Bronchiolitis is a disorder most commonly caused in infants(mostly 3 -6 months of age) by viral lower respiratory tract infection (LRTI). It is the most common lower respiratory infection in this age group. It is characterized by acute inflammation, edema and necrosis of epithelial cells lining small airways, increased mucus production, and bronchospasm.
RSV is the most common pathogen (85%), but other organisms occasionally produce a similar clinical picture.
- Adenovirus (11%) occasionally causes a similar syndrome with a more virulent course.
- Epidemics of bronchiolitis due to parainfluenza virus usually begin earlier in the year and tend to occur every other year.
- Other less common etiologic agents include the following:
- Mycoplasma pneumoniae
- Influenza virus
- Chlamydia pneumoniae
- Necrosis of the respiratory epithelium is one of the earliest lesions in bronchiolitis and occurs within 24 hours of the acquisition of infection.
- Proliferation of goblet cells results in excessive mucus production, whereas epithelial regeneration with nonciliated cells impairs elimination of secretions.
- Lymphocytic infiltration may result in submucosal edema.
- The pathology results in obstruction of bronchioles from inflammation, edema, and debris, leading to hyperinflation, increased airway resistance, atelectasis, and ventilation-perfusion mismatching.
Infants are affected most often because of their small airways, high closing volumes, and insufficient collateral ventilation. Recovery begins with regeneration of bronchiolar epithelium after 3-4 days, but cilia do not appear for as long as 2 weeks. Macrophages remove mucus plugs.
Signs and symptoms are typically rhinitis, tachypnea, wheezing, cough, crackles, use of accessory muscles, and/or nasal flaring. Many viruses cause the same constellation of symptoms and signs.
Most patients with bronchiolitis have the following signs:
- Tachypnea, often at rates over 50-60 breaths per minute (most common physical sign)
- Fever, usually in the range of 38.5-39°C
- Mild conjunctivitis or pharyngitis
- Diffuse expiratory wheezing
- Nasal flaring
- Intercostal retractions
- Inspiratory crackles
- Otitis media
- Apnea, especially in infants younger than 6 weeks
- Palpable liver and spleen from hyperinflation of the lungs and consequent depression of the diaphragm
- Respiratory rate in otherwise healthy children changes considerably,
- mean of approximately 60 breaths per minute upto 2 months of age
- approximately 50 breaths per minute from 2 months to 12 months of age and
- 40 breaths per minute from 12 months to 5 years of age.
- Counting respiratory rate over the course of 1 minute may be more accurate than measurements extrapolated to 1 minute but observed for shorter periods.
- The absence of tachypnea correlates with the lack of LRTIs or pneumonia (viral or bacterial) in infants.
- hyperinflation is present in bronchiolitis(due to obstruction pathway) but absent in pneumonia.
Physical examination findings of importance include respiratory rate, increased work of breathing as evidenced by accessory muscle use or retractions, and auscultatory findings such as wheezes or crackles.
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Acute bronchiolitis is associated with
- a) a higher incidence in infants than in school children
- b) the production of copious amounts of purulent sputum
- c) widespread fine crackles
- d) a polymorphonuclear leucocytosis
- e) respiratory syncitial virus infection
- true :a,c,e
- purulent sputum indicates bacterial infection
- Lymphocytic infiltration is present
The following statements are true of bronchiolitis
- a) up to 50% of patients continue to wheeze after recovery
- b) the typical pathogen is para influenza virus
- c) corticosteroid therapy is beneficial
- d) tachypnoea is invariable
- e) air-trapping is normally present
- RSV is the most common pathogen
- air trapping due to airway obstruction leads to hyper-inflated lungs
The following are known to cause bronchiolitis in infants EXCEPT:
- Para influenza
- Streptococcus pneumoniae
- Human metapneumovirus
Which of the following is correct regarding bronchiolitis?
a) It is more common in the summer months.
b) Parainfluenza virus is the commonest cause.
c) The disease is most common in children aged 2-4 months.
d) Wheezing is a highly specific symptom for bronchiolitis.
ans:c) The disease is most common in children aged 2-4 months.
Bronchiolitis is more common in winter. Respiratory syncytial virus (RSV) is the most common cause. Although wheezing is often seen in bronchioloitis, it may also be seen in many other respiratory conditions.
A. Epidemics often occur during winter.
B. A chest radiograph usually shows a poorly inflated chest.
C. Poor feeding is an indication for treatment with ribavirin.
D. The disease is more benign in infants born prematurely.
E. Respiratory syncytial virus is the most common causative virus.
A 12 months old baby has fever. Recently, two other family members had an upper respiratory tract infection. On examination of the baby you find that his body temperature is 37.5 degree celsius and chest auscultation reveals bilateral wheezing. What is the MOST LIKELY cause?
ans: a(age group & family history of upper respiratory infection along with wheeze suggests it )
In acute viral bronchiolitis of infancy which one of the following is TRUE
A.Crepitations are rarely heard
B.Bronchodilators are not indicated because they aggravate hypoxaemia
C.Adenovirus causes a more severe illness than respiratory syncytial virus
D.High dose intravenous corticosteroids will modify the course of the disease
E.Intravenous fluid at twice maintenance volumes is indicated