**How much extra bed capacity do you need ?**

Having enough bed capacity is important for a good flow of patients through the hospital. Insufficient bed capacity leads to a constant pressure on operations. Too much bed capacity is very costly.

The necessary bed capacity is (of course) closely related to demand. Not the average demand, but demand as it is hour per hour, day per day. Healthcare workers experience each day that this demand is highly variable. ‘Hollen en stilstaan’ (to run and stand still) is a Dutch saying among nurses to indicate this variability.

So, let’s look at an example to see how much extra bed capacity is needed.

There are 3 hospitals: hospital LOW (left in the picture), hospital MEDIUM (in the middle), hospital HIGH (right in the picture).

All 3 hospitals have the same average patient census (number of beds occupied day per day) of **100 beds**/patients.

Hospital LOW has a low variability in patient census, indicated by a standard deviation of 10 beds.

Hospital MEDIUM has a medium variability in patient census, indicated by a standard deviation of 20 beds.

Hospital HIGH has a high variability in patient census, indicated by a standard deviation of 30 beds.

If each of these hospitals wants to calculate how much bed capacity it needs, for example based on **the objective to have sufficient beds in 95% of the days**. Then that would mean that these 3 hospitals need the following amount of beds:

Hospital LOW needs 16 beds extra (on top of the average of 100 beds) to have sufficient beds in 95% of the days. Hospital MEDIUM needs 30 extra beds, and hospital HIGH 46 extra beds.

That is +16%, +30%, +46% extra bed capacity!

Are the MEDIUM and HIGH hospitals unrealistic examples ? Where do you think that your hospital is in the LOW-MEDIUM-HIGH range ?

Most hospitals are in the MEDIUM-HIGH range, taking them to a need of at least +25% bed capacity.

What happens if we recalculate the example with a new objective **to have sufficient beds in 99% of the days **? The amount of necessary extra bed capacity will increase. How much ? Let’s have a look:

The necessary extra bed capacity goes up to +23%, +44%, +69%!

**How much extra bed capacity do you need ? **

You can easily calculate it if you have the data of your patient census patterns.

Use any of these 2 methods, which can be done in excel:

*Method 1 – the percentile method*

**=percentile(E5:E164;0,99)** (*in Dutch: =percentiel(E5:E164;0,99)* ), where E5:E164 is the selected data range, and 0,99 is the 99^{th} percentile (having sufficient beds in 99% of the days).

*Method 2 – calculation based on the mean and the standard deviation*

Calculate the mean and the standard deviation of your data range. Use the formula **=NORM.INV((1-$B$1);E2;E3)**, where $B$1 is the objective à fill in 0,01 or 1% in the cell if your objective is to have sufficient beds in 99% of the days. E2 is the mean of your data range, and E3 is the standard deviation of your data range.

**Attention!**

In one of the upcoming articles I will dive into the following question: ** How much extra bed capacity is normal ?** The calculations above show the amount of extra bed capacity needed without interventions to optimize bed capacity usage. Luckily the discipline of Patient Flow Management/Hospital-Wide Capacity Management has defined a series of interventions that can be used to optimize bed capacity usage. They will be covered in one of the next articles.

**To think about…**

*In this series we don’t just provide answers. We try to trigger your thinking by posing questions that you have to answer…*

So, let’s start…

- Have you ever calculated the amount of extra bed capacity that your ward/your hospital needs ?
- Where is your hospital in the LOW-MEDIUM-HIGH range ?
- Have you defined an objective to specify the amount of days with sufficient bed capacity ?
- Do you experience a constant pressure on operations to provide the right bed for each patient ? Could it have to do with the way your bed capacity is divided among the Specialties or wards ?

*Written by Gwen Roosemont ; 5 July 2021*