You and your partner are called to a pediatrician’s office for an emergency transfer to a pediatric intensive care center. On arrival at the office, you’re met by the pediatrician who tells you the patient you’re transporting has respiratory syncytial virus (RSV) and “is going to stop breathing.” The pediatrician further states that the patient is in exam 2 with his mom and that you should load and get to the hospital right away. Aircraft are grounded by severe weather, and it’s a 35-minute transport time.
The patient is a 42-day-old infant who’s being held in his mother’s arms. As you approach the infant, you perform a quick assessment from across the room. The baby’s acting appropriately (as far as you know); his skin is normal, and there are no signs of distress, such as nasal flaring or retractions. The baby’s young mom seems oblivious to what’s going on.
The doctor returns to the room and asks why you haven’t left yet. You respond, “We need to do a quick assessment to determine what we are dealing with.” Your partner applies a pediatric/infant nasal cannula capnography filter line. After seeing the waveform (C-1) your partner says, “OK, we need to head to the hospital now and get set up to assist breathing. This kid is grunting; we’re going to have to help him. His lungs sounds are hard to hear. I think he might have some slight wheezes, but not every breath.”
Seven minutes into transport the baby stops breathing. You get out the pediatric bag-valve mask (BVM) and ventilate the child while turning the positive end-expiratory pressure (PEEP) valve attachment to about 6. As you squeeze the bag, you notice the waveforms squared off with PEEP. You continue to ventilate the baby, carefully watching the end-tidal carbon dioxide (EtCO2) reading to keep it at about 40 mmHg (see Figure 1).
On arrival at the Pediatric Intensive Care Unit, the pediatric intensivist commends you on the care you rendered. Stat blood gases come back to normal, and the respiratory therapist gives you a smile and a thumbs up as you complete your run report. The team gathers around the infant and intubates him. They prepare to hook him up to a ventilator. There’s some discussion about the PEEP settings.
The intensivist asks, “How much PEEP did you have on him?”
“6,” you reply.
“Sounds good to me; let’s start him there because it worked well for them.” The team sets the same amount for the ventilator settings.
What was going on in this case? RSV causes a narrowing of the smaller bronchioles because of an infection and inflammation. As these tiny airways narrow and the baby exhales, the venture effect collapses the alveoli on exhalation, causing atelectasis. The baby is grunting to keep the alveoli open.
In other words, he’s “PEEPing” himself. Therefore, when the baby stopped breathing, the EMS providers had to take over breathing for the infant. But they also had to secure PEEP because the baby was grunting to keep his alveoli open. Had the medic not have known this or even not had a PEEP valve on his BVM, he couldn’t have adequately ventilated.
What’s amazing is that the initial triage in this case showed the grunting and the effects of the baby grunting. The first two waveforms show the obstruction to flow starting, but when the baby grunted, it squared off. That’s objective, reliable and accurate. That’s a clinical upgrade if there ever was one. There’s no way the paramedic would have even known how much PEEP to set, so he used the waveforms as his guide. He set the minimum PEEP to keep the waveforms square.
Seizures or Seizure-Like Activity
Generalized seizures, including tonic clinic and absence epilepsy affect both hemispheres of the brain and the medulla. So when a person has a seizure, they do not breathe. They make noise; this is involuntary and has been described as an “epileptic cry.” This isn’t effective ventilation, and it manifests itself as a small, erratic waveform with very low values on a capnogram (see Figure 2).
The period after the seizure is called the post-ictal phase. During this time, the skeletal muscle activity may have ceased, but the patient may still be seizing. The neuronal discharges in the brain continue, but the muscles aren’t moving. The capnogram reads this as apnea. This is evidence that ventilatory support is needed and that anti-seizure medications may also be needed. Note that the post-ictal phase is defined by the fact that the patient is breathing with normal waveforms, and more importantly, with a normal CO2 value (see Figure 3).
This is where capnography is particularly useful. After the seizure, the EMS provider can readily assess the adequacy of ventilation. This is important, especially for cases in which a benzodiazepine was used to control or break the seizure.
In the case of absence epilepsy, these seizures involve blank stares and maybe eye fluttering. Some patients even appear to be daydreaming or act like they’re falling asleep. In such a case, capnography will detect the apnea during the event and can differentiate simple fainting from another condition.
The following capnogram was taken from the case a 6-year-old boy who “fell asleep in class,” falling out of his chair and hitting his head on the desk next to him. The child was acting appropriately on scene and was transported as a “precaution.” En route, while conversing with medics, the boy stopped talking mid-sentence and just stared motionless with a few eyelid flutters. The paramedic’s noticed that the capnogram went flat line for 24 seconds. Then the child picked up his sentence on the exact word he left out (see Figure 4).
Then he just snapped out of it with no recollection of the event. At the hospital, the paramedics reported their findings and a neurology consult was ordered. The following day, an EEG revealed absence of epilepsy, previously undiagnosed. You may recall absence epilepsy is a generalized seizure (formerly called petit mal). Because it’s generalized seizure, these patients won’t breathe either. Most attacks are brief—less than 15 seconds—but could go longer. Capnography makes an excellent assessment for the patient who has seizures or seizure-like activity.
Any time a patient is sedated for any reason, you have to carefully monitor their respiratory status for signs of respiratory depression. Capnography has been proven in numerous prospective trials to be the most accurate and only objective measurement of breathing adequacy in the sedated patient.1–4 In fact, hospitals are enhancing patient safety during procedures. When patients are on a patient-controlled analgesia (PCA) pump, they use capnography as a safety and as an early warning of respiratory depression or other adverse airway events. Many hospitals are purchasing PCA pumps with a capnography override to prevent inadvertent doses or overdose from being given.
With a capnogram, detecting respiratory depression is simple. Place it on a patient for initial baseline and record. Then, using continuous monitoring, trend the EtCO2. If it trends higher, then respiratory depression is occurring. However, a slowing rate and an increase in EtCO2 can mean the same thing. Obviously if a patient becomes apneic, the waveform will disappear with the first breath they don’t take.
How to Get Capnography
Remember the full clinical value of capnography can be appreciated only when devices are set up with the right capnography default settings. The waveform and the value should both be on the screen. This warm-up preset will allow for faster assessments. Providers should also get into the habit of printing the capnogram; you can’t analyze it properly on the scope.
My students often cite ignorance or cost as the reason they don’t use capnography for the non-intubated patient. As an educator, I can fix the ignorance part. Financially speaking, services should partner with others, including hospitals that will also be using them for in-hospital use to increase buying power to keep the costs as low as possible.
This technology should be budgeted in as the costs of doing business. Remember when you prioritize purchases, capnography is a tool with the ability to assess all patients. Get creative; many vendors sell the same filter lines. Let them compete for your business. Negotiate a price for buying a year or two-year’s supply; lock in the price, and then purchase them as you need them.
Back to education. If you have a device now but aren’t sure how to use it, get help. Seek out those who know. There’s some excellent resource material that can help you study up on the subject. You’ll need some hands-on practice to see what normal capnograms look like and the things that make them look abnormal. Bust open a case of oral/nasal cannulas and have your squad play with them. Wear them while you talk (talking capnogram) and while you cough, sneeze, sign and hiccup.
Breathe quickly, breathe slowly, give oxygen through it, put on continuous positive airway pressure and see what it does. Watch the effects of the waveform and the values. Do your own research. One group of volunteers discovered that the average respiratory rate for an adult at rest was 8. So much for 12–20, huh?
Another group uses a designated breather who wears capnography during scenario labs and breathes with the manikin to feel what it’s like for a patient. The other students get to see what the capnogram looks like before they need to do it on a real patient. The goal is to get the students and EMS personnel as much experience as they can reading normal and “normal abnormal” waveforms. Comfort reading capnograms will lead to increased usage and better patient assessments.
I teach about 60–70 classes a year all over the world on this subject, and I must admit it’s more accepted today than it was in 1998 when I started teaching my course. I’ve noticed, however, some other issues. Through student sampling, I’m getting to the crux of the matter.
I think part of the reason for the slow adoption is the general lack of knowledge about how this technology really works and how it applies to the field practice. CO2 detection (purple to yellow) was out front for at least a decade before the ability to measure CO2 via a nasal cannula ever came out. This has led to a paradigm of using capnography only as a device to confirm tube placement. Some states have even required and endorsed its use for intubation only.
Add to this early sidestream devices required 300 mL of airflow per minute to get good reading; also, the technology had to be calibrated and compensated for gases other than CO2. Today’s nasal oral cannula devices can accomplish the task with specific CO2 sensors and flow rates as little as 50mL per minute. Early nasal cannulas didn’t work well with mouth breathers, but today’s oral/nasal cannula filter lines can pick up from either.
Although the technology is much improved, there’s still distrust among some. Some critics say it’s, “just another fancy tool to make you treat it, not the patient.” I’ve heard that many times before. Changing to a new way of doing things is never easy. We resist change. However, this is one of the most beneficial ways we can increase our “clinical quotient.”
Bottom line: Capnography is a clinical upgrade that enhances your ability to assess, manage and maintain the patient’s ABCs. The time for capnography is now. I’ve been watching it grow in the EMS field for more than a decade. I’ve heard of some great uses all over the world. It takes courage and support to make this change for the intubated and non-intubated patient.
Disclosure: The author has reported receiving no honoraria and/or research support, either directly or indirectly, from the sponsor of this supplement.
1. Maddox RR, Williams CK, Oglesby H, et al. Clinical experience with patient-controlled analgesia using continuous respiratory monitoring and a smart infusion system. Am J Health Syst Pharm. 2006;63(2):157–164.
2. Deitch K, Miner J, Chudnofsky CR, et al. Does end-tidal CO2 monitoring during emergency de-partment procedural sedation and analgesia with propofol decrease the incidence of hypoxic events? A randomized, controlled trial. Ann Emerg Med. 2010;55(3):258–264.
3. Krauss B, Hess DR. Capnography for procedural sedation and analgesia in the emergency depart-ment. Ann Emerg Med. 2007;50(2):172–181.
4. Lightdale JR, Goldmann DA, Feldman HA, et al. Microstream capnography improves patient monitoring during moderate sedation: A randomized, controlled trial. Pediatrics. 2006;117(6):e1170–1178.