Decreased Ventilator-Free Days in Intubated Patients With Hypercapnia and Suspected Pneumonia

Monday, March 23, 2026

2:30 PM - 3:30 PM Central Time

Location: Connections Central - RST 18

Daniel H. Ryan, n/a (he/him/his)

Northwestern University, Illinois

Disclosure(s): No relevant financial relationship(s) to disclose.
VG

Vijeeth Guggilla, BA

Student
Northwestern University Feinberg School of Medicine

Disclosure information not submitted.
Catherine Gao, MD MS (she/her/hers)

Northwestern University

Disclosure(s): No relevant financial relationship(s) to disclose.
MC

Marina S. Casalino-Matsuda, PharmD, PhD

Research Associate Professor
Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine

Disclosure information not submitted.
AM

Ali Mahmoud, MD

Student
Northwestern University Feinberg School of Medicine

Disclosure information not submitted.
RW

Richard G. Wunderink, MD

Professor
Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine

Disclosure information not submitted.
PS

Peter H.S. Sporn, MD

Professor
Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine; Research Service, Jesse Brown Veterans Affairs Medical Center

Disclosure information not submitted.
TW

Theresa L. Walunas, PhD

Associate Professor
Division of General Internal Medicine, Northwestern University Feinberg School of Medicine

Disclosure information not submitted.

Introduction: Hypercapnia impairs innate immunity in mice and is a risk factor for mortality in patients with severe acute and chronic lung disease. Whether hypercapnia increases risk for ventilator-associated pneumonia (VAP), prolongs time on the ventilator, or increases mortality in intubated patients is unclear. We hypothesized that hypercapnia may worsen these outcomes in patients intubated for suspected pneumonia.

Methods: We utilized data from Successful Clinical Response in Pneumonia Therapy (SCRIPT), a single-center prospective cohort study of critically ill, mechanically ventilated patients with suspected pneumonia. Pneumonia diagnosis was based on bronchoalveolar lavage and adjudicated by a clinical committee. Time-weighted arterial PaCO2 average from the 72 h following intubation was used to classify patients as hypocapnic (PaCO2 < 35 mmHg), normocapnic (35-45 mmHg), or hypercapnic (>45 mmHg); patients who received ECMO were excluded. LLMs used for coding; authors reviewed and take responsibility. Linear and logistic regression were used to test the association between PaCO2 grouping and VAPs/1000 intubated days, ventilator-free days to day 28 (VFD), and a composite of unfavorable outcomes (death, discharge to hospice, requiring lung transplantation).

Results: 449 patients were included; median age 65 years; 45% female; 60% White, 21% Black/African American, 5% Asian; and 19% Hispanic/Latino. 29% had at least one VAP, median VFD was 10 days, and 43% had an unfavorable outcome. 37% were immunocompromised, and median Charlson Comorbidity Index score was 5. 47% of patients were normocapnic, 32% hypocapnic, and 21% hypercapnic. Patients with hypercapnia had fewer VFD than those with normocapnia (median 0, Q1-Q3: 0-18 days vs median 15, Q1-Q3: 0-23 days; p < 0.001). VAPs/1000 intubated days and odds of unfavorable outcome were not different between the hypercapnic and normocapnic groups.

Conclusions: In intubated patients with suspected pneumonia, hypercapnia was associated with fewer VFD, but not a greater incidence of VAP or composite unfavorable outcomes than normocapnia. The relationship between hypercapnia and VAP incidence and poor clinical outcomes in specific subsets of intubated patients, such as those with pre-existing lung disease or who are immunocompromised, should be further elucidated.