Adenovirus infection accounted for 4% − 10% (3) of the pathogens causing pneumonia in children. About 20% − 50% of the patients still had respiratory complications after adenovirus pneumonia treatment(1), such as bronchiolitis obliterans(4), bronchiectasis, hyperlucenct lung, pleurisy, atelectasis, chronic pneumonia, unilateral(4) clear lung syndrome, etc. The most common werebronchiolitis obliterans (BO) and recurrent asthma Interest. According to the data of 92 cases of adenovirus pneumonia, Li l et al. found that 52.6% of severe children had BO(5), a kind of chronic irreversible obstructive pulmonary disease caused by chronic inflammation and injury of the airway and the repair of airway fibrosis, thus leading to small airway obstruction and / or occlusion. The histological classification of BO can be divided into proliferation type and constriction type(6). Mauad T and other studies have found that 97% of bronchiolitis obliterans in children are constrictive type(7). There are three forms of BO: post infection BO, lung transplantation BO, and bone marrow transplantation (BMT) or hematopoietic stem cell transplantation (HSCT), among which post infectious BO (PiBO) was the most common one so far, as well as being common in children with adenovirus infection.
After adenovirus infection, epithelial cells were damaged and necrotic, replaced by T cells and neutrophils, followed by matrix degradation, collagen deposition and fibroblast stimulation, resulting in fibrosis of airway BO (8).Studies have shown that glucocorticoids can inhibit inflammatory response and slow down the process of fibrosis(9) , being part and parcel in the treatment of BO. There is no clear conclusion about the duration of inflammation in patients with BO. Studies have shown that long-term oral glucocorticoid treatment can improve the hypoxemia of patients with bronchiolitis obliterans, significantly reducing the number of wheezing and hospitalization (8). Pulmonary fibrosis (10)of BO may be caused by granulation tissue with loose connective tissue or scar formed by dense connective tissue. Glucocorticoid can reduce the former reversibly. When granulation tissue extends to the alveoli, the lesion is called tissue pneumonia (BOOP), whose study has shown that glucocorticoids can completely eliminate alveolar granulation(11). Our study found that glucocorticoids were used earlier in the non BO group than in the BO group. The timing of glucocorticoid use was based on the duration of the disease to the use of corticosteroids. It is speculated that the use of glucocorticoids in the early stage of adenovirus pneumonia may reduce the incidence of BO by reducing granulation tissue formation. This conclusion is consistent with the literature that glucocorticoid should be used during the development of the disease and agreed as soon as possible before the formation of airway fibrosis Give agreement as soon as possible(6). On the other hand, our research on the use of gamma globulin in BO shows that gamma globulin has no obvious effect on reducing the formation of BO caused by adenovirus infection. Relevant studies have found that gamma globulin can effectively shorten the treatment time of severe adenovirus pneumonia, and will not increase the incidence of adverse reactions. However, there is no clear effect on reducing the formation of BO.
Bronchiolitis obliteration is the result of the centripetal narrowing of the wall fibrosis and the collapse of the small airway after inflammation. Cytokines are major factors in the establishment and maintenance of fibrosis, and IL-6, as one of the cytokines, is associated with the severity of adenovirus infection(12). Another study showed that fibrosis depends on IL-6(13), which increases rapidly under stress, and IL-6 is almost always increased in chronic inflammation(14). In this study, IL-6 in BO group was significantly higher than that in non BO group. It was speculated that inflammatory response in BO group wsbstronger than that in non BO group. However, whether the determination of IL-6 value can help us identify BO earlier remains to be discussed.
There are many hypothesised risk factors for the formation of thin post infection, including but not limited to viral load, environmental and genetic factors, length of hospital stay, etc. Many studies have shown that mechanical ventilation is a risk factor for the formation of BO(15, 16), 67.7% (155 / 229) of children with severe adenovirus pneumonia received different levels of oxygen support. The rate of mechanical ventilation and hypoxemia were significantly higher in the wave group than in the non-wave group (39.1% and 7.1%, respectively,P = 0.000), suggesting that the risk factors for mechanical ventilation and hypoxemia were adenovirus infection due to bronchiolitis obturator, which is consistent with Wu Pei qiong et al(17). On the one hand, hypoxemia significantly affects the expression of cytokines, chemokines and chemokine receptors, which significantly increases the incidence and severity of BOS. Colom AJ et al. Regarded the presence of hypoxemia in patients with post infectious BO as an important indicator of BO score, so as to highly accurately predict the diagnosis of postinfectious BO(15). Based on the above study, we believe that hypoxemia as a BO score index is reasonable and worthy of promotion.
It was found that LDH in BO group was significantly higher than that of non-BO group. The best cut-off value for diagnosing BO was 914iu / L, with a sensitivity of 46.5% and a specificity of 84.9%. Literature shows that LDH exists in all important organs as a cytoplasmic enzyme, LDH is associated with many lung diseases, such as obstructive disease, microbial lung disease and interstitial lung disease. Chen x (18)showed that LDH was as high as 1458.5 (634.8-3244.8) in 8 children with severe adenovirus pneumonia who needed modified outer membrane oxygenation support, which was significantly higher than that in children with ordinary adenovirus pneumonia (408.0 (282.0-639.0). Therefore, it can be inferred that patients with significantly elevated LDH (especially those ≥ 914 IU/ L) should be on alert for bronchiolitis obliterans. There was no significant difference in fever peak, gender, age, hemoglobin, C-reactive protein, PCT, ALT levels, D-dimer and FIB between the two groups, Hadith little effect on distinguishing whether bronchiolitis obliterans occurred after severe adenovirus infection.
This study showed that more than half of the children in the two groups were complicated with Mycoplasma pneumoniae infection. Patients with more than two pathogens and two kinds of bacterial infection in BO group were more than those in non BO group (P < 0.05). It is consistent with the literature that bacterial and viral infections increase the risk of BO(6). The prevalence of adenovirus co infection may be related to the increased susceptibility to bacterial infection after viral infection.Research (19)has showed that viral infection can increase bacterial binding and decrease barrier function in innate and adaptive immune level, and cause secondary bacterial infection. The interaction between bacteria and virus can affect the severity of disease.
The imaging diagnosis of bronchiolitis obliterans includes direct signs such as wall thickening and occlusion of bronchioles, and indirect signs such as bronchiectasis, mosaic perfusion, and lung volume reduction(20), In this study, we found that both groups had patchy or consolidation imaging, most of which were patchy shadows. Typical mosaic perfusion signs were seen, with unilateral or bilateral lung involvement being seen as well. The proportion of double lung involvement in BO group was 82.6%, and 63.9% in non BO group (P < 0.05).
the follow-up time limited the assessment of long term prognosis.