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Flashcards in 43 Pediatric Pulmonary Diseases 1 Deck (17):
1

Airway diseases

  • Among the most common reasons for doctor visits during the winter months
  • Asthma and bronchiolitis
  • The single most common cause of hospitalization among children
  • The major reason for loss of school days
  • Comprise the vast majority of the kinds of problems seen by the pediatric pulmonologist

2

History

  • Always take a birth history
  • Did the problem arise within the 1st 6 months of life? 
  • What triggers the cough or wheeze? 

  • Always take a birth history
    • Gravity, parity, prematurity, intubation, and meconium are all important to ask about.
  • Did the problem arise within the 1st 6 months of life?
    • Congenital airway malformations are fairly common and always become symptomatic within the first 6 months of life
    • This is not to say that all wheezing that occurs in the first 6 months is due to airway malformations, but persistent wheezing within the first 6 months should raise your index of suspicion for congenital airway malformations
  • What triggers the cough or wheeze?
    • “Triggers” are extremely important
    • Unlike children over age 4 to 5 and adults, allergy is only a rare cause of or trigger for asthma in infants and toddlers
    • The single most common trigger for pediatric wheezing is viral respiratory tract infection (VRI)
      • This is one reason there is such a seasonal predisposition for asthma hospitalizations in this country
    • When the wheezing is not associated with a VRI you should consider other triggers, like gastro-esophageal reflux (more on this later) or, in the older child (>5), allergy to house dust mite

3

History

  • Response or lack of response to therapy
  • What is the nature of the cough? 
  • Does the cough awaken the infant from sleep? 

  • Response or lack of response to therapy 
    • Just as a good response to a bronchodilator is useful in establishing a diagnosis of asthma, a lack of response to a bronchodilator should make you question that diagnosis
  • What is the nature of the cough?
    • Is it wet or dry?
      • Unlike adult asthmatics, most infants and young children with asthma have a dry, hacking cough
      • A wet sounding cough implies that there is purulence in the airways and is worrisome for bacterial disease
    • Just the same, viral respiratory infections can on occasion induce production of a great deal of mucus and secretions, so a wet-sounding cough is not specific for bacterial lower airway disease
    • A chronic wet cough in a child is typical of cystic fibrosis and can be seen in another disease of impaired mucociliary clearance: primary ciliary dyskinesia (PCD)
      • Kartagener’s syndrome is one form of PCD: it is the original description with complete situs inversus, sinusitis, and bronchiectasis
    • Children of smokers may get a bronchitis from passive smoking and get a wet cough from this
      • Cigarette smoke poisons the cilia and can lead functionally to a pattern similar to that of PCD with recurrent OM, sinusitis, and bronchitis
  • Does the cough awaken the infant from sleep?
    • A cough that awakens a child from sleep is not specific to one diagnosis or another but is a RED FLAG
    • The cough that awakens a child from a sound sleep is generally reflective of significant pathology and requires medical attention
    • Most simple colds, by comparison, don’t awaken one from sleep

4

History

  • Family medical history
  • Environmental history

  • Family medical history
    • Ask about the “atopic triad:” asthma, eczema, allergies
    • Most new CF diagnoses have negative FMH (typical of autosomal recessive diseases)
    • When you hear “emphysema, CAD, CVA, lung Ca, think cigarette
  • Environmental history
    • Cigarette smoke exposure is the most common environmental evil
      • Ask about exposure in the home and in the car and remember that “a home with a smoking area is like a swimming pool with a peeing area”
    • Also ask about animal danders, house dust mite, occupational dusts, wood burning stoves, cockroaches, etc

5

Review of systems

  • Gastro-esophageal reflux (GER)
  • Recurrent otitis media (OM), sinusitis, and pneumonia/bronchitis/bronchiolitis 
  • Stool history

  • Gastro-esophageal reflux (GER)
    • Symptoms of GERD include arching/pain behaviors – especially at night – spitting, hoarseness/stridor, recurrent croup, and occasionally apnea
    • The presence of dried vomitus in the crib in the morning is NEVER normal and should be considered a sign of pathological reflux
  • Recurrent otitis media (OM), sinusitis, and pneumonia/bronchitis/bronchiolitis 
    • Suggests humoral immunodeficiency
    • Most commonly this is an IgA and/or IgG subclass deficiency
    • Primiary ciliary dyskinesia (PCD) or Kartagener’s syndrome is associated with recurrent OM, sinusitis, and bronchitis/bronchiectasis
      • It is much less common, 1:20,000
    • Cystic fibrosis is associated with recurrent bronchitis and with sinusitis but NOT with otitis media
      • Its incidence is 1:3,000, so it’s fairly common
  • Stool history
    • Oil or grease in the stool (steatorrhea) is suggestive of CF
      • Half of newborns with CF do NOT malabsorb
    • Failure to thrive is a red flag and should suggest a diagnosis of CF
      • It is neither sensitive nor specific for CF

6

Physiology of pediatric airway disease

  • The primary difference between the physiology of the infant chest and the adult chest
  • 2 kinds of airway diseases

  • The primary difference between the physiology of the infant chest and the adult chest
    • For the first six months of life the infant’s chest wall is excessively compliant
  • 2 kinds of airway diseases
    • Those of the LARGE airways
      • Uncomplicated LARGE airway obstruction does NOT lead to hypoxemia
      • Ex. the infant born with a floppy trachea or bronchus (tracheomalacia or bronchomalacia) who is otherwise normal
        • That baby is the typical “happy wheezer” – he has chronic noisy breathing but NEVER has respiratory distress, and is always normoxemic (has normal oxygen levels and saturations)
    • Those of the SMALL airways

7

Physiology of pediatric airway disease

  • Hypoxemia in infants is almost always due to...
  • Resistance and compliance (straw and balloon)

  • Hypoxemia in infants is almost always due to...
    • Ventilation-perfusion (V/Q) mismatching due to SMALL airway disease
    • In this situation, the alveolus is well perfused but poorly ventilated
    • The low oxygen tension in the alveolus depresses the oxygen tension in the blood returning to the heart, and leads to a low saturation, detectable with a simple non-invasive test, the pulse oximeter
  • Resistance and compliance (straw and balloon)
    • Imagine a straw tied to the mouth of an inflated balloon
    • The balloon has compliance, and the straw has resistance
    • The properties of both the balloon and the straw determine the emptying time of that unit
    • A thin straw will slow down deflation, and a stretched-out, baggy balloon will empty more slowly even through a normal straw

8

Physiology of pediatric airway disease:
Resistance

  • General
  • Units
  • Poiseuille's equation
  • Essential equation

  • The difficulty inherent in pushing air through a tube
    • Smaller and longer tubes lead to greater resistance
  • Defined in units of pressure/flow
  • In areas of laminar flow, this is defined by Poiseuille’s equation:
    • R = 8nL/πr4
    • “n” is the viscosity constant of air
    • “L” is the length of the airway
    • “r” is the radius of the airway
  • Since we cannot change n without Heliox, we don’t change L except with growth, and π is a constant, this equation is essentially...
    • R α 1/r4
    • Resistance is proportional to the inverse of the radius to the 4th power
    • Small changes in radius lead to large changes in resistance
    • Ex. If you decrease the radius by 2, resistance goes up by 16

9

Physiology of pediatric airway disease:
Compliance

  • Refers to...
  • Units
  • Think about blowing up that balloon
  • Primary diseases characterized by compliance changes 
    • Infants
    • Adults
  • Increased compliance seen in emphysema might be seen in...

  • Refers to the alveolus and lung parenchyma
    • Should be thought of as “stretchability”
  • Defined in units of volume/pressure
  • Think about blowing up that balloon
    • A non-compliant lung unit is STIFF
      • Not much volume resulting from a lot of pressure
    • An overly complaint lung unit (like in emphysema) is baggy
      • A lot of volume from not much pressure
  • Primary diseases characterized by compliance changes
    • Rare in infants
      • Occasionally see decreased compliance in infants and children in the setting of interstitial lung disease
    • More typically seen in the adult population
      • (1) non-compliant, stiff lungs are typified by idiopathic pulmonary fibrosis
      • (2) overly compliant lungs are typified by emphysema
  • Increased compliance seen in emphysema might be seen in...
    • Bronchopulmonary dysplasia (BPD)
    • In a focal manner in congenital lobar emphysema (CLE)

10

Physiology of pediatric airway disease:
Time constant

  • Equation
  • Units
  • Emptying is a logarithmic function
  • Ex. an infant with RSV bronchiolitis
  • ​Air trapping

  • The mathematical product of resistance (R) and compliance (C)
    • τ (tau) = R • C
  • The unit of the time constant is seconds
    • τ (tau) = (pressure/flow) x (volume/pressure) = volume / (volume/time) = liters / (liters/sec) = sec
  • Emptying is a logarithmic function
    • Think of τ as a kind of half life, but one based on natural log, so it’s more like a third life (e is 2.7)
      • It takes roughly 3 times the time constant for that lung unit to empty
    • Small airway diseases in infants lead to longer time constants and thus longer emptying times for the lung units
  • Ex. an infant with RSV bronchiolitis
    • Those little airways are narrowed from the edema and inflammation induced by the respiratory syncitial virus (decreased r for radius)
      • This makes for increased resistance (R) and consequently a longer time constant
    • Infants with respiratory problems NEVER breathe more slowly, regardless of whether it might be a better breathing strategy
      • This infant will breath more rapidly (tachypnea)
    • The more rapid pattern will mean that the lung units will not have time to fully deflate before they start reinflating
    • This leads to stacking of breaths, and air trapping
  • ​Air trapping
    • The affected lung units are not being ventilated with fresh air, so the alveolar PO2 drops
    • This leads to hypoxemia
    • The air trapping over-expands the lungs, pushing the diaphragm away from the chest wall, and leads to subcostal retractions, as the contracting diaphragm pulls inward on the compliant chest wall

11

Physical examination:
Inspection

  • (1)
  • Respiratory rate
  • The isolated presence of subcostal retractions (RTX) 
  • Cyanosis

  • Look at the breathing pattern
  • Measure the respiratory rate
    • Resting respiratory rate changes with age
    • Normal for a 2 week old is up to 50, for a 6 month old is up to 44, for a 1 year old is up to 32
  • The isolated presence of subcostal retractions (RTX)
    • Almost always is a sign of the hyperinflation or air trapping that accompanies small airways disease (exception: severe UAO)
    • Intercostal and suprasternal RTX indicates a breathing pattern in which excessive negative pleural pressure is used, such as a severe pneumonia, RDS, or an interstitial lung disease
  • Cyanosis is hard to detect
    • Don’t trust your eyes when it comes to oxygenation

12

Physical examination:
Palpation

  • Hand placement
  • Palpable vibrations
  • Unilateral vibrations
  • Indrawing

  • Rest your hands on the chest
  • Palpable vibrations usually indicate partial obstruction of large airways
  • Unilateral vibrations are typical of bronchomalacia, foreign body, or a mucus plug
  • Feel the lower end of the ribcage for indrawing, which indicates loss of the zone of apposition
    • This is the result of a diaphragm that is out of position pulling inward on the overly compliantchest wall of the infant
    • It suggests a diagnosis of small airways disease

13

Physical examination:
Percussion

  • Determine the location of...
  • Percussion note
  • You might find...

  • Determine the location of the domes of the diaphragms relative to tips of the scapulae
  • The tone of what you hear is called the percussion note: hyperresonant vs. dull
  • You might find an elevated hemidiaphragm with unilateral diaphragmatic paralysis or eventration
    • In the latter diagnosis, the diaphragm is replaced by a thin, non-contractile sheet of fibrous tissue

14

Physical examination:
Auscultation

  • Normal breath sounds vary with...
  • If you listen over the large airways, inspiratory and expiratory...
  • As you listen further out, the sounds become...
  • Over the periphery, the breath sounds...
  • The sounds are much louder on...
  • ALL breath sounds...
  • ​Most of what we hear with a stethoscope originates in...
  • As you go more peripherally, the flow becomes...
  • Infants have...

  • Normal breath sounds vary with...
    • Location and timing in the respiratory cycle
  • If you listen over the large airways, inspiratory and expiratory...
    • Times are similar
    • Sounds are tubular (bronchial)
  • As you listen further out, the sounds become...
    • Bronchovesicular (mid 1/3) and then vesicular
  • Over the periphery, the breath sounds...
    • Are called vesicular
    • Have a longer expiratory phase
  • The sounds are much louder on...
    • Inspiration (sound is moving towards you) than on expiration (sound is moving away from you)
  • ALL breath sounds...
    • Emanate from the airway
  • Most of what we hear with a stethoscope originates in...
    • The central airways, where there is the most turbulence of flow
  • As you go more peripherally, the flow becomes...
    • More laminar and is quieter
    • The air makes NO sound as it fills the alveolus, contrary to popular belief
  • Infants have...
    • Fewer generations of airways
    • Coarser breath sounds

15

Physical examination:
Auscultation

  • The 2 main abnormal breath sounds 
  • The way to differentiate between them 
  • Either can be...

  • The 2 main abnormal breath sounds
    • Crackle vs wheeze
  • The way to differentiate between them
    • Crackle
      • A discontinuous sound
      • More prominent on inspiration
    • Wheeze
      • A continuous sound
      • More prominent on expiration
  • Either can be...
    • Inspiratory or expiratory

16

Physical examination:
Auscultation

  • Monophonic 
  • Polyphonic

  • Monophonic
    • No matter where you listen, it sounds the same; a single sound
    • Typical of tracheo- and bronchomalacia, vascular ring, and bronchial foreign body
    • All of these are characterized by a single location of partial obstruction in the large airway
  • Polyphonic
    • Many different pitches
    • Characterize a diffuse airway lesion such as asthma or bronchiolitis
    • You hear vibrations coming from various-sized, partially obstructed airways

17

Physical examination:
Auscultation

  • Crackle
  • Wheezes

  • Crackle (or rale)
    • A popping sound produced by a fluid meniscus in an airway
    • Fine or coarse
      • Fine crackles emanate from smaller airways
      • Coarse crackles emanate from larger airways
    • Also found in interstitial lung disease (sound like Velcro)
  • Wheezes
    • Result from the vibration of walls of narrowed airways as air flows through them
    • Monophonic or polyphonic

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