25 February 2021

The Ebb and Flow of COVID-19 in Arizona's ICUs

Unlike other states coping with the winter surge in serious COVID-19 cases in their hospitals, Arizona never ran out of available Intensive Care Unit (ICU) bed space.

Here's a chart from the Arizona Department of Health Services COVID-19 data dashboard, which shows the daily percentage usage of ICU beds in the state, including for COVID-19 patients from 10 April 2020 through 20 February 2021:

Arizona Number of Intensive Care Unit (ICU) Beds Available and In Use at Arizona Hospitals, with Data for COVID-19 Patients from 10 April 2020 through 20 February 2021

ICU bed usage peaked at 93% on 30 December 2020, as the number of open ICU beds in the state dropped to 121, the lowest figure recorded during the state's experience with the coronavirus pandemic.

But while this chart ably communicates the percentage share of ICU beds that were either open, used by COVID-19 patients, or by non-COVID-19 patients, it doesn't communicate the story of how Arizona was able to avoid the situation that states like California faced in running out of ICU beds during the same period of time.

The following chart reveals that part of Arizona's secret to avoiding running out of ICU bed capacity was to increase its supply of ICU beds. In the chart, we've shown the daily numbers of open ICU beds, the ICU beds used by both COVID-19 and non-COVID patients, and also the total number of ICU beds in the period from 10 April 2020 through 20 February 2021, against the backdrop of the major turning points driving the number of COVID-19 cases in Arizona.

Arizona ICU Bed Usage, 10 April 2020 through 20 February 2021

Here, we find that Arizona went from an average total of roughly 1,650 ICU beds early in the coronavirus pandemic to over 1,800 at its peak.

We also see that the number of COVID-19 and non-COVID-19 patients are inversely related, with one rising while the other falls, which points to another secret to Arizona's relative success in managing its limited ICU capacity. Hospital officials proactively managed non-COVID-19 patient ICU bed usage, which helped ensure ICU beds would be available for COVID patients.

At the same time, treatments available for COVID-19 patients have improved from lessons learned during the state's first wave of SARS-CoV-2 coronavirus infections. These improved treatments helped keep a considerable COVID-19 patients from needing to be placed in ICU beds.

That can be seen by the relative number of COVID-19 patients in Arizona hospital ICU beds. That number peaked at 970 during the state's first wave, and peaked at 1,183 during the state's second wave, a 22% increase.

By contrast, the rolling seven day moving average for the number of patients admitted to Arizona hospitals for COVID-19 peaked at 315 per day on 16 July 2020 during Arizona's first wave, and at 535 per day on 8 January 2021 during the state's second wave, a 70% increase. The much smaller percentage increase in ICU bed usage during Arizona's second wave may therefore be attributed to improved care and treatments available for COVID-19 patients at Arizona's hospitals.

The story of how Arizona's hospitals have managed its periodically worst-in-the-nation surge of COVID-19 has been absent in media reports. We thought it was time that somebody addressed even a small part of what looks to be an all-too-rare good news story.

Previously on Political Calculations

Here is our previous coverage of Arizona's experience with the coronavirus pandemic, presented in reverse chronological order.

References

We've continued following Arizona's experience during the coronavirus pandemic because the state's Department of Health Services makes detailed, high quality time series data available, which makes it easy to apply the back calculation method to identify the timing and events that caused changes in the state's COVID-19 trends. This section links that that resource and many of the others we've found useful throughout the coronavirus pandemic.

Arizona Department of Health Services. COVID-19 Data Dashboard. [Online Application/Database].

Stephen A. Lauer, Kyra H. Grantz, Qifang Bi, Forrest K. Jones, Qulu Zheng, Hannah R. Meredith, Andrew S. Azman, Nicholas G. Reich, Justin Lessler. The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application. Annals of Internal Medicine, 5 May 2020. https://doi.org/10.7326/M20-0504.

U.S. Centers for Disease Control and Prevention. COVID-19 Pandemic Planning Scenarios. [PDF Document]. Updated 10 September 2020.

More or Less: Behind the Stats. Ethnic minority deaths, climate change and lockdown. Interview with Kit Yates discussing back calculation. BBC Radio 4. [Podcast: 8:18 to 14:07]. 29 April 2020.