Capnography is a term which most of us have not heard in our lifetime, but, in the medical community, this is a very common term. As I encountered with this term a few days back, I tried researching on it all the basic questions like what Capnography is, what it is used for, what are its types, etc. but sadly, I couldn’t find all the information at just one-two websites. I had to struggle hard to find all the information. That’s why I thought of writing this article in a FAQ format so that you get all the best quality information in the least amount of time.
The focal point of this article is to talk about the impact of COVID-19 on capnography monitoring devices, however, I am starting with the basic questions. As you understand the basics of it, it will be really helpful to you to understand the “impact of COVID-19” section clearly. So here we go ladies and gentlemen.
Section – I
We will be covering the following FAQs. Click to directly jump to the specific question.
- What are Capnography devices?
- What is the difference between Capnometry, Capnography, Capnometer, and Capnograph?
- What are the three types of Capnography?
- How do we measure EtCO2?
- What is the normal range of EtCO2?
- What causes high EtCO2?
Section – II
Impact of COVID-19 on Capnography Devices
SECTION – I
FREQUENTLY ASKED QUESTIONS
Frequently Asked Questions
What are Capnography devices?
That’s the first question even I had in my mind but before I dive straight to the main course, let’s have starters first. Ahm Ahm, I meant let’s look back at the history of Capnography first. *wink*
Capnometry was first used in World War II to monitor the internal environment. Its application in healthcare was first seen in 1950 to measure the amount of carbon dioxide (CO2) released during anesthesia but it was in the early 1980s when it was actually practiced by doctors. Slowly, when the devices started getting smaller in size, Capnography officially marked its presence in the field of anesthesia.
So, by now you would have guessed what’s in the “main course”. Isn’t it? Smart people For better clarity, please refer to the below definition.
“Capnography monitor or device is something used mostly in hospitals to keep a check on the CO2 level in the respiratory gases (or the air we exhale) of the patients.”
What is the difference between Capnometry, Capnography, Capnometer, and Capnograph?
Often people get confused with these three terms which are usually used interchangeably. But after reading the definition, you will understand how these three terms differ from each other.
Capnometry: Capnometry is the measurement and display of carbon dioxide in numeric form only, i.e., end-tidal and inspired CO2.
Capnography: Capnography is the exhaustive measurement and display of carbon dioxide in not the only numeric format but also in the form of Capnogram (real-time CO2 waveform).
Capnometer: The device which is responsible for measuring and displaying the end-tidal and inspired CO2.
Capnograph: The device which is responsible for measuring and displaying the CO2 in a waveform.
What are the three types of Capnography?
Three types of Capnograph are: Sidestream, Mainstream, and Microstream. Let’s understand each one in brief.
Sidestream: Sidestream monitor is placed away from the breathing passage of the patient. Therefore, it relies on the other monitor connected to the patient’s breathing passage by a tube. Through the ventilator circuit, the gas samples are aspirated from the exhaled gas. Sidestream monitors are specifically used in non-intubated patients.
Mainstream: Mainstream monitor is used in the case of intubated patients wherein it is directly placed at the breathing passage of the patient to measure the CO2. Hence, within a short period, the doctors get the required amount of sample gas which is smaller compared to sidestream monitoring. However, the disadvantage mainstream monitor offer is that it cannot be used in non-intubated patients and it also adds weight to the airway.
Microstream: Microstream is the new type of capnograph that uses molecular correlation spectrography for accurate results. The Microstream monitors also give rapid results and can be used in both intubated and non-intubated patients.
How do we measure EtCO2?
EtCO2 stands for End Tidal CO2. It is the level of CO2 that has been released at the end of an exhaled breath. To measure the EtCO2, you need to consider three things: The EtCO2 value, the respiratory rate (RR), and the waveform shape. The numerical data is easily understandable, however, understanding the waveform shape requires special knowledge, hence, please focus on the information below:
There are 4 phases while we measure the EtCO2. Have a look!
Phase 1: Exhalation will start and the concentration of the CO2 will be zero.
Phase 2: The CO2 will increase gradually as the alveolar gas exits the breathing passage of the patient.
Phase 3: In the 3rd phase, the CO2 concentration will be comparatively constant and by the end of phase 3rd, the CO2 concentration will be maximum.
Phase 4: Inhalation will start and CO2 will reduce to zero again.
What is the normal range of EtCO2?
The normal EtCO2 has the following features:
- The waveform always starts with zero and ends at zero after the completion of the process.
- The maximum CO2 is reached with every breath that corresponds to the EtCO2.
- The width of the waveform depends on the expiratory time.
- The amplitude of the waveform depends on the concentration of the EtCO2.
- The normal range of EtCO2 is 5%-6% CO2 which is equivalent to 35-45 mmHg or 4.0-5.7 kPa.
- Waveform should be rectangular in shape with rounded corners.
- For adults who are on ventilation, the rate should be 10-12 bpm and without ventilation, the rate should be 12-20 bpm. Children should be ventilated and the rate should be 15-30 bpm and in the case of infants, it should be 25-50 bpm.
What causes high EtCO2?
The end tidal CO2 can be caused by many reasons. Majorly there are 4 reasons which are enlisted below:
- Rapid increase in body temperature (malignant hyperthermia)
- Decrease in metabolic rate
- Decrease in respiratory rate (hypoventilation)
- Decrease in tidal volume (hypoventilation)
SECTION – II
IMPACT OF COVID-19 ON CAPNOGRAPHY DEVICES
Impact of COVID-19 on Capnography Devices
The following table will help you understand how the capnography market was behaving pre-COVID and how it is behaving post-COVID. Have a look!
| S.No. | Scope | Pre-COVID | Post-COVID |
| 1. | Resource Allocation | The Anesthesiologists and certified registered CRNAs (nurse anesthetists) were earlier looking after the Operating Room (OR) patients as surgeries used to happen in that room. | Post-COVID, the Anesthesiologists and certified registered CRNAs have been relocated to the ICUs, which have now become COVID-19 units, as surgeries have got canceled due to COVID and their expertise is beneficial for the COVID patient’s recovery. |
| 2. | Remote monitoring of EtCO2 | Pre-COVID, doctors were measuring the EtCO2 in real-time without maintaining any social distancing or working remotely. | To follow the social distancing and supporting the conservation of the PPE, capnography devices are connected to a remote monitoring platform, such as Vital Sync remote monitoring technology, to measure the CO2. |
| 3. | Scope | The scope of capnography was limited to monitoring ventilation. | The scope has expanded dramatically. Now, apart from ventilation, capnography has been used to access the airway patency and placement, assessment of intervention and treatment effectiveness, assisting in the identification of coagulation problems such as emboli, PE, DVT, etc. |
| 4. | Filtration of the capnography sampling line | Not required | As the size of the COVID virus is very small compared to the size of aerosol (through which COVID enters the body) droplets, the Anesthesia Patient Safety Foundation (APSF) has created COVID-19 specific resources for filtering the capnography sampling line. |
Conclusion
Capnography is the device that is used by healthcare facilities to monitor the EtCO2. There are three types of capnography: Sidestream, Mainstream, and the latest Microstream. There is a total of 4 phases of measuring the EtCO2 wherein the normal range features zero waveforms at the start and returning back to zero at the end.
The causes of high end tidal CO2 are mainly an increase in the body temperature, and a decrease in the metabolic rate, respiratory rate, and tidal volume. Finally, we have discussed the impact of COVID-19 on capnography devices wherein we found some interesting facts. If you have mistakenly jumped at the conclusion section, please do check out the table to get insights into the impact of COVID-19 on capnography devices.
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