DISCUSSION

Despite the low mortality, bronchiolitis has high morbidity. Death by respiratory failure in bronchiolitis is rare, affecting 5.3 per 100,000 infants under 12 months old in the USA, where resources for intensive care and research advance and reduce this rate.10Also, the mortality rate was low even in children with comorbidities (e.g., low weight, young age, and premature birth) and those under IMV for a long period (i.e., more than seven days).11-13This rate was associated with low breathing patterns in children with bronchiolitis. However, children with bronchiolitis under IMV and who progressed to SARS presented increased complications and mortality rates since it is a viral infection that impairs the respiratory system.11,13
Two children with low birth weight died in this study; one had congenital heart disease, and the other had SARS. Although both children were under IMV, they died due to severe bronchiolitis, which caused hemodynamic instability.14,15 Similarly, severe bronchiolitis was previously associated with young and low-weight children who developed ARF followed by SARS since bronchiolitis may increase the respiratory pattern by sixfold. 1,13
Younger (i.e., less than six months old) and premature infants presented severe bronchiolitis with adverse respiratory impairment, needing ventilatory support. Mechanical factors (e.g., small airway caliber) may increase airway resistance, which is further increased by the inflammation and swelling of the airways due to the disease. Also, immunological factors, such as the weak immune system in younger and premature infants, may hamper innate immune responses, and these infants become susceptible to viral infections and require ventilatory support.16,17
The NIV is one of the initial supportive measures for acute bronchiolitis, which may progress to IMV in severe cases, especially in children with comorbidity and low weight. These cases require continuous positive airway pressure and BiPAP, which may not reverse the respiratory distress.12 Corroborating this data, one child in the present study was intubated even after using NIV. However, a previous study showed that children under early NIV improved their respiratory condition, requiring only nasal cannula oxygen therapy with a low flow. 18 Thus, ventilatory support using NIV may avoid IMV and its complications in most cases.19
The treatment of bronchiolitis depends on its severity since this disease may impair lung function on the fifth day. Thus, oxygen therapy is designated and changed to NIV in case of increased severity, progressing to intubation with IMV in case of NIV failure. In this sense, the three measures are related, and the inverse process may also occur (i.e., an extubated patient may need NIV followed by oxygen therapy in case of improved condition). These measures are commonly combined with salbutamol, hypertonic solution, and bronchodilators, especially in children with respiratory distress and requiring nasogastric tube feeding.4,5
In this study, the risk of severe bronchiolitis caused by RSV was higher in male than female children, possibly due to differences in lung structure, airway development, and genetic factors.20The present study corroborated previous studies considering male gender, congenital heart disease, and young age (from one to six months) as risk factors for bronchiolitis; these conditions require bronchial washing and aspiration due to excess mucus.21-23 The comorbidities with the highest risk for bronchiolitis were congenital heart disease and bronchopulmonary dysplasia.20
Children younger than 24 months old, with less than 37 gestational weeks, and low weight birth also presented an increased risk for prolonged hospitalization in PICU.17,24 Although the hospitalization period was not associated with aspiration, children under IMV and NIV were hospitalized for longer than those without IMV and NIV. Even with technological advances in ventilatory support, which reduced hospitalization costs and period and support-related lung injury, the most severe cases required IMV, NIV, and prolonged hospitalization to obtain clinical improvement and stability.12,24,25,26
In the present study, the hospitalization period ranged from 5 to 15 days in cases requiring IMV or NIV, with a mean of 12 days in PICU and 15.71 days of the total hospitalization period. Also, 94.52% of children were discharged to the ward, and two were discharged for home care. In this sense, the hospitalization period was directly associated with the virus incubation (about four to five days) and factors increasing the condition severity. Long hospitalization was previously associated with high costs, emotional burdens, and health-related issues.21 Parents accompanying the children during hospitalization missed workdays, affecting their income. In addition, anxiety was associated with the children condition, which may cause long-term consequences for the family.21