Expired CO₂ Measurement in Intubated or Spontaneously Breathing Patients from the Emergency Department

During this video, we are going to discover two practical applications of expired carbon dioxide monitoring in artificially ventilated patients. Firstly, to verify that the endotracheal tube has been well inserted. Secondly, for monitoring the patient and for adaptation of the ventilation.

In the second half of the video, we shall talk about CO2 measurement in spontaneously breathing patients, which shall give a brief description of the devices used, and then we shall talk about the example of monitoring ventilation. In the case of procedural sedation, we can use different types of material. For example, the size stream type with aspiration of carbon dioxide, the micro stream type or more modern type of equipment or the mainstream type.

Whatever the material used, the captor is placed behind the filter to avoid any secretions flowing into the side main or micro stream tube. Let's take the example of this patient who has been intubated and ventilated in an out of hospital situation. We immediately place the carbon monoxide detector and we note that it records values of approximately 62 millimeters of mercury, concluding that the intubation has been successful.

In other words, endotracheal. As soon as we are certain that the tube has been placed correctly, we place the CO2 detector behind the filter, which allows us to monitor the expired CO2 tracing during Transport. In this patient Presenting head trauma, we are going to verify by the monitoring of expired CO2 if his ventilation is adequate.

So we observe that the expired CO2 oscillates between let's say 40 and 50 millimeters of mercury, but this information alone needs to be compared with the arterial CO2 value measured in the arterial blood gas. And we observe in the same patient that the expired CO2 value of 45 millimeters of mercury corresponds to an arterial blood measure of 59.8 millimeters of mercury. This corresponds thus to an arterial CO2 value that is too high as we would like it to be.

And for this reason, we're going to adapt the ventilation parameters of this patient. We will either increase the ventilation pressure or the volume administered. We can also increase the very respiratory rate, and as a result, we'll notice that the expired CO2 value is reduced in parallel to the arterial blood gas value.

Inversely, if the patient was in hypercapnea, we would have to reduce the ventilation parameters, which is the volume or the pressure, or in other words, reduce the respiratory rate. Now let's take the time to revise the material available for CO2 expiration measurement in patients that are spontaneously breathing. Firstly, the capna mask, which allows to administer oxygen or therapy and detect CO2 simultaneously.

Secondly, we have nasal prongs that in this case, uniquely detect CO2, and then this model of nasal prongs allows both oxygen administration and CO2 detection. These nasal prongs have at the end a nasal bcal spatula attached to the prongs that optimize the CO2 detection. And finally, this dual tube system allows equally oxygen administration and CO2 Detection.

Here's an example Of a patient for whom we would like to monitor the expired CO2 during an act that requires sedation, for example, the reduction of ated elbow, so we can see the capnograph on the monitor with the kana mask in place. If we administer oxygen to the kana mask, this modifies the CO2 value on the capnograph. Thus, this value is reduced.

As a consequence, this measurement is not very reliable as a real measure of CO2, but what is important is that the curve remains sinus all and that is what is important to follow. Now, if we add five liters of oxygen, we have an elevated FE O2 value more than that of 60 millimeters of mercury. So what is feared in the case of sedation is that the patient goes into apnea.

So of course it is in our interest to preoxygenate the patient. We can of course, tolerate a certain length of apnea, but if this apnea is prolonged, we might have to carefully ventilate the patient manually, keeping in mind that these patients have a full stomach. In this case, we'll lose the possibility to Monitor expired CO2.

When we realize that the patient is recovering and is re-reading spontaneously, we can remove the manual ventilation system and reinsert the cabinet and the curve of CO2 Reappears. The same procedure Can be performed with nasal prongs. In this case, the administration of oxygen and the measure of CO2 can be done spontaneously with the mouth open or the mouth closed.

The quality of the curve remains the same, but if we add oxygen, in this case five liters, the end tidal value of CO2 doesn't really change, but the quality of the curve is modified, so the administration of oxygen modifies the curve. Another difference with the capna mask is that the FE O2 value that we can reach is not as high as with the capna mask. If the patient goes again into apnea and we have to manually ventilate the maneuver is easier in this case.

So after changing the oxygen arrival tube, we can place the manual ventilation system over the nasal prongs, so the expired CO2 can continue to be measured despite manual ventilation. This is an advantage of the nasal prong System. So once spontaneous Ventilation is rea attained by the patient, we can just disconnect the oxygen arrival tube, replace it in the nasal prongs, and continue to monitor the CO2.