Bicarbonate levels on admission predict recurrent acute hypercapnic respiratory failure in COPD

<bold>Background:</bold> Acute exacerbation of COPD with acute hypercapnic respiratory failure (AHRF) results in high mortality and heavy burden to healthcare. There have been inconsistent findings of predictors of outcomes, and limited evidence on inpatient initiation of long- term NIV after AECOPD with AHRF. <bold>Objectives:</bold> To evalulate the 1- year clinical outcomes following admission for AHRF, and to identify the associated predcitors thus high- risk groups who may benefit from long- term NIV. <bold>Methods:</bold> This is a retrospective cohort on COPD patients with first episode of AHRF in 12- month period requiring ventilatory support, admitted to a regional hospital in Hong Kong from 2018 to 2020. <bold>Results:</bold> 26.2% of 271 patients died in index admission, with lung cancer and severe renal impairment being risk factors. The overall 1- year recurrent AHRF, AECOPD and mortality rates were 39%, 65% and 25% respectively. History of CHF and higher bicarbonate level upon initiation of ventilator predicted worse AHRF- free survival. Bicarbonate level that was greater than or equal to 34.3 mmol/L predicted 90- day readmission for AHRF among patients discharged without long- term NIV, with sensitivity and specificity being 80.6% and 56.9% respectively. <bold>Conclusion:</bold> 1- year outcomes following AHRF remain alarming despite advance in medical care in COPD patients. Identification of important comorbidities may facilitate timely palliative care referral and long- term NIV initiation. The implication of bicarbonate level on chronicity of disease and benefit of long- term NIV in high- risk group warrants further study.