Endotracheal intubation: Oral intubation by direct laryngoscopy - Airway management techniques

Endotracheal intubation

Oral intubation by direct laryngoscopy

We prefer to intubate the trachea when we need to have more control of the patient’s airway, ventilate his lungs, and protect against aspiration of gastric con-tents. The use of a cuffed tracheal tube (Fig. 2.4) reduces the risk of aspiration in the adult.¹ Our first step is to confirm all necessary equipment is at hand:

·           a properly checked anesthesia machine, or a self-inflating bag or Mapleson system with source of compressed oxygen, and a tight fitting mask;

·           endotracheal tubes (ETT) of appropriate sizes (see Table 2.2). Generally we like to have an extra tube ¹/₂ size smaller than that anticipated . . . just in case;

·           a stylet that fits in the ETT – sometimes required to stiffen and shape the tube;

·           a syringe to inflate the ETT cuff;

·           an oral airway, in case intubation and mask ventilation prove to be difficult;

·           laryngoscope handle and appropriate blades (Fig. 2.5), usually at least a curved (Macintosh) and straight (Miller), with confirmation that the light works!

·           suction – for the inevitable oral secretions and potential regurgitation; induction drugs;?>

·           an assistant schooled in application of cricoid pressure: manual pressure applied to the cricoid ring, compressing the esophagus against the vertebral body beneath, in hope of preventing passive regurgitation.

The smooth placement of an endotracheal tube requires skill and practice. Usually we start with denitrogenating (pre-oxygenating) the patient’s lungs before ren-dering the patient unconscious and immobile (including paralysis of the muscles of respiration) for the intubation. If the patient cannot breathe and we are unable to ventilate his lungs, his life is in danger. Fortunately, we can usually identify those patients in whom conventional endotracheal intubation will be difficult. It is vitally important to recognize them before administering medications that induce apnea.

Intubation is typically performed with direct visualization of the larynx, that is, we like to watch the tube pass through the vocal cords. Unfortunately, without an instrument such as the laryngoscope, no direct line of sight exists through the open mouth to the larynx. Instead, we must find a way to bring the larynx into view – enter “direct laryngoscopy.” Here we position the patient’s head in the “sniffing position:” flexed at the lower cervical spine and extended at the atlanto-occipital joint (see Fig. 2.6). Then we advance a laryngoscope to the level of the epiglottis and use it to pull the lower jaw and tongue up and out of the way, opening up a line of sight to the larynx (usually). The exposure of the larynx varies and has been classified by Cormack and Lehane (Fig. 2.7).

Thus, to intubate a patient with a “normal airway,” first position, denitrogenate (pre-oxygenate), and induce the patient as described above, then proceed as follows:

·           Take the laryngoscope in your left hand; the right hand is responsible for everything else.

·           Place the right hand on top of the patient’s head and accentuate neck exten-sion. Note that some prefer to perform a scissor-like maneuver with the right thumb and index finger to open the patient’s jaw.

·           Advance the laryngoscope down the right side of the mouth to the level of the tonsillar pillars. Sweep the tongue to the left as you bring the laryngoscope to the midline.

·           With a straight blade, lift the epiglottis; with a curved blade, place it at the base of the epiglottis. As above, lift forward and upward (in the direction of the laryngoscope handle). Do not pry or crank with the laryngoscope! Teeth might be broken.

·           When you can see the glottic opening clearly, grasp the endotracheal tube (hold it like a pencil – not a dagger) with the right hand (preferably without losing sight of the glottis), and advance the tip into the trachea just until the cuff disappears completely beyond the vocal cords.

·           Inflate the cuff only to the point of no air leakage, and confirm trachealposition.

This last point is very important. Patients do not die from esophageal intubation; they die when esophageal intubation is not recognized! You must be absolutely sure the tube is in the right place! A fiberoptic bronchoscope that finds the tip of the tube below the cords and above the carina would be ideal but is impractical as a clinical routine. A chest radiograph, both PA and lateral, confirming location in the trachea would also work, but is similarly impractical for OR applications. Instead, we must use clinical clues and technology.

i.               Confirmation of exhaled CO₂ is the gold standard, either by quantitative capno-graphy as in the operating room, or the more mobile colorimetric sensors. Note, however, that this only guarantees ventilation of the lungs. It does notspecifically identify the ETT as placed in the trachea. Pharyngeal position of the tube with ventilation (as with an LMA) may yield CO₂. Conversely, duringcardiovascular collapse, with minimal or no pulmonary blood flow, little or no CO₂ will be returned to the lungs from the periphery, and end-tidal CO₂ mightnot be measurable. Place a sensor anyway because the return of detectable CO₂ will indicate effective resuscitative efforts and perfusion of the lungs.

ii.               Breath sounds While not definitive for tracheal placement, breath soundsshould be present across the chest and absent over the stomach. We can rule out endobronchial intubation when we hear good breath sounds bilaterally. Emphasis on the bilaterally; listening close to one side of the sternum, we often mistake breath sounds transmitted from the other side.

iii.               Condensation While reassuring, condensation in the clear plastic ETT duringexhalation is no ironclad guarantee either.

iv.               Palpation of the ETT cuff Still not flawless, but when combined with the pres-ence of exhaled CO₂, palpation of the cuff in the suprasternal notch (notable by the bounce felt while squeezing the pilot balloon) does confirm tracheal position.

v.               Chest excursion should be symmetric.