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Background The Joint British Thoracic Society/Intensive Care Society (BTS/ICS) guidelines 1 recommend prompt initiation of acute non-invasive ventilation (NIV) for patients presenting with acute hypercapnic respiratory failure (AHRF) that does not respond to initial optimal medical management. We analyzed the short, medium, and long-term survival and in-hospital mortality for patients treated with acute NIV for AHRF with different levels of acidosis on initiation. Current evidence suggests poor outcome in patients with lower pH (especially pH of <7.25).2 Aim To evaluate the clinical outcomes in patients initiated on NIV for AHRF and whether the level of acidosis predicts short, medium, and long-term outcomes.Methods Retrospective analysis of data from electronic case records of a tertiary hospital between January and December 2024. Patients were categorized into 3 groups according to their pH (Group 1 = pH 7 to 7.15, Group 2 = 7.16 to 7.25 and Group 3 = 7.26 to 7.35).Results 99 patients were ventilated for various etiologies. 15 patients presented with severe acidosis (group 1) with a median age of 70 years. In-hospital mortality was 46.7% (n = 7). Group 2 comprised 42 patients with a median age of 74.5 years. In-hospital mortality was 38.1% (n= 16). Group 3 included 42 patients with a median age of 72 years. The inpatient mortality was lowest at 19% (n = 8). Mortality was higher in Group 1 at 3 months and in Group 3 at 12 months. The mortality rate in Group 2 was lower than both groups at 3 months and lower than Group 3 at 12 months.Abstract P233 Table 1Conclusion Admission pH predicts in-hospital mortality in patients presenting with AHRF. The 3-month and 12-month mortality is comparable, but the p-value is likely skewed due to a low sample size. There were no significant differences in the overall long-term success and re-admission rates among the various groups. In conclusion, although lower pH can predict poor outcome, a trial of NIV in AHRF can be considered in various pH categories if the patient population is carefully selected and the care provided on a dedicated ventilation unit.References BTS/ICS guideline for the ventilatory management of acute hypercapnic respiratory failure in adults. Thorax 2016 Apr;71(Suppl 2):ii1–35. doi: 10.1136/thoraxjnl-2015-208209A chart of failure risk for noninvasive ventilation in patients with COPD exacerbation. European Respiratory Journal 2005;25(2):348–355; DOI: doi.org/10.1183/09031936.05.00085304