Temporal patterns of respiratory rate exposure and mortality in critically ill patients: a retrospective multi-database cohort study
In brief
Early ICU tachypnoea tracks higher mortality; risk is lowest near 16 breaths/min
In 160,075 critically ill adults across three databases, spending more of the first ICU day breathing rapidly was consistently associated with higher mortality; the lowest estimated risk was near 16 to 17 breaths per minute. Slow breathing was not reliably associated with mortality when exposure was limited to that first day, so respiratory rate is best viewed as an early-warning signal, not a treatment target.
- Journal
- Frontiers in medicine (Q1)
- Published
- 30 September 2026
- Study design
- Retrospective cohort
- Evidence level
- Level 3, Low (CEBM 3b)
- Authors
- Jingqing Xu, Min Li, Zhulin Wang, Linqian Jiang, Xiankun Lin, Xiuling Shang, et al.
- PMID
- 42877019
- DOI
- 10.3389/fmed.2026.1900968
Why clinicians should know about it
- Picked for Critical Care and Intensive Care Medicine (paper of the day, 19 October 2026): Respiratory rate patterns and mortality in ICU
Abstract
OBJECTIVES: To investigate the associations between respiratory rate (RR) exposure patterns-both intensity and duration-and mortality in critically ill patients. METHODS: This retrospective cohort study analysed 160,075 adult ICU patients from three international databases (HiRID, MIMIC-IV, eICU). The primary analysis used a landmark design: RR exposure and all covariates were ascertained during the first 24 h after ICU admission, and outcome follow-up began at the 24-hour landmark. Heatmap visualisation examined RR intensity-duration patterns. Cox and logistic regression models related the proportion of monitoring time spent in each RR range to mortality, adjusted for demographics, disease severity, laboratory values, comorbidities, treatment limitations, ventilation and sedation. Restricted cubic splines assessed the dose-response relationship for time-weighted mean RR. Sensitivity analyses examined alternative exposure windows, competing risks, multiple imputation, hospital-level clustering and a harmonised in-hospital mortality outcome. RESULTS: A greater proportion of time in the 12-20 breaths/min range was associated with lower 28-day mortality in MIMIC-IV (HR 0.988, 95% CI 0.987-0.989 per 1 percentage point) and lower in-hospital mortality in eICU (OR 0.991, 95% CI 0.990-0.991). Risk rose progressively across the tachypnoeic ranges (>35 breaths/min: HR 1.026, 95% CI 1.023-1.028). Spline analysis identified a nadir of risk at a time-weighted mean RR of 16.3 breaths/min, with a markedly asymmetric relationship (P for non-linearity <0.001): the adjusted hazard ratio reached 1.38 at 20 and 2.19 at 24 breaths/min but rose only modestly below the nadir. The bradypnoea-mortality association seen with whole-stay exposure (HR 1.029) was absent under the landmark design (HR 0.990) in both databases. Tachypnoeic associations were robust to stratification by ventilation and sedation, clustering and multiple imputation. CONCLUSIONS: Respiratory rate showed an asymmetric, non-linear relationship with mortality, with lowest risk at approximately 16-17 breaths/min. The cumulative burden of tachypnoea during the first 24 h was consistently associated with higher mortality across three databases and robust to controls for reverse causation, ventilation and sedation; the apparent association for bradypnoea was not, and likely reflects terminal-phase respiratory depression. Respiratory rate should be regarded as a monitoring and early-warning signal that integrates both magnitude and duration, rather than as a therapeutic target.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.