Admission arterial partial pressure of carbon dioxide (PaCO₂) and outcomes after out of-hospital cardiac arrest: a single-centre retrospective cohort study

Q: What is the clinical evidence from this study?

Study design: Cohort. Population: Out-of-hospital cardiac arrest (n=617). Intervention: Admission arterial partial pressure of carbon dioxide (PaCO₂, per 10-mmHg increase) vs. Lower admission PaCO₂ (continuous per 10-mmHg; reference ≤50 mmHg in categorical models). Primary outcome: One-month all-cause mortality (aOR 1.45, 95% CI 1.24-1.70, p=<0.001).

Q: What does this research mean for the field?

Higher admission arterial carbon dioxide tension (PaCO₂) is independently associated with increased one-month mortality and worse neurological outcomes in out-of-hospital cardiac arrest patients. Novelty: ClaimNovelty.CONFIRMATORY. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

To evaluate the association between admission arterial partial pressure of carbon dioxide (PaCO₂) and one-month mortality and neurological recovery following out-of-hospital cardiac arrest.

Mei Li; Qinghui Hu; Lifeng Du

doi:10.62838/jccm-2026-0039

October 30, 2026The Journal of Critical Care MedicineOpen Access

Admission arterial partial pressure of carbon dioxide (PaCO₂) and outcomes after out of-hospital cardiac arrest: a single-centre retrospective cohort study

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Key result

Each 10-mmHg increase in admission PaCO₂ was associated with higher one-month mortality after out-of-hospital cardiac arrest (aOR 1.45, 95% CI 1.24-1.70; p < 0.001).

Why the study?

The prognostic utility of admission arterial carbon dioxide tension (PaCO₂) for one-month survival and neurological recovery following out-of-hospital cardiac arrest (OHCA) remained poorly defined.

Does elevated admission arterial partial pressure of carbon dioxide (PaCO₂) predict increased one-month all-cause mortality and worse neurological outcomes in adults resuscitated from out-of-hospital cardiac arrest?

Key Points

To evaluate the association between admission arterial partial pressure of carbon dioxide (PaCO₂) and one-month mortality and neurological recovery following out-of-hospital cardiac arrest.
Single-center retrospective cohort study of 617 adult out-of-hospital cardiac arrest patients treated between 2014 and 2023.
Patients were grouped by admission PaCO₂ into three tiers: 60 mmHg or less, 61 to 100 mmHg, and greater than 100 mmHg.
Multivariable logistic regression evaluated one-month mortality and neurological status using the Cerebral Performance Category scale, adjusting for prehospital confounders and metabolic markers.
One-month mortality was 73.6% (454/617) overall, rising across PaCO₂ groups from 49.7% (≤ 60 mmHg) to 81.1% (61–100 mmHg) and 90.7% (> 100 mmHg; p < 0.001).
Each 10-mmHg increase in PaCO₂ was associated with higher mortality (aOR 1.45, 95% CI 1.24-1.70; p < 0.001) and worse neurological outcomes (common aOR 1.53, 95% CI 1.31-1.79).
The mortality association attenuated after adjusting for lactate, base excess, and PaO₂ (aOR 0.80, 95% CI 0.64-1.01; p = 0.063), and adding PaCO₂ yielded minimal discrimination gain (AUC 0.794 to 0.816; ΔAUC 0.022, 95% CI 0.002-0.043).

Study Design

Type

Cohort (n=617)

Multicenter

No

Structured PICO

Does elevated admission arterial partial pressure of carbon dioxide (PaCO₂) predict increased one-month all-cause mortality and worse neurological outcomes in adults resuscitated from out-of-hospital cardiac arrest?

P

Population

617 adults (median age 67 years, 40.5% female) resuscitated from out-of-hospital cardiac arrest with an available admission arterial blood gas sample, followed for 1 month.

E

Exposure

Admission arterial partial pressure of carbon dioxide (PaCO₂) evaluated continuously (per 10-mmHg increase) and across higher hypercapnic categories (>50-70 mmHg and >70 mmHg; or 61-100 mmHg and >100 mmHg in abstract)

C

Comparator

Lower admission PaCO₂ category (≤50 mmHg in main text; ≤60 mmHg in abstract)

O

Outcome

One-month all-cause mortalityhard clinical

Main Result

Odds Ratio: 1.45 (95% CI 1.24–1.7)

p-value: p=<0.001

Limitations

Retrospective, single-center design limiting generalizability
Admission PaCO₂ is a treatment-dependent variable influenced by unmeasured resuscitation factors (CPR duration/quality, airway and ventilation management, ventilator settings, and ROSC-to-sampling interval)
Strong collinearity between PaCO₂ and acid-base markers (pH, base excess, lactate) prevents separation of PaCO₂ effects from global metabolic acidosis
Missing data on detailed comorbidities, shock on admission, and targeted temperature management
Outcome ascertainment restricted to one month and survivor-restricted neurological analysis based on few events (n=17)
Retrospective and single-center design, which limits generalizability
Admission PaCO₂ is a treatment-dependent exposure influenced by unrecorded resuscitation variables (no-flow/low-flow intervals, CPR quality, airway management, ventilation settings, and ROSC-to-sampling interval)
Detailed comorbidity, shock on admission, and targeted temperature management data were unavailable
Strong collinearity between PaCO₂ and acid-base variables prevents separating its contribution from global acidosis
Outcome ascertainment was restricted to one month and the survivor-restricted analysis rested on few events (17 events among 163 survivors)

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Implication

Higher admission PaCO₂ after out-of-hospital cardiac arrest is associated with increased one-month mortality and worse neurological outcomes, though it adds minimal incremental prognostic discrimination beyond established clinical factors and likely reflects overall arrest severity and resuscitation quality.

Abstract

Background: The prognostic utility of arterial carbon dioxide tension (PaCO₂) following out-of-hospital cardiac arrest (OHCA) remains poorly defined. We hypothesized that elevated admission PaCO₂ is independently associated with increased one-month mortality and worse neurological outcomes in OHCA patients. This study aimed? to evaluate the association between admission PaCO₂ and one-month survival and neurological recovery after OHCA. Material and Methods: In this single-center retrospective cohort study, 617 adult OHCA patients (2014–2023) were categorized into three PaCO₂ groups: 60 mmHg or less, 61 to 100 mmHg, and greater than 100 mmHg. The primary outcomes were one-month mortality and neurological outcome, classified as favorable (Cerebral Performance Category 1 or 2) or unfavorable (Cerebral Performance Category 3 to 5). Multivariable logistic regression was used to assess the independent association between PaCO₂ (analyzed as both a continuous and categorical variable) and the outcomes, adjusting for potential confounders. Results: One-month mortality was 73.6% (454/617) and rose across PaCO₂ groups (49.7%, 81.1%, and 90.7%; p < 0.001). Each 10-mmHg increase in PaCO₂ was associated with higher mortality after adjustment for measured confounders (adjusted odds ratio [aOR] 1.45, 95% CI 1.24-1.70; p < 0.001), with a concordant gradient for the ordinal CPC outcome (common aOR 1.53, 95% CI 1.31-1.79) and among survivors (aOR 1.91, 95% CI 1.25-2.91). The graded association was robust across categorization schemes but was attenuated after additional adjustment for concurrent acid-base and gas-exchange markers (lactate, base excess, PaO₂; aOR 0.80, 95% CI 0.64-1.01; p = 0.063), consistent with strong collinearity between PaCO₂ and acid-base status. Adding PaCO₂ to a clinical model produced a minimal incremental improvement in discrimination of uncertain clinical utility (AUC 0.794 to 0.816; ΔAUC 0.022, 95% CI 0.002-0.043; optimism-corrected AUC 0.802). Calibration was assessed via bootstrap validation (calibration slope: 0.98, 95% CI 0.89-1.07; calibration-in-the-large: -0.04, 95% CI -0.21 to 0.13), indicating adequate agreement between predicted and observed risks. Conclusions: Higher admission PaCO₂ is independently associated with increased one-month mortality and worse neurological outcomes after OHCA. Admission PaCO₂ is a strong prognostic marker; whether its early correction improves outcomes warrants further study.

Discussion

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Cite This Study

Li et al. (2026) conducted a cohort in Out-of-hospital cardiac arrest (n=617). Admission arterial partial pressure of carbon dioxide (PaCO₂, per 10-mmHg increase) vs. Lower admission PaCO₂ (continuous per 10-mmHg; reference ≤50 mmHg in categorical models) was evaluated on One-month all-cause mortality (aOR 1.45, 95% CI 1.24-1.70, p=<0.001). Each 10-mmHg increase in admission PaCO₂ was associated with higher one-month mortality after out-of-hospital cardiac arrest (aOR 1.45, 95% CI 1.24-1.70; p < 0.001).

synapsesocial.com/papers/6aee6bc771a7594806220bbe https://doi.org/10.62838/jccm-2026-0039

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Admission arterial partial pressure of carbon dioxide (PaCO₂) and outcomes after out of-hospital cardiac arrest: a single-centre retrospective cohort study

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

Admission arterial partial pressure of carbon dioxide (PaCO₂) and outcomes after out of-hospital cardiac arrest: a single-centre retrospective cohort study

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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