Multiple casualties are brought to you from a house fire. There are four victims:
- A 5’11” 70 kg woman with a GCS of 8
- A 5’9” 140 kg man with circumferential burns of the chest and neck
- A 20 month-old with a pedi-GCS of 10
- An elderly, 5’6” 65 kg man with no burns, but a history of severe CHF and complaining of chest pain and dyspnea
You determine that they all require intubation for various indications. You choose RSI as the method for all except the morbidly obese patient, who you intend to intubate awake, with sedation and topical airway anesthesia.
How would you position each of these patients to optimize your chances of successful intubation on the first attempt?
The purposes of positioning a patient prior to an airway intervention are twofold: 1) to optimize laryngoscopy, and 2) to facilitate gas exchange.
It is impossible to orally intubate a patient under visual guidance alone using direct laryngoscopy if there is not a straight visual path from the open mouth to the cords. This requires alignment of the oral, pharyngeal and laryngeal axes of the airway. Positioning the patient facilitates this alignment, and the laryngoscope blade displaces any remaining soft tissue to permit visualization of the cords. The degree to which the three axes are malaligned depends primarily on the body habitus of the patient. The marker of successful positioning for laryngoscopy in all of these patients is the same, regardless of their varied body types. In all cases, you want to bring the ear hole (excuse the use of highly technical jargon, please) to the plane of either the jugular notch or the anterior surface of the shoulder joint (Figure 1).
Optimal position is most simply described as flexion on the lower C-spine with some extension at the atlanto-occipital joint (A-O). Whether supine or seated, a patient with the occiput and back against the mattress will require changes in the relative positions of their head and torso to achieve optimal alignment.
In patients with a normal body habitus, a 4 to 6 cm pad beneath the occiput will adequately flex the lower C-spine. Manual extension at the A-O joint will complete the proper position.
In morbidly obese patients, the head tends to drop back resulting in lower C-spine extension and A-O flexion. A simple pad beneath the occiput will not suffice – these patients need to have a ramp of towels or sheets built beneath the upper torso, neck and head to elevate their ear hole to the proper plane. This should be done well in advance, as part of the first “P” of RSI – preparation. Care must be taken to ensure that A-O joint extension is also achieved prior to laryngoscopy, as inappropriate construction of the ramp may lead to A-O flexion.
In infants and toddlers the occiput is relatively large, and the neck tends to flex at both the lower C-spine and the A-O joint when the patient is supine. Here, the torso needs to be elevated to permit extension at the A-O joint and relieve the “tucked chin” position.
Facilitating Gas Exchange
Laying flat reduces the functional residual capacity (FRC) of the lungs. Normally, this is of no consequence. However, it can be of critical importance in patients with structural lung disease or increased lung water, where FRC may be halved simply by occupying a supine position. As such, you want to keep patients with CHF, advanced COPD, extreme age, pneumonia, ARDS, etc., seated until the last possible moment prior to intubation to exploit the maintenance of FRC that accompanies the upright posture. Some patients may need to be intubated in the seated or semi-seated position because of compromised respiratory reserve. Similarly, patients who are obese, have massive ascites, or who are advanced in pregnancy will have restriction of lung capacity when supine – all those abdominal contents push upwards on the diaphragm and interfere with their excursion. Keep them seated, or tilt the head of the bed upwards, to prevent this.
Bagging of obese patients is more effective in the seated, or head up, position. Pre-oxygenation with tidal breathing is also more effective when the posture is more upright.
Positioning is FREE!
We should do it on every patient, every time, unless contraindicated. Our goal is to maximize first-pass success with intubation, and not settle for mere success after multiple attempts. Proper positioning is absolutely guaranteed to improve your intubation success rate. Achieving proper position is easy…just do whatever it takes line up the ear hole with either the front of the shoulder or the jugular notch.
I expect, and happily anticipate, vast increases in our ED laundry bill.
Original text by Steven Carleton, MD PhD, edited and reviewed by Mike Steuerwald, MD