A Derivation Study of a Cardio-Nutrition-Inflammation-Oxygen Index and 3-Month Functional Outcomes After Outpatient...

Short-term functional outcomes after outpatient pulmonary rehabilitation are heterogeneous. We examined whether a study-derived cardio-nutrition-inflammation-oxygen (CNIO) index integrating echocardiographic filling pressure, nutritional status, inflammation, and oxygen requirement was associated with 3-month functional outcomes in chronic respiratory disease.

This single-center retrospective cohort study included 60 adults with chronic obstructive pulmonary disease, interstitial lung disease, or bronchiectasis who completed outpatient pulmonary rehabilitation and had baseline and 3-month functional assessments. The CNIO index was calculated as standardized E/e' plus standardized ln(neutrophil-to-lymphocyte ratio) plus standardized resting oxygen flow rate minus standardized Geriatric Nutritional Risk Index, and the summed score was then standardized to mean 0 and SD 1. The primary outcome was 3-month 6 min walk test (6MWT) distance, and the exploratory secondary outcome was 3-month Short Physical Performance Battery (SPPB) score. The primary 6MWT analysis used multivariable analysis of covariance adjusted for baseline 6MWT, age, sex, body mass index, and diagnosis, whereas the exploratory SPPB analysis used ordinal logistic regression adjusted for baseline SPPB and the same covariates.

Mean 6MWT increased from 340.3 ± 61.0 m to 368.0 ± 102.0 m, corresponding to a mean change of 27.7 ± 90.3 m. Each 1-SD increase in CNIO was associated with a lower 3-month 6MWT distance (β = -43.42 m; 95% confidence interval [CI], -77.55 to -9.30; p = 0.014). In the exploratory ordinal logistic regression model for SPPB, each 1-SD increase in CNIO was associated with lower odds of being in a higher 3-month SPPB category, although the estimate was fragile and the confidence interval was close to the null (odds ratio = 0.39; 95% CI, 0.15 to 0.99; p = 0.048). Bootstrap internal stability analysis for the primary 6MWT model showed a wide percentile bootstrap 95% CI of -76.05 to -13.97 m per 1-SD increase in CNIO, supporting the need for cautious interpretation.

In this hypothesis-generating derivation study, a higher standardized CNIO index was associated with lower 3-month 6MWT distance among adults with chronic respiratory disease who completed outpatient pulmonary rehabilitation. The association with SPPB was weaker and should be interpreted cautiously. These findings are not generalizable to patients who discontinue rehabilitation or are hospitalized for exacerbation during follow-up, and prospective external validation in larger, diagnostically stratified cohorts is required before CNIO can be considered for clinical risk stratification or rehabilitation planning.