Airway Management

Prepared byDr. Mahmoud Abdel-Khalek

Introduction

In order to ensure adequate oxygenation and ventilation throughout the insults of anesthesia and surgery, the anesthesiologist must take active measures to maintain the patency of the airway as well as ensuring its protection from aspiration

Airway Anatomy

The airways can be divided into 2 parts

namely:

The upper airway.

The lower airway.

Anatomy of the Upper Airway

Upper airway– Airway structures

above the vocal chords

Larynx– Divides upper and

lower airways

Pharynx– Extends from the

nose and mouth to the esophagus and trachea Nasopharynx Oropharynx Laryngopharynx

Upper and Lower Airway

Upper Airway

Anatomy of the Upper Airway

Oral Cavity

Adenoids and tonsils may become swollen and infected may cause upper airway obstruction

Larynx

Marks where the upper airway ends and lower airway begins

Thyroid cartilage– Formed by two plates

that form the laryngeal prominence (Adam’s apple)

Cricoid cartilage is the first ring of the trachea

Cricothyroid membrane: ligament between the thyroid and cricoid cartilage site for emergency surgical and nonsurgical access to the airway (cricothyrotomy)

Larynx Glottis: Space between the

vocal cords Vallecula

– Pocket between base of tongue and epiglottis

– Important landmark for ET intubation

Arytenoid cartilages– Posterior attachment of the

vocal cords– Valuable guides for ET

intubation Laryngospasm: spasmodic

closure of the vocal cords seals off the airway

Trachea

Begins below the cricoid cartilage About 12cm length in adults 1st tracheal ring anterior to C6 Supported by 17-18 C-shaped cartilages (open

posteriorly; membranous aspect overlies esophagus

Trachea ends at level of carina at T5 Divides into right and left mainstem bronchi Right mainstem bronchus larger in diameter and

deviates at less acute angle than left (therefore aspiration or endobronchial intubation usu. to right side)

Routine airway management

Routine airway management associated with general anesthesia consists of: Airway assessment Preparation and equipment check Patient positioning Preoxygenation Bag and mask ventilation (BMV) Intubation (if indicated) Confirmation of endotracheal tube placement Intraoperative management and troubleshooting Extubation

Airway Assessment: Mouth opening

An incisor distance of 3 cm or greater is desirable in an adult

Thyromental Distance: Thyromental distance

Thyromental distance: the distance between the mentum and the superior thyroid notch

A distance greater than 3 fingerbreadths is desirable

Airway Assessment: Mallampati Classification

Examines the size of the tongue in relation to the oral cavity

Large sized tongue obstructs the view of the pharyngeal structures and may add difficulty to intubation

Conditions Associated with Difficult Intubation

Preparation and equipment check Preparation is mandatory for all

airway management scenarios The following equipment is routinely

needed in airway management situations– An oxygen source– BMV capability– Laryngoscopes (direct and video)– Several endotracheal tubes of

different sizes– Other (not endotracheal tube)

airway devices (e.g., oral, nasal airways)

– Suction– Oximetry and CO2 detection– Stethoscope– Tape– Blood pressure and ECG monitors– Intravenous access

Preparation

Laryngoscopes

Oral artificial airway sizes Sizes: 00-6 Correct size by

measuring from corner of mouth to bottom of earlobe

Adult oral airways typically come in small (80 mm [Guedel No. 3]), medium (90 mm [Guedel No. 4]), and large (100 mm [Guedel No. 5]) sizes.

Endotracheal tubes

The face mask

Patient Positioning

Relative alignment of the oral andpharyngeal axes is achieved by having the patient in the “sniffing” position

Preoxygenation When possible, preoxygenation with face mask oxygen

should precede all airway management interventions Oxygen is delivered by mask for several minutes prior to

anesthetic induction. The FRC, the patient’s oxygen reserve, is purged of

nitrogen. Up to 90% of the normal FRC of 2 L following

preoxygenation is filled with O2

Considering the normal oxygen demand of 200–250 mL/min, the preoxygenated patient may have a 5–8 min oxygen reserve.

Thus improving safety by allowing more time before desaturation in if ventilation following anesthetic induction is delayed.

Conditions that increase oxygen demand (e.g., sepsis, pregnancy) and decrease FRC (e.g. morbid obesity, pregnancy) reduce the apneic period before desaturation ensues.

The use of face mask

In current practice the face mask is only used 1. In preoxygenation

before tracheal intubation or insertion of the laryngeal mask

2. During short non-invasive procedures, e.g. Orthopedic manipulations and dental anaesthesia

Technique of face mask

selection of the correct fit is important to provide a gas-tight seal

For children, a mask with excessive dead space should be avoided (Rebreathing)

The mandible is held ‘into’ the mask by the anesthetist and forward to prevent obstruction of the airway by the tongue

The importance of observation of the airway during mask anesthesia cannot be overemphasized

Maintenance of the airway may be assisted further by the use of an oropharyngeal (Guedel) airway in anesthetized patients

Technique….

Disadvantages

It “ties up” the anesthesiologist’s hands It does not protect against aspiration or

laryngospasm (closure of the cords in response to noxious stimuli at light planes of anesthesia)

Upper airway obstruction may occur, particularly in obese patients or patients with very large tongues

Laryngeal Mask Airway (LMA)

LMA consists of a wide bore tube whose proximal end connects to a breathing circuit with a standard 15-mm connector, and whose distal end is attached to an elliptical cuff that can be inflated through a pilot tube.

The deflated cuff is lubricated and inserted blindly into the hypopharynx so that, once inflated, the cuff forms a low-pressure seal around the entrance to the larynx.

This requires anesthetic depth and muscle relaxation slightly greater than that required for the insertion of an oral airway.

Advantages and disadvantages

Indications To provide a clear airway without the need for the

anesthetist’s hands to support a face mask. To avoid the use of tracheal intubation during

spontaneous ventilation. In a case of unanticipated difficult intubation

Contraindications ‘Full stomach’ A patient in whom the risk of regurgitation of

gastric contents into the esophagus is increased (e.g. hiatus hernia).

Oral operations as it may prevent surgical access

Size selection& Techniqueq

Technique of LMA insertion

Tracheal Intubation

ET tube

Most commonly made of PVC The shape and rigidity of TT’s can be altered by inserting a

stylet The patient end of the tube is beveled to aid visualization and

insertion through the vocal cords (the Murphy eye) to decrease the risk of occlusion Most adult TT’s have a cuff inflation system consisting of a

valve, pilot balloon, inflating tube, and cuff

Indications Provision of a clear airway, e.g. anticipated

difficulty in using mask anesthesia in the edentulous patient

An ‘unusual’ and prolonged position, e.g. prone or sitting. A reinforced non-kinking tube may be necessary.

Operations on the head and neck, e.g. ENT, dental A nasotracheal tube may be required.

Protection of the respiratory tract against aspiration e.g. from blood during upper respiratory tract or oral surgery and from inhalation of gastric contents in emergency surgery or patients with oesophageal obstruction.

During anesthesia using IPPV and muscle relaxants

To facilitate suction of the respiratory tract During thoracic operations

Contraindications for Intubation

Patients with an intact gag reflex Patients likely to react with laryngospasm to an

intubation attempt. e.g. Children with epiglottitis Basilar skull fracture – avoid naso-tracheal

intubation and nasogastric/pharyngeal tube.

Technique Position the patient

supine, open the airway with a head-tilt chin-lift maneuver.(Suspected spinal injury, attempt naso-tracheal intubation, spine in neutral position.).

Open mouth by separating the lips and pulling on upper jaw with the index finger.

Hold laryngoscope in left hand, insert scope into mouth with blade directed to right tonsil.

Technique

Once right tonsil is reached, sweep the blade to the midline keeping the tongue on the left.

This brings the epiglottis into view.” DO NOT LOOSE SIGHT OF IT!”

Advance the blade until it reaches the angle between the base of the tongue and epiglottis.( vallecular space)

Lift the laryngoscope upwards and away from the nose – towards the chest. This should bring the vocal cords into view. It may be necessary for a colleague to press on the trachea to improve the view of the larynx.

Technique Place the ETT in the right hand. Keep the

concavity of the tube facing the right side of the mouth.

Insert the tube watching it enter through the cords Insert the tube just so the cuff has passed the cords and then inflate the cuff.

Listed for air entry at both apices and both axillae to ensure correct placement using a stethoscope.

Technique

Confirmation of Tube Placement

End Tidal Carbon Dioxide Monitor

Stethoscope

Complications

Nasotracheal Intubation

Nasotracheal intubationAdvantages: Comfortable for prolong intubation in postoperative

period Suitable for oral surgery : tonsillectomy , mandible

surgery For blind nasal intubation Can take oral feeding Resist for kinking and difficult to accidental

extubation

Disadvantages Trauma to nasal mucosa Risk for sinusitis following prolonged intubation Risk of bacteremia Smaller diameter than oral route

Contraindication for nasoendotracheal intubation

Fracture base of skull

Large adenoids

Coagulopathy

Nasal cavity obstruction

Retropharyngeal abscess

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