The 11-week period of evaluation during the fall 2009 pandemic period included a median of 2,774 (IQR 2,219–3,319) admissions and 19,283 (IQR 15,842–21,315) bed-days (Table 1). Median overall inpatient occupancy was 95% (IQR 85%–99%), whereas median overall occupancy during the 2008–09 seasonal influenza period was 101% (IQR 96%–110%) and, for the entire calendar year 2008, 91% (IQR 87%–95%). Hospitals’ experiences varied considerably, with hospital-level median occupancy ranging from 57.4% to 128.0% (Technical Appendix). To reach 100% occupancy during the pandemic period, for every 10 beds of each type, hospitals would have needed to admit a median of 0.2 (IQR 0.1–0.3) additional patients per day for non-ICU beds and 0.7 (IQR 0.5–0.9) per day for ICU beds (Table 2).

For the 26 hospitals for which ED and inpatient data were available, the median ED-to-hospital admission rate for IRI patients was 5.4% (IQR 3.3%–8.1%). Different hypothetical scenarios for ED IRI volume and admission rates would have differently affected the frequency of hospital days exceeding the 100% occupancy threshold for exhausting capacity reserves (Table 3). The actual experience in 2009 (scenario A) resulted in 23.3% of hospital days with >100% occupancy across the 26 hospitals. Had the hospitals instead experienced the IRI admit rate from the 2003–04 influenza season (14.0%) applied to the same volume of patients, 37.6% of hospital days would have been >100% full (scenario B). Had the admission rate been 30% for 2× the volume of patients, 85.7% of hospital days would have been >100% full, exhausting capacity reserves (scenario F).

Figure

Figure. Predictive model of hospital occupancy during 11-week outbreak of pandemic influenza A (H1N1) 2009 in the United States, by ED IRI admission rate and ED IRI volume, using fall 2009 pandemic...

Individual hospital experience varied considerably (Figure). For each hospital, the dot-plots we constructed show the distribution of occupancy data across hospitals for each of the 6 scenarios. For our worst-case scenario (scenario F), median occupancy would have been 132% (IQR 124%–145%).

We examined the effect on children’s hospitals’ resources during fall 2009 when pandemic influenza A (H1N1) 2009 virus was active. We demonstrated that children’s hospitals faced high levels of occupancy (median 95%) in regular inpatient care areas and ICUs, but this situation did not differ from typical levels of high occupancy commonly experienced at some hospitals. Despite the mild virulence of pandemic (H1N1) 2009 virus, children’s hospitals needed only <1 additional admission per 10 inpatient beds to reach 100% occupancy. Additionally, the pandemic occurred during early fall, when viruses that cause respiratory and gastrointestinal illnesses (which typically increase occupancy at children’s hospitals) were not circulating widely. Models representing an outbreak of a more virulent influenza virus based on historical comparisons demonstrate that modest increases in ED visits or ED admission rates would have resulted in substantial overcrowding among the large cohort of children’s hospitals in our study.

These findings are notable in the context of national disaster planning related to children. The National Commission on Children and Disasters’ 2010 Report to the President and Congress recommended that additional resources provide a “formal regionalized pediatric system of care to support pediatric surge capacity” and emphasizes that children’s hospitals are central to such regionalization (18). Our study shows that children’s hospitals, the central component of this proposed regionalized system, routinely operate so close to capacity that little available reserve exists for even a modest surge of inpatients. For a hospital with 150 non-ICU beds and 50 ICU beds, an additional 3.0 non-ICU and 3.5 ICU admissions per day would have exhausted capacity. Although the 2009 influenza pandemic did not do so, surge capacity is scarce, as demonstrated by the many hospitals that are already operating at or near maximum capacity in their EDs and inpatient areas (17,29).

Federal planners have suggested that surge capacity should accommodate 500 inpatients per million population, but such capacity does not exist for children under normal circumstances; capacity for only 193 inpatients per million children is available during typical winter weekdays (29–31). Although we expressed our findings in terms of hospital occupancy rather than on a population basis, our findings are similar to those raising alarm about limited inpatient capacity in the face of a pandemic or disaster.

Pandemics extend over many weeks and affect large regions, if not the entire country. Although the hospitals may be able to handle such levels of occupancy on a short-term basis, whether they could do so for prolonged periods is unclear. Even though a health care system’s capacity reserve cannot be designed on a daily basis to handle a pandemic, the frequent level of high occupancy already experienced by children’s hospitals and the resulting lack of a buffer for a pandemic-associated surge should be considered by individuals and organizations involved with planning and disaster preparedness (32,33). Planning for such events at hospital and regional levels may be improved with data about current capacity reserves and how perturbations can affect that capacity.

In previous studies of large-scale epidemics, hospitals have altered standards of care—as occurred in Toronto during the 2003 outbreak of severe acute respiratory syndrome—to meet increased patient needs (30,34,35). During the outbreak of severe acute respiratory syndrome, restrictions on scheduled (i.e., elective) admissions were imposed in Toronto (36). Although we did not study scheduled admissions, our analysis suggests in a more virulent pandemic (scenario F), hospitals would have run out of space even if they had rescheduled the 15%–25% of scheduled pediatric admissions; this percentage includes the 20% of elective admissions for chemotherapy, a treatment that is not amenable to prolonged postponement (37).

Our findings are subject to several limitations. The 34 hospitals in this study represent a subset of the ≈250 US children's hospitals and may not be representative of these children’s hospitals or of other hospitals that admit children, even though the study included children’s hospitals in all regions of the country. The analysis did not consider measures that individual hospitals and regional systems might use to reduce occupancy, such as canceling scheduled admissions, which would have caused us to overestimate occupancy. On the other hand, our assumption about length of stay would have caused us to underestimate occupancy. Our analysis used midnight census; actual daytime occupancy most likely was higher (38), and thus true surge capacity was even lower than estimated. Finally, the modeled scenarios were based on historical comparisons, which represent a range of potential demands on the health care system.

For hospitals and government agencies, the results of our study should prompt review of preparedness planning and reconsideration of surge capacity. Systemwide resource limitations must be considered because ambulatory and inpatient services interrelate. The outbreak of low-virulence pandemic (H1N1) 2009 virus affected EDs disproportionately but left inpatient services relatively unaffected (13). Exploring the parameters of more severe epidemics might allow planners at individual hospitals, as well as regional health administrators, to consider what alterations in standards may be necessary.