Fig. 6.4 Upper lip bite test. Class I: The patient is able to bite the upper vermilion line with the lower incisors. Class II: The patient is able to bite the upper mid-lip with the lower incisors. Class III: The patient cannot bite the upper lip with the lower incisors.
4th Step: Assess Range of Motion of the Cervical Spine
The fourth step of the test is to evaluate the mobility of the cervical spine. This is accomplished by asking the patient to flex and extend the neck. Patients should be able to perform this without discomfort. Disease of the C-spine (rheumatoid arthritis [RA], osteoarthritis [OA]), previous injury, or surgical fusion may limit neck extension, which may create difficulties during intubation attempts. This is certainly true if the atlantooccipital joint is involved, as restriction of this joint’s mobility may impair the ability to visualize the larynx.
“Non-reassuring airway” findings:
A number of clinical findings can be used to predict difficulty with direct laryngoscopy and intubation (Table 6.1). When these findings are present, clinicians often describe the patient as having a “non-reassuring” airway. These findings may be used to plan alternate techniques to direct laryngoscopy for intubation.
Evaluation of the Lower Airway:
Lastly, an attempt should be made to ascertain any difficulty with the lower airway (glottis, larynx, and trachea). This is particularly important in patients who have experienced a previous airway injury or surgery on their airway, such as a tracheostomy. Observe the patient for hoarseness, stridor, or a previous tracheostomy scar that would suggest a potential underlying tracheal stenosis.
Fig. 6.5 shows visualization of the laryngeal structures at the time of laryngoscopy. Just as the view of the oropharyngeal structures has been classified, the view of the laryngeal structures has been graded from 1 to 4. While there is not a perfect correlation between the oropharyngeal class and the laryngeal grade, we anticipate that a patient with a class 1 oropharyngeal view and no other identified airway abnormalities will have a grade I laryngeal view. Similarly, a class 4 oropharyngeal view predicts difficulty in visualizing laryngeal anatomy.
Fig. 6.5 Cormack and Lehane Grading of the best laryngeal view obtained with direct laryngoscopy. (Cormack RS, Lehane J. Anaesthesia 1984;39:1105-1111).
A BASIC MAD POSTER
Before proceeding with intubation prepare for success with the mnemonic “A BASIC MAD POSTER”
“A BASIC MAD POSTER” preparation for intubation explained.
Assessment: The preparation for intubation begins with an assessment of the airway.
Bag-mask: A bag-mask system should be checked and capable of delivering oxygen with positive pressure.
Airways: Oropharyngeal and nasopharyngeal airways should be immediately available.
Suction: A tonsillar Yankauer suction device with a tapered tip should be immediately available next to the patient’s head.
Intravenous: Intravenous access should be established.
Capnometry: Capnometry (ETCO2 monitoring) should be immediately available to confirm correct endotracheal placement.
Monitors: Monitors, including pulse oximetry, ECG, and blood pressure (BP), should be attached.
Audible: The saturation monitor should be configured to provide an audible tone during the procedure.
Drugs: Drugs should be prepared and labelled.
Position: The patient should be in an optimal position for tracheal intubation.
Oxygen: Oxygen should be administered to preoxygenate the patient prior to the procedure.
Stylet: A stylet should be positioned in the ETT.
Tape: Tape should be immediately available to secure the ETT.
ETT: An appropriate-sized endotracheal tube and functioning laryngoscope should be prepared and checked.
Rescue: Rescue medications and backup airway plans should be considered before intubation.
Common rescue medications include midazolam, fentanyl, and propofol for sedation. Ephedrine and phenylephrine may be required to treat hypotension after intubation. Prior to proceeding with intubation, there should be clearly thought out airway backup plans. Plans may include having special equipment present (e.g., Glidescope or LMA™).
Clinical Pearl:
Always ensure that the saturation monitor emits an audible tone when performing tracheal intubation. The audible tone provides immediate information to the operating room team about the patients’ heart rate, saturation, and well being that may otherwise go unnoticed during the procedure.
Tracheal Intubation:
The technique of tracheal intubation involves five steps.
I. Position the patient
II. Open the patient’s mouth
III. Perform laryngoscopy
IV. Insert the ETT between the vocal cords and remove the laryngoscope
V. Confirm correct ETT placement and secure the ETT
Fig. 6.6 Axes of the airway. A combination of cervical flexion and atlanto-occipital extension aligns the axis of the pharynx (A.P.), larynx (A.L.) and mouth (A.M.). Forward displacement of the mandible then facilitates visualization of the glottis during direct laryngoscopy.
Fig. 6.7 Left image: poor positioning for direct laryngoscopy. Right image: optimized positioning for direct laryngoscopy. Note the horizontal alignment of the middle