All images provided by the author.
It’s the end of a warm evening, one of those nights where the air is soft and the streets are busy in that slow summer way, restaurant patios spilling out onto sidewalks, kids on bikes, someone two blocks over grilling something that smells unreasonably good.
You and your partner grabbed iced coffees about an hour ago, and yours is mostly ice now, which is fine because you’ve been sipping it slowly enough to make it last. You’re in a comfortable silence when the CAD chirps. Unconscious male found-down at an apartment complex on the south end. Caller states they are unable to arouse the patient.
You tap enroute and start your way over to the address, it takes about three minutes. You pull up to a two-story garden apartment with an open stairwell and a parking lot that’s about two-thirds full. A young woman is standing at the edge of the lot, arms crossed over her chest, shifting from foot to foot. She waves you over immediately.
She tells you before you can get in a greeting or handshake. I called. He’s upstairs in apartment 214. I live next door. I could hear the TV blasting earlier, and then nothing for hours, and I just, I got a bad feeling. I knocked and the door was unlocked so I just…”
You let her know “You did the right thing. What’s his name?”
She replies quickly with “Cody. He’s 29. I don’t know much else about him. We’ve only talked a few times.”
You grab your bag of tricks and box of life, and you and your partner head up the exterior stairs, down the breezeway. The door to 214 is slightly ajar. You push it open.
The apartment is cool. Television on, muted on a cooking competition with subtitles. A fan oscillating in the corner.
The couch is against the far wall, and Cody is reclined back into it, head tilted to the left, arms slack at his sides. You call out “EMS”. You call his name from the doorway. Nothing. You make your way over to him.
You look at his lips before you’re even all the way across the room: just a hint of purple at the margins. His chest is barely moving, you watch for three full seconds to be sure. It’s there, but it’s slow. Very slow. Six, maybe seven breaths per minute, each one shallow.
You ask: “Cody! Can you hear me?”
You do a once over Cody to see if you see any bleeding or other signs that might point you to why he is like this. You then put your knuckles firmly on his sternum. A low groan but not purposeful, not protective. His eyes don’t open.
You check pupils with your penlight: pinpoint, bilaterally. Both sides. Equal. You don’t need the story yet; the story is already written.
Your partner hooks up the monitor while you check for trauma, no signs of a struggle, no falls, no injuries visible. You note the coffee table: a water bottle, a phone face-down, and an orange prescription bottle on its side. The label is not Cody’s name. You pick it up with a gloved hand and note the medication: oxycodone. Almost empty.
Your partner turns the monitor toward you.
You look over and uncontrollably blurt out “82!” Your partner already has the BVM out and moving towards Cody’s face. You look at your partner as call out “if you’ve got ventilations, I’ll get the Narcan drawn up. Your partner concurs. You let them know you are going to start with .4mg and titrate to breathe.
Your partner has a good mask seal and begin ventilating at about twelve per minute with the BVM, ensuring adequate tidal volume, you want the chest to rise. Within two assisted breaths, you watch the capnography:
The number is moving. You’re breathing for him, and his lungs are accepting it. That normal waveform was the promise: the airways are open, the alveoli are ready, they just need someone to run the pump.
You push the Naloxone in slowly through the IV you got real quick. You timestamp it on the monitor and both you and your partner keep an eye on the capnography waveform.
After about forty seconds. Cody takes a shallow breath that your partner didn’t initiate. Then another. They ease back on the BVM, watching. His rate climbs: eight, ten, twelve. His eyes flutter open. He looks up at the ceiling, then at you, then at the BVM over his face, then back at you.
You start of talking to Cody with a calm “Hey Cody… what’s going on?” He replies with “What happened?”
“Your name is Cody, right? You stopped breathing. We’re helping you breathe. You’re going to be okay.”
You can see he starts to panic “I stopped… what?” You let him know he wasn’t breathing. You follow up with “Can you tell me what you took tonight?”
He looks away. A long pause and replies with “Some pills.”
You reassuringly reply “Okay. I’m not here to judge you. I’m here to make sure you’re okay. Are you having any pain anywhere? Any other symptoms?”
He replies with “No. Just… tired.”
You let him know “We’re going to take you to the hospital, okay? Narcan wears off, and I want you to be somewhere safe when that happens.”
He nods once. You take a peek over at the monitor and are reassured to find.
You look at the waveform—still normal morphology, normal rate now, normal value. The architecture was always fine. You just had to turn the light back on.
You package Cody and transport. His RR is 14 by the time you’re rolling. He’s asking where he is again, which is actually a reassuring sign the naloxone’s peak effect is giving him some clarity. You tell him, briefly and without drama.
You hand off at the ED with a clear and complete report, including the pill bottle information, the naloxone dose and time, the capnography trend before and after, and a reminder that he’ll probably need continued monitoring for re-narcotization as the naloxone clears before the oxycodone does.
The Capno-Recap: The Shape v. The Number—Why Both Matter
Here’s the nuance that separates good capnography interpretation from great capnography interpretation: the waveform morphology and the numerical value are telling you two different things, and you need both.
Cody’s waveform is morphologically normal. Each of those infrequent, slow breaths is producing a well-formed CO2 waveform. That tells you the following: his airways are patent, his alveoli are participating in gas exchange, and the mechanics of the breath itself are intact. The architecture of his respiratory system is fine.
But the value is 82 mmHg. So he is either making too much and can’t keep up exhausting it (think high metabolism) with a high RR or he isn’t ventilating well with a low RR. At a respiratory rate of seven. That tells you the rate and volume of breathing are so profoundly insufficient that CO2 is accumulating faster than it can be exhaled.
This is pure hypoventilation, not a lung problem, not a perfusion problem, not an airway problem an exhaust problem. Cody’s brainstem is not telling his diaphragm to fire with enough frequency or depth to clear what his metabolism is producing.
Opioid-induced respiratory depression occurs at the mu-opioid receptors in the brainstem specifically in the pre-Bötzinger complex, which generates the rhythmic firing that drives the breathing cycle. When these receptors are saturated, respiratory rate and tidal volume both decrease. The result is hypoventilation: CO2 accumulates because the body continues producing it through normal cellular metabolism, but the minute ventilation (RRxTV) is insufficient to eliminate it so it gets backed up and retained.
The key clinical teaching from Cody’s presentation is that a high EtCO2 with a normal waveform morphology tells you the gas exchange architecture is intact. The alveoli are open and functional. Each breath, however infrequent, is producing a geometrically correct CO2 curve. Your intervention target is the rate and depth of breathing, not the airway, not the vasculature, not the alveoli. You ventilate, you reverse, you watch.
This pattern stands in sharp contrast to the shark-fin of obstructive disease, where the mechanics of airflow are compromised, or the flat low-value waveform of poor perfusion, where CO2 isn’t being delivered to the alveoli at all. Normal shape plus high value equals rate and depth problem. Always look at both.
*** Street Trick: If the waveform looks normal and the EtCO2 is high look right at the RR. If low go right to assisting their ventilations and watch the number fall. If it falls readily with bag-mask ventilation, you’ve confirmed your diagnosis: the problem is drive, not mechanics. The lung is fine. The light switch is off. Your job is to turn it back on slowly, so you don’t set off the alarm when you do.***
Chris Kroboth has been a career paramedic/firefighter for over 17 years and in EMS for over 23. He has been in prehospital and in-hospital education for the past 18 years. His last assignment before returning to operations was as the EMS training captain in charge of continuing education programs and certification. He is also affiliate faculty with the Virginia Commonwealth University Paramedic Program. He is the U.S. clinical education manager for iSimulate and also facilitates national conference clinical challenges to include EMS World, ENA and NTI.
