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Laryngoscopes and tracheal intubation equipment


Laryngoscopes

These devices are used to perform direct laryngoscopy and to aid in tracheal intubation ( Fig. 7.1 ). They can also be used to visualize the larynx or pharynx for suctioning, removal of foreign body, placing of nasogastric tube and throat packs.

Fig. 7.1, Performing direct laryngoscopy. The vocal cords are visualized by lifting the laryngoscope in an upward and forward direction (see arrow) .

Components

  • 1.

    The handle houses the power source (batteries) and is designed in different sizes.

  • 2.

    The blade is fitted to the handle and can be either curved or straight. There is a wide range of designs for both curved and straight blades ( Fig. 7.2 ).

    Fig. 7.2, A wide range of laryngoscope blades. (A) Miller blades (large, adult, infant, premature); (B) Macintosh blades (large, adult, child, baby); (C) Macintosh polio blade; (D) Soper blades (adult, child, baby); (E) left-handed Macintosh blade; (F) Wisconsin blades (large, adult, child, baby, neonate); (G) Robertshaw blades (infant, neonate); (H) Seward blades (child, baby); (I) Oxford infant blade.

Mechanism of action

  • 1.

    Usually the straight blade is used for intubating neonates and infants. The blade is advanced over the posterior border of the relatively large, floppy, V-shaped epiglottis, which is then lifted directly in order to view the larynx ( Fig. 7.3B ). Larger-size straight blades can be used in adults.

    Fig. 7.3, Use of the laryngoscope with (A) curved and (B) straight blade.

  • 2.

    The curved blade (Macintosh blade) is designed to fit into the oral and oropharyngeal cavity. It is inserted through the right angle of the mouth and advanced gradually, pushing the tongue to the left and away from the view until the tip of the blade reaches the vallecula. The blade has a small bulbous tip to help lift the larynx ( Fig. 7.3A ). The laryngoscope is lifted upwards, elevating the larynx and allowing the vocal cords to be seen. The Macintosh blade is made in five sizes: neonate (0), infant (1), child (2), adult (3) and large adult (4).

  • 3.

    In the standard designs (colour-coded black) ( Fig. 7.4 ), the light source is a bulb screwed/positioned onto the blade and an electrical connection is made when the blade is opened and ready for use. In more recent designs, the bulb is placed in the handle and the light is transmitted to the tip of the blade by means of fibreoptics (colour-coded green). Opening the blade turns the light on by forcing the bulb down to contact the battery terminal. Acrylic fibre is used in the disposable blades. The two systems are not cross-compatible.

    Fig. 7.4, Conventional standard laryngoscope blade with the light bulb mounted on the blade (left) ; fibreoptics laryngoscope blade with the bulb mounted on the handle (right) .

  • 4.

    A left-sided Macintosh blade is available. It is used in patients with right-sided facial deformities, making the use of the right-sided blade difficult ( Fig. 7.5 ).

    Fig. 7.5, Penlon left-sided Macintosh blade.

  • 5.

    The McCoy laryngoscope (Penlon Ltd, Abingdon, UK) is based on the standard Macintosh blade. It has a hinged tip that is operated by the lever mechanism present on the back of the handle. It is suited for both routine use and in cases of difficult intubation ( Fig. 7.6 ). Another McCoy design based on the Seward blade ( Fig. 7.7 ) is also available.

    Fig. 7.6, Penlon Macintosh McCoy blade.

    Fig. 7.7, Penlon Seward McCoy blade.

  • 6.

    A modified design called the Flexiblade exists in which the whole distal half of the blade can be manoeuvred rather than just the tip, as in the McCoy. This can be achieved using a lever on the front of the handle.

  • 7.

    The blades are designed to be interchangeable among different manufacturers and laryngoscope handles. Two international standards are used: ISO 7376/2009 (green system) and ISO 7376/1 (black system) with a coloured marking placed on the blade and handle. The two systems have different dimension hinges and with different light source positions. The ‘green system’ is the most commonly used fitting standard.

  • 8.

    Magnetic resonance imaging (MRI) compatible laryngoscope handles and blades are available.

Problems in practice and safety features

  • 1.

    The risk of trauma and bruising to the different structures (e.g. epiglottis) is higher with the straight blade.

  • 2.

    It is of vital importance to check the function of the laryngoscope before anaesthesia has commenced. Reduction in power or total failure due to the corrosion at the electrical contact point is possible.

  • 3.

    Patients with large amounts of breast tissue present difficulty during intubation. Insertion of the blade into the mouth is restricted by the breast tissue, impinging on the handle. To overcome this problem, specially designed blades are used such as the polio blade ( Fig. 7.2 ). The polio blade is at about 120 degrees to the handle, allowing laryngoscopy without restriction. The polio blade was first designed to intubate patients ventilated in the iron lung during the poliomyelitis epidemic in the 1950s. A Macintosh laryngoscope blade attached to a short handle can also be useful in this situation.

  • 4.

    To prevent cross-infection among patients, a disposable blade ( Fig. 7.8 ) is used.

    Fig. 7.8, Intersurgical fibreoptic single-use plastic laryngoscope blade with the handle. From left to right : Macintosh blade sizes 4, 3 and 2; Miller blade sizes 1 and 0.

  • 5.

    Laryngoscope handles must be appropriately decontaminated between patients to prevent cross-infection.

Laryngoscopes

  • Consist of a handle and a blade. The latter can be straight or curved.

  • The bulb is either in the blade or in the handle.

  • Different designs and shapes exist.

Exam tip:

It is important to have knowledge about the different design laryngoscope blades and their advantages and disadvantages. An understanding of the difference between a fibreoptic laryngoscope blade and a standard blade with a mounted light bulb is important.

Flexible intubation videoscope/bronchoscopes

These devices have made a huge impact on airway management in anaesthesia and intensive care. Single-use portable devices with their high-resolution monitor screens are becoming more popular ( Fig. 7.9 ) over the traditional fibreoptic scopes. As single-use devices, the need for cleaning/sterilization and continuous maintenance has been eliminated. They are used to perform oral or nasal tracheal intubation ( Figs. 7.10 and 7.11 ); to evaluate the airway in trauma, tumour, infection and inhalational injury; to confirm tube placement (tracheal, endobronchial, double lumen or tracheostomy tubes) and to perform tracheobronchial toilet.

Fig. 7.9, Ambu aScope 4 Broncho Regular endoscope.

Fig. 7.10, Performing fibreoptic nasal intubation.

Fig. 7.11, Views of the vocal cords as seen through a fibreoptic laryngoscope.

The Ambu aScope 4 Broncho Regular consists of an insertion cord of 600 mm length and 5 mm diameter with a digital camera and 2 light-emitting diode (LED) light sources at its distal tip, offering an 85-degree viewing field. Other sizes are available: slim 3.8-mm diameter and large 5.8-mm diameter.

The lightweight handheld control unit consists of the following:

  • a.

    tip deflection control lever. This allows the distal part of the cord to bend with an angle range up to180 degrees upwards and 180 degrees downwards.

  • b.

    button that activates the suction with a suction port that can be connected to an external suction device. A purpose-built, closed-loop container can be attached to collect any aspirated samples.

  • c.

    a working channel (2.2-mm diameter) port with Luer-Lok allows the installation of fluids or local anaesthetic. Its distal end is positioned at the distal tip of the cord.

A tracheal tube can be attached to the proximal end of the cord using the ‘retention rings/discs’. It can be railroaded into the trachea to facilitate intubation. A size 6.0-mm ID tracheal tube or larger can be used. A double lumen tracheal tube of 41 Fr size or larger can also be used.

The unit is attached to a high-definition monitor screen via a separate cable.

Other equipment may be needed, e.g. endoscopic face mask, oral airway, bite block, defogging agent.

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