Definition of "Bronchiolitis"
[Acute viral] bronchiolitis is inflammation of the bronchioles (smallest airways in the lungs). It develops over 1-2 days.
Patient information
Anything-itis means inflammation of that thing. Easy peasy! So bronchio-litis is inflammation of the bronchioles. But what are bronchioles?They're the lower portion of the airways, right down at the lungs. They're also the narrowest portions.
Wait... wasn't asthma... or airway-itis, also inflammation of the bronchioles?
Yep, but asthma was an allergic type thing. This is where an evil bug is invading 
!
- Starts w/ flu-like URTI Sx (rhinorrhea, cough, fever) for 2 days
- Then turns into LRTI:
- Expiratory wheeze (stethescope)
- Crackles (stethescope)
- SOB
- Cough
- Severe bronchiolitis:
- Poor feeding (<50% of usual fluid intake in preceding 24 hours)
- Hx of apnea
- Nasal flaring, grunting
- Intercostal recession
- Hyperexpansion of the chest
- Hypoxemia, eventually cyanosis
- RR >70/min → compensate for SOB
- Tachycardia → compensate for SOB
- Lethargy → fatigue from overcompensating
Patient information
What happens in inflammation of the narowest lower parts of the airways?So it starts like an infection of the upper airways, so a runny nose, cough, and fever. It then turns into an infection of the lower airways, so you get wheeze, crackles, difficulty breathing, and a cough.
What happens if it becomes really bad?
Yeah. It can. So because it usually happens in kids <2yo, you'll get things that is more evident because the patient is a kid rather than an adult. So poor feeding, especially drinking <50% of what is normal. Signs of difficulty breathing, like nostrils widening when breathing, grunting sounds, the rib's muscles pulling in. There's also stuff that happens because of difficulty breathing, so low oxygen in blood, causing blue skin, increased breathing rate, fast heart rate. And because of all this effort, bub will feel tired.
- Following inhalation/ingestion of a virus, there is infection of the upper airway epithelium, causing inflammation → nasal congestion, runny nose
- The virus eventually makes it's way down to infecting the bronchioles, thus causing inflammation (swelling, exudation, eventually mucus plugging), narrowing the airways → wheezing, crackles, SOB, cough
- There is air trapping, because air cannot escape → hyperexpansion
- Usually caused by RSV (respiratory syncytial virus) (70% of cases), thus much more common in winter months
- Can also be caused by other airway viruses (metapneumovirus MPV, parainfluenza, influenza, coronavirus, adenovirus, rhinovirus)
Patient information
You earlier said an evil bug. Which one specifically causes inflammation of the narrowest parts of the airways?Some virus
, usually the RSV virus.
Wait... how does inflammation of the the narrowest parts of the airways differ from the cold? Isn't that a viral infection of the airways?
The cold is a viral infection of the upper airways. Although bronchiolitis starts out like a cold, it branches down to the lower airways.
Isn't pneumonia lower airway-itis?
It is, but pneumonia is even further down - at the alveoli. This is just before that - at the bronchioles.
Where does croup fit into all this then?
Croup is also known as laryngotracheobronchitis. It means it involves the larynx, trachea and large bronchi. So that's just the portion of the airways before the bronchioles, but just below the upper airways.
- Infectious risks:
- Close contact to sick Pt's
- Winter and autumn → ?indoor play may result in closer contact between kids
- Poor immunity
- Age <2yo → airways narrower
- Prematurity (<34 weeks) → airways even narrower
- Lung disease
- 2nd hand smoke exposure → preexisting damage thus inflammation
- Low birth weight
- Congenital heart disease
- C-section
Protective factors:
- Breastfeeding
Patient information
What makes it more likely that you will have inflammation of the narrowest portions of the airways?Young age is the biggy, so we only see it in bubs <2yo, and that's because their airways are narrower, hence the narrowest airways are truly very narrow. Being born prematurely, which is <34 weeks, as their airways are even more narrow. If someone nearby has recently had an infection, poor immunity, or winter months, as it makes the RSV viral infection more likely. And there are also other things that might affect the lungs, like lung disease, 2nd hand smoke exposure, low birth weight, congenital heart defect.
Can anything reduce the likelihood of inflammation of the narrowest portions of the airways?
Yes. By breastfeeding.
- Age<2yo
- Sx
- CXR, to exclude pneumonia. CXR can also be used to assess the severity of bronchiolitis by:
- Peribronchial cuffing (aka bronchial wall thickening, or donut sign, where the edges are thicker and center contains air), indicating atelectasis (i.e. collapse/closure of lung)
- Air trapping/hyperinflation
- Nasal swab, to NAAT or PCR for RSV. It has little effect on Mx so not routinely done
Patient information
How can you find out if bub has inflammation of the narrowest portions of the airways?So bub should be under 2yo. They should have the symptoms. You can do an x-ray of the chest, to make sure that it's not infection further down at the lungs, rather than just above at the bronchioles. You can also do a nasal swab, to try to find RSV, but it's not routinely done because it doesn't really change what we do.
- Asthma → not Dx <2yo
- Pneumonia (alveoli) → usually no wheeze, CXR shows consolidation
- Foreign body aspiration → asymmetry, especially proclivity for entrance into (R) bronchus
- Chronic lung disease
- URTI → no wheeze
- Croup → barking cough
Patient information
What diseases can we easily confuse for inflammation of the narrowest portions of the airways?Asthma, which is differentiated by the fact that we don't diagnose it in bubs <2yo, so if theyr'e <2yo it's bronchiolitis. Pneumonia, which usually doesn't have a wheeze, and an x-ray of the chest will show water in the lungs. If bub has swallowed an object, which usually only causes problems on a single side, especially the right side. An upper breathing tract infection. And croup, which is infection of the larynx, trachea and bronchi, which has a unique barking cough, because it affects the voice production area of the breathing tract.
- Oxygen
- Fluids/nutrition by gastric tube/IV
- Prevention:
- Hygiene (handwashing)
- Avoid exposure to those w/ respiratory infection
- Breastfeeding (esp 1st month of life) → receive immunoprotection from mom's
- Avoid second hand smoke exposure
- Immunizations for premature infants who meat certain criteria (some cardiac and respiratory disorders), including Palivizumab (monoclonal antibody against RSV)
- Insufficient evidence for bronchodilators, adrenaline, hypertonic saline (inhaled salt solution, which draws water out of inflammed tissue), corticosteroids, antibiotics, and ribavirin (antiviral). Bronchodilators (salbutamol) can provide Sx relief
Patient information
What do we do about inflammation of the narrowest portions of the airways?We might need to give oxygen. If bub isn't eating, we need to sure bub is getting enough fluids and food. There's not much more we can do. The evidence for bronchodilators, adrenaline, saline, corticosteroids, and even antivirals is insufficient.
Don't they sometimes use bronchodilators, which is used for asthma?
Yes, they can provide relief from the symptoms. But, there's insufficient evidence that shows that it helps for an RSV viral infection.
Why aren't antibiotics used?
Because bronchiolitis is caused by a virus.
- After acute illness, airways can remain sensitive for several weeks causing recurrent cough/wheeze
- Respiratory failure
- 2-3mo infants can have secondary infection by bacteria (usually UTI)
- ?Asthma → correlation may not equate causation
Patient information
What bad things can result from inflammation of the narrowest portions of the airways?There can be inadequate gas exchange achieved by the breathing system. There can also be a secondary infection on top of the the viral infection, by bacteria, usually due to a urinary infection. And there's also asthma later on in life, although it's unclear why there's this link.
- Common, with up to 33% of kids affected by 1yo
- 90% w/ bronchiolitis are between 1-9mo, especially 3-6mo
- Usually affects kids <2yo
- Bronchiolitis is most common cause of hospitalization <1yo
- It is epidemic in winters
- Of 1.65 million hospitalizations, it results only in 500 deaths
Patient information
Why does bronchiolitis almost specifically target younguns, it seems a bit mean
?Bronchioles are more narrow in newborns, so they are more susceptible to their airways being blocked.
- Asthma
- Pneumonia (DDx)
- Bronchitis (do not confuse)
- LRTI (category)
- Croup (aka laryngotracheobronchitis, the bronchioles just anatomically below the bronchi)
- Bronchitis (the bronchioles just anatomically below the bronchi)
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