Week 12 airway management

Airway Management

“The best preparation for managing the difficult airway is

being excellent at the management of routine airways.

Patients are not harmed by inadequate intubation but rather

inadequate ventilation”Nagelhout 4th ed. p. 441

Anatomy and Physiologyof the Airway

Airway A & P: the noseThe nose comprises a large surface area. It helps to warm, humidify & filter but provides 2/3 of the resistance to breathing

Branches of 3 arteries supply the mucosa:

FacialOpthalmicMaxillary

Branches of the facial nerve

innervate the nose;

sensory is from divisions of the

trigeminal nerve.

Sympathetic stimulation results in vasoconstriction of nasal tissue. Depression of the SNS by general anesthesia may produce engorged nasal tissue which may bleed easily with tube insertions.

Airway A & P: the mouthThe hard palate is

stationary.

The soft palate is able to rise, but also may become more

movable (obesity,age..) and

fall against the nasal passages during sleep producing

obstruction.

The uvula protects the oropharynx.

The large, space

occupying, muscular

tongue may obstruct the airway when

it relaxes.

Airway A & P: the nasopharynxLies anterior to C1

Superior border: base of skullInferior border: soft palate

Adenoid tonsils and eustachian tubes are within the nasopharynx. Maxillary nerve provides sensory innervation.

Airway A & P: the oropharynx

Lies anterior to C12-C3

Superior border: soft palateInferior border: epiglottis

Opens into the mouth through the tonsillar pillars

Airway A & P: the hypopharynx

Lies posterior to the larynx

Superior border: epiglottisInferior border: cricoid cartilage (C5-C6)

The upper esophageal sphincter, which helps prevent conscious regurgitation, lies at the inferior border. The sphincter arises from the cricopharyngeal muscle.

Airway A & P: the pharynxGag reflex diagram

Afferent/sensory stimuli is carried by glossopharyngeal (IX)to the medulla

Synapse occurs in the medulla with the vagus (X) & spinal accessory (XI)

Efferent /motor response returns

through the vagus (X) causing

the pharyngeal muscles to

constrict and elevate -“gag”

Airway A & P: the pharynxSLN & RLN

Superior Laryngeal nerve:Internal →sensory above cordsExternal→motor to cricothyroid muscle

Recurrent Laryngeal nerve:Sensory→below glottisMotor→ all other muscles of larynx

Branches off the vagus and loops around the aorta (design flaw or developmental physiology?)

Loops around the innominate

artery

Anesthesia concerns with the RLNDamage to the RLN interferes with airway control.

Acute bilateral injury → unopposed tension→ vocal cord adduction →stridorUnresolved stridor leads to respiratory distress and possibly death.

Vocal cord paralysis video

Airway A & P: the larynx

Valeculla – the space above the epiglottis. The Macintosh intubating blade is placed into this space. The blade lifts structures to view the glottis.

1 bone (hyoid) + 9 cartilagesCricoid cartilage is the only complete ringTracheal rings are incomplete posteriorly to accommodate food in the esophagus

Another view of the larnyx

Cormack & Lehane laryngoscopy grades

cords arytenoids epiglottis base of tongue

Oxygen Administration and

Mask Ventilation

Oxygen administration –spontaneously breathing patient

The simple oxygen mask administers 40-60% FIO2 (assuming normal respiration) by increasing the anatomic reservoir.

The nasal cannula administers 24-40% FIO2 (assuming normal respiration).

A 4% increase in FIO2 for each liter (except the 1st which is 3%) ex. 1 lpm =24%, 2 lpm=28% , 3 lpm = 32%...

Oxygen administration and the anatomic reservoir

Difficult ventilation

The inability to maintain an oxygen saturation > 90%

while using a face mask & 100% oxygen

Proper positioning

The sniffing position – the tragus/auditory meatus of the ear aligns with the sternal notch

The sniffing position + hyperextension align the axis

Sniffing position video

PreoxygenationAdministration of 100% oxygen is intended to replace nitrogen (denitrogenation) in the FRC with the goal of increasing the safe apneic period.

Techniques:Normal tidal volume breaths with high flow 100 % oxygen for 3 mins.8 vital capacity breaths with 100% oxygen over 1 minute. 4 vital capacity breaths with 100% oxygen over 30 secs.(less effective)

Concept of DesaturationThe FRC is the “reservoir.”

Preoxygenation fills the “reservoir”. Oxygen consumption empties the “reservoir”.

FRC (or 35ml/kg in adult)

Oxygen consumption (or 3 ml/kg for an adult)

2500 ml 250 ml/min

(Need to also consider closing capacity)

SaO2 vs time (after succinylcholine)

Anesthesiology 1997 87:979-982

Mask Ventilation Technique-a vital skill for an airway expert

1.Establish a snug fit over the bridge of nose and at the chin.2.The left thumb and forefinger create a “C” over the mask

pressing down towards the floor.3.The remaining fingers rest on the mandible. They may secure

and lift loose tissue onto the mandible.4. To improve ventilation, repositioning, hyperextension or an oral

airway may be required.

Mask ventilation video

Oral* and Nasal Airways

•Used to facilitate ventilation •Always size before inserting•Consider the risk vs. benefit•Risks include:

damage to teethtissue trauma → bleedinglaryngospasmeliciting a gag reflex →vomitingfurther obstruction

*Are not bite blocks!

Bite Blocks* & Teeth protectors

*Are not airways!

Supraglottic Airways-LMA’sDO NOT prevent aspiration, or stomach inflation (keep

inflation pressure <20 cm H2O)

Are easily inserted blindly

Laryngeal Mask Airways (LMA’s) were introduced in 1989

Is properly positioned in the hypopharynx, above the epiglottis

With overinflation, may open the upper esophageal sphincter

With malposition, may produce airway obstruction

LMA insertion video

LMA Supreme

Endotracheal Intubation• The gold standard for airway management and protection.• It’s usually facilitated by direct laryngoscopy.• Indications include:

a full stomacha high risk for aspirationcritically ill pts.significant lung abnormalitieslung isolationsurgical need for prolonged muscle relaxationa difficult airwaypt. positioning

The endotracheal tube

Stylets

Laryngoscopes and blades

Common straight and curved blades

Technique to open mouth

Placement of a curved blade

Placement of a straight blade

Tongue displacement

B-U-R-P technique

Confirmation of ETT placementVisualization of tube passing through the glottis

With first breath, observe chest rise

Observe condensation in the ETT

Observe for a sustained normal capnogram (>3 breaths)

Listen for equal bilateral breath sounds

Listen for absence of gurgling over the epigastrum

Intubation Risks•trauma to mouth and/or teeth•endobronchial or esophageal intubation•aspiration•perforation of the pharnyx or trachea•endotracheal tube (ET)obstruction: kinking biting, tissue, secretions•ET ignition/fire•laryngospasm•Croup•Sore throat

Trauma to mouth/teeth•Assess the mouth and teeth preop and post extubation.•All attempts must be made to find fragments before aspiration.•Consider a chest x-ray to find missing fragments.

Esophageal/Endobronchial intubationEnsure endotracheal intubation by confirming

placement.

Visualize the ET cuff pass through the glottis.Observe for condensation and chest rise with the first manual breath.Observe for sustained end tidal carbon dioxide capnogram.Listen for equal bilateral breath sounds and absence of gurgling over stomach.Further confirmation may include CXR or fiberoptic scope

AspirationRemains a significant cause of morbidity and mortality in obstetrics.Prophylaxis goals are to decrease the contents (<25 ml) and change the pH of the contents (<2.5)

use non-particulate antacids (Bicitra)gastrokinetics (metoclopramide)H2 antagonists or proton pump inhibitors

Use a rapid sequence induction (RSI) technique for any at risk patient full stomachobstructed boweldiabetictraumasevere, ongoing painobesityobstetrics

RSI video

LaryngospasmReflex constriction of the laryngeal muscles producing spasmodic closure of the glottis. Causes include secretions on the cords and extubation in a light plane of anesthesia

Identify & eliminate the stimulus

Insert oral/nasal airway

Administer positive pressure ventilation with 100% oxygen

Perform jaw thrust with concomitant pressure of laryngeal notch

Deepen anesthetic level with propofol

Consider succinylcholine

Sore Throat

The most common postoperative complaint.

Factors may include:ET size irritation from instrumentationfemale gender

4 skill areas

1. Note the time in the room.2. Move the “pt/student” from the

stretcher to the table.3. Apply monitors.4. Properly position “pt” for intubation. 5. Apply mask and administer air.6. Properly position table height.7. Instruct “pt” in preoxygenation.

Attempt mask ventilation.Oral airway insertion.Nasal airway insertion.LMA insertionIntubation.