CPAP. We studied 20 (9 male), ambulatory adult patients with EDAC and/or TBM: mean ±SD age 60±13 years, height 1.67 ±0.86 m, and BMI 34.1±6.6 kg/m 2 . The NRDI was 356 ±182 AU while self-ventilating and reduced when CPAP was applied (231±122 AU; p<0.001). The 6MWT while on opti- mal CPAP was increased comparing to self-ventilation and sham CPAP (296±112 m vs 264±120 m vs 252±125 m, respectively; p<0.001) (figure 1). The treatment effect between sham and optimal CPAP was 31±39 m (95% CI: 13 to 50 m). While on optimal CPAP, 12 patients increased their 6MWT more than 30 m compared to self-ventilation (res- ponders). Comparing responders with non-responders, differ- ences were identified for NRDI (167±110 AU vs. 63 ±90 AU, respectively; p=0.039) and 6MWT while self-venti- lating (203±94 m vs. 336±133 m, respectively; p=0.022). In conclusion, CPAP reduces neural respiratory drive and increases exercise capacity in patients with EDAC/TBM. Fur- thermore, the degree of functional limitation and off-loading of the respiratory muscles on CPAP can identify those likely to have a reduction in neural respiratory drive and enhanced exercise tolerance. S135 TIMING OF ACIDAEMIA ONSET IN EXACERBATIONS OF COPD REQUIRING ASSISTED VENTILATION AND IN- HOSPITAL MORTALITY 1 TM Hartley, 1 ND Lane, 1 J Steer, 2 C Echevarria, 1 SC Bourke. 1 Northumbria Healthcare NHS Foundation Trust, North Shields, UK; 2 The Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK 10.1136/thoraxjnl-2017-210983.141 Introduction Predicting which patients are likely to benefit from assisted ventilation in exacerbations of COPD (ECOPD) is difficult. Existing prognostic scores did not assess the prog- nostic value of timing of acidaemia onset relative to admission during development. The 2011 National Chronic Obstructive Pulmonary Disease Resources and Outcomes Project (NCROP) report identified this as a potentially important marker of non-invasive ventilation (NIV) success but further study has been limited. We investigated the relation of timing of respira- tory acidaemia to NIV outcomes in ECOPD. Of importance, in both participating hospitals few patients are denied NIV on grounds of assumed futility. Methods A retrospective cohort of consecutive, unique patients, hospitalised with a primary diagnosis of ECOPD were identified from known cohorts, hospital coding records coding and ventilation service records. Other selection criteria included: age 35+years, smoking history 10+pack years, air- flow obstruction on spirometry; received assisted ventilation (either NIV or invasive) for acidaemic respiratory failure; and absence of comorbidity expected to limit survival to <12 months (principally metastatic cancer). Population descriptors, ventilation details and outcome data were collected from notes and electronic records. Results 489 consecutive patients were identified between 30/ 11/08 and 19/5/13; 124 (25.4%) died in-hospital. Median time to ABG prompting ventilation was 2 hour 42 m (IQR 1 hour 2m – 15 hour 28 m). Most (94.5%) received NIV alone, 5.5% received invasive ventilation (+/-NIV). In patients requiring assisted ventilation within 12 hours of admission, mortality was 18.3% (65/356), compared to 44.3% (59/133) in all those treated after 12 hours (p<0.01). Discussion Our study has several strengths including objective confirmation of COPD, capture of consecutive patients and liberal NIV use. Compared to patients with respiratory acidea- mia on or shortly after admission, later development was asso- ciated with progressively higher mortality. 12 and 48 hours were identified as clinically useful thresholds. Of note, lower pH, FEV1 and prior LTOT prescription do not account for worse outcome. Older age, greater comorbidity, frailty (eMRCD5b: requiring help washing and dressing when recently stable), and a strong trend towards increasing pneu- monia are associated with later development of acidaemia. Timing of acidaemia should be considered when deciding whether to initiate NIV. Abstract S135 Table 1 Key population descriptors and inpatient mortality grouped by timing of acidaemia onset Time Up to 12 hours 12–48 hours >48 hours N 356 69 64 Age 71.9 (9.9) 73.8 (10.0) 76 (9.8) * FEV1% 37.1 (15.6) 42.8 (18.9) * 38.1 (17.4) BMI 24.9 (7.5) 24.7 (5.9) 22.8 (7.2) † LTOT 109 (30.6%) 18 (26.1%) 16 (25.0%) eMRCD eMRCD 5a eMRCD 5b 5a (4–5a) 120 (33.7%) 63 (17.7%) 5a (4–5a) 25 (36.2%) 13 (18.8%) 5a (4–5b) † 19 (29.7%) 24 (37.5%) * Charlson Index 1 (1–2) 2 (1–3) 2 (1–3) * Consolidation at NIV 157 (44.1%) 38 (55.1%) 36 (56.3%) pH at NIV 7.23 (0.09) 7.26 (0.08) † 7.26 (0.08) † PCO2 at NIV 10.3 (2.5) 10.0 (2.4) 9.3 (1.8) * Peak Pressure (IPAP) 20 (18–22) 19 (17–20) 18 (16–20) † Inpatient Mortality 65 (18.3%) 22 (31.9%) † 37 (57.8%) † t-test, Mann Whitney U or c 2 test for parametric, non-parametric and categorical data respectively. *p<0.05; †p<0.01: compared to “Up to 12 hours group” S136 LUNG PROTECTIVE MECHANICAL VENTILATION FOR ACUTE RESPIRATORY FAILURE IS NOT BEING IMPLEMENTED IN UK CLINICAL PRACTICE 1 R Samanta, 1 A Dixit, 2 S Harris, 2 NS MacCallum, 2 DA Brearley, 3 PJ Watkinson, 4 A Jones, 5 S Ashworth, 4 R Beale, 5 SJ Brett, 3 JD Young, 2 M Singer, 1 C Summers, 1 A Ercole. 1 Dept of Medicine, University of Cambridge School of Clinical Medicine, Cambridge, UK; 2 Bloomsbury Institute of Intensive Care Medicine, University College London, London, UK; 3 Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK; 4 Department of Intensive Care, Guy’s and St Thomas’ NHS Foundation Trust, London, UK; 5 Centre for Perioperative Medicine and Critical Care Research, Imperial College Healthcare NHS Trust, London, UK 10.1136/thoraxjnl-2017-210983.142 Introduction The benefits of lung protective ventilation have been replicated in multiple trials. 1,2 However, we suspected that adherence to this standard of care remained poor. Using the NIHR critical care Health Informatics Collaborative (ccHIC) database, we analysed data from 11 teaching hospital intensive care units (22 524 patient episodes) to investigate real-world clinical practice. Methods 1248 patient episodes, where ventilation was contin- ued for 48 hours, with 232,600 hours of concurrent mechanical ventilation and blood gas data were identified as suitable for analysis. Short gaps in ventilation (<6 hours) were imputed based on the median of nearest known values, and Spoken sessions Thorax 2017;72(Suppl 3):A1–278 A81 on June 26, 2020 by guest. Protected by copyright. http://thorax.bmj.com/ Thorax: first published as 10.1136/thoraxjnl-2017-210983.142 on 15 November 2017. Downloaded from