Analysis of Factors Associated with SMPP Progression to OB
Of 47 (46.8%) pediatric SMPP patients with mucous emboli, 22 patients developed OB and no OB was found in children without mucous emboli; thus, OB incidence in children with mucous emboli was significantly higher than in children without mucous emboli (P < 0.001). All 8 cases (100%) with plastic bronchitis determined via bronchoscopy exhibited different degrees of OB. During the convalescent stage, OB occurred in 4 of 183 cases (2.2%) reporting two or fewer prior bronchoscopies and 18 of 30 cases (60%) with at least 3 prior bronchoscopies. The incidence of OB in children with two or fewer bronchoscopies was significantly lower than OB incidence in children with at least three prior bronchoscopies (P < 0.001). Importantly, of 142 children (6.3%) who had the first bronchoscopy within 10 days of disease onset, 9 developed OB (6.3%); of 71 children who had their first bronchoscopy on or after 10 days of disease onset, 13 (76.5%) developed OB. Therefore, OB incidence of children undergoing bronchoscopy within 10 days of disease onset was significantly lower than that of children undergoing bronchoscopy at or after 10 days post-disease onset (P < 0.007). Moreover, the average chest CT number for children with acute stage obstructive bronchitis was 26 u, while the average CT number for children without OB was 19 u. Thus, chest CT values of children with OB were significantly higher than those of children without OB, with the difference between groups reaching statistical significance (P < 0.05). Notably, OB was found in all 6 cases afflicted with necrotizing pneumonia (100%), as detected via pulmonary imaging (Table 2, Figure 3).