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Waveform capnography is a tool that EMS providers at any level can use.
By Jake Mellor
A previous article provided five training scenarios to help BLS providers better understand common capnography waveforms and how this information can lead to more adequate treatment for a patient.
Below are three more scenarios, which will spur discussion about more complex yet still common conditions that providers may encounter in the pre-hospital setting. In each scenario, students will see how waveform capnography can be vital to a quicker diagnosis and better patient care.
The goal for students completing these scenarios should be to recognize a few more common and distinct waveforms, as well as next treatment steps.
Waveform Capnography Scenario 1: Congestive heart failure
EMS arrives on scene to find a 68-year-old male patient with a chief complaint of difficulty breathing. Patient is situated in a tripod position, and vital signs are quickly obtained:
HR: 122 BP: 160/100 RR: 24 and labored SpO2: 88 percent ETCO2: 30 mmHg Lung sounds: Rales, bilaterally
Show students this waveform: a shorter, rounded arch found to be specific to CHF patients.
It’s important for students to know that this waveform will not appear in every CHF patient, but if it is present, it will work in conjunction with other findings to confirm CHF.
Waveform Capnography Scenario 2: Curare cleft
Two paramedics have intubated a patient with full-thickness burns on 40 percent of his body via rapid-sequence intubation. EMTs are present to assist during transport to a burn center. Vital signs post-RSI are as follows:
HR: 134 BP: 84/52 RR: assisted SpO2: 100 percent on ETT ETCO2: 41 mmHg LS: Clear bilaterally
Provide the students with this waveform, a clear example of curare cleft.
Explain to students what is going on during each brief downward spike in the alveolar plateau of phase III. For a patient intubated via RSI, this cleft is very likely an indicator that the neuromuscular blockade is wearing off, and the patient is now trying to breathe on his own against the tube.
Make it clear that now is not the proper time for extubation, even though the patient wants to breathe on his own, and that another dose of paralytic medications is what this patient needs. Although EMT students will not be familiar or trained in giving these drugs, being able to recognize curare cleft and alerting the paramedics will greatly increase the efficacy of the intubation and help patient comfort.
Waveform Capnography Scenario 3: CPR and ROSC
Have students simulate running a code.
CPR has been in progress for 10 minutes, providers have placed an oropharyngeal airway and are ventilating with a BVM that has inline capnography, and after two defibrillation attempts, the patient is still in ventricular fibrillation.
After another round of CPR and administering a third shock, give students this capnography waveform.
When a patient reaches ROSC, the CO2 that had been building up during insufficient peripheral perfusion is suddenly washed out as blood begins moving more effectively again, resulting in a sudden spike on the waveform.
Ensure that students know that if they see this spike, they should alert the rest of their crew and perform a pulse check to verify ROSC. While this condition is certainly an improvement, students should know that patients in ROSC could easily re-arrest. Patients going back into cardiac arrest will have a decline in ETCO2 that is just as significant as the original ROSC spike.
Waveform capnography is a tool that EMS providers at any level can use. Even if the intervention that the waveform demands is beyond the scope of practice of a provider, recognition of a pattern and communication with other members of the crew can be the difference for a critical patient.
About the author
Jake Mellor is a firefighter/paramedic student intern with the Town of Madison (Wis.) Fire Dept.
This article, originally published in October 2018, has been updated.
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