OROTRACHEAL INTUBATION

Many conscious patients require emergency intubation. They may be unable to clear the airway spontaneously of secretions require mechanical ventilation, have aspirated, or lack protective airway reflexes. Most are lying supine on gurneys.

The clinical assessment of oxygenation and ventilation is unreliable in a chaotic emergency department. Oximetry is the noninvasive bedside monitoring of arterial oxygen saturation. Remember that isolated oximetry yields no clue regarding the status of alveolar ventilation. Capnography allows estimation of the Paco2 based on the waveform display of the end-tidal Pco2. Capnometry is the nunmerical display. In combination, both of these noninvasive modalities aid in determining the need for more aggressive airway interventions.

Capnography can also hdlp verify tube placement in perfusing patients and thus prevent consequential esophageal intubation. A sudden drop in the end-tidal CO2 may reflect endobronchial tube migration. When electronic capnography is unavailable, consider using disposable capnometric devices.

Technique

-Take a brief time to evaluate the upper airway anatomy. Examination of the teeth, oral cavity size, mentum-cricoid distance, mobility and posterior depth of the mandible, and neck mobility may clue the operator to anticipate a difficult airway.

- check and arrange the necessary equipment (While calling for an assistant). The appropriate-size tube and an additional tube 0.5 to 1 mm in size smaller should be selected, and the cuff checked for air leaks. Selecting a tube with the proper diameter is essential.
Tubes with high-volume low-pressure cuffs are best for adults. In patients younger than 6 to 8 years, use uncuffed tubes. Note that lidocaine jelly can form a clear film and eventually occlude the lumen of small pediatric tubes. Thin-walled cuffs prevent aspiration when properly inflated better than medium-walled cuffs. Microcirculation to the tracheal mucosa will be impaired if the cuff pressure exceeds 40 cm H2O. After nasogastric decompression, the cuff pressure should initially be deflated to 15 to 20 cm H2O, or just to the point of eliminating audible air leaks. Cuff overinflation can compromise the ET tube lumen.
- Laryngoscope

Test the light on the laryngoscope and pick your blade.
The straight Magill blade directly and physically lifts the epiglottis. The curved Macintosh blade rests in the vallecula above the epiglottis and indirectly lifts it off the larynx because of traction on the frenulum.
The curved blade may be less traumatic and reflex-stimulating since it does not directly touch the larynx. It also allows more room for adequate visualization during tube placement. The straight blade is mechanically easier to insert in many patients who do not have large central incisors.
In adults, the curved Macintosh no.3 or 4, or the straight Miller no.2 or 3, is most often ideal.

- the patient is placed in the sniffing position. Flexion of the lower neck with extension at the atlantoocipital joint (sniffing position) aligns the oropharyngeolaryngeal axis, allowing a direct view of the larynx. Placing a folded towel or small pillow under the occiput is often helpful.

- If time permits, the patient should be oxygenated with 100% oxygen prior to intubation.

- Begin with the laryngoscope in the left hand and an ET tube on tonsil suction catheter in the right hand. After removal of dentures and any obscuring blood, secretions, or vomitus, the suction catheter is exchanged for the ET tube and inserted during the same laryngoscopy.

- Insertion of the blade
The blade is inserted into the right corner of the patient’s mouth. If a curved Macintosh blade is used, the flange will push the tongue to the left side of the oropharynx. If the blade is inserted down the middle, the tongue forces the line of sight posteriorly-yet another reason for the putative “anterior larynx.”

 -After visualization of the arytenoids, lift the epiglottis directly with the straight blade or indirectly with the curved blade. The larynx is exposed by pulling the handle in the direction that it points, that is, 90o to the blade. (avoid the most common error, overly deep insertion of the blade, by looking for the arytenoids cartilages).
- If only the posterior commissure is visible, have an assistant apply pressure on the cricoid the Sellick maneuver. Watch the cuff as it passes completely through the cords to avoid an error. ( Always be willing to abort the attempt if visualization of the larynx is not successful, and resume mask ventilation) Continuous pulse oximetry during intubation can identify hypoxia quickly.
- The tube is advanced until the cuff disappear below the cords. Correct tube placement is about 2 cm above the carina. From the corner of the mouth, this is approximately 23 cm in men and 21 cm in women. The base of the pilot tube is usually at teeth level. The tube is also positioned by palpating its tips at the suprasternal notch and advancing it 2 to 3 cm.
- The cuff is inflated, an oropharyngeal airway or bite block is inserted and auscultated to verify bilateral lung expansion.

Aid to intubation

- One aid to intubation with direct vision is the use of a thin, flexible intubation stylet. This type of stylet can be inserted blindly around the epiglottis into the trachea. Then the ET is threaded over it into the trachea and the stylet removed. The Eschmann stylet (gum clastic bougie) is a common choice.
-Another option is to use the tip on the laryngeal tracheal anesthesia kit. With either stylet, orient the tube so that Murphy’s eye is in the twelve-o’clock position.
- Visualization of the larynx prior to cervical spine clearance is difficult, since alignment of the oropharyngeolaryngeal axis is not possible. One way to move the tip of the tube anteriorly is to use a slightly flexed directional-tip tube (Endotrol) coupled with a Sellick maneuver.
- Another is a flexible stylet, the Flexiguide, that passes through the tube and has a trigger similar to the Endotrol. The final option is to aim the tip anteriorly with Magill forceps while an assistant advances the tube.
-Syringe aspiration technique It is a useful adjunct to the standard techniques for intratracheal tube confirmation. This may be especially useful in the prehospital setting. A catheter-tipped 60 mL syringe is snugly inserted through the adaptor at the proximal end of an ET tube. The tube must be at least size 7.0 ID. Resistance to aspiration reflects occlusion from esophageal collapse. If there is no aspiration reflects occlusion from esophageal collapse. If there is no resistance during aspiration, the tube is in the trachea. Commercial esophageal intubation detectors are also available. The adaptor on the detector’s syringe fits over the 15 mm ET tube connector. The tube may be obstructed by a bulging cuff, secretions, kinding, or biting. Subsequently neck movement can also displace the tube.

Complications

- Inadvertent endobronchial intubation is usually on the right side. Cut and secure the tube, being careful not to impede cervical venous return with the umbilical tape. Ideally use a modified clove-hitch knot or a commercial fixation. Avoid tying and kinking the pilot tube.
- If the cuff leaks, tube replacement is possible with or without direct visualization. A length of nasogastric tubing two and on-half to three times the length of the ET tube can be inserted as a guide.
- Endobronchial or esophageal intubation will result in hypoxia or hypercarbia. Disposable capnographic devices can confirm ET tube placement.
- Arytenoids cartilage displacement, usually on the right, prevents the patient from phonating properly.
- Chordal synechiae may develop anteriorly, or commissural stenosis posteriorly. - Subglottic stenosis is the most disastrous complication. Prevent tube motion in the larynx and trachea. This usually occurs in combative patients or those on ventilators.