Obese patients can make an intubator timid, apprehensive and weak hearted. They’re soo difficult to intubate – or are they?

Obese patients are difficult to ventilate. They’re usually not difficult to intubate. Not in a controlled environment in the OR. Provided you’ve taken the necessary precautions:

As all other patients, they should have their ear-to-sternal-notch. To achieve this in obese patients, you need to ramp them. A lot. A special ramping pillow is easy to use, but if you don’t have one handy, you can just use lots of sheets and blankets to build up a ramp underneath the patient. Keep going until you’re satisfied. Don’t stop a blanket short. You want this preparation to be perfect. Wait until someone has brought you that final sheet you needed to get perfect ear-to-sternal-notch. You want this intubation to go smoothly.
An added bonus from this inclined position is that it alleviates some of the pressure from their abdomen on the thorax for pre-oxygenation and if you need to mask ventilate them.

Pre-oxygenate. Well.
Obese patients desaturate quickly. According to the cpap machine reviews, if you “pre-oxygenate” with the mask half a centimeter above the patient’s face because the patient finds a tight mask uncomfortable, just imagine if it might be slightly more uncomfortable seeing the patient’s saturation plummet below 50% during induction… Pre-oxygenate with a tightly sealed mask. Apply a little PEEP. Don’t go for mediocrity. When you have a patient that probably will be hard to ventilate, you’ll want to optimize the time available for your intubation.

Prepare for RSI, so you don’t have to ventilate them. They’re also at increased risk of regurgitation, so RSI makes sense either way. This isn’t a strict RSI protocol. The idea is to use induction and paralytic agents as per RSI so you can go straight to intubation without struggling with difficult ventilation.

Still, while waiting for your RSI doses to work, it can be a good idea to try to ventilate them. Remember, this is an elective case and strict RSI protocol isn’t necessary. If they’re easy to ventilate, good. keep doing that until intubation. But avoid high pressures, which increases risk of gastric insufflation. If they’re difficult to ventilate, don’t force it, just continue with RSI protocol.

If all this is unfamiliar territory, you should of course have someone with experience available to assist you. And as always, consider your back-up plan as well as other management options. Awake fiberoptic intubation in an inclined position is always a good way to go. And preceding all of this is a standard pre-operative assessment. If there are any other indications of a difficult airway, awake fiberoptic might be the way to go.

Review article
After writing this post, I found this excellent review article “Airway management and morbid obesity”, Eur J Anaesthesiology 2010, by Michael Seltz Kristensen, a consultant anaesthetist at Copenhagen University Hosptial, Rigshospitalet, with a glowing interest in airway management and head of their specialised ENT anaesthetic division. His article is a great read, and goes into more detail and more references on this issue.

Michael Kristensen is also course director for the excellent Airway Management for Anaesthesiologists course held in the start of December every year in Copenhagen. I’ve had the pleasure of working with Michael, but also, a few years before that, I attended this airway course, and can highly recommend it. It’s worth it just to let Michael’s enthusiasm envigorate you!

Wether the obese patient is more difficult to intubate has been debated in the literature. Large cohort studies will often find obesity as a predictor for difficult intubation. Others argue that obesity is not a problem as long as you take the proper precautions and make the proper arrangements, and use prospective studies to show their point. It seems clinics that are used to dealing with obese patients don’t have increased intubation problems with this patient group. So some of the problems reported might be due to managing them the same way as lean patients. It seems to be about anaesthetic management.

Here’s a very large Danish cohort study. They’ve kept a very good anaesthesia database for many years, and from over 90.000 patients, intubated by registrars and consultants and in various settings. Still, BMI was only a weak predictor of difficult intubation. One flaw with the study is that they excluded all planned fiberoptic intubations, without looking at any predictors for that group. Still, a very large study with a wide variety of patients.

“High body mass index is a weak predictor for difficult and failed tracheal intubation: a cohort study of 91,332 consecutive patients scheduled for direct laryngoscopy registered in the Danish Anesthesia Database”, Anesthesiology, 2009.

“High BMI is a weak but statistically significant predictor of difficult and failed intubation and may be more appropriate than weight in multivariate models of prediction of difficult tracheal intubation”.

However, some go even further, and say obesity is not a predictor at all. In prospective studies, where they have probably taken the necessary precautions, many of them find no increased difficulties with intubating obese patients. The following article is an example of this. As can be seen in their paper, some of the positive predictors for difficult intubation might stem from obesity, like higher airway class, but BMI is not a predictor per se.

“The incidence of class zero airway and the impact of Mallampati score, age, sex, and body mass index on prediction of laryngoscopy grade”, Anesthesia and Analgesia, 2001.

“Some studies have shown obesity to be a risk factor for difficult intubation, yet others have found that the incidence of difficult intubation in morbidly obese patients is not more frequent than in normal subjects. In our patients, an increased BMI was not correlated with a high laryngoscopy grade”.

And here’s a prospective study on 180 patients with a mean BMI of 49(!) presenting for bariatric surgery. Only six (3.3%) had a difficult intubation, defined as three or more attempts, but all were successfully intubated by anaesthesiology residents using a conventional approach. The authors contribute this low rate of difficult intubations to ramping.

“Obstructive sleep apnea is not a risk factor for difficult intubation in morbidly obese patients”, Anesth Analg, 2009.

So my take is that fat people are not hard to intubate, but they require special attention to airway management and obesity should get some lights flashing for making the proper preparations.

Additional references
“Shoulder and head elevation improves laryngoscopic view for tracheal intubation in nonobese as well as obese individuals”, J Clin Anesth, 2012.

“Preoxygenation is more effective in the 25 degrees head-up position than in the supine position in severely obese patients: a randomized controlled study”, Anesthesiology, 2005.

“Positive end-expiratory pressure during induction of general anesthesia increases duration of nonhypoxic apnea in morbidly obese patients”, Anesth Analg, 2005.

“Increased body mass index per se is not a predictor of difficult laryngoscopy”, Can J Anaesth, 2003.

Another article on difficult intubation predictors. BMI was not one of them:
Predictors of a difficult intubation in the bariatric patient: does preoperative body mass index matter? Surg Obes Relat Dis, 2012.

Also, be aware that this subject is debatable. Here’s a contrarian view, holding on to obesity as a predictor for difficult intubation: “Difficult Tracheal Intubation Is More Common in Obese Than in Lean Patients”, Anesth Analg, 2003

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