“Should the ultrasound probe replace your stethoscope?”: a review of the SICS-I sub-study comparing lung ultrasound and pulmonary auscultation in the critically ill
There is no doubt that Critical Care Ultrasound and Echocardiography have greatly influenced our practice of intensive care medicine [1-3]. Their role in the future may even evolve to be indispensable . In this context, Cox et al compared lung Ultrasound (LUS) to pulmonary auscultation and concluded a poor correlation (κ statistic 0.25) . The authors elaborated further the question whether the US probe will eventually replace the stethoscope.
The work focused only on pulmonary oedema and was a sub-study of the “Simple Intensive Care Studies-I (SICS-I)”. In comparison to LUS, the overall diagnostic accuracy of auscultation was 67% (98.5% CI 64–70), but was marginally better at 69% in the non-mechanically ventilated subgroup (p < 0.001). LUS was not feasible in 15% of the patients (n=149).
Based on previous studies showing LUS superiority, the authors rejected the use of Chest X-ray as a “gold standard” . They conducted a sensitivity analysis which confirmed poor correlation between CXR and LUS (κ statistic 0.12). There was a 4-hour lag on average between performing LUS and CXR.
STUDY STRENGTHS & LIMITATIONS
1- Prospective Pre-registered study with pre-defined statistical analysis.
2- The authors did admit many limits; most importantly the non-standardised auscultation performed by less expert staff and non-blindness to the diagnosis.
1- Generalisability is a main issue due to multiple factors: Single centre, one pathology studied, examiner’s expertise and auscultation methodology. Also, the applicability in resource limited settings may prove challenging.
2- No reference method means auscultation accuracy cannot be precisely determined.
3- The title of the paper is debatable and does not reflect the conclusion. On top of the limits mentioned by the authors, LUS was not feasible in 15% of the cases, leaving no bedside alternative apart from clinical examination and CXR.
4- Barriers for LUS had not been mentioned: light condition, bed space, combative patients, position and exposure, to mention but a few. To note, a recent work showing poor to moderate reproducibility for B-lines using LUS .
5- The usual limits and bias of observational study.
TAKE HOME MESSAGE
The study raises a point about how technology can challenge traditional medicine in Intensive Care Medicine. While the title is attractive, it may become a matter of debate for some time. As such, the study can represent a step forward for the role of Critical Care Ultrasound and does require further research.
This article review was prepared and submitted by Dr Ashraf Roshdy, Whipps Cross University Hospital – Barts Health NHS Trust, London, United Kingdom, on behalf of the ESICM Journal Review Club.
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5- Cox EGM, Koster G, Baron A, Kaufmann T, Eck RJ, Veenstra TC et al. Should the ultrasound probe replace your stethoscope? A SICS-I sub-study comparing lung ultrasound and pulmonary auscultation in the critically ill. Crit Care. 2020;24(1):14.
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7- Haaksma ME, Smit JM, Heldeweg MLA, Pisani L, Elbers P, Tuinman PR. Lung ultrasound and B-lines: B careful! Intensive Care Med. 2020 Jan 29. doi: 10.1007/s00134-019-05911-8