A patient arrives with altered mental status. He called EMS initially for shortness of breath. When they arrived, he was found slumped over on his front porch drooling and confused. His wife told them he has a history of COPD. He arrives altered, eyes closed, and guppy breathing. EMS started a nebulizer en route. His HR is 110, BP 142/95, and O2 98% on a non-rebreather. He has poor respiratory effort, and his VBG shows a respiratory acidosis with elevated pCO2. You feel he is past the stage where noninvasive ventilation will work, and the decision is made to intubate to protect his airway and give his respiratory muscles a chance to recover. You proceed with RSI, and all goes smoothly. Initial post intubation VS are improved, with his HR now in the 90's. 10 minutes later, you are called back in the room by the nurse, who tells you "This guy is crashing." His BP is now 60/40, HR 126 with frequent ectopy, and the vent alarm is going nuts. What is the first thing you do? What happened to this guy?
What Do You Do First?
Should you do some push dose pressors? Needle decompress? Sign out to your colleagues and go get lunch? The choices are infinite, but only one is right. When you intubate a COPD or asthmatic patient, and they are crashing after intubation, the first thing you should do is disconnect the patient from the vent and listen for a rush of air or prolonged expiration from the endotracheal tube. You do this, and you hear a prolonged expiration with a rush of air. You attach a bag and note that each expiration is prolonged. His vital signs return to their previous more normal state.
Likely, he began stacking his breaths and air trapping. This led to severe hyperinflation of already hyper inflated lungs (or auto PEEP). When this gets bad enough, you can limit venous return to the heart due to high intrathoracic pressure, which can lead to hypotension and cardiac arrest.
What Should I Do Next?
Once stabilized, reattach the vent and check your vent settings. Too often, we just let our respiratory therapist handle our vent settings. They know what they're doing, but we should know everything about our patients. For the intubated asthmatic of COPD patient, remember that these are diseases of ventilation, meaning we need to make sure they have time to breathe out. We do not want them to stack breaths, and we do not want them retaining CO2. So here is what you want to set:
- Tidal volume: 6-8 cc/kg ideal body weight (note, IDEAL, not actual)
- PEEP: < 5, consider no PEEP. Remember PEEP helps recruit dead lung space by giving the lungs pressure to stay open. These guys have enough pressure, keeping alveoli open is not their problem.
- FiO2: you can start at 100%, but consider dropping this quickly. Many COPD patients do not live at 100% saturations, and hyperoxia is not what you want in COPD patients (want to know why? Check this out). Drop to 40% and titrate to a saturation in the low 90's.
- I:E ratio: This is the most important piece of the vent settings for these patients. Remember the pink puffer with pursed lip breathing? Think about how long they breathe out versus in. Again, this is a problem of ventilation, not inspiration. Give those lungs time to deflate a bit and breathe out. Your I:E ratio should be at 1:4.
Other COPD Intubation Considerations
- Try avoiding it at all. If you can, try non-invasive ventilation. Call for BiPAP. You want BiPAP here to give them expiratory time, and again remember you want prolonged expiration compared to inhalation time.
- Remember, avoid over bagging everyone. Just after intubation, as your adrenaline is going, you have a tendency to bag fast. I have even heard people suggest we bag these COPD patients at an increased rate to help blow off some CO2. Bad idea. Again, the more you inflate their lungs and the less expiratory time they have, the more they auto PEEP and the closer you get to the scenario above. Giving them time to exhale will help them blow off the CO2, not jacking up the reparatory rate. Just like with everyone, over bagging does not help. If you notice they are tough to bag, consider giving a bear hug (patient satisfier?) or compressing the anterior chest to try to help deflate those lungs a bit while giving a nice prolonged expiratory phase in between bagging.
- If you take off the ventilator and you do not hear a rush of air or prolonged expiration, look for other causes of post intubation hypotension. Post intubation hypotension is bad, as we all know. Look for pneumothorax, dehydration, sepsis, etc.
- Make sure your sedation is dialed in. Sedate appropriately and do not forget the analgesia (morphine, fentanyl) as part of your sedation package. I prefer a fentanyl infusion (good hemodynamic profile, short lived). You want them to rest those fatigued respiratory muscles.
- Do not over react to PIP (peak inspiratory pressure) alarms. PIP has no correlation to barotrauma or risk for pneumothorax. What you care abut are keeping your plateau pressures around 30 or less.
- Remember to keep treating the condition. Intubating does not solve the problem. Give steroids, and especially continue nebulizer therapy while they are on the vent.
Are you interested in more vent talk?
I am by no means a vent guru. Far and away the best vent lecture I have ever heard for EP's is Scott Weingart's (@emcrit) two part lecture series "Dominating the Vent." Part one covers overall vent settings for lung injured and non-lung injured patients. Part two covers COPD and asthmatics (much more brilliantly than I can, I might add). Do yourself a favor and listen to these. If you have not already, subscribe to the EMCrit podcast, and follow the EMCrit blog at www.emcrit.org.