Transcript 18 Basics of Pediatric Airway Anatomy Physiology and Management

Basics of Pediatric Airway
Anatomy, Physiology and
Management
Christine Mai, MD
Claudine Mansour, MD
Faculty Advisor: Ruth Padilla, MD
Boston University Medical Center
Department of Anesthesiology
The Pediatric Airway
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Introduction
Normal Anatomy
Physiology
Airway evaluation
Management of
normal vs. abnormal
airway
• Difficult airway
Introduction
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Almost all of pediatric codes are due to respiratory origin
80% of pediatric cardiopulmonary arrest are primarily due
to respiratory distress
Majority of cardiopulmonary arrest occur at <1 year old
1990 Closed Claim Project by ASA
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Respiratory events are the largest class of injury (34%)
More common in children than adults
92% of claims occurred between 1975-1985 before continuous
pulsoximetry and capnography (Brain damage and death in 85%
of cases)
With continuous O2 sat and ETCO2 monitoring after 1990s,
decrease in brain damage and death (56% 1970s to 31% 1990s)
Normal Pediatric Airway Anatomy
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Larynx composed of hyoid
bone and a series of
cartilages
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Single: thyroid, cricoid,
epiglottis
Paired: arytenoids,
corniculates, and cuneiform
Pediatric Anatomy cont.
Laryngeal folds consist of:
• Paired aryepiglottic folds extend from epiglottis posteriorly to
superior surface of arytenoids
• Paired vestibular folds (false vocal cords) extend from thyroid
cartilage posteriorly to superior surface of arytenoids
• Paired vocal folds (true vocal cords) extend from posterior surface
of thyroid plate to anterior part of arytenoids
• Interarytenoid fold bridging the arytenoid cartilages
• Thyrohyoid fold extend from hyoid bone to thyroid cartilage
Sensory Innervation:
Recurrent Laryngeal Nerve-supraglottic larynx
Internal Branch of Superior Laryngeal Nerve-infraglottic larynx
Motor Innervation:
External branch of Superior Laryngeal Nerve-cricothyroid muscle
Recurrent Laryngeal Nerve-all other laryngeal muscles
Blood Supply
Laryngeal branches of the superior and inferior thyroid arteries
5 Differences between Pediatric and Adult
Airway
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More rostral larynx
Relatively larger tongue
Angled vocal cords
Differently shaped epiglottis
Funneled shaped larynx-narrowest part of
pediatric airway is cricoid cartilage
More rostral pediatric larynx
Laryngeal apparatus develops from brachial clefts and descends caudally
Infant’s larynx is higher in neck (C2-3) compared to adult’s (C4-5)
Relatively larger tongue
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Obstructs airway
Obligate nasal breathers
Difficult to visualize larynx
Straight laryngoscope blade
completely elevates the epiglottis,
preferred for pediatric
laryngoscopy
Angled vocal cords
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Infant’s vocal cords have more
angled attachment to trachea,
whereas adult vocal cords are
more perpendicular
Difficulty in nasal intubations
where “blindly” placed ETT may
easily lodge in anterior
commissure rather than in trachea
Image from: http://www.utmb.edu/otoref/Grnds/Pedi-airway-2001-01/Pediairway-2001-01-slides.pdf
Differently shaped epiglottis
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Adult epiglottis broader, axis parallel to trachea
Infant epiglottis ohmega (Ώ) shaped and angled away
from axis of trachea
More difficult to lift an infant’s epiglottis with
laryngoscope blade
Funneled shape larynx
ADULT
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narrowest part of infant’s
larynx is the undeveloped
cricoid cartilage, whereas in
the adult it is the glottis
opening (vocal cord)
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Tight fitting ETT may cause
edema and trouble upon
extubation
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Uncuffed ETT preferred for
patients < 8 years old
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Fully developed cricoid
cartilage occurs at 10-12
years of age
INFANT
Image from: http://www.hadassah.org.il/NR/rdonlyres/59B531BDEECC-4FOE-9E8114B9B29D139B1945/AirwayManagement.ppt
Pediatric Respiratory Physiology
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Extrauterine life not possible until 24-25 weeks of gestation
Two types of pulmonary epithelial cells: Type I and Type II
pneumocytes
• Type I pneumocytes are flat and form tight junctions that
interconnect the interstitium
• Type II pneumocytes are more numerous, resistant to oxygen
toxicity, and are capable of cell division to produce Type I
pneumocytes
Pulmonary surfactant produced by Type II pneumocytes
at 24 wks GA
Sufficient pulmonary surfactant present after 35 wks GA
Premature infants prone to respiratory distress syndrome
(RDS) because of insufficient surfactant
Betamethasone can be given to pregnant mothers at 24-35wks GA to
accelerate fetal surfactant production
Pediatric Respiratory Physiology cont.
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Work of breathing for each kilogram of body weight is
similar in infants and adult
Oxygen consumption of infant (6 ml/kg/min) is twice that
of an adult (3 ml/kg/min)
Greater oxygen consumption = increased respiratory rate
Tidal volume is relatively fixed due to anatomic structure
Minute alveolar ventilation is more dependent on
increased respiratory rate than on tidal volume
Lack Type I muscle fibers, fatigue more easily
FRC of an awake infant is similar to an adult when
normalized to body weight
Ratio of alveolar minute ventilation to FRC is doubled,
under circumstances of hypoxia, apnea or under
anesthesia, the infant’s FRC is diminished and
desaturation occurs more precipitously
Physiology: Effect Of Edema
Poiseuille’s law
R = 8nl/ πr4
If radius is halved, resistance increases 16 x
Image from: http://www.hadassah.org.il/NR/rdonlyres/59B531BD-EECC-4FOE-9E81-14B9B29D139B1945/AirwayManagement.ppt
Normal Inspiration and Expiration
turbulence
Image from: http://www.hadassah.org.il/NR/rdonlyres/59B531BD-EECC-4FOE-9E81-14B9B29D139B1945/AirwayManagement.ppt
Obstructed Airways
turbulence &
wheezing
Image from: http://www.hadassah.org.il/NR/rdonlyres/59B531BD-EECC-4FOE-9E81-14B9B29D139B1945/AirwayManagement.ppt
Airway Evaluation
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Medical History
URI predisposes to coughing,
laryngospasm, bronchospasm,
desat during anesthesia
Snoring or noisy breathing
(adenoidal hypertrophy, upper
airway obstruction, OSA)
Chronic cough (subglottic
stenosis, previous
tracheoesohageal fistula
repair)
Productive cough (bronchitis,
pneumonia)
Sudden onset of new cough
(foreign body aspiration)
Inspiratory stridor
(macroglossia, laryngeal web,
laryngomalacia, extrathoracic
foreign body)
Hoarse voice (laryngitis, vocal
cord palsy, papillomatosis)
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Asthma and bronchodilator
therapy (bronchospasm)
Repeated pneumonias (GERD,
CF, bronchiectasis,
tracheoesophageal fistula,
immune suppression, congenital
heart disease)
History of foreign body aspiration
Previous anesthetic problems
(difficulty intubation/extubation
or difficulty with mask
ventilation)
Atopy, allergy (increased airway
reactivity)
History of congenital syndrome
(Pierre Robin Sequence, Treacher
Collins, Klippel-Feil, Down’s
Syndrome, Choanal atresia)
Environmental: smokers
Signs of Impending Respiratory Failure
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Increase work of breathing
Tachypnea/tachycardia
Nasal flaring
Drooling
Grunting
Wheezing
Stridor
Head bobbing
Use of accessory muscles/retraction of muscles
Cyanosis despite O2
Irregular breathing/apnea
Altered consciousness/agitation
Inability to lie down
Diaphoresis
Airway Evaluation
Physical Exam
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Facial expression
Nasal flaring
Mouth breathing
Drooling
Color of mucous membranes
Retraction of suprasternal,
intercostal or subcostal
Respiratory rate
Voice change
Mouth opening
Size of mouth
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Mallampati
Loose/missing teeth
Size and configuration of palate
Size and configuration of
mandible
Location of larynx
Presence of stridor
(inspiratory/expiratory)
Baseline O2 saturation
Global appearance (congenital
anomalies)
Body habitus
Diagnostic Testing
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Laboratory and radiographic evaluation extremely helpful
with pathologic airway
AP and lateral films and fluoroscopy may show site and
cause of upper airway obstruction
MRI/CT more reliable for evaluating neck masses,
congenital anomalies of the lower airway and vascular
system
Perform radiograph exam only when there is no
immediate threat to the child’s safety and in the presence
of skilled personnel with appropriate equipment to
manage the airway
Intubation must not be postponed to obtain radiographic
diagnosis when the patient is severely compromised.
Blood gases are helpful in assessing the degree of
physiologic compromise; however, performing an arterial
puncture on a stressed child may aggravate the underlying
airway obstruction
Airway Management: Normal Airway
• Challenging because of unique anatomy
and physiology
• Goals: protect the airway, adequately
ventilate, and adequately oxygenate
• Failure to perform any ONE of these tasks
will result in respiratory failure
• Positioning is key!
Bag-Mask Ventilation
•Clear, plastic mask with inflatable rim
provides atraumatic seal
•Proper area for mask application-bridge
of nose extend to chin
•Maintain airway pressures <20 cm H2O
•Place fingers on mandible to avoid
compressing pharyngeal space
•Hand on ventilating bag at all times to
monitor effectiveness of spontaneous breaths
•Continous postitive pressure when needed
to maintain airway patency
Image from: http://www.hadassah.org.il/NR/rdonlyres/59B531BD-EECC-4FOE-9E81-14B9B29D139B1945/AirwayManagement.ppt
Oropharyngeal Airway
SIZE
PROPER
POSITION
Image from: http://www.hadassah.org.il/NR/rdonlyres/59B531BD-EECC-4FOE-9E81-14B9B29D139B1945/AirwayManagement.ppt
Oropharyngeal Airway Placement
Image from: http://depts.Washington.edu/pccm/Pediatric%20Airway%20management.ppt
Nasopharyngeal Airway
•Distance from nares to angle of mandible approximates the proper length
•Nasopharyngeal airway available in 12F to 36F sizes
•Shortened endotracheal tube may be used in infants or small children
•Avoid placement in cases of hypertrophied adenoids - bleeding and
trauma Image from: http://www.hadassah.org.il/NR/rdonlyres/59B531BD-EECC-4FOE-9E81-14B9B29D139B1945/AirwayManagement.ppt
Sniffing Position
Patient flat on operating table, the oral (o),
pharyngeal (P), and tracheal (T) axis pass through
three divergent planes
A blanket placed under the occiput aligns the
pharyngeal (P) and tracheal (T) axes
Extension of the atlanto-occipital joint
aligns the oral (O), pharyngeal (P), and
tracheal (T) axes
Image from:
http://depts.Washington.edu/pccm/Pediatric%20Airway%20management.ppt
Selection of laryngoscope blade:
Miller vs. Macintosh
• Miller blade is preferred for infants and younger
children
• Facilitates lifting of the epiglottis and exposing
the glottic opening
• Care must be taken to avoid using the blade as a
fulcrum with pressure on the teeth and gums
• Macintosh blades are generally used in older
children
• Blade size dependent on body mass of the patient
and the preference of the anesthesiologist
Endotracheal Tube
Age
Wt
ETT(mm ID) Length(cm)
Preterm
1 kg
1-2.5 kg
2.5
3.0
3.0-3.5
3.5-4.0
4.0-5.0
Neonate-6mo
6 mo-1
1-2 yrs
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7-9
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12
New AHA Formulas:
Uncuffed ETT: (age in years/4) + 4
Cuffed ETT: (age in years/4) +3
ETT depth (lip): ETT size x 3
Complications of Endotracheal Intubation
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Postintubation Croup
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Incidence 0.1-1%
Risk factors: large ETT, change in patient position introp,
patient position other than supine, multiple attempts at
intubation, traumatic intubation, pts ages 1-4, surgery >1hr,
coughing on ETT, URI, h/o croup
Tx: humidified mist, nebulized racemic epinephrine, steroid
Laryngotracheal (Subglottic) Stenosis
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Occurs in 90% of prolonged endotracheal intubation
Lower incidence in preterm infants and neonates due to relative
immaturity of cricoid cartilage
Pathogenesis: ischemic injury secondary to lateral wall pressure
from ETT
edema, necrosis, and ulceration of mucosa, infx
Granulation tissues form within 48hrs leads to scarring and
stenosis
Cuff vs Uncuffed Endotracheal Tube
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Controversial issue
Traditionally, uncuffed ETT recommended in children < 8 yrs old to
avoid post-extubation stridor and subglottic stenosis
Arguments against cuffed ETT: smaller size increases airway
resistance, increase work of breathing, poorly designed for pediatric
pts, need to keep cuff pressure < 25 cm H2O
Arguments against uncuffed ETT: more tube changes for long-term
intubation, leak of anesthetic agent into environment, require more
fresh gas flow > 2L/min, higher risk for aspiration
-Concluding RecommendationsFor “short” cases when ETT size >4.0, choice of cuff vs uncuffed
probably does not matter
Cuffed ETT preferable in cases of: high risk of aspiration (ie. Bowel
obstruction), low lung compliance (ie. ARDS, pneumoperitoneum,
CO2 insufflation of the thorax, CABG), precise control of ventilation
and pCO2 (ie. increased intracranial pressure, single ventricle
physiology)
Golden, S. “Cuffed vs. Uncuffed Endotracheal tubes in children: A review” Society for Pediatric Anesthesia. Winter 2005 edition.
Laryngeal Mask Airway
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Supraglottic airway device developed by Dr. Archie Brain
Flexible bronchoscopy, radiotherapy, radiologic procedures, urologic,
orthopedic, ENT and ophthalmologic cases are most common
pediatric indications for LMA
Useful in difficult airway situations, and as a conduit of drug
administration (ie. Surfactant)
Different types of LMAs: Classic LMA, Flexible LMA, ProSeal
LMA, Intubating LMA
Disadvantages: Laryngospasm, aspiration
LMA size
1 .0
1.5
2.0
2.5
3.0
4.0
5.0
Weight
Max cuff volume (mL)
Neonate/Infants ≤ 5kg
4
Infants 5-10kg
7
Infants/children 10-20kg
10
Children 20-30kg
14
Children/small adult > 30kg
20
Normal/large adolescent/adult
30
Large adolescent/adult
40
ETT (mID)
3.5
4.0
4.5
5.0
6.0 cuff
7.0 cuff
8.0 cuff
Other Supraglottic Devices
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Laryngeal tube
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Latex-free, single-lumen silicone tube, which is closed at distal end
Two high volume-low pressure cuffs, a large proximal oropharyngeal cuff
and a smaller distal esophageal cuff
Both cuffs inflated simultaneously via a single port
Situated along length of oropharynx with distal tip in esophagus
Sizes 0-5, neonates to large adults (only sizes 3-5 available in US)
Limited data available for its use in children
Cobra Perilaryngeal Airway
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Perilaryngeal airway device with distal end shaped like a cobra-head
Positioned into aryepiglottic folds and directly seats on entrance to glottis
Inflation of the cuff occludes the nasopharynx pushing the tongue and soft
tissues forward and preventing air leak
Available in sizes pediatric to adult ½ to 6
No studies currently available evaluating this device in children
Difficult Airway Management Techniques
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Rigid bronchoscopy
Flexible bronchoscopy
Direct laryngoscopy
Intubating LMA
Lighted stylet
Bullardscope
Fiberoptic intubation
Surgical airway
Airway Management
Classification of Abnormal Pediatric Airway
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Congenital Neck Masses (Dermoid cysts, cystic teratomas, cystic
hygroma, lymphangiomas, neurofibroma, lymphoma, hemangioma)
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Congenital Anomalies
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Congenital Syndromes (Pierre Robin Syndrome, Treacher Collin,
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Inflammatory (Epiglottitis, acute tonsillitis, peritonsillar
(Choanal atresia,tracheoesophageal fistula,
tracheomalacia, laryngomalacia, laryngeal stenosis, laryngeal web, vascular
ring, tracheal stenosis)
Turner, Down’s, Goldenhar , Apert, Achondroplasia, Hallermann-Streiff,
Crouzan)
abscess,retropharyngeal abscess, laryngotracheobronchitis,bacterial
tracheitis,adenoidal hypertrophy,nasal congestion, juvenile rheumatoid
arthritis)
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Traumatic/Foreign Body (burn,laceration,lymphatic/venous
obstruction,fractures/dislocation, inhalational injury, postintubation
croup (edema),swelling of uvula
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Metabolic (Congenital hypothyroidism, mucopolysaccharidosis,
Beckwith-Wiedemann Syndrome,glycogen storage disease, hypocalcemia
laryngospasm)
Congenital Neck Masses
Image from:
http://bms.brown.edu/pedisurg/fetal/seminar/imagebank.html
http://bms.brown.edu/pedisurg/Brown/IBImages/Teratoma/Br
onchospyTeratoma.html
Congenital Anomalies
Tracheoesphageal Fistula
Radiograph of a neonate with
suspected esophageal atresia.
Note the nasogastric tube coiled
in the proximal esophageal pouch
(solid arrow). The prominent
gastric bubble indicates a
concurrent tracheoesphageal
fistula (open arrow)
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Feeding difficulties (coughing, choking and
cyanosis) and breathing problems
Associated with congenital heart (VSA, PDA,
TOF), VATER, GI, musculoskeletal and urinary
tract defects
Occurs in 1/ 3000-5000 births
Most common type is the blind esophageal pouch
with a fistula between the trachea and the distal
esophagus (87%)
Clark, D. “Esophageal atresia and tracheoesophageal fistula” American Family Physician. Feb 15,
1999. Vol 59(4) http://www.aafp.org/afp/99021ap/910.htlm
Congenital Anomalies
Choanal Atresia
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Complete nasal obstruction of
the newborn
Occurs in 0.82/10 000 births
During inspiration, tongue
pulled to palate, obstructs oral
airway
Unilateral nare (right>left)
Bilateral choanal atresia is
airway emergency
Death by asphyxia
Associated with other
congenital defects
Tewfik, T. “Choanal atresia” emedicine.com
http://www.emedicine.com/ent/topic330.htm
Congenital Syndromes
Pierre Robin Sequence
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Occurs in 1/8500 births
Autosomal recessive
Mandibular hypoplasia,
micrognathia, cleft palate,
retraction of inferior dental arch,
glossptosis
Severe respiratory and feeding
difficulties
Associated with OSA, otitis
media, hearing loss, speech
defect, ocular anomalies, cardiac
defects, musculoskeletal
(syndactyly, club feet), CNS
delay, GU defects)
Tewfik, T. “Pierre Robin Syndrome” emedicine.com
http://www.emedicine.com/ent/topic150.htm
Congenital Syndrome
Treacher Collins Syndrome
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Mandibulofacial dysotosis
Occurs in 1/10 000 births
Cheek bone and jaw bone
underdeveloped
External ear anamolies, drooping
lower eyelid, unilateral absent
thumb
Respiratory difficulties
Underdeveloped jaw causes
tongue to be positioned further
back in throat (smaller airway)
Associated with OSA, hearing
loss, dry eyes
www.ccakids.com/syndrome/treacher.pdf
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Congenital Syndrome
Down’s Syndrome
Trisomy 21
Occurs in 1/660 births
Short neck, microcephaly,
small mouth with large
protruding tongue, irregular
dentition, flattened nose, and
mental retardation
Associated with growth
retardation, congenital heart
disease, subglottic stenosis,
tracheoesophageal fistula,
duodenal atresia, chronic
pulmonary infection, seizures,
and acute lymphocytic
leukemia
Atlantooccipital dislocation
can occur during intubation
due to congenital laxity of
ligaments
http://www.nlm.nih.gov/medlineplus/ency/article/0000997.htm
Inflammatory
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Etiology: Haemophilus influenzae
type B
Occurs in children ages 2-6 years
Disease of adults due to
widespread H. influenza vaccine
Progresses rapidly from a sore
throat to dysphagia and complete
airway obstruction (within hours)
Signs of obstruction: stridor,
drooling, hoarseness, tachypnea,
chest retraction, preference for
upright position
OR intubation/ENT present for
emergency surgical airway
Do NOT perform laryngoscopy
before induction of anesthesia to
avoid laryngospasm
Inhalational induction in sitting
position to maintain spontaneous
respiratory drive
(Sevo/Halothane)
Range of ETT one-half to one size
smaller
Inflammatory
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Etiology: Parainfluenza virus
Occurs in children ages 3 months
to 3 years
Barking cough
Progresses slowly, rarely requires
intubation
Medically managed with oxygen
and mist therapy, racemic
epinephrine neb and IV
dexamethasone (0.25-0.5mg/kg)
Indications for intubation:
progressive intercostal retraction,
obvious respiratory fatigue, and
central cyanosis
Metabolic
Beckwith-Wiedemann Syndrome
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Occurs in 1/13000-15000 births
Chr 11p.15.5
Autosomal dominant
Macroglossia, Exomphalos,
Gigantism
Associated with mental retardation,
organomegaly, abdominal wall defect,
pre- and postnatal overgrowth,
neonatal hypoglycemia, earlobe pits,
Wilms tumor
Ferry, R “Beckwith-Wiedemann Syndrome” emedicine.com
http://www.emedicine.com/ped/toic218.htm
Pediatric Difficult Airway Algorithm