Acute bronchiolitis

Introduction to acute bronchiolitis In the past 20 years, there has been a significant increase in the understanding of diseases such as bronchiolitis (with or without occlusion) involving small airways inflammatory lesions. Some people call it bronchiolarsyndrome, including many different diseases or Other pathological conditions associated with the disease, the name is messy. Rapid onset, rapid increase in breathing and cough and asthma within 1 to 3 days, accompanied by irritability, vomiting, loss of appetite and other performance. Upper respiratory catarrhal symptoms and cough are often a precursor to the onset of bronchiolitis. Some children may have vomiting and diarrhea, but generally not serious. basic knowledge The proportion of sickness: 0.2% Susceptible people: more common in children Mode of infection: non-infectious Complications: pneumonia, respiratory failure

Cause of acute bronchiolitis

Syncytial virus infection (35%):

Respiratory syncytial virus is the most common pathogen of bronchiolitis, followed by parainfluenza virus type 1 and type 3. In addition, adenovirus, rhinovirus, enterovirus, influenza virus and mycoplasma pneumoniae also account for a certain proportion, in different regions. There is a certain difference in the proportion of these pathogens. About 55% of children with bronchiolitis are caused by respiratory syncytial virus. In 1994, in the United States, 5 years old children with bronchiolitis accounted for 50% to 75% of the infection; domestic Reported from 57.9% to 88.2%, the hospitalized children were higher, the infection caused by parainfluenza virus accounted for about 11%, the disease is more dangerous, the mortality rate is high, rare pathogens have coronavirus, rubella virus, mumps virus, with Herpes zoster virus, influenza virus, rhinovirus and parvovirus.

After infection (most common in children) (20%):

(1) Acute bronchiolitis: acute bronchiolitis (acute bronchilitis) is a viral-based infectious (post-) bronchiolitis that occurs in infants and young children under 2 years of age, occasionally in older children and adults. Clinically characterized by respiratory distress, wheezing, expiratory obstruction and hypoxia, the disease has the names of acute catarrhal bronchitis, interstitial bronchitis, asthmatic bronchopneumonia and obstructive bronchitis, 1940 It was identified as an independent disease, which was named as diffuse panbronchiolitis (DPB) by pediatrics in the 1950s.

(2) occlusive bronchiolitis: herpes simplex virus, HIV, cytomegalovirus, rubella virus, parainfluenza virus (type III), adenovirus, Chlamydia pneumoniae, Klebsiella, Haemophilus influenzae, Legionella pneumophila , Serratia marcescens, Bordetella pertussis, Group B Streptococcus, Cryptococcus neoformans, Nocardia star, Pneumocystis carinii.

Inhalation injury (15%):

Toxic gases (such as nitrogen oxides), dust, irritating gases (such as chlorine), metal dust, organic dust (allergic pneumonia), cigarettes, cocaine, burning fumes.

Drug resistance (10%):

Penicillamine, hexamethylamine, L-tryptophan, busulfan (white blood Fuen), gold preparation, cephalosporin, amiodarone, acebutolol, paraquat poisoning.

Idiopathic (10%):

(1) No related diseases: cryptogenic constrictive bronchiolitis, respiratory bronchiolitis-related interstitial lung disease, cryptogenic organizing pneumonia (ie, idiopathic bronchiolitis with organizing pneumonia), Diffuse panbronchiolitis, primary diffuse hyperplasia of pulmonary neuroendocrine cells.

(2) related to other diseases: organ transplantation (bone marrow, cardiopulmonary) related; connective tissue disease related: rheumatoid arthritis, Sjogren's syndrome, systemic lupus erythematosus, polymyositis dermatomyositis; distal bronchial obstruction ( Obstructive pneumonia); ulcerative colitis; chronic eosinophilic pneumonia.

(3) Other occasional related diseases: radiation pneumonitis; aspiration pneumonia; idiopathic pulmonary fibrosis; malignant histiocytosis; acute respiratory distress syndrome; vasculitis, especially Wegener granulomatosis; chronic thyroiditis.

According to histopathology, it can be divided into two types, proliferative and constrictive bronchiolitis. The above various clinical syndromes can be summarized according to their pathology.

Pathogenesis

Immunohistological studies have shown that viral pneumonia is caused by direct damage to respiratory syncytial virus, while bronchiolitis is the result of type I allergic reactions. Serum IgG1 and IgG3 also play an important role in protecting children from lower respiratory tract infections. After the initial infection of respiratory syncytial virus, CD4 and CD8 lymphocyte subsets participate in and stop the viral replication process, with CD8 playing a major role. IL-4 can induce IgE production, which is closely related to the occurrence of bronchiolitis. In bronchiolitis, cell clones producing IL-2 and IFN- are inhibited, while IL-4-releasing cell clones are preferentially activated, resulting in increased IL-4 secretion, and IL-4 specifically induces B-cell synthesis of IgE. And promotes IgE production by inhibiting IFN- production, IL-4 and other lymphokines activate degranulation of neutrophils and macrophages, triggering allergic reactions, elevated specific IgG and IgE in serum and bronchial secretions, and Increased airway responsiveness.

The lesions are mainly involved in bronchioles, bronchi, alveoli, affected epithelial cells, cilia shedding, necrosis, followed by cell proliferation to form ciliated flat or columnar epithelial cells, wall edema, mucus secretion, and filled with epithelial cells Cells, white blood cells, macrophage debris and exudates formed by fibrin, causing partial obstruction of the bronchial lumen, significant emphysema at the distal end, and a large amount of cellular infiltration around the bronchioles, most of which are mononuclear Cells, submucosa and adventitial edema, in addition to bronchial lesions, there is edema in the alveolar wall around it, there is also inflammatory exudate in the alveolar cavity, lesions are more common in the lower lobe and lung bottom.

Although small bronchioles and bronchioles show general inflammation, the pathophysiological changes caused by them are very significant. Inflammation and edema tend to cause poor drainage of bronchial lumen in infants and young children. Necrotic substances and fibrin-forming emboli can make The bronchioles are partially or completely obstructed, and the distal part of the partially obstructed lumen is over-inflated. Complete obstruction leads to atelectasis. These lesions cause increased airflow resistance, decreased tidal volume, reduced ventilation, and uneven gas distribution in the lungs. Abnormal ventilation/perfusion rate, eventually causing hypoxemia, and finally due to carbon dioxide retention, hypercapnia, airway obstruction, airway resistance increased significantly (2.7 times more than normal), lung compliance decreased (normal 1/3), the tidal volume is reduced, the respiratory rate is increased, which causes a series of clinical symptoms. The lesions may involve the alveolar wall, leading to interstitial inflammation, occasionally involving the alveolar cavity and exudation.

Acute bronchiolitis prevention

1. Reasonable feeding, usually enhance physical fitness, so that the body adapts to the environment.

2. Actively treat rickets, malnutrition and various infectious diseases.

3. Infants should avoid contact with respiratory patients.

Acute bronchiolitis complications Complications pneumonia respiratory failure

Bronchiolitis and pneumonia can also exist at the same time. Individuals can still see pleural reaction, and severe patients can have respiratory failure.

Acute bronchiolitis symptoms Common symptoms High fever upper respiratory tract catarrh symptoms tachycardia wheezing sounds appetite loss of dyspnea dyspnea convulsions diarrhea

Rapid onset, rapid increase in breathing and cough and asthma in 1 to 3 days, accompanied by irritation, vomiting, loss of appetite, etc., upper respiratory tract symptoms and cough are often a precursor to the onset of bronchiolitis, often 1 in the aura ~7 days of mild fever, after the lower respiratory tract is involved, there is severe cough and high fever, cough is a prominent symptom of bronchiolitis, first for paroxysmal dry cough, followed by cough, mostly white sticky sputum, at the same time There are different kinds of wheezing. Compared with ordinary pneumonia, the symptoms of wheezing are more serious and appear earlier. The breathing is shallow and fast, accompanied by expiratory wheezing, and the respiratory rate is 60-80 times per minute or more. Fast, due to excessive ventilation and insufficient fluid intake, some patients have dehydration and acidosis. When there is severe hypoxia, there may be signs of encephalopathy such as confusion, convulsions and coma. When severe hypoxemia occurs, cyanosis may occur. Some children may have Vomiting, diarrhea, but generally not serious, lung examinations have been unvoiced, auscultation of breath sounds reduced, full of wheezing or whistle sounds, can be heard when the asthma is relieved, the majority of patients have obvious " Three concave sign The nose flaps, irritability and cyanosis, heart failure is very rare, as the disease progresses, sometimes although the body temperature has dropped to normal, tachycardia has become a prominent symptom, auscultation varies greatly, wheezing with or without popping, breathing Difficulties worsened, and the corresponding positive signs of pulmonary auscultation were found to be reduced, suggesting that obstruction aggravation and respiratory failure are imminent.

Examination of acute bronchiolitis

Severe cases with hypercapnia.

The imaging performance of the chest is not typical. It can be found that the lung transillumination is increased, the intercostal space is widened, the diaphragm is flat, the hilar shadows on both sides are increased, the lung texture is increased, the thickness is increased, and the density around the bronchi is uneven. Irregular linear shadows, generally no infiltration of lung parenchyma, if the alveolar involvement is obvious, there are small spots or scattered in the form of slab shadows, small areas of atelectasis can be seen in many areas, difficult to identify with common pneumonia infiltration, respiratory tract When the syncytial virus is infected, the bronchial blood vessels are prominent.

Diagnosis and diagnosis of acute bronchiolitis

diagnosis:

Diagnosis based on clinical manifestations, age and epidemiological data. The isolation of the virus in respiratory secretions, especially nasal washes, has a definite value. Most of the bronchiolitis caused by the virus can be isolated by tissue culture within 3 to 7 days. Viral antigens, especially respiratory syncytial virus, can also be detected from respiratory secretions within a few hours using rapid pathogen diagnostic techniques. Serological examination is of little help to the diagnosis. It takes at least 2 to 4 weeks to detect the serum in the recovery period, which is not helpful for clinical treatment; and the antibodies obtained from the mother in infants and young children have an impact on the diagnosis.

Differential diagnosis

Many diseases can cause dyspnea and wheezing similar to bronchiolitis, and are difficult to identify, especially when the baby is first ill. Common diseases to be identified are acute laryngotracheitis (crops), bronchial asthma, asthmatic bronchitis and pneumonia.

Acute laryngotracheal bronchitis mainly presents inspiratory difficulties and characteristic snoring sounds.

Bronchial asthma, although rare in infants and young children, may be similar to bronchiolitis in the first episode. The child may have a history of family allergies, asthma can be quickly relieved after treatment with adrenergic receptor agonists or aminophylline, and the efficacy of bronchiolitis is not obvious, thereby being identified. Of course, bronchial asthma and bronchiolitis can also exist at the same time.

Asthmatic bronchitis and mild bronchiolitis are sometimes difficult to distinguish. The main point of identification is that there is no obvious emphysema in the former, cough and asthma are not serious, and there is no symptoms of poisoning, and it can be repeated.

The main difference in pneumonia is adenoviral pneumonia. The disease also has obvious symptoms of poisoning, but the course of disease is long, the wheezing appears late, the signs of pneumonia are more obvious, and large fusion lesions are visible on the chest X-ray.

In addition, patients with wheezing need to be identified with gastric reflux, airway foreign body obstruction, and posterior pharyngeal abscess. The occurrence of part-specific infantile wheezing is often caused by respiratory syncytial virus infection. In general, patients with bronchiolitis during the epidemic of non-respiratory syncytial virus occur in children with idiopathic quality. Conversely, children with bronchiolitis during the epidemic of respiratory syncytial virus are mostly not specific.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.