In the reporting period 1 April 2006 to 31 March 2013, there were 2,195 PICU admissions for asthma in children less than 15 years resident in England. There were 78,615 children, including 15 years and above, admitted during the study period, of which 2,110 children were for asthma (2.7%).
Epidemiology
PICU admissions with a primary diagnosis of asthma are described in Table 1. The highest proportion of admissions was in those aged 0–4 years (51.1%, 1129/2195) with a male predominance (58.6%, 1286/2195).
Table 1
Admissions with asthma as the primary reason for admission in PICU in England with percentages by age-groups and males therein and age-standardised rate per million (number (n), percentages (%) and 95% confidence interval (95% CI))
| Asthma admissions | 0–4 years | 5–9 years | 10–14 years | Age-standardised rate per million |
| n | % | male % | % | male % | % | male % | (95% CI) |
2006-07 | 266 | 45.5 | 66.9 | 28.6 | 56.5 | 25.9 | 51.3 | 28.9 (28.4–29.5) |
2007-08 | 296 | 49.3 | 59.6 | 26.4 | 55.6 | 24.3 | 47.4 | 31.9 (31.3–32.4) |
2008-09 | 328 | 55.2 | 65.2 | 19.8 | 56.1 | 25.0 | 47.7 | 34.8 (34.2–35.4) |
2009-10 | 326 | 54.9 | 63.7 | 17.2 | 56.0 | 27.9 | 48.2 | 34.3 (33.7–34.9) |
2010-11 | 327 | 54.4 | 60.7 | 20.5 | 63.4 | 25.1 | 56.7 | 34.0 (33.4–34.6) |
2011-12 | 283 | 45.9 | 60.0 | 24.4 | 58.3 | 29.7 | 59.4 | 29.6 (29.0-30.1) |
2012-13 | 369 | 52.6 | 55.2 | 23.0 | 57.8 | 24.4 | 60.0 | 37.6 (37.0-38.2) |
Overall | 2,195 | 51.1 | 61.6 | 22.8 | 57.7 | 26.0 | 53.0 | |
The estimated number of PICU admissions per million children in England, from age-standardised rates were 28.9 (95% CI: 28.4–29.5) in 2006-07 and 37.6 (95% CI: 37.0-38.2) in 2012-13.
Severity:-
The PIM2 score was assessed as a marker of disease severity. PIM2 was less than 1% in 72.5% admissions and over 30% in 0.4% admissions. Median PIM2 were similar in both girls and boys over the study period (median 0.4% (IQR 0.2-1.0%) vs 0.4% (IQR 0.2–1.1%) (H = 1.67, p = 0.196). Overall trend in PIM2 significantly decreased (4.4% (95%CI: 2.3–6.5%; p = 0.000052) when age, sex and EIMD were controlled (Supplementary Table S1, S2).
Compared to 0-4-year-olds, PIM2, when controlled for year and EIMD in the model, was 1.13 times (95% CI: 1.01–1.26, p = 0.031) significantly higher in 5-9-year-olds and 1.95 times (95% CI: 1.74–2.19, p < 0.00001) significantly higher in 10–14 year, indicating greater severity with increasing age (Supplementary Table S2, S3).
Healthcare resource utilisation
Mechanical ventilation data was missing for two admissions (N = 2,193) and LoS was missing in three admissions (N = 2,192). These admissions are reported in overall numbers but excluded from mechanical ventilation and LoS analyses.
Table 2 shows the distribution of ventilation in asthma admissions in PICU in England.
Table 2
Number and percentages of paediatric admissions in England in the financial years in PICANet by ventilation provided
| No ventilation | Only non-invasive ventilation | Only invasive ventilation | Received both invasive and non-invasive ventilation | Denominator |
| n | % | n | % | n | % | n | % | |
2006-07 | 149 | 56.2 | 8 | 3.0 | 101 | 38.1 | 7 | 2.6 | 265 |
2007-08 | 174 | 59.0 | 12 | 4.1 | 101 | 34.2 | 8 | 2.7 | 295 |
2008-09 | 196 | 59.8 | 12 | 3.7 | 114 | 34.8 | 6 | 1.8 | 328 |
2009-10 | 208 | 63.8 | * | * | 103 | 31.6 | * | * | 326 |
2010-11 | 201 | 61.5 | * | * | 114 | 34.9 | * | * | 327 |
2011-12 | 157 | 55.5 | 8 | 2.8 | 112 | 39.6 | 6 | 2.1 | 283 |
2012-13 | 207 | 56.1 | 14 | 3.8 | 141 | 38.2 | 7 | 1.9 | 369 |
Overall | 1,292 | 58.9 | 73 | 3.3 | 786 | 35.8 | 42 | 1.9 | 2,193 |
*one of those counts were less than 5, hence four are starred to prevent disclosure |
Over one-third of all admissions to PICU with asthma were mechanically ventilated (37.8%, 828/2,193). 35.8% (95%CI: 35.5–36.2; 786/2,193) admissions received only invasive ventilation, while 1.9% (95%CI: 1.9-2.0; 42/2,193) received both invasive and non-invasive ventilatory support. Tracheostomy was performed in 0.7% admissions. Any form of ventilation support was more commonly provided to 0-4-year-olds (49.4 (95%CI: 46.0-52.8), 409/828), in males (62.3 (95%CI: 59.0-65.6), 516/828) (Supplementary Table S3) and no difference was found over time (years).
Length of stay in PICU: Median LoS was 1.4 days (IQR 0.8–2.6) and remained much the same over the study period, when controlled for age, sex, EIMD (p = 0.31) (Supplementary Tables S1, S4). LoS was similar across sex and age groups: males median 1.4 (IQR 0.8–2.6), females 1.5 (0.9–2.6), 0–4 years 1.4 (0.8–2.6), 5–9 years 1.4 (0.8–2.8), 10–14 years 1.3 (0.8–2.5) days (Supplementary Table S3).
Socioeconomic status
The number of asthma PICU admissions increased with increase in deprivation (Table 3), which was irrespective of age (F = 37.2, p < 0.001).
Table 3
Severity and outcomes of PICU admissions with asthma as primary diagnosis or as underlying condition for death, by socio-economic status in England during 2006-07 to 2012-13
| Number of admissions (%) | PIM2 % (median, IQR) | Any form of ventilation support (%, 95% CI) | Length of stay (median, IQR) | Deaths n (%) |
EIMD1 least deprived | 249 (11.3) | 0.5 (0.2–1.2) | 108 (13.0 (10.7–15.3)) | 1.6 (0.8–2.5) | 2 (13.3 (11.0-15.7)) |
EIMD2 | 251 (11.4) | 0.6 (0.3–1.2) | 117 (14.1 (11.8–16.5)) | 1.6 (0.9–2.6) | 1 (6.7 (5.0-8.4)) |
EIMD3 | 366 (16.7) | 0.4 (0.2-1.0) | 139 (16.8 (14.2–19.3)) | 1.5 (0.8–2.6) | 1 (6.7 (5.0-8.4)) |
EIMD4 | 505 (23.0) | 0.5 (0.2–1.1) | 204 24.6 ((21.7–27.6)) | 1.5 (0.8–2.8) | 3 (20.0 (17.3–22.7)) |
EIMD5 most deprived | 824 (37.5) | 0.4 (0.2-1.0) | 260 (31.4 (28.2–34.6)) | 1.3 (0.7–2.4) | 8 (53.3 (49.9–56.7)) |
Overall | 2,195 (100.0) | 0.4 (0.2–1.1) | 828 (100.0) | 1.4 (0.8–2.6) | 15 (100) |
After adjusting for age, sex and year, PIM2 score was 1.28 times higher (95% CI: 1.10–1.49) in the least deprived areas compared to those in the most deprived areas. Any form of ventilation support increased with deprivation (p = 0.000423): 13.0% in least deprived to 31.4% in most deprived (Table 3). Compared to no ventilation, in the multinomial regression it was found that any form of ventilation support was significantly less: in females than in males (p = 0.007), in 5-9-year-olds (p = 0.08) and 0-4-year-olds (p = 0.01) than in 10-14-year-olds and in most to least deprived areas (p = 0.001) (Supplementary Table S4).
LoS was not significantly different across SES in England (Supplementary Table S5): 1.3 vs 1.6 median days in the most deprived versus the least deprived (Table 3). After adjusting for year and EIMD, LoS was 1.14 times (95% CI: 1.04–1.25, p = 0.006) higher in 10-14-year-olds compared to 0-4-year-olds and 9% lesser in males than in females (95% CI: 2–15), p = 0.017) (Supplementary Table S5).
Survival
15 deaths occurred in children admitted to PICU with a primary diagnosis of asthma, with the majority in the 10–14 years olds group (73%, 11/15) and none in the pre-school group (Supplementary Table S3). Mortality rate was 0.7% (15/2195). Median PIM2 was higher amongst the non-survivors (31.7%, IQR 2.6–95.3%) compared to the survivors (0.4%, IQR 0.2–42.3%). Of the 15 who died, 14 (93.3%) required invasive ventilation. The one child who died without any ventilation support was in PICU for less than an hour. Children who died had a longer LoS than the survivors (median 2.9 (1.9–11.4) vs 1.4 (0.8–23.8) days). 60.7% admissions from the deprived neighbourhoods (EIMD 4, 5) contributed to 73% deaths (11/15) (Table 3). From ONS records, there were 127 deaths in England in under 15-year-olds from asthma as the underlying cause in the seven calendar years during 2006-12. We found in the financial years 2006-13, around 11.8% (15/127) of them were in PICU.