Hb-O2 affinity parameters as prognostic factors for 28-day mortality in ARDS patients: A prospective study

Measuring hemoglobin-oxygen (Hb-O 2 ) affinity might be helpful in prognosis of acute respiratory distress syndrome (ARDS) patients. We conducted a single-center prospective cohort study at the ICU department of Beijing Ditan Hospital Capital Medical University. The study enrolled 43 consecutive adult ARDS patients (≥ 18 years) admitted to ICU from November 2023 to January 2025. Data obtained from medical records and Hb-O 2 affinity parameters were compared between survivors and non-survivors. Logistic regressions were performed to screen potential prognosis factors in ARDS patients. A total of 42 patients were included in analysis. In a 28-day duration, 10 (23.8 ​%) patients died. We found significantly lower APACHE II scores (p=0.04) and SOFA scores (p=0.02) in the survival group at baseline. We further analyzed patients’ dynamics during ICU stays and found that P 50 significantly increased in survivors than non-survivors (p ​< ​0.01), and the decrease in P 50 (odds ratio: 1.29, 95 ​% confidence interval 0.62–0.98, p=0.03) was an independent risk factor for poor outcomes. In 23 patients, we found significantly lower baseline theoretical oxygen release (TOR) in the survival group (p=0.02). Also, TOR significantly increased in the survival group but decreased in the non-survival group (p ​< ​0.01) during the study period. We concluded that increases in P 50 and TOR are associated with better health outcomes in ARDS patients admitted to ICU, and Hb-O 2 affinity parameters may serve as potential prognostic indicators. • Oxygenation-dissociation analyzers are tools to detect hemoglobin-oxygen affinity. • P 50 is the partial pressure of oxygen at which hemoglobin is half saturated with oxygen. • Change in P 50 is a risk factor for mortality in acute respiratory distress syndrome patients.