Results
Four hundred seventy-one patients hospitalized with diagnoses of acute bronchiolitis were initially included in the study. However, 31 patients were subsequently excluded, 16 diagnosed with congenital heart disease, four with metabolic disease, three with histories of sibling deaths, and eight whose families declined to take part. Four hundred forty patients aged between one and 24 months were thus finally enrolled.
Two hundred seventy-seven (63%) of the 440 patients were boys, and 163 (37%) were girls. The mean age of the patients was 6.16±4.99 months. Patients were divided into two groups, severe bronchiolitis (85 patients) and mild-moderate bronchiolitis (355 patients). No difference was determined between the two groups in terms of age or sex, although weight-for-age z-scores were significantly lower in the severe bronchiolitis group compared to the mild-moderate bronchiolitis group (p<0.001). No significant differences were observed between the two groups in terms of birth week, cesarean delivery, receipt of mother’s milk only, atopic disease, GERD, or history of admission to the NICU. However, attack numbers were significantly higher in the severe bronchiolitis group than in the mild-moderate group (Table 1).
No statistically significant difference was determined between the two groups in terms of parental histories of asthma (p=0.240). No significant difference was also found between the groups in terms of maternal histories of smoking during pregnancy and paternal active smoking histories, although the proportion of mothers with active smoking histories was significantly higher in the severe bronchiolitis group (20%) than in the mild-moderate bronchiolitis group (11.3%) (p=0.050, p=0.617, and p=0.046, respectively). No significant difference was observed between the two groups in terms of maternal education levels, but paternal education levels were lower in the severe bronchiolitis group (p=0.414 and p=0.028, respectively). No significant difference was also observed between the two groups in terms of place and type of residence, and type of heating employed. A history of being the only child in the home was significantly lower in the severe group than in the mild-moderate group (p=0.010), while the number of individuals in the household was higher in the severe group than in the mild-moderate group (p=0.011) (Table 2).
Feeding was lower, subcostal retraction and cyanosis were more common, times between onset of symptoms and worsening of findings and presentation to hospital were shorter, oxygen saturation was lower, HFNC and intubation requirements were more frequent, and hospital stays were longer in the severe bronchiolitis group compared to the mild-moderate bronchiolitis group (Table 3).
Mean Hb values were 10.83±1.47 g/dL in the severe bronchiolitis group and 11.19±1.21 g/dL in the mild-moderate bronchiolitis group (p=0.021). Mean absolute neutrophil count was 5.34±4.45 /mm3 in the severe bronchiolitis group and 4.38±3.32 /mm3 in the mild-moderate group (p=0.004). CRP values were 1.74±2.78 mg/dL in the severe bronchiolitis group and 0.96±1.79 mg/dL in the mild-moderate group (p=0.002).
Each demographic, clinical, and laboratory variable of the patients included in the study was individually subjected to univariate logistic regression analysis in order to identify parameters potentially associated with the development of bronchiolitis. Accordingly, weight-for-age z-score, time between onset of symptoms and admission, time between onset of symptoms and worsening of findings, number of previous bronchiolitis attacks, history of maternal smoking during pregnancy, history of maternal active smoking, being an only child, number of individuals in the household, decreased feeding, hemoglobin levels, absolute neutrophil count, lymphocyte count, and CRP emerged as significant at the p <0.05 level. The above parameters emerging as significant at univariate logistic regression analysis were than subjected to multivariate logistic regression analysis (backward LR model). Parameters identified at multivariate logistic regression analysis such as a low weight-for-age z-score, a short time between onset of symptoms and admission, a higher number of previous attacks, and low hemoglobin emerged as independent predictors of severe bronchiolitis development. Low weight-for-age z-score was found to increase the risk of severe bronchiolitis development 0.56-fold (CI: 0.409 – 0.760), a short time between onset of symptoms and admission increased the risk 0.62-fold (CI: 0.519 – 0.735), previous history of frequent bronchiolitis attacks increased the risk 1.84-fold (CI: 1.135 – 2.968), and low hemoglobin levels increased the risk 0.72-fold (CI: 0.537 – 0.969) (Table 4).