Virtual Disaster Medicine

Training Center (VDMTC)

Module 1

Basic Review of Endotracheal Intubation

for Providers at a Mass Casualty

Technique for Orotracheal Intubation

Equipment needed for endotracheal intubation include a properly sized tracheal tube, laryngoscope, functioning suction catheter with Yankauer tip, appropriate anesthetic drugs and facilities to provide positive pressure ventilation of the lungs with oxygen.⁵  (During a mass casualty, oxygen may be in short supply and the patient will have to be ventilated with air.)

Preoxygenation

Preoxygenation (also known as denitrogenation) should be performed in all cases before intubation if time permits.^2,10  Preoxygenation allows the replacement of the nitrogen volume of the lung (around 69% of the functional residual capacity [FRC] when the patient is breathing room air) with oxygen, to provide a reservoir for diffusion into the alveolar capillary blood after the onset of apnea.^2,11  Preoxygenation with 100% O₂ and spontaneous ventilation with a tight-fitting face mask for 3-5 minutes can furnish up to 10 minutes of oxygen reserve following apnea (in a patient without significant cardiopulmonary disease and a normal oxygen consumption).^2,12

In a study of healthy, non-obese patients who were allowed to breathe 100% O₂ preoperatively, they maintained an oxygen saturation of greater than 90% for 6 ± 0.5 min. This finding is in contrast to obese patients who experienced oxyhemoglobin desaturation to less than 90% in 2.7 ± 0.25 min.^{2 ,13}  The patient who breathes room air (21% O₂) will experience oxyhemoglobin desaturation to less than 90% after approximately 2 min under ideal conditions.²

Patients with pathologies such as respiratory failure, or with conditions affecting metabolism or lung volumes, frequently develop desaturation sooner owing to increased O₂ extraction, decreased FRC, or right-to-left transpulmonary shunting. The most common reason for not achieving a maximum alveolar FIO₂ during preoxygenation is a loose-fitting mask, allowing the entrainment of room air.^2,10   This can be prevented by holding the mask tightly to the patient’s face, ensuring a secure seal during preoxygenation, thereby preventing entrainment of room air.

Less time-consuming methods of preoxygenation have also been described. Using a series of 4 vital capacity breaths of 100% O₂ over a 30-sec period, a high arterial PaO₂ (339 torr) can be achieved, but the time to desaturation is consistently shorter as compared to techniques of breathing 100% O₂ for 5 min.^2,14

Another method described is the modified vital capacity technique.  When using this technique, the patient is asked to take eight deep breaths of 100% oxygen in a 60-sec period.^2,10,15

Pharyngeal insufflation of oxygen can also be used to prolong the duration that an apneic patient maintains an oxyhemoglobin saturation of >90%.  In this technique, oxygen is insufflated at a rate of 3 l·min^–1 via a catheter passed through the nares with nasal cannula.  This technique relies upon the phenomenon of apneic oxygenation.  That is a process by which gases in the upper airway move down the airway by mass movement to replace oxygen taken up in the alveoli.^2,16  This entrainment can provide enough oxygen to sustain hemoglobin saturation for prolonged periods.  So passive oxygenation employing nasal cannula may be helpful during the intubation process, especially with a difficult to intubate individual.²

TYPES OF LARYNGOSCOPES

All common types of laryngoscopes consist of a handle and a blade which has a light source allowing the intubator to see the larynx.  There are two major types of blades used with laryngoscopes, curved (Macintosh blades) or straight (Miller blade).

Curved (Macintosh) Blade

When intubating with a curved (Macintosh) blade, the tip of the curved blade is placed into the space between the base of the tongue and the pharyngeal surface of the epiglottis.  The Macintosh blade is inserted by opening the patient’s mouth and inserting the laryngoscope into the mouth (while holding the laryngoscope in the left hand).

The mouth opening is usually achieved by extending the patient’s neck.  This prevents the gloved hands from becoming contaminated with oral secretions from the patient’s mouth.  An alternative technique to open the mouth is by “scissoring” the mouth open with the thumb and index finger of the right hand.  However, this technique contaminates the right hand and necessitates removal of the glove on the right hand to prevent contamination of equipment with the patient’s oral secretions.

The blade is inserted along the right lateral aspect of the tongue to displace the tongue to the left.  With an abnormal anatomy often encountered in casualty patients with distorted anatomy, it is a good idea to find the uvula which indicates where “midline” structures might be found.  Following this line for about an inch (2.5 cm), the epiglottis will readily be found.  (Note: the tendency to insert (or “sink”) the laryngoscope blade to the hilt, and then start looking around, is not advisable in patients with potential distorted anatomy of the upper airway.)

The blade is inserted into the vallecula and then lifted with an anterior movement, away from the upper teeth.  This movement is sometimes described as “lifting towards the patient’s feet”, which stretches the hypo-epiglottic ligament, thereby elevating the epiglottis and exposing the glottic opening.

Straight (Miller) Blade

When using the Miller blade, the tip of the straight blade is passed beneath (posterior to) the laryngeal surface of the epiglottis, (thereby “picking up” the epiglottis).  Anterior movement of the blade “lifting towards the patient’s feet”, away from the upper teeth, directly elevates the epiglottis and exposes the glottic opening.

Table 2 shows the sizes and lengths of endotracheal tubes to be used for each age as modified from references 2 and 5.

An alternative method of calculating the size of the endotracheal tube is to divide the age by 4 and add 4 to give the size of the tube in millimeters internal diameter

For instance for size:

            A   4 year old child     4 divided by 4 equals 1, then add 4 = 5 mm tube

            An 8 year old child     8 divided by 4 equals 2, then add 4 = 6 mm tube

            A 12 year old child   12 divided by 4 equals 3, then add 4 = 7 mm tube

An alternative method of calculating length of an oral endotracheal tube for a child:

            Measure the distance from the corner of the mouth to the ear and add half that length.

INTUBATION SEQUENCE

If intubating from an operating table, the table height should be adjusted so that the patient’s face is approximately at the level of the standing intubator’s xiphoid process.

Place the Patient’s Head in the “Sniffing Position”

The sniffing position is based on the concept of : “the elderly gentleman sniffing the early morning air.”  The person is standing and “pushes the head forward” while “lifting the chin up.”  (Note: the head is vertical, or perpendicular to the ground)

To optimize the intubating position the patient’s head should be elevated 8 to 10 cm with pads under the occiput and the shoulders remaining on the table.  The neck is therefore lifted forward, while the head is flexed.  The plane of the face is now horizontal or parallel to the ground.  In obese subjects, the pillow under the head must be enlarged, until the plane of the face is at the same height as the anterior chest wall.

(Note: in this position, the laryngoscope blade is pulled towards the subject’s feet, i.e. downwards, and not towards the ceiling as in the extension position described in many textbooks.)

The flexion position serves to align the pharyngeal and laryngeal axes.

Next the patient’s head is extended at the atlanto-occipital joint which aligns the oral axis with the pharyngeal and laryngeal axes.  This will allow a straight line for passage of the endotracheal tube from the lips to the glottic opening.  This position is known as the sniffing position.⁵

Insertion of Laryngoscope

Using the right hand, an index finger is placed on the patient’s upper central incisors; place the thumb on the lower incisors, in front of the index finger.  Push the thumb away from you (a scissoring action) thus opening the patient’s mouth.

Holding the mouth open with the right index finger and thumb, carefully insert the blade of the laryngoscope into the mouth with the left hand, avoiding contact with the exposed teeth and moving from the right corner of the mouth toward the midline of the mouth and pharynx to move (sweep) the tongue to the left side of the mouth and pharynx.

Once the laryngoscope blade has been inserted, rotate the blade within the mouth counterclockwise (i.e., from right to left), thus further sweeping the tongue out of the way.  Avoid contact of the laryngoscope with the teeth during the intubation process.

(Note: do not use the teeth as a point of leverage for the laryngoscope;  pull the laryngoscope blade away from the upper teeth, i.e. pull towards the feet.)

Using the heel of the right hand on the patient’s forehead to extend the head, open the patient’s mouth further to expose the epiglottis and vocal cords by lifting up on the laryngoscope handle.  Lift in the same direction as the plane of the handle as shown by this diagram below.  Do not use the front upper teeth as a fulcrum for the laryngoscope,  This will cause breakage of the teeth.  Pull the laryngoscope away from the upper teeth.

 Visualize the structures of the pharynx.  Look for the epiglottis.  If you do not see the epiglottis, but see only mucosal folds, the laryngoscope blade is probably in the esophagus and you will need to carefully withdraw the blade into the mouth.  As you slowly withdraw, the epiglottis should come into view.

If you are using a curved (Macintosh) blade, the tip of the blade is positioned behind the epiglottis in the vallecula, and the floor of the mouth is raised by lifting the handle of the laryngoscope,  This raises the epiglottis too and it (and the vocal cords) will come into view.

If you are using a straight (Miller) blade, the tip of the blade is inserted just beyond the epiglottis which is then raised by the tip of the blade under the epiglottis, and the vocal cords will come into view.

When the vocal cords are under direct visualization, the endotracheal tube is inserted between the cords, into the trachea. 

Insert the tube through the cords until the cuff goes out of view.  Check the depth of insertion - typically the 19-21 cm marks should be at the level of the teeth.

Remove the laryngoscope carefully to prevent damage to the teeth.

Firmly grasp the newly inserted endotracheal tube and carefully remove the stylet.

Inflate the cuff on the endotracheal tube noting the pressure in the pilot balloon by palpation.Remove the stylet.  Connect the endotracheal tube to a ventilation circuit.

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