Standardizing persistent and chronic critical illness: impact of definitions variability on prevalence and mortality

Standardization of terminology and definitions is essential for scientific communication. Without such standardization, some studies may use different terms to express similar conditions, and other studies may use the same term with different definitions. Such diversities in medical language creates inconsistencies in scientific reporting, thereby hindering us from properly understanding the condition.

In this regard, persistent critical illness (PerCI) and chronic critical illness (CCI) are two terms used to describe prolonged critical conditions beyond the acute phase [1, 2]. However, the absence of standardized definitions leads to substantial variability in their clinical implications. Recently, Critical Care published a systematic scoping review highlighting the heterogeneity in definitions, epidemiology, and outcomes of PerCI and CCI [3]. We commend the authors for their comprehensive analysis, which synthesizes data obtained from numerous studies, performs a meta-analysis on specific patient populations (e.g., overall populations, sepsis, trauma, and COVID-19), and offers valuable recommendations for future research.

To further expand on the insights provided by Ohbe et al., we conducted an exploratory analysis to illustrate how different PerCI/CCI definitions impact reported prevalence and in-hospital mortality. From the 99 studies included in Ohbe et al.’s scoping review [3], we selected those explicitly reporting PerCI/CCI definitions, prevalence, and in-hospital mortality. We then created a scatter plot, where each dot represents a study, with PerCI/CCI prevalence on the x-axis and in-hospital mortality on the y-axis (Fig. 1), using Excel version 16.94. Dots were color-coded according to the PerCI/CCI definition applied in each study. This visualization underscores the substantial variability in prevalence and mortality based on the chosen definition.

Fig. 1

Prevalence and hospital mortality according to the different persistent/chronic critical illness definitions

Full size image

Studies defining PerCI/CCI as “ICU stay ≥ 14 days with persistent organ dysfunction” (orange) reported higher prevalence compared to other definitions. This trend may be attributed to the study populations, which predominantly consisted of septic patients. Given that sepsis is strongly associated with organ dysfunction and prolonged ICU stays [4], it is reasonable to expect a higher prevalence of PerCI/CCI. Conversely, studies employing the definition “ICU stay ≥ 10 days” (yellow) primarily included non-specific ICU patients (53.3%), resulting in a lower prevalence.

Studies using the definitions “ICU stay ≥ 8 days and one of six eligible clinical conditions" (gray) reported lower prevalence but higher in-hospital mortality. Among these six clinical conditions, prolonged mechanical ventilation was the most common [5], likely selecting a smaller but more critically ill patient group with worse outcomes.

Meanwhile, studies defining PerCI/CCI as “mechanical ventilation ≥ 14 days or tracheostomy” (blue) showed lower prevalence and lower in-hospital mortality. These study populations were predominantly composed of trauma patients, suggesting that the lower mortality rate reflects the relatively favorable prognosis of trauma patients, who typically have fewer comorbidities compared to septic patients.

Our exploratory analysis highlights the pressing need for a standardized PerCI/CCI definition. Establishing a uniform definition is essential for accurate identification, risk stratification, targeted interventions, and shared decision-making. We urge multidisciplinary discussions to optimize long-term care strategies for critically ill patients.

Further information on the original manuscript is available from the corresponding authors upon reasonable request.

PerCI:

Persistent critical illness

CCI:

Chronic critical illness

ICU:

Intensive care unit

1. Lamas D. Chronic critical illness. N Engl J Med. 2014;370:175–7.

   Article CAS PubMed Google Scholar

2. Darvall JN, Boonstra T, Norman J, Murphy D, Bailey M, Iwashyna TJ, et al. Persistent critical illness: baseline characteristics, intensive care course, and cause of death. Crit Care Resusc. 2019;21:110–8.

   PubMed Google Scholar

3. Ohbe H, Satoh K, Totoki T, Tanikawa A, Shirasaki K, Kuribayashi Y, et al. Definitions, epidemiology, and outcomes of persistent/chronic critical illness: a scoping review for translation to clinical practice. Crit Care. 2024;28:435.

   Article PubMed PubMed Central Google Scholar

4. Mira JC, Gentile LF, Mathias BJ, Efron PA, Brakenridge SC, Mohr AM, et al. Sepsis pathophysiology, chronic critical illness, and persistent inflammation-immunosuppression and catabolism syndrome. Crit Care Med. 2017;45:253–62.

   Article PubMed PubMed Central Google Scholar

5. Kahn JM, Le T, Angus DC, Cox CE, Hough CL, White DB, et al. The epidemiology of chronic critical illness in the United States. Crit Care Med. 2015;43:282–7.

   Article PubMed PubMed Central Google Scholar

Download references

Not applicable.

Not applicable.

Authors and Affiliations

1. Department of Intensive Care Medicine, Kameda Medical Center, 929 Higashi-Cho, Kamogawa, Chiba, 296-8602, Japan

   Toshinobu Nakai, Yuki Kotani & Yoshiro Hayashi

Authors

1. Toshinobu NakaiView author publications

   You can also search for this author in PubMed Google Scholar

2. Yuki KotaniView author publications

   You can also search for this author in PubMed Google Scholar

3. Yoshiro HayashiView author publications

   You can also search for this author in PubMed Google Scholar

Contributions

TN, YK, and YH wrote and approved the final manuscript.

Corresponding author

Correspondence to Yuki Kotani.

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Reprints and permissions

Cite this article

Nakai, T., Kotani, Y. & Hayashi, Y. Standardizing persistent and chronic critical illness: impact of definitions variability on prevalence and mortality. Crit Care 29, 102 (2025). https://doi.org/10.1186/s13054-025-05335-5

Download citation

• Received: 16 February 2025

• Accepted: 22 February 2025

• Published: 07 March 2025

• DOI: https://doi.org/10.1186/s13054-025-05335-5

Share this article

Anyone you share the following link with will be able to read this content:

Get shareable link

Sorry, a shareable link is not currently available for this article.

Copy to clipboard

Provided by the Springer Nature SharedIt content-sharing initiative