ORIGINAL ARTICLE Daily intra‐abdominal pressure, Sequential Organ Failure Score and fluid balance predict duration of mechanical ventilation Dushyant Iyer 1,2 | Leanne Hunt 1,3,4 | Steven A. Frost 1,2,3,4 | Anders Aneman 1,2 1 Department of Intensive Care, Liverpool Hospital, Sydney, Australia 2 South Western Sydney Clinical School, University of New South Wales, Sydney, Australia 3 Western Sydney University, Sydney, New South Wales, Australia 4 Centre for Applied Nursing Research, Ingham Institute of Applied Medical Research, Sydney, Australia Correspondence: Anders Aneman, Intensive Care Unit, Liverpool Hospital, SWSLHD, Locked Bag 7103, Liverpool BC, NSW 1871, Australia (Anders.Aneman@sswahs.nsw.gov. au). Background: Elevated intra‐abdominal pressure (IAP) is a common occurrence in mechanically ventilated patients in the intensive care unit (ICU). This study was undertaken to determine the relationship between IAP, pulmonary compliance and the duration of mechanical ventilation. Methods: A prospective study of 220 consecutively enrolled mechanically venti- lated patients admitted to a mixed surgical‐medical ICU in a tertiary referral hospital. The IAP was measured at least twice daily, benchmarked against consensus guide- lines. Dynamic pulmonary compliance was calculated together with admission Acute Physiology and Chronic Health Evaluation (APACHE III) score and daily Sequential Organ Failure Assessment (SOFA) score. Results: No relationship between highest IAP for the day and pulmonary compli- ance (P = 0.61) was found. For each 5 mm Hg increase in IAP, the risk of remaining intubated increased 19% (HR = 1.19, 95% CI: 0.98‐1.44); for each standard devia- tion increase in SOFA score (3.7 points), the risk of remaining intubated increased by 14% (HR = 1.14, 95% CI: 0.98‐1.33); and for each 1 L increase in fluid balance, the risk of remaining intubated increased by 11% (HR = 1.11, 95% CI: 1.04‐1.19). A nomogram was developed to predict the probability of extubation based on daily highest IAP for the day, SOFA score and fluid balance. Conclusion: IAPs did not correlate with pulmonary compliance in critically ill patients. Increased IAP was associated with a longer duration of mechanical ventila- tion. A nomogram integrating daily IAP, SOFA score and fluid balance may be used to predict the duration of mechanical ventilation. KEYWORDS intra-abdominal pressure, mechanical ventilation, prediction tool, pulmonary compliance 1 | INTRODUCTION Intra‐abdominal pressures (IAP) are frequently elevated in intensive care unit (ICU) patients 1-3 and are associated with impaired respira- tory mechanics as well as pathophysiological changes in many other systems leading to significant morbidity and mortality. 2,4 Specifically in relation to respiratory mechanics, an elevated IAP results in a cephalad shift of the diaphragm, reduced intra‐thoracic volume and increased intra‐thoracic pressure. 5 The consequent atelectasis, reduc- tion in functional residual capacity, increased physiological dead space and reduction in pulmonary compliance may initiate or exacer- bate ventilation‐perfusion mismatch leading to progressively severe hypoxaemia, hypercarbia and necessitate increased ventilatory support. 6 Received: 29 October 2017 | Accepted: 7 June 2018 DOI: 10.1111/aas.13211 Acta Anaesthesiol Scand. 2018;1–7. wileyonlinelibrary.com/journal/aas © 2018 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd | 1