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Respiratory critical care
P66 Inter-observer reliability of ultrasound to measure rectus femoris cross-sectional area in critically ill patients
  1. B Connolly1,2,
  2. Z Puthucheary1,2,3,
  3. H Montgomery3,
  4. J Moxham1,
  5. N Hart1,2
  1. 1Department of Asthma, Allergy & Respiratory Science, Division of Asthma, Allergy and Lung Biology, King's College London, London, UK
  2. 2Guy's & St Thomas' NHS Foundation Trust and King's College London, National Institute of Health Research Comprehensive Biomedical Research Centre, London, UK
  3. 3Institute of Health and Human Performance, University College London, London, UK

Abstract

Introduction Ultrasound is a relatively simple, non-invasive, non-irradiating effort-independent tool to measure quadriceps rectus femoris cross-sectional area (RFCSA) in critically ill patients. We investigated the inter-observer reliability of the technique to validate its clinical utility in this group of patients.

Methods Critically ill patients either in, or within 48 h discharge from, the Intensive Care Unit (ICU) underwent measurement of RFCSA using real-time B-mode ultrasonography using an 8MHz 5.6 cm linear transducer (PLM805, Toshiba Medical Systems Ltd, Crawley, UK) at a distance three-fifths from the anterior superior iliac spine to the superior patellar border. Where complete visualisation of RFCSA was not possible at this point, a more distal point of 2/3 of this distance was used. Ultrasound measurements were performed in turn by two critical care clinicians trained in ultrasound in a random order. The average of three consecutive measurements within 10% was taken as RFCSA for each patient. Both clinicians were blinded to the results of the other.

Results 24 patients had RFCSA measurements performed using ultrasound (M:F 14:10; mean age 55.3±20.1 years). Inter-observer reliability was assessed by considering the level of agreement between RFCSA measurements for each patient between the two clinicians using intra-class correlation coefficients (ICC) adopting a two-way, random effects model for absolute agreement. An ICC of 0.99 (95% CI 0.97 to 0.99) was observed. Abstract P66 Figure 1 shows RFCSA images from both clinicians for one patient.

Abstract P66 Figure 1

Ultrasound images from each clinician for one patients; RFCSA outlined in blue.

Conclusion These data demonstrate high levels of inter-observer reliability between two trained critical care clinicians using ultrasound as a measurement technique for RFCSA in critically ill patients. RFCSA can be used as a novel, reproducible technique to track the trajectory of muscle loss in critically ill patients.

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