Segment:1 Macintosh Laryngoscope (Curved Blade): Introduction.
While there are many types of laryngoscopes available, this narrative will only discuss the basic principles of direct laryngoscopy using a curved and a straight blade laryngoscope. The Macintosh laryngoscope has two parts, a handle and a blade, which connect with a hook fitting. Most contemporary Macintosh laryngoscope handles contain a blade and a bulb providing the light conducted through a fiber-like bundle to the distal end of the blade.
The blade is designed to facilitate displacement and control of the tongue. The tip is designed to be placed in the vallecula to lift the epiglottis and expose the glottis.
The battery and light source of the laryngoscope should be checked for optimal condition prior to its use. A proper size endotracheal tube should be selected. The cuff should be checked for leaks and must be completely deflated to avoid obscuring the glottis during intubation.
In some situations, a well-lubricated malleable stylet may be necessary to stiffen and shape the tube as required.
Denitrogenation of the patient is required prior to the intubation attempt. The patient's head and neck is placed in a sniffing position. The laryngoscope handle is held by the left hand, while the right hand is used to open the mouth while ensuring that the lips and teeth are clear of the blade.
The blade is slowly advanced to the base of the tongue, which is displaced the left of the blade. Once the epiglottis is identified, the tip of the blade is then advanced into the vallecula and the hyoepiglottic ligament is pressed. The laryngoscope is lifted gently to avoid damage to upper dentition. If the epiglottis cannot be seen clearly, external pressure applied to the larynx can be used to improve the view.
Once the glottis is visualized, the endotracheal tube is introduced at the right corner of the mouth. The endotracheal tube is then placed through the cords and advanced until the cuff passes beyond the cords. Correct placement of the tracheal tube should be confirmed by the presence of end-tidal CO2 and auscultation.
Despite proper patient evaluation, device preparation, and good intubating technique, laryngoscopic intubation remains difficult in 1% to 3% of the population.
Optimal external laryngeal manipulation has been shown to consistently improve laryngeal view as shown in this video. The Eschmann tracheal introducer is particularly useful when only the epiglottis can be seen using a laryngoscope. Under these circumstances, the Eschmann introducer can be hooked underneath the epiglottis and advanced into the trachea. If it is correctly placed in the trachea, a subtle tactile clicking sensation can be felt as the tip of the Eschmann introducer slides over the tracheal rings.
Failing to feel these clicks, the introducer can be gently advanced until hold up is felt as introducer is lodged into distal bronchus. With the Eschmann introducer positioned-- at about 22 centimeters, at the corner of the mouth-- the tracheal tube can then be advanced over the Eschmann introducer into the trachea. To facilitate the advancement of the endotracheal tube over the Eschmann introducer and into the airway, the tongue and epiglottis must be elevated by a gentle jaw lift or preferably by the laryngoscope already in place.
Segment:5 Phillips Laryngoscope (Straight Blade): Introduction.
The handle for the Phillips laryngoscope is the same as for the Macintosh laryngoscope. The Phillips blade integrates the straight blade design with a gentle curved distal tip, specifically designed for direct lifting of the epiglottis to provide greater visibility. It incorporates a c-shaped cross section to provide an improved view of laryngeal structures and sufficient room for passage of an endotracheal tube as opposed to the Miller blade.
Similar to the curved blade, the battery and light source of the laryngoscope and the cuff of the tracheal tube should be checked for optimal conditions prior to their use.
Oxygenation of the patient is required prior to any intubating attempt. The patient's head and neck should be placed in maximum extension with a slight rotation of the head to the left.
As with the curved Macintosh laryngoscope, the techniques can be divided into four steps-- insertion of laryngoscope and passage along the paraglossal gutter, optimization of the position of the laryngoscope and the view of the larynx, passage of the tracheal tube, and confirmation of intubation. The laryngoscope handle is held by the left hand, while the mouth is open by the right hand to ensure that the lips and teeth are clear of the blade.
The laryngoscope is inserted lateral to the tongue on the right and advanced carefully along the paraglossal gutter. Continued application of a moderate lifting force with the laryngoscope during its passage helps maintain anterior displacement of the mandible, and control of the tongue, and to reduce contact between the laryngoscope and the maxillary teeth. As the laryngoscope is advanced, the epiglottis comes into view, and the tip of laryngoscope is passed posterior to the epiglottis.
The direction of lifting of the laryngoscope should be at right angles to the line of the straight laryngoscope blade, and it's produced by lifting in the line of the laryngoscope handle. The laryngoscope is lifted gently, and the glottis can be seen readily. If the glottis cannot be seen clearly, external pressure applied to the larynx can be used to improve the view.
Once the glottis is visualized, the endotracheal tube is introduced at the right corner of the mouth, down the lumen of the blade. An assistant can help to retract the cheek at the angle of the mouth to make room for the tube placement through the mouth. The endotracheal tube is then placed through the cords and advance until the cuff passes beyond the cords.
Following intubation, the cuff is inflated and correct placement of the tube should be confirmed as described above.
Visualization of the glottis is generally easier with the Phillips straight blade laryngoscope. But the placement of the endotracheal tube through the glottis can be challenging, as the glottic view is generally obscured by the advancing endotracheal tube. The Eschmann introducer is particularly useful when the glottic opening cannot be clearly seen using a laryngoscope.
Tracheal intubation under direct laryngoscopy remains the gold standard technique, and it's generally easier for most patients. However, successful intubation requires proper preparation of the patient and equipment, proper positioning of the head and neck, as well as good intubating technique. Occasionally, a styletted endotracheal tube or a tracheal introducer may be required to facilitate the placement of the endotracheal tube in patients with difficult laryngoscopy.