Acute bronchiolitis is an inflammatory obstruction of the bronchi of small caliber (bronchioles), usually developing in young children against the background of a viral infection. The initial signs resemble acute respiratory viral infections, which are soon joined by the phenomena of bronchial obstruction (expiratory dyspnea, spastic cough, tachypnea, crepitating or wheezing wheezes, cyanosis of the nasolabial triangle, etc.). Diagnosis of acute bronchiolitis is based on data from X-ray examination of the chest organs and blood gas composition. The basis of therapy for acute bronchiolitis is adequate oxygenation, oral or parenteral hydration, and the use of interferon.
ICD 10
J21 Acute bronchiolitis
Meaning
Acute bronchiolitis is a diffuse inflammatory lesion of the terminal parts of the respiratory tract, occurring with the phenomena of bronchial obstruction and respiratory failure. In most cases, the disease develops in children of the first two to three years of life against the background of acute respiratory viral infection; the maximum peak of morbidity occurs at the age of 5-7 months.
Every year, acute bronchiolitis is carried by 3-4% of young children, 0.5-2% of them in severe form; a fatal outcome is registered in 1% of patients. Severe course of acute bronchiolitis is observed in children with a burdened background: premature infants suffering from congenital lung abnormalities and heart defects. The wide prevalence of pathology and the high frequency of hospitalizations make the problem of acute bronchiolitis extremely relevant for practical pediatrics and pulmonology.
Causes of acute bronchiolitis
Up to 70-80% of all cases of acute bronchiolitis in children of the first year of life are etiologically associated with respiratory syncytial virus (RSV). Since RS infection occurs with annual seasonal epidemic outbreaks (in winter and early spring), more than half of young children carry RS infection, and the instability of post-infectious immunity causes frequent reinfection.
Other viral agents (adenoviruses, rhinoviruses, influenza and parainfluenza viruses, enteroviruses, coronaviruses, etc.) account for about 15% of cases of acute bronchiolitis. In recent years, there has been an increase in the role of human metapneumovirus in the development of bronchoobstructive syndrome in children. The reduction of morbidity among infants is facilitated by early application to the breast and the receipt of colostrum with a high IgA content by the child.
In children of the second year of life, the significance of viruses that cause acute bronchiolitis changes: the RS virus gives way to enteroviruses and rhinoviruses. In preschool and school-age children, mycoplasmas and rhinoviruses predominate among the pathogens of bronchiolitis, and RS viruses usually cause viral pneumonia and bronchitis. In addition to traditional etiological agents, the cause of acute bronchiolitis can also be cytomegalovirus, chlamydia, measles viruses, chickenpox, mumps, herpes simplex. Among children of the older age group and adults, people with immunodeficiency who have undergone organ and stem cell transplantation, elderly patients become ill with acute bronchiolitis.
During the first day after the penetration of respiratory viruses, necrosis of the epithelium of bronchioles and alveocytes develops, mucus formation increases, active release of inflammatory mediators occurs, lymphocytic infiltration and swelling of the submucosal layer occurs. Airway obstruction in acute bronchiolitis is caused not by bronchospasm (as, for example, in obstructive bronchitis), but by edema of the walls of bronchioles, accumulation of mucus and cellular detritus in their lumen. Together with the small diameter of the bronchi in children, these changes lead to an increase in resistance to air movement, especially on exhalation, according to the type of valve mechanism.
Emphysema develops due to increased air filling of the affected areas and compensatory hyperventilation of intact areas of lung tissue. With complete obstruction of the bronchioles and the inability of air to enter the alveoli, atelectasis may develop. A sharp violation of the respiratory and ventilation function of the lungs leads to the development of hypoxemia, and in severe respiratory failure – hypercapnia. With a favorable course of acute bronchiolitis, a gradual regression of pathological changes begins after 3-4 days, but bronchial obstruction persists for 2-3 weeks.
Symptoms of acute bronchiolitis
The onset of the disease resembles ARVI: the child becomes restless, refuses to eat; body temperature rises to subfebrile values, rhinitis develops. After 2-5 days, signs of damage to the lower respiratory tract are added – an obsessive cough, wheezing, shortness of breath of an expiratory nature. At the same time, hyperthermia increases to 39 ° C and above, moderate pharyngitis and conjunctivitis occur.
Pathognomonic signs of acute bronchiolitis are tachypnea (BH up to 60-80 per minute), tachycardia (heart rate 160-180 beats. in min.), participation in the breathing of auxiliary muscles, inflating of the wings of the nose, retraction of intercostal spaces and hypochondria, perioral cyanosis or cyanosis of all skin. Premature babies or children with birth trauma may have episodes of sleep apnea. Due to the increased airiness of the lungs and the flattening of the diaphragm dome, the liver and spleen protrude 2-4 cm from under the costal arches. Intoxication, refusal of food and vomiting lead to dehydration and disruption of water-electrolyte homeostasis.
Of extrapulmonary complications, otitis media, myocarditis, and extrasystole may occur. The severity of the patient’s condition with bronchiolitis is due to the degree of acute respiratory failure. Weakened patients may develop respiratory distress syndrome, and a fatal outcome may occur.
Diagnostics
When making a diagnosis of acute bronchiolitis, a pediatrician or a pulmonologist takes into account the connection of bronchial obstruction with a viral infection, characteristic clinical and physical data. A typical auscultative picture of a “wet lung” includes multiple wheezes (small bubbly, crepitating), elongated exhalation, distant whistling wheezes. Due to increased lung swelling, a percussive sound with a boxy tinge is determined.
To assess the parameters of oxygenation, pulse oximetry, a study of the gas composition of the blood is carried out. The radiological picture in the lungs is characterized by signs of hyperpneumatization and peribronchial infiltration, increased pulmonary pattern, the presence of atelectasis, flattening of the diaphragm dome. Of the laboratory tests, the most valuable is the express analysis for determining RSV in a nasopharyngeal smear by ELISA, RIF or PCR. Bronchoscopy data (diffuse catarrhal bronchitis, a significant amount of mucus) in acute bronchiolitis are not indicative. Spirography cannot be performed in young children.
Acute bronchiolitis has to be differentiated with obstructive bronchitis, bronchial asthma, CHF, pneumonia (aspiration, viral, bacterial, mycoplasma), whooping cough, foreign bodies of the respiratory tract, cystic fibrosis of the lungs, gastroesophageal reflux.
Treatment of acute bronchiolitis
To date, etiotropic treatment of acute bronchiolitis has not been developed. Inhaled use of ribavirin is considered inappropriate due to insufficient efficacy and frequent hypersensitivity reactions. The appointment of bronchodilators, physiotherapy, and inhaled steroids is also not recommended. The basis of the basic therapy of acute bronchiolitis is sufficient oxygenation and hydration of the patient. Young children are subject to hospitalization and isolation.
The supply of moistened oxygen is carried out using a mask or an oxygen tent. With repeated apnea, preservation of hypercapnia, general severe condition, a transfer to a ventilator is indicated. The replacement of fluid losses is provided by frequent fractional drinking or infusion therapy (under the control of diuresis, electrolyte composition and blood CBS). To remove mucus from their respiratory tract, it is aspirated with an electric pump, vibratory chest massage, postural drainage, salt inhalation with a hypertonic solution or inhalation of adrenaline through a nebulizer.
Interferon preparations are used to eliminate viral infection. Glucocorticoids can be used in a short course to relieve bronchial obstruction. The clinical efficacy of including the drug fenspiride, which has a pronounced anti-inflammatory effect, in the treatment regimen for acute bronchiolitis, has been proven. Antibacterial agents should be prescribed only if bacterial complications are suspected.
Prognosis and prevention
In mild cases, acute bronchiolitis can be resolved independently, without special pathogenetic therapy. After 3-5 days, improvement occurs, although bronchial obstruction and cough may persist for up to 2-3 weeks or longer. In the next five years after acute bronchiolitis, children retain bronchial hyperreactivity and a high risk of developing bronchial asthma. Deaths are recorded mainly in persons with a burdened concomitant background.
A specific immunoglobulin palivizumab with anti-RSV activity has been developed as a means of passive immunoprophylaxis. The drug is intended for use during periods of the rise of RS infection in categories of children and adults threatened by the development of severe forms of acute bronchiolitis.
Literature
- Respiratory syncytial virus. Seidenberg J. Internist (Berl). 2019 Nov;60(11):1146-1150. link
- Respiratory syncytial virus bronchiolitis: clinical aspects and epidemiology. Boeck KD. Monaldi Arch Chest Dis. 1996 Jun;51(3):210-3. link
- Bronchiolitis: from empiricism to scientific evidence. Carraro S, Zanconato S, Baraldi E. Minerva Pediatr. 2009 Apr;61(2):217-25. link
- Respiratory syncytial virus bronchiolitis. Leung AK, Kellner JD, Davies HD. J Natl Med Assoc. 2005 Dec;97(12):1708-13. link
- Respiratory syncytial virus infection in infants and young children. Levy BT, Graber MA. J Fam Pract. 1997 Dec;45(6):473-81. link
