromised airways, and those who are at risk for losing consciousness after extubation. 

Many hospitals use pulse oximetry to monitor patients as they recover from procedural sedation. However, carbon dioxide monitoring catches deteriorating breathing first, before it leads to low oxygen levels in the blood.

Sleep Studies

CO2 monitoring is also frequently used in sleep studies. For patients who have sleep issues, capnography can be used clinically to diagnose sleep apnea and hypoventilation. 

Ways to Monitor CO2

There are several ways to monitor carbon dioxide. It can be displayed using visual data, called capnography, or numerical data, called capnometry. It can be read using a sensor directly attached to the patient’s airway, called mainstream monitoring, or one located within the capnograph machine, called sidestream monitoring.

Keep reading to understand the options and determine which is best for your clinical situation.

Capnography vs Capnometry

For simplicity, CO2 monitoring is usually called “capnography.” But capnography specifically means the visual waveform of expired CO2 which is displayed on a monitor. This gives health care professionals an ongoing visual of the patient’s breathing status.

On the other hand, capnometry measures the end-tidal CO2, or ETCO2. This is one number that summarizes how well the patient is exhaling carbon dioxide. If it falls below the normal ETCO2 of 30-45 mm Hg, the patient is failing to breathe out effectively. 

Mainstream CO2 Monitoring

Mainstream CO2 monitoring can only be used with intubated patients. It uses a sensor that attaches right to the airway and sends its data to the monitor to be displayed. 

Because the mainstream sensor reads the CO2 levels directly from the ET tube, gives the most accurate data. Its waveform readings are on phase, which means they happen exactly as the patient exhales. 

Sidestream CO2 Monitoring 

In sidestream carbon dioxide monitoring, the sensor is located inside the CO2 monitor. A portion of tubing diverts from the main breathing circuit to the monitor, allowing the capnograph to analyze the patient’s breathing inside the monitor. This eliminates the need for a second piece of machinery, namely the external mainstream sensor.

Sidestream sensors can be used with nasal cannula, so they are used with non-intubated patients. They can also be used with intubated patients if needed. 

However, with sidestream monitoring, because it takes longer for the patient’s expired air to reach the sensor, the waveform is out of phase. It is an accurate reading, but slightly delayed.  

CO2 Monitoring Equipment

There are many types of monitors to choose from. Most models can do only sidestream or mainstream monitoring, but a few can do both.

A high-quality CO2 monitor will display the CO2 waveform and the end-tidal CO2. Practitioners can see the whole picture of the patient’s status at a glance.

Good CO2 monitors also display other vital signs and important data. This keeps all the relevant information in one location so that it’s easy for health care professionals to see. 

Reliable Medical Equipment You Can Trust

In today’s medical world, it’s crucial to understand carbon dioxide monitoring and know how to use it to get the best patient outcomes. Infinium Medical offers the industry’s most reliable CO2 monitor, along with all the accessories for a fully functional system.

To improve your clinic’s CO2 monitoring process, take a look at our state-of-the-art capnography monitor. It is the top-quality solution to meet your needs. 

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