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. 2024 Nov;50(11):1861-1872.
doi: 10.1007/s00134-024-07609-y. Epub 2024 Sep 2.

Epidemiology of acute hypoxaemic respiratory failure in Australian and New Zealand intensive care units during 2005-2022. A binational, registry-based study

Ryan Ruiyang Ling #  1   2   3 , Mallikarjuna Ponnapa Reddy #  4   5   6 , Ashwin Subramaniam  7   6   8   9 , Benjamin Moran  10   11   12 , Kollengode Ramanathan  13   14 , Mahesh Ramanan  15   16   17   18 , Aidan Burrell  7   19 , David Pilcher  7   19   20 , Kiran Shekar  17   21   22   23
Affiliations

Epidemiology of acute hypoxaemic respiratory failure in Australian and New Zealand intensive care units during 2005-2022. A binational, registry-based study

Ryan Ruiyang Ling et al. Intensive Care Med. 2024 Nov.

Abstract

Purpose: Acute hypoxaemic respiratory failure (AHRF) is a common reason for intensive care unit (ICU) admission. However, patient characteristics, outcomes, and trends over time are unclear. We describe the epidemiology and outcomes of patients with AHRF over time.

Methods: In this binational, registry-based study from 2005 to 2022, we included all adults admitted to an Australian or New Zealand ICU with an arterial blood gas within the first 24 h of ICU stay. AHRF was defined as a partial pressure of oxygen/inspired oxygen ratio (PaO2/FiO2) ≤ 300. The primary outcome was adjusted in-hospital mortality, categorised based on PaO2/FiO2 (mild: 200-300, moderate: 100-200, and severe < 100, and non-linearly). We investigated how adjusted mortality evolved based on temporal trends (by year of admission), sex, age, admission diagnosis and the receipt of mechanical ventilation.

Results: Of 1,560,221 patients, 826,106 (52.9%) were admitted with or developed AHRF within the first 24 h of ICU stay. Of these 826,106 patients, 51.4% had mild, 39.3% had moderate, and 9.3% had severe AHRF. Compared to patients without AHRF (5.3%), patients with mild (8%), moderate (14.2%) and severe (29.9%) AHRF had higher in-hospital mortality rates. As PaO2/FiO2 ratio decreased, adjusted in-hospital mortality progressively increased, particularly below an inflection point at a PaO2/FiO2 ratio of 200. The adjusted in-hospital mortality for all patients decreased over time (13.3% in 2005 to 8.2% in 2022), and this trend was similar in patients with and without AHRF.

Conclusion: The healthcare burden due to AHRF may be larger than expected, and mortality rates remain high in severe AHRF. Although mortality has decreased over time, this may reflect improvements in ICU care in general, rather than specifically in AHRF. More research is required to earlier identify AHRF and stratify these patients at risk of deterioration early, and to validate our findings.

Keywords: AHRF; Acute hypoxaemic respiratory failure; Hypoxaemia; Intensive care; Mortality; PaO2/FiO2; Respiratory failure.

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Conflict of interest statement

RRL receives research support from the Clinician Scientist Development Unit, Yong Loo Lin School of Medicine, National University of Singapore. AB is a recipient of the National Health and Medical Research Council Emerging Leader Fellowship (201110). DP is the chairman of the ANZICS Centre for Outcomes and Resources Evaluation Clinical Quality Registry and is the vice-president and board member of ANZICS. All other authors declare no competing interests. KS acknowledges Metro Health. No other conflicts of interest for other authors.

Figures

Fig. 1
Fig. 1
Proportion of patients who were admitted with or developed acute hypoxaemic respiratory failure within 24 h from ICU admission across a the whole cohort, and b stratified based on severity of respiratory failure
Fig. 2
Fig. 2
Association between PaO2/FiO2 ratios and adjusted mortality in the overall cohort of patients. Mortality increases as PaO2/FiO2 ratio decreases. An inflection point is noted at the PaO2/FiO2 ratio of 200, where mortality substantially increases with each decrement of PaO2/FiO2 ratio below 200
Fig. 3
Fig. 3
Association between time (year of admission) and adjusted mortality in the overall cohort of patients, and stratified by severity of respiratory failure. In general, mortality has decreased over time
See this image and copyright information in PMC

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