week 2 Flashcards
1
Q
the anatomy of the upper airway
A
pharynx nose mouth larynx trachea main-stem bronchi
2
Q
mouth and pharynx
A
The mouth and pharynx are also a part of the upper gastrointestinal tract. The laryngeal structures in part serve to prevent aspiration into the trachea
3
Q
nose
A
nose-which leads to the nasopharynx
4
Q
mouth
A
mouth -which leads to the oropharynx
These passages are separated anteriorly by the palate, but they join posteriorly in the pharynx
5
Q
pharynx
A
is a U-shaped fibromuscular structure that extends from the base of the skull to the cricoid cartilage at the entrance to the esophagus.
It opens anteriorly into the nasal cavity, the mouth, the larynx, and the nasopharynx, oropharynx, and laryngopharynx, respectively.
6
Q
Nasopharynx
A
is separated from the oropharynx by an imaginary plane that extends posteriorly.
At the base of the tongue, the epiglottis functionally separates the oropharynx from the laryngopharynx (or hypopharynx).
7
Q
epiglottis
A
The epiglottis prevents aspiration by covering the glottis—the opening of the larynx—during swallowing.
8
Q
larynx
A
The larynx is a cartilaginous skeleton held together by ligaments and muscle.
The larynx is composed of nine cartilages: thyroid, cricoid, epiglottic, and (in pairs) arytenoid, corniculate, and cuneiform.
9
Q
thyroid cartilage
A
The thyroid cartilage shields the conus elasticus, which forms the vocal cords.
10
Q
v1v2v3
A
The mucous membranes of the nose are innervated by the ophthalmic division (V1) of the trigeminal nerve anteriorly (anterior ethmoidal nerve) and by the maxillary division (V2) posteriorly (sphenopalatine nerves).
The palatine nerves provide sensory fibers from the trigeminal nerve (V) to the superior and inferior surfaces of the hard and soft palate.
The olfactory nerve (cranial nerve I) innervates the nasal mucosa to provide the sense of smell.
11
Q
the lingual nerve
A
(a branch of the mandibular division [V3] of the trigeminal nerve) and the glossopharyngeal nerve (the ninth cranial nerve) provide general sensation to the anterior two-thirds and posterior one-third of the tongue, respectively.
12
Q
facial and glossopharyngeal
A
Branches of the facial nerve (VII) and glossopharyngeal nerve provide the sensation of taste to those areas, respectively.
The glossopharyngeal nerve also innervates the roof of the pharynx, the tonsils, and the undersurface of the soft palate.
13
Q
superior laryngeal branch- external and internal
A
The superior laryngeal branch of the vagus divides into an external (motor) nerve and an internal (sensory) laryngeal nerve that provide sensory supply to the larynx between the epiglottis and the vocal cords.
14
Q
recurrent laryngeal nerve
A
Another branch of the vagus, the recurrent laryngeal nerve, innervates the larynx below the vocal cords and the trachea.
15
Q
vagus nerve
A
The vagus nerve (the tenth cranial nerve) provides sensation to the airway below the epiglottis.
16
Q
Sensory innervation from the mucosal lining of the larynx above the vocal folds is done by the internal laryngeal branch of the superior laryngeal nerve (CNX).
A
The recurrent laryngeal nerve, a branch of vagus nerve (CNX) innervates the Larynx below the vocal folds.
17
Q
posterior Cricoarytenoids
A
abduct vocal cords (dilate)
18
Q
lateral cricoartyenoid
A
adduct adduct vocal cords (close)
19
Q
cricothyroids
A
cords tense
20
Q
thyroarytenoids
A
they relax
21
Q
unilateral right recurrent laryngeal nerve damage
A
clinical picture- hoarseness results
this is the most common injury after subtotal thyroidectomy. this injury is characterized by horseless and a paralyzed cord that assumes an intermediated position (midway between abduction and adduction)
22
Q
bilateral recurrent laryngeal nerve damage
A
clinical picture- aphonia and airway obstruction. (stridor)
this injury results in aphonia and paralyzed cords. each paralyzed cord assumes an intermediate position (midway between abduction and adduction) the cords can flop together causing airway obstruction during inspiration intubation is required.
23
Q
phonation
A
phonation involves complex simultaneous actions by several laryngeal muscles. Damage to the motor nerves innervating the larynx leads to a spectrum of speech disorders
Unilateral denervation of a cricothyroid muscle causes very subtle clinical findings.
24
Q
chronic bilateral recurrent laryngeal nerve loss
A
Airway problems are less frequent in chronic bilateral recurrent laryngeal nerve loss because of the development of various compensatory mechanisms.
25
bilateral superior laryngeal nerve damage
bilateral palsy of the superior laryngeal nerve may result in hoarseness or easy tiring of the voice, but airway control is not jeopardized
26
larynx blood supply
The blood supply of the larynx is derived from branches of the thyroid arteries.
27
cricothyroid artery blood supply
The cricothyroid artery arises from the superior thyroid artery itself, the first branch off the external carotid artery), and crosses the upper cricothyroid membrane, which extends from the cricoid cartilage to the thyroid cartilage
28
slide 19
The superior thyroid artery is found along the lateral edge of the cricothyroid membrane.
29
the trachea
The trachea begins beneath the cricoid cartilage and extends to the carina, the point at which the right and left main-stem bronchi divide.
Anteriorly, the trachea consists of cartilaginous rings; posteriorly, the trachea is membranous.
30
routine airway management
listen to stomach first
```
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
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31
airway assessment
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Mouth opening
Upper lip bite test
Mallampati classification
Thyromental distance
Neck circumference
Airway assessment is the first step in successful airway management. Several anatomical and functional maneuvers can be performed to estimate the difficulty of endotracheal intubation.
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32
mouth opening and upper lip bite test
An incisor distance of 3 cm or greater is desirable in an adult.
The lower teeth are brought in front of the upper teeth. The degree to which this can be done estimates the range of motion of the temporomandibular joints
33
Mallampati classification
Class I: the entire palatal arch, including the bilateral faucial pillars, are visible down to their bases.
Class II: the upper part of the faucial pillars and most of the uvula are visible.
Class III: only the soft and hard palates are visible.
Class IV: only the hard palate is visible.
34
cricoid pressure
apply 3-5kg pressure/30 newtons
35
neck circumference
Neck circumference: a neck circumference of greater than 17 in is suggestive of difficulties in visualization of the glottic opening
36
thyromental distance
Thyromental distance: the distance between the mentum and the superior thyroid notch. A distance of 3 fingerbreadths or more is desirable. Less than 3 fingerbreadths is non-reassuring
37
Equipment
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 electrocardiography (ECG) monitors
Intravenous access
38
oral and nasal airways
Loss of upper airway muscle tone in anesthetized patients allows the tongue and epiglottis to fall back against the posterior wall of the pharynx.
Repositioning the head or a jaw thrust is the preferred technique for opening the airway. To maintain the opening, an artificial airway can be inserted through the mouth or nose to maintain an air passage between the tongue and the posterior pharyngeal wall.
Awake or lightly anesthetized patients with intact laryngeal reflexes may cough or even develop laryngospasm during airway insertion. Placement of an oral airway is sometimes facilitated by suppressing airway reflexes, and, in addition, sometimes by depressing the tongue with a tongue blade.
39
nasal and oral airways including contraindications and sizing
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.
The length of a nasal airway can be estimated as the distance from the nares to the meatus of the ear and should be approximately 2-4 cm longer than oral airways.
Because of the risk of epistaxis, nasal airways are less desirable in anticoagulated or thrombocytopenic patients.
Also, nasal airways (and nasogastric tubes) should be used with caution in patients with basilar skull fractures, where there has been a case report of a nasogastric tube entering the cranial vault.
All tubes inserted through the nose (e.g., nasal airways, nasogastric catheters, nasotracheal tubes) should be lubricated before being advanced along the floor of the nasal passage.
40
The face mask
Can facilitate the delivery of oxygen or an anesthetic gas from a breathing system to a patient by creating an airtight seal with the patient’s face.
The rim of the mask is contoured and conforms to a variety of facial features. The mask’s 22-mm orifice attaches to the breathing circuit of the anesthesia machine through a right-angle connector.
Transparent masks allow observation of exhaled humidified gas and immediate recognition of vomitus.
Retaining hooks surrounding the orifice can be attached to a head strap so that the mask does not have to be continually held in place
41
Face mask- how to hold
If the mask is held with the left hand, the right hand can be used to generate positive-pressure ventilation by squeezing the breathing bag.
The mask is held against the face by downward pressure on the mask body exerted by the left thumb and index finger.
The middle and ring finger grasp the mandible to facilitate extension of the atlantooccipital joint.
Finger pressure should be placed on the bony mandible and not on the soft tissues supporting the base of the tongue, which may obstruct the airway.
The little finger is placed under the angle of the jaw and used to thrust the jaw anteriorly, the most important maneuver to allow ventilation to the patient.
42
face mask with two hands -how much cm of h20
In difficult situations, two hands may be needed to provide adequate jaw thrust and to create a mask seal. An assistant may be needed to squeeze the bag, or the machine’s ventilator can be used.
The thumbs hold the mask down, and the fingertips or knuckles displace the jaw forward. Obstruction during expiration may be due to excessive downward pressure from the mask or from a ball-valve effect of the jaw thrust.
It is often difficult to form an adequate mask fit with the cheeks of edentulous patients.
Positive-pressure ventilation using a mask should normally be limited to 20 cm of H2O to avoid stomach inflation.
43
care with face mask
Most patients’ airways can be maintained with a face mask and an oral or nasal airway.
Mask ventilation for long periods may result in pressure injury to branches of the trigeminal or facial nerves.
Because of the absence of positive airway pressures during spontaneous ventilation, only minimal downward force on the face mask is required to create an adequate seal.
If the face mask and mask straps are used for extended periods, the position should be regularly changed to prevent injury.
Care should be used to avoid mask or finger contact with the eye, and the eyes should be taped shut to minimize the risk of corneal abrasions.
44
patient positioning
Relative alignment of the oral and pharyngeal axes is achieved by having the patient in the “sniffing” position.
When cervical spine pathology is suspected, the head must be kept in a neutral position during all airway manipulations.
In-line stabilization of the neck must be maintained during airway management in these patients, unless appropriate films have been reviewed and cleared by a radiologist or neurological or spine surgeon.
45
alignments of the oral axis
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oral axis (oa)
pharyngeal axis(pa)
laryngeal axis (la)
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46
positioning for morbid obesity
Patients with morbid obesity should be positioned on a 30° upward ramp, as the functional residual capacity (FRC) of obese patients deteriorates in the supine position, leading to more rapid de-oxygenation should ventilation be impaired.
47
preoxygenation
If possible, preoxygenation with face mask oxygen should precede all airway management interventions.
Oxygen is delivered by mask for several minutes prior to anesthetic induction. In this way, the functional residual capacity, the patient’s oxygen reserve, is purged of nitrogen.
The preoxygenated patient may have a 5-8 min oxygen reserve.
Increasing the duration of apnea without desaturation improves safety, 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.
48
Bag Mask Ventilation
Bag and mask ventilation (BMV) is the first step in airway management in most situations, with the exception of patients undergoing rapid sequence intubation.
In emergency situations, BMV precedes attempts at intubation in an effort to oxygenate the patient, with the understanding that there is a risk of aspiration.
As noted above, the anesthetist’s left hand supports the mask on the patient’s face. The face is lifted into the mask with the third, fourth, and fifth fingers of the anesthesia provider’s left hand. The fingers are placed on the mandible, and the jaw is thrust forward, lifting the base of the tongue away from the posterior pharynx opening the airway. The thumb and index finger sit on top of the mask. If the airway is patent, squeezing the bag will result in the rise of the chest.
If ventilation is ineffective (no sign of chest rising, no end-tidal CO2 detected, no mist in the clear mask), oral or nasal airways can be placed to relieve airway obstruction secondary to redundant pharyngeal tissues.
Difficult mask ventilation is often found in patients with morbid obesity, beards, and craniofacial deformities.
49
supraglottic airway devices
Supraglottic airway devices (SADs) are used with both spontaneously and ventilated patients during anesthesia.
Can aid endotracheal intubation when both BMV and endotracheal intubation have failed.
These airway devices occlude the esophagus with varying degrees of effectiveness, reducing gas distension of the stomach.
None offer the protection from aspiration pneumonitis offered by a properly seated, cuffed endotracheal tube.
50
laryngeal mask
A laryngeal mask airway (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.
51
LMA air volume
3- 20air
4- 30air
5- 30-40air
52
LMA insertion
Although insertion is relatively simple attention to detail will improve the success rate.
An ideally positioned cuff is bordered by the base of the tongue superiorly, the pyriform sinuses laterally, and the upper esophageal sphincter inferiorly.
If the esophagus lies within the rim of the cuff, gastric distention and regurgitation become possible.
Anatomic variations prevent adequate functioning in some patients. However, if an LMA is not functioning properly after attempts to improve the “fit” of the LMA have failed, most practitioners will try another LMA one size larger or smaller.
The shaft can be secured with tape to the skin of the face
The laryngeal mask ready for insertion. The cuff should be deflated tightly with the rim facing away from the mask aperture. There should be no folds near the tip. B: Initial insertion of the laryngeal mask. Under direct vision, the mask tip is pressed upward against the hard palate. The middle finger may be used to push the lower jaw downward. The mask is pressed forward as it is advanced into the pharynx to ensure that the tip remains flattened and avoids the tongue. The jaw should not be held open once the mask is inside the mouth. The non-intubating hand can be used to stabilize the occiput. C: By withdrawing the other fingers and with a slight pronation of the forearm, it is usually possible to push the mask fully into position in one fluid movement. Note that the neck is kept flexed and the head extended. D: The laryngeal mask is grasped with the other hand and the index finger withdrawn. The hand holding the tube presses gently downward until resistance is encountered. (Reproduced, with permission, from LMA North America.)
53
lma size and weight
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1-<5kg
1.5-5-10kg
2-10-20kg
2.5-20-30kg
3-30-50kg
4- 50-70kg
5- 70-100kg
6 >100kg
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54
The LMA provides an alternative to ventilation through a face mask
Relative contraindications include:
Relative contraindications include:
patients with pharyngeal pathology (ex, abscess)
pharyngeal obstruction
full stomachs (ex, pregnancy, hiatal hernia)
low pulmonary compliance (ex, restrictive airways disease) requiring peak inspiratory pressures greater than 30 cm H2O.
**Traditionally, the LMA has been avoided in patients with bronchospasm or high airway resistance, but new evidence suggests that because it is not placed in the trachea, use of an LMA is associated with less bronchospasm than ETT.
55
lma during unable to intubate or ventilate
A life-saving temporizing measure in patients with difficult airways (those who cannot be ventilated or intubated) because of its ease of insertion and relatively high success rate (95% to 99%).
It has been used as a conduit for an intubating stylet (e.g., gum-elastic bougie), ventilating jet stylet, flexible FOB, or small-diameter (6.0-mm) TT. Several LMAs are available that have been modified to facilitate placement of a larger TT, with or without the use of a FOB.
Insertion can be performed under topical anesthesia and bilateral superior laryngeal nerve blocks, if the airway must be secured while the patient is awake.
56
lma complications
Sore throat is a common side effect following use
Injuries to the lingual, hypoglossal, and recurrent laryngeal nerve have been reported.
Correct device sizing, avoidance of cuff hyperinflation, and gentle movement of the jaw during placement may reduce the likelihood of such injuries
57
esophageal- tracheal combitube
The esophageal-tracheal Combitube consists of two fused tubes, each with a 15-mm connector on its proximal end.
The longer blue tube has an occluded distal tip that forces gas to exit through a series of side perforations. The shorter clear tube has an open tip and no side perforations.
The Combitube is usually inserted blindly through the mouth and advanced until the two black rings on the shaft lie between the upper and lower teeth. The Combitube has two inflatable cuffs, a 100-mL proximal cuff and a 15-mL distal cuff, both of which should be fully inflated after placement.
58
King laryngeal tube
King laryngeal tubes (LTs) consist of tube with a small esophageal balloon and a larger balloon for placement in the hypopharynx.
Both tubes inflate through one inflation line. The lungs are inflated from air that exits between the two balloons.
A suction port distal to the esophageal balloon is present, permitting decompression of the stomach.
The LT is inserted and the cuffs inflated. Should ventilation prove difficult, the LT is likely inserted too deep.
Slightly withdrawing the device until compliance improves ameliorates the situation.
59
ETT charesterics
Standards govern TT manufacturing (American National Standard for Anesthetic Equipment; ANSI Z-79).
TTs are most commonly made from polyvinyl chloride. In the past, TTs were marked “I.T.” or “Z-79” to indicate that they had been implant tested to ensure nontoxicity.
The shape and rigidity of TTs can be altered by inserting a stylet. The patient end of the tube is beveled to aid visualization and insertion through the vocal cords.
Murphy tubes have a hole (the Murphy eye) to decrease the risk of occlusion, should the distal tube opening abut the carina or trachea.
60
child sizing internal diameter and cut length
| uncuffed
age/4+4-internal diameter
age/2+14=cut length
age+16/4=uncuffed
61
issues for uncuffed tubes
ASPIRATION AND DISPLACEMENT FOR UNCUFFED TUBES
62
ett
Most adult ETTs have a cuff inflation system consisting of a valve, pilot balloon, inflating tube, and cuff.
The valve prevents air loss after cuff inflation. The pilot balloon provides a gross indication of cuff inflation. The inflating tube connects the valve to the cuff and is incorporated into the tube’s wall.
By creating a tracheal seal, TT cuffs permit positive-pressure ventilation and reduce the likelihood of aspiration.
Uncuffed tubes are often used in infants and young children to minimize the risk of pressure injury and post intubation croup; however, in recent years, cuffed pediatric tubes have been increasingly favored.
63
ett
```
There are two major types of cuffs:
high pressure (low volume)
low pressure (high volume)
High-pressure cuffs are associated with more ischemic damage to the tracheal mucosa and are less suitable for intubations of long duration.
```
Low-pressure cuffs may increase the likelihood of sore throat (larger mucosal contact area), aspiration, spontaneous extubation, and difficult insertion (because of the floppy cuff).
Nonetheless, because of their lower incidence of mucosal damage, low-pressure cuffs are generally employed.
64
cuff pressure
Cuff pressure depends on several factors:
inflation volume
diameter of the cuff in relation to the trachea
tracheal and cuff compliance
intrathoracic pressure (cuff pressures increase with coughing).
65
specialized endotracheal tubes
Tubes have been modified for a variety of specialized applications. Flexible, spiral-wound, wire-reinforced TTs (armored tubes) resist kinking and may prove valuable in some head and neck surgical procedures or in the prone patient.
66
laryngoscopes
A laryngoscope is an instrument used to examine the larynx and to facilitate intubation of the trachea.
The handle usually contains batteries to light a bulb on the blade tip.
The Macintosh and Miller blades are the most popular curved and straight designs
The choice of blade depends on personal preference and patient anatomy.
MAC: Vallecula Miller: Epiglottis
67
Video Laryngoscopes
Video- or optically-based laryngoscopes have either a video chip (DCI system, GlideScope, McGrath, Airway) or a lens/mirror (Airtraq) at the tip of the intubation blade to transmit a view of the glottis to the operator.
These devices differ in the angulation of the blade, the presence of a channel to guide the tube to the glottis, and the single use or multiuse nature of the device.
Great for difficult airways or to minimize manipulation of the neck
68
video laryngoscopes
Varieties of indirect laryngoscopes include:
Storz DCI system.
The McGrath laryngoscope
The GlideScope
Airtraq is a single-use optical laryngoscope
Video intubating stylets have a video capability and light source. The stylet is introduced, and the glottis identified. Intubation with a video stylet may result in less cervical spine movement than with other techniques.
69
flexible fiberscoptic bronchoscopes
Patients with unstable cervical spines, poor range of motion of the temporomandibular joint, or certain congenital or acquired upper airway anomalies—laryngoscopy with direct or indirect laryngoscopes may be undesirable or impossible.
A flexible FOB allows indirect visualization of the larynx in such cases or in any situation in which awake intubation is planned.
Bronchoscopes are constructed of coated glass fibers that transmit light and images by internal reflection (i.e., a light beam becomes trapped within a fiber and exits unchanged at the opposite end).
Directional manipulation of the insertion tube is accomplished with angulation wires. Aspiration channels allow suctioning of secretions, insufflation of oxygen, or instillation of local anesthetic.
70
Indications for Intubation:
Inserting a tube into the trachea has become a routine part of delivering a general anesthetic.
A TT is generally placed to protect the airway and for airway access
Patients who are at risk of aspiration
Those undergoing surgical procedures involving body cavities or the head and neck.
Review table 16-4 for pathology influencing airway management
71
Preparation for Direct Laryngoscopy
Preparation for intubation includes checking equipment and properly positioning the patient:
The TT should be examined. The tube’s cuff inflation system can be tested by inflating the cuff using a 10-mL syringe. Maintenance of cuff pressure after detaching the syringe ensures proper cuff and valve function
The connector should be pushed firmly into the tube to decrease the likelihood of disconnection.
If a stylet is used, it should be inserted into the TT, which is then bent to resemble a hockey stick. This shape facilitates intubation of an anteriorly positioned larynx.
The desired blade is locked onto the laryngoscope handle, and bulb function is tested. The light intensity should remain constant even if the bulb is jiggled.
An extra handle, blade, TT (one size smaller than the anticipated optimal size), and stylet should be immediately available.
A functioning suction unit is needed to clear the airway in case of unexpected secretions, blood, or emesis.
72
Preparation for Direct Laryngoscopy
Often depends on correct patient positioning.
The patient’s head should be level with the CRNA’s waist or higher to prevent unnecessary back strain during laryngoscopy.
Direct laryngoscopy displaces pharyngeal soft tissues to create a direct line of vision from the mouth to the glottic opening.
Moderate head elevation (5-10 cm above the surgical table) and extension of the atlantooccipital joint place the patient in the desired sniffing position.
The lower portion of the cervical spine is flexed by resting the head on a pillow or other soft support
73
direct laryngoscopy- oxygenation
Preparation for induction and intubation also involves routine preoxygenation.
Administration of 100% oxygen provides an extra margin of safety in case the patient is not easily ventilated after induction.
Preoxygenation can be omitted in patients who object to the face mask; however, failing to preoxygenate increases the risk of rapid desaturation following apnea.
Because general anesthesia abolishes the protective corneal reflex, care must be taken during this period not to injure the patient’s eyes by unintentionally abrading the cornea. The eyes are routinely taped shut, often after applying an ophthalmic ointment before manipulation of the airway.
74
Orotracheal Intubation
The laryngoscope is held in the left hand. With the patient’s mouth opened the blade is introduced into the right side of the oropharynx—with care to avoid the teeth. The tongue is swept to the left and up into the floor of the pharynx by the blade’s flange. Successful sweeping of the tongue leftward clears the view for TT placement.
The tip of a curved blade is usually inserted into the vallecula, and the straight blade tip covers the epiglottis. With either blade, the handle is raised up and away from the patient in a plane perpendicular to the patient’s mandible to expose the vocal cords.
Trapping a lip between the teeth and the blade and leverage on the teeth are avoided.
The TT is taken with the right hand, and its tip is passed through the abducted vocal cords. The “backward, upward, rightward, pressure” (BURP) maneuver applied externally moves an anteriorly positioned glottis posterior to facilitate visualization of the glottis. The TT cuff should lie in the upper trachea, but beyond the larynx. The laryngoscope is withdrawn, again with care to avoid tooth damage
75
orotracheal intubation
The cuff is inflated with the least amount of air necessary to create a seal during positive-pressure ventilation to minimize the pressure transmitted to the tracheal mucosa.
Over inflation beyond 30 mm Hg may inhibit capillary blood flow, injuring the trachea. Compressing the pilot balloon with the fingers is not a reliable method of determining whether cuff pressure is either sufficient or excessive.
76
can co2 be found in the stomach
yes- temporary
77
Orotracheal Intubation
After intubation, the chest/epigastrium are immediately auscultated, and a capnograph tracing monitored
End-tidal CO2 will not be produced if there is no cardiac output
FOB through the tube and visualization of the tracheal rings and carina will likewise confirm correct placement.
The persistent detection of CO2 by a capnograph is the best confirmation/definitive test of tracheal placement of a TT, it cannot exclude bronchial intubation.
The earliest evidence of bronchial intubation often is an increase in peak inspiratory pressure.
Proper tube location can be reconfirmed by palpating the cuff in the sternal notch while compressing the pilot balloon with the other hand. The cuff should not be felt above the level of the cricoid cartilage, because a prolonged intralaryngeal location may result in postoperative hoarseness and increases the risk of accidental extubation.
Tube position can also be documented by chest radiography.
**If there is doubt as to whether the tube is in the esophagus or trachea, repeat the laryngoscopy to confirm placement.
78
Orotracheal Intubation
A failed intubation should not be followed by identical repeated attempts.
Changes must be made to increase the likelihood of success, such as repositioning the patient (table 16-8), cricoid pressure (table 16-10) decreasing the tube size, adding a stylet, selecting a different blade, using an indirect laryngoscope, attempting a nasal route, or requesting the assistance of another anesthesiologist.
If the patient is also difficult to ventilate with a mask, alternative forms of airway management (e.g., LMA, Combitube, cricothyrotomy with jet ventilation, tracheostomy) must be immediately pursued.
The guidelines developed by the American Society of Anesthesiologists for the management of a difficult airway include a treatment plan algorithm
79
Nasotracheal Intubation
Tube is advanced through the nose and nasopharynx into the oropharynx before laryngoscopy.
The nostril through which the patient breathes most easily is selected in advance and prepared. Phenylephrine nose drops (0.5% or 0.25%) vasoconstrict vessels and shrink mucous membranes.
If the patient is awake, local anesthetic ointment (for the nostril), spray (for the oropharynx), and nerve blocks can also be utilized.
80
steps for nasotracheal intubation
A TT lubricated with water-soluble jelly is introduced along the floor of the nose, below the inferior turbinate, at an angle perpendicular to the face. The tube’s bevel should be directed laterally away from the turbinates.
To ensure that the tube passes along the floor of the nasal cavity, the proximal end of the TT should be pulled cephalad. The tube is gradually advanced, until its tip can be visualized in the oropharynx. Laryngoscopy, as discussed, reveals the abducted vocal cords.
Often the distal end of the TT can be pushed into the trachea without difficulty. If difficulty is encountered, the tip of the tube may be directed through the vocal cords with Magill forceps, being careful not to damage the cuff.
Nasal passage of TTs, airways, or nasogastric catheters carries greater risk in patients with severe mid-facial trauma because of the risk of intracranial placement
81
flexible fiber optic intubation
Fiber Optic intubation (FOI) is routinely performed in awake or sedated patients with problematic airways. FOI is ideal for:
A small mouth opening
Minimizing cervical spine movement in trauma or rheumatoid arthritis
Upper airway obstruction, such as angioedema or tumor mass
Facial deformities, facial trauma
82
awake fiberoptic
FOI can be performed awake or asleep via oral or nasal routes.
Awake FOI: predicted inability to ventilate by mask, upper airway obstruction
Asleep FOI: Failed intubation, desire for minimal C spine movement in patients who refuse awake intubation
Oral FOI: Facial, skull injuries
Nasal FOI: A poor mouth opening
83
performing a flexible fiberoptic intubation
The airway is anesthetized with a local anesthetic spray, and patient sedation is provided, as tolerated.
If nasal FOI is planned, both nostrils are prepared with vasoconstrictive drops. The nostril through which the patient breathes more easily is identified. Oxygen can be insufflated through the suction port and down the aspiration channel of the FOB to improve oxygenation and blow secretions away from the tip.
The lubricated shaft of the FOB is introduced into the TT lumen. It is important to keep the shaft of the bronchoscope relatively straight (so that if the head of the bronchoscope is rotated in one direction, the distal end will move to a similar degree and in the same direction.
As the tip of the FOB passes through the distal end of the TT, the epiglottis or glottis should be visible. The tip of the bronchoscope is manipulated, as needed, to pass the abducted cords.
cricoid pressure may improve visualization in difficult cases. If the patient is breathing spontaneously, grasping the tongue with gauze and pulling it forward may also facilitate intubation.
Once in the trachea, the FOB is advanced to within sight of the carina. The presence of tracheal rings and the carina is proof of proper positioning. The TT is pushed off the FOB. The acute angle around the arytenoid cartilage and epiglottis may prevent easy advancement of the tube. Use of an armored tube usually decreases this problem due to its greater lateral flexibility and more obtusely angled distal end. Proper TT position is confirmed by viewing the tip of the tube an appropriate distance (3 cm in adults) above the carina before the FOB is withdrawn.
Oral FOI proceeds similarly, with the aid of various oral airway devices to direct the FOB toward the glottis and to reduce obstruction of the view by the tongue.
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Surgical Airway Techniques
“Invasive” airways are required when the “can’t intubate, can’t ventilate” scenario presents and may be performed in anticipation of such circumstances in selected patients.
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surgical airway techniques
Catheter-based salvage procedures can also be performed. A 16- or 14-gauge intravenous cannula is attached to a syringe and passed through the CTM toward the carina. Air is aspirated. If a jet ventilation system is available, it can be attached. The catheter MUST be secured, otherwise the jet pressure will push the catheter out of the airway, leading to potentially disastrous subcutaneous emphysema.
Short (1 s) bursts of oxygen ventilate the patient. Sufficient outflow of expired air must be assured to avoid barotrauma. Patients ventilated in this manner may develop subcutaneous or mediastinal emphysema and may become hypercapnic despite adequate oxygenation.
Transtracheal jet ventilation will usually require conversion to a surgical airway or tracheal intubation.
Should a jet ventilation system not be available, a 3-mL syringe can be attached to the catheter and the syringe plunger removed. A 7.0-mm internal diameter TT connector can be inserted into the syringe and attached to a breathing circuit or an ambu bag. As with the jet ventilation system, adequate exhalation must occur to avoid barotraumas.
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Retrograde Intubation
over the catheter into the trachea. Retrograde intubation is another approach to secure an airway.
A wire is passed via a catheter placed in the CTM. The wire is angulated cephalad and emerges either through the mouth or nose. The distal end of the wire is secured with a clamp to prevent it from passing through the CTM. The wire can then be threaded into an FOB with a loaded endotracheal tube to facilitate and confirm placement.
Conversely, a small endotracheal tube can be guided by the wire into the trachea. Once placed, the wire is removed. Alternatively, an epidural catheter can be placed via an epidural needle in the CTM. After the distal end is retrieved from the mouth, an endotracheal tube may be passed
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Problems Following Intubation
Anesthesia staff MUST confirm that the tube is correctly placed with bilateral ventilation immediately following placement.
Detection of end-tidal CO2 remains the gold standard for this.
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Problems Following Intubation
Should the end-tidal CO2 decline suddenly, pulmonary (thrombus) or venous air embolism should be considered. Likewise, other causes of a sudden decline in cardiac output or a leak in the circuit should be considered.
A rising end-tidal CO2 may be secondary to hypoventilation or increased CO2 production, as occurs with malignant hyperthermia, sepsis, a depleted CO2 absorber, or breathing circuit malfunction.
Increases in airway pressure may indicate an obstructed or kinked endotracheal tube or reduced pulmonary compliance. The endotracheal tube should be suctioned to confirm that it is patent and the lungs auscultated to detect signs of bronchospasm, pulmonary edema, endobronchial intubation, or pneumothorax.
Decreases in airway pressure can occur secondary to leaks in the breathing circuit or inadvertent extubation
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techniques of extubation
Most often, extubation should be performed when a patient is either deeply anesthetized or awake. In either case, adequate recovery from neuromuscular blocking agents should be established prior to extubation.
If neuromuscular blocking agents are used, the patient has at least a period of controlled mechanical ventilation and likely must be weaned from the ventilator before extubation can occur.
Extubation during a light plane of anesthesia (i.e., a state between deep and awake) is avoided because of an increased risk of laryngospasm.
The distinction between deep and light anesthesia is usually apparent during pharyngeal suctioning: any reaction to suctioning (e.g., breath holding, coughing) signals a light plane of anesthesia, whereas no reaction is characteristic of a deep plane. Similarly, eye opening or purposeful movements imply that the patient is sufficiently awake for extubation.
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more on extubation
Extubating an awake patient is usually associated with coughing (bucking) on the TT. This reaction increases the heart rate, central venous pressure, arterial blood pressure, intracranial pressure, intraabdominal pressure, and intraocular pressure.
It may also cause wound dehiscence and increased bleeding. The presence of a TT in an awake asthmatic patient may trigger bronchospasm.
Some practitioners attempt to decrease the likelihood of these effects by administering 1.5 mg/kg of intravenous lidocaine 1-2 min before suctioning and extubation; however, extubation during deep anesthesia may be preferable in patients who cannot tolerate these effects (provided such patients are not at risk of aspiration and/or do not have airways that may be difficult to control after removal of the TT).
Regardless of whether the tube is removed when the patient is deeply anesthetized or awake, the patient’s pharynx should be thoroughly suctioned before extubation to decrease the potential for aspiration of blood and secretions.
Patients should be ventilated with 100% oxygen in case it becomes difficult to establish an airway after the TT is removed.
Just prior to extubation, the TT is untaped or untied and its cuff is deflated. The tube is withdrawn in a single smooth motion, and a face mask is applied to deliver oxygen.
Oxygen delivery by face mask is maintained during the period of transportation to the postanesthesia care area.
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complications of laryngoscopy and intubation include
The complications of laryngoscopy and intubation include:
hypoxia
hypercarbia
dental and airway trauma
tube malpositioning
physiological responses to airway instrumentation, or tube malfunction.
These complications can occur during laryngoscopy and intubation, while the tube is in place, or following extubation
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Airway Trauma
Instrumentation with a metal laryngoscope blade and insertion of a stiff TT often traumatizes delicate airway tissues.
Tooth damage is a common cause of (relatively small) malpractice claims against anesthesiologists. Laryngoscopy and intubation can lead to a range of complications from sore throat to tracheal stenosis.
Most of these are due to prolonged external pressure on sensitive airway structures. When these pressures exceed the capillary-arteriolar blood pressure (approximately 30 mm Hg), tissue ischemia can lead to a sequence of inflammation, ulceration, granulation, and stenosis.
Inflation of a TT cuff to the minimum pressure that creates a seal during routine positive-pressure ventilation (usually at least 20 mm Hg) reduces tracheal blood flow by 75% at the cuff site. Further cuff inflation or induced hypotension can totally eliminate mucosal blood flow.
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airway trauma
Post intubation croup caused by glottic, laryngeal, or tracheal edema is particularly serious in children.
Vocal cord paralysis from cuff compression or other trauma to the recurrent laryngeal nerve results in hoarseness and increases the risk of aspiration. The incidence of postoperative hoarseness seems to increase with obesity, difficult intubations, and anesthetics of long duration.
Smaller tubes (size 6.5 in women and size 7.0 in men) are associated with fewer complaints of postoperative sore throat.
Repeated attempts at laryngoscopy during a difficult intubation may lead to periglottic edema and the inability to ventilate with a face mask, thus turning a bad situation into a life-threatening one.
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Errors of Tracheal Tube Positioning
Unrecognized esophageal intubation can produce catastrophic results.
Prevention of this complication depends on direct visualization of the tip of the TT passing through the vocal cords, careful auscultation for the presence of bilateral breath sounds and the absence of gastric gurgling while ventilating through the TT, analysis of exhaled gas for the presence of CO2 (the most reliable automated method), chest radiography, or the use of an FOB.
Even though it is confirmed that the tube is in the trachea, it may not be correctly positioned. Overly “deep” insertion usually results in intubation of the right (rather than left) main-stem bronchus because of the right bronchus’ less acute angle with the trachea
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errors of tracheal tube positioning
Clues to the diagnosis of bronchial intubation include unilateral breath sounds, unexpected hypoxia with pulse oximetry, inability to palpate the TT cuff in the sternal notch during cuff inflation, and decreased breathing-bag compliance (high peak inspiratory pressures).
Inadequate insertion depth will position the cuff in the larynx, predisposing the patient to laryngeal trauma. Inadequate depth of insertion can be detected by palpating the cuff over the thyroid cartilage.
Because no one technique protects against all possibilities for misplacing a TT, minimal testing should include chest auscultation, routine capnography, and occasionally cuff palpation.
If the patient is repositioned, tube placement must be reconfirmed. Neck extension or lateral rotation most often moves a TT away from the carina, whereas neck flexion most often moves the tube toward the carina.
At no time should excessive force be employed during intubation. Esophageal intubations can result in esophageal rupture and mediastinitis.
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Physiological Responses to Airway Instrumentation
Laryngoscopy and tracheal intubation violate the patient’s protective airway reflexes and predictably lead to hypertension and tachycardia when performed under “light” planes of general anesthesia.
Hemodynamic changes can be attenuated by intravenous administration of lidocaine, opioids, or β-blockers or deeper planes of inhalation anesthesia in the minutes before laryngoscopy.
Cardiac arrhythmias—particularly ventricular bigeminy—sometimes occur during intubation and may indicate light anesthesia
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laryngospasm
Laryngospasm is a forceful involuntary spasm of the laryngeal musculature caused by sensory stimulation of the superior laryngeal nerve.
Triggering stimuli include pharyngeal secretions or passing a TT through the larynx during extubation. Laryngospasm is usually prevented by extubating patients either deeply asleep or fully awake, but it can occur—albeit rarely—in an awake patient.
Treatment of laryngospasm includes providing gentle positive-pressure ventilation with an anesthesia bag and mask using 100% oxygen.
Administering intravenous lidocaine (1-1.5 mg/kg). If laryngospasm persists and hypoxia develops, small doses of succinylcholine (0.25-0.5 mg/kg) may be required (perhaps in combination with small doses of propofol or another anesthetic) to relax the laryngeal muscles and to allow controlled ventilation
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laryngospasm
The large negative intrathoracic pressures generated by a struggling patient during laryngospasm can result in the development of negative-pressure pulmonary edema, even in healthy patients.
Whereas laryngospasm may result from an abnormally sensitive reflex, aspiration can result from depression of laryngeal reflexes following prolonged intubation and general anesthesia.
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Bronchospasm
Bronchospasm is another reflex response to intubation and is most common in asthmatic patients.
Bronchospasm can sometimes be a clue to bronchial intubation. Other pathophysiological effects of intubation include increased intracranial and intraocular pressures.
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Tracheal Tube Malfunction
Tubes do not always function as intended. Polyvinyl chloride tubes may be ignited by cautery or laser in an oxygen/nitrous oxide-enriched environment.
Valve or cuff damage is not unusual and should be excluded prior to insertion. TT obstruction can result from kinking, from foreign body aspiration, thick secretions in the lumen.
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congenital syndroms associated with difficult endotracheal intubation
trisomony 21- large tongue, small mouth
goldenhar- mandibular hypoplasia and cervical spine abnormality
klippel-feil- neck rigidity because of cervical vertebral fusion
pierre robin- small mouth, large tongue, mandibular anomaly
teacher collins- laryngoscopy difficult
turner- high likelihood of difficult endotracheal intubation
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superior laryngeal internal division
sensory supply to the larynx between the epiglottis and the vocal cords. epiglottis, base of the tongue, supraglottic mucosa, thyroepiglottic joint, cricothyroid joint
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superior laryngeal external division
motor- cricothyroid membrane
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recurrent laryngeal
sensory subglottic mucosa, muscle spindles.
motor- throarytenoid membrane
lateral cricoartynoid membrane interarytenoid membrane, posterior cricoarytenoid membrane
