Adapting hospital capacity to meet changing demands during the COVID-19 pandemic

The baseline capacity of overnight beds, nurses, junior doctors and senior doctors, split by general and acute (G&A) and critical care (CC), and ventilators, was estimated for England using National Health Service (NHS) data in the pre-pandemic phase [9‐11, 13]. In England, hospital capacity and patient occupancy data are available by NHS trust level (Additional file 1). To account for seasonal fluctuations in capacity, adjusted with respect to seasonal fluctuations in expected demand, we assumed average daily numbers of beds and staff from April–June 2019. This period is most representative of what current capacity and occupancy would have been, without implementation of hospital provision interventions. CC bed numbers include beds in intensive care and high dependency units. We included G&A and CC beds and staff from all acute and community provider NHS trusts but excluded children’s trusts. CC paediatric beds and occupancy are distinguished from adult beds which was reflected in our estimates, but this distinction could not be made for G&A [9, 10]. However, the majority of hospitalised COVID-19 cases are adults and while some hospitals may have converted paediatric beds to treat adults, we do not anticipate this substantially altering the outcome of the analysis [22]. We further distinguished between senior and junior doctors to reflect the requirement of senior clinical decision-makers on wards. Staff numbers are considered in units of full-time equivalents (FTEs) to account for staff employed on a part-time basis or absent due to illness and the possibility of staff working in various wards. Electronic Staff Records (ESR) data were filtered for staff categories normally working on these wards. For example, midwives, general practitioners and paediatric staff were excluded. According to the number of beds in each trust, a weighted average of daily FTE was calculated for each staff category at a national level.

Staff-to-beds ratios specified by the Royal College of Nursing, the Royal College of Physicians and the Faculty of Intensive Care Medicine [16‐18] were used to quantify required safe staffing levels per category. These were kept constant throughout the analysis. The baseline capacity of ventilators and other parameters in the model were derived from various sources (Additional file 2 [4, 9‐21]).

For the post-surge phase, we estimated the number of elective patients who could be accommodated under decreasing numbers of COVID-19 patients, for different intervention scenarios. This is referred to as post-surge reintroduction of elective surgery patients. This was facilitated by splitting non-COVID-19 patients into emergency patients, who continue to receive care throughout the pandemic, and elective patients (Fig. 1b). The number of patients that can be accommodated was determined by the number of patients for which all necessary resource categories displayed spare capacity (i.e. a non-negative value). Hospital provision interventions were assessed for their potential long-term feasibility based on official recommendations for the second phase of the NHS response to COVID-19 [4].

Both the number of COVID-19 patients and number of elective patients were varied, with the number of COVID-19 patients being reduced from the observed maximum in 10% intervals. This was done to consider scenarios of 0 to 100% of the maximum applied to both CC and G&A COVID-19 patients. We assumed that elective patients requiring G&A and CC will be introduced simultaneously. Using the previous analysis of HES and baseline occupancy data [9, 10, 27], we derived the expected number of elective patients that could be accommodated based on pre-pandemic demand and quantified a linear relationship between the number of elective patients in G&A and in CC (Additional file 3). Therefore, the daily number of G&A elective patients was varied in bands of 500, and the equivalent value for CC derived via this relationship.

All analysis was undertaken on R and is available publicly on Github.¹

This research involved evaluating the impact of strategies already adopted by the NHS, and therefore, research questions, outcome measures and dissemination of study results were not developed or informed by patient or public involvement.

We estimated that before the COVID-19 pandemic (pre-March 2020), there was a daily spare capacity of 817 CC beds, 9769 G&A beds, 6757 ventilators, 642 CC nurses, 14,394 G&A nurses, 745 CC senior doctors, 265 CC junior doctors, 6693 G&A senior doctors and 4306 G&A junior doctors nationally.

All resources estimated for this period are in excess, although the extent of this excess differs amongst the resources. On a per-patient-added basis, CC variables are the most limiting. The most restrictive of the CC resources is CC nurses, with the spare capacity of this only allowing for an extra 642 patients. Whereas, under the staff-to-beds ratios, the spare capacity of both CC junior doctors and CC senior doctors can accommodate an extra 2120 patients and 11,175 CC patients respectively.

Given estimates of baseline capacity in the absence of hospital provision interventions, and when factoring in COVID-19 related staff absence rates, up to 327 and 9769 COVID-19 patients could have been accommodated in CC and G&A care, respectively (Fig. 2). These patients would be in addition to the current patient population on any day, and we assume the recommended staff-to-beds ratios are observed. These numbers are far below the observed peak COVID-19 patient numbers of 3100 and 15,700 in CC and G&A, respectively. In CC, nurses persisted as the limiting resource at a national level, although CC beds and junior doctors would also have been insufficient to accommodate these 3100 COVID-19 CC patients. Conversely, there would have been enough daily capacity of ventilators and CC senior doctors to accommodate all COVID-19 CC patients during the surge phase even without interventions (Fig. 2a). In G&A care, only bed capacity would have been exceeded (Fig. 2b), but G&A beds had the largest deficit for the observed peak number of COVID-19 G&A patients (Table 1).

To prevent overwhelming hospital capacity, several interventions were implemented in England across March and April 2020. The main interventions which could be quantified on a national level were those managing patient admissions and those increasing the supply of resources (Table 2). Cancellation of elective surgery and setting up of field hospitals increased available bed capacity, whereas deployment of newly qualified and final year medicine and nursing students and the return of former healthcare staff increased staff capacity. The use of private hospitals led to increases in beds, ventilators and staff.

Combining the interventions as parameterised in Table 2 provides an illustration of true capacity within NHS England during the surge phase. We estimate that these interventions would allow for up to 2627 and 62,267 COVID-19 patients to be accommodated in CC and G&A on any day, respectively (Fig. 2).

The most limiting resources were CC nurses, beds and junior doctors and G&A beds. The intervention that made the largest contribution to increasing their capacity was cancellation of elective surgery (Table 1, Fig. 2). Use of private hospitals and deployment of former staff were also essential to increase the capacity of CC nurses. Additionally, under the observed peak number of COVID-19 patients, setting up of field hospitals and use of private hospitals each led to large increases of around 130% in spare G&A bed capacity compared with no interventions, and deployment of medical students increased spare capacity of G&A nurses and G&A junior doctors by 175% and 229%, respectively (Table 1).

At the time of peak demand, with the combination of interventions in place, there was spare capacity in G&A beds (with a spare 46,500 beds) (Table 1) as well as capacity in staff (42,800 G&A nurses, 17,100 G&A doctors and 570 CC senior doctors) and equipment (6400 ventilators). Whilst we estimate a small deficit in CC beds, CC nurses and CC junior doctors at the time of the peak number of hospitalised COVID-19 patients, additional interventions which could not be quantified at the national level could have been used. For example, converting 474 G&A beds to CC beds and upskilling 359 G&A nurses to CC nurses would have overcome this deficit.

As we enter the post-surge phase (Fig. 1a), attention has now turned to reintroducing elective surgery [3, 4]. We estimate that there were 989 elective patients requiring CC beds and 36,818 requiring G&A beds on an average day before the pandemic.

At the time of peak demand, even with the full supply-side package of interventions (Table 2), there was no capacity to treat elective patients in CC. This full supply-side package of interventions would allow 10% of elective patients requiring CC to be accommodated when COVID-19 CC patients have fallen to 2530. If no interventions were applied, then the baseline capacity would only allow accommodation of 10% of CC electives with at most 1210 COVID-19 patients in CC. To accommodate all elective patients requiring CC at average pre-pandemic levels with the full supply-side intervention package in place, the number of COVID-19 patients in CC must fall below 1550 (Fig. 3a). This is a substantial improvement upon the no-intervention scenario, in which COVID-19 patients in CC must fall below 320 for all elective patients requiring CC to be accommodated. The deficit in CC capacity is primarily being driven by nurses, which is why field hospitals, and deployment of medical and nursing students, provide no improvement over the no-intervention scenario.

However, there is greater national capacity to treat G&A patients. Without interventions, the estimated baseline capacity in NHS England could accommodate nearly 10,000 COVID-19 patients, and still treat all of the average number of elective surgery patients requiring overnight admission to G&A (Fig. 3b). The full supply-side intervention package substantially increases this capacity, allowing for demand from all G&A patients to be comfortably met even at the observed peak number of COVID-19 patients in G&A, and for more than the daily pre-pandemic number of elective patients to be accommodated (Fig. 3b). When implementing the full supply-side interventions, as above for CC, the number of COVID-19 patients that could be accommodated with all G&A elective patients rises to over 25,000.

As long as field hospitals remain operational, capacity is sufficient to meet pre-pandemic demand from all G&A patients regardless of the number of COVID-19 patients (Fig. 3b). The full supply-side intervention package could accommodate up to 46,500 elective G&A patients requiring hospital care on a daily basis, and once G&A COVID-19 patients drop to below 7500 the increase in capacity from the set-up of field hospitals is equivalent to the full supply-side intervention package. However, it is important to note that even under this intervention and with the additional deployment of students, spare capacity in G&A for COVID-19 patients was limited at the time of peak demand.