EDITORIAL

Preventing intercostal vessel trauma: Ultrasound to the rescueonce more?

Key words: artery, diagnosis, haemorrhage, intercostal,ultrasound.

Chest tube placement is an essential part of medicalcare for many patients with pleural disease. Yet thisprocedure is fraught with risk,1 for it involves the pen-etration of a major body cavity, frequently by non-surgical personnel, often in a non-theatre setting andusually without general anaesthesia. Thus, chestdrainage should only be performed by trained opera-tors under prescribed conditions.2

Until recently, a significant hazard was the ‘blind’nature of the procedure. Even experienced cliniciansare unable to distinguish between dullness on percus-sion due to fluid and dullness due to solid organs. Inone study, 10% of clinically identified sites for pleuralintervention would have led to organ perforation.3

Thankfully, the advent of bedside ultrasound guid-ance has ameliorated this risk.4 Ultrasound guidanceis now recommended whenever chest tubes areinserted to drain fluid.5 It is possible for clinicians toperform ultrasound-guided drainage procedures assafely as radiologists.6

Although ultrasound guidance has reduced the riskof organ perforation, other problems have yet to beaddressed. The risk of intrapleural haemorrhage fromintercostal artery trauma at the time of chest tubeinsertion remains a significant concern. Such bleed-ing can be uncontrollable due to a combination ofnegative intrapleural pressure, a large potential spacein the pleural cavity and inaccessibility to externalcompression.

The intercostal artery is at greatest risk within 6 cmof the spinal column, where its course is oftenexposed within the intercostal space. This has beenconfirmed by historical and modern cadaveric dissec-tion,7 computed tomography (CT) studies8 and thora-coscopic observation.9 Current guidelines thereforewarn against the posterior approach for chest tubeinsertion, urging instead for mid-axillary placementwithin the ‘safe triangle’, where the intercostal arteryis more likely to be shielded by the inferior edge of itscorresponding rib.5 They also advise that chest tubesshould be placed at the superior rib border, away fromthe main intercostal vessels. However, these measurescan neither predict anatomical variation nor antici-pate the path of an additional collateral intercostalartery that may run inferiorly within the space.8

So, is there a more reliable method of preventingintercostal vessel injury? The current issue of Respirol-ogy features a novel study addressing this very ques-tion. Salamonsen et al.10 assess the accuracy of

ultrasound to detect an exposed vessel in the inter-costal space, potentially furnishing clinicians with themeans to avoid intercostal artery laceration. Fiftypatients underwent ultrasound examination at threeintercostal locations. Radio-opaque markers werethen placed at the sites of ultrasound examination toenable immediate verification by the gold standard ofchest CT.

The authors should be congratulated on a numberof fronts. They have performed the first prospectiveinvestigation in the hands of pulmonary physicians toexamine the sensitivity and specificity of ultrasoundfor detection of intercostal vessels. They also ensuredthat every patient received both ultrasound and CT,and that each test was interpreted blinded to theresults of the other. Finally, they measured other clini-cally relevant outcomes, such as the time taken toidentify a vessel on ultrasound, the test characteristicsof portable versus high-end ultrasound machines andthe performance of a chest physician compared withan experienced sonographer.

The study’s primary objective was to determine thesensitivity, specificity and negative predictive value ofultrasound to detect an exposed vessel. While sensi-tivity was reasonably high (0.86), specificity and nega-tive predictive value were poor (0.30 and 0.27,respectively). Interestingly, the percentage of positiveultrasounds (when an exposed vessel was detected)was not significantly greater in CT positive cases thanin CT negative cases (0.86 vs 0.75, two-sample test ofproportions; P = 0.08). In other words, there is a pos-sibility that the study’s results arose by chance andultrasound may have no ability to discriminatebetween exposed and shielded vessels.

The study does have some limitations that mayhave impacted on test performance. These includethe different patient positions employed for ultra-sound and CT, and the predominantly posterior scan-ning locations chosen by the investigators. Becausevessels located posteriorly are more often exposed inthe intercostal space, very few vessels in the studywere categorized as ‘hidden’ on CT, lowering thenumber of true negatives in relation to false negativesand depressing the negative predictive value.

The authors responded to the low diagnostic testperformance by undertaking a post hoc analysis basedon reclassifying vessels seen on ultrasound. Their new‘protected’ category includes vessels determined onultrasound to lie within the upper 15% of the inter-costal space, which would previously have been con-sidered ‘exposed’. This modified analysis may bescientifically justified because false positive ultra-

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© 2013 The AuthorsRespirology © 2013 Asian Pacific Society of Respirology

Respirology (2013) 18, 891–892doi: 10.1111/resp.12136

sounds in the initial analysis could have arisen due toinadvertent upward tilting of the ultrasound probeduring scanning, bringing into view vessels actuallyhidden behind a rib on CT.

The authors’ modification in diagnostic classifica-tion dramatically boosted specificity for ultrasounddetection of a vulnerable vessel to 0.97 (and sensitiv-ity to 0.95). However, we would caution that explora-tory post hoc analyses are notoriously prone to bias,and this potentially important result will remainspeculative until their new diagnostic threshold for aprotected vessel is independently validated as a pre-specified outcome in another prospective study.

In conclusion, the work by Salamonsen et al. pro-vides important methodological insights for futureresearch in this area. Their work suggests that ultra-sound may be able to detect an exposed intercostalartery, especially one that is vulnerable to iatrogenicdamage during intervention. However, this premisemust be confirmed prospectively in a robustlydesigned study. The present study has not only high-lighted important design issues for this research area,but also equipped future investigators with the meth-odology and outcomes needed to conduct a trulypractice-changing study.

Mark Hew, MBBS, PhD, FRACP1 andNajib Rahman, DPhil, MSc, MRCP2

1Department of Allergy, Immunology & RespiratoryMedicine (AIRMED), The Alfred Hospital, Prahran,Victoria, Australia, and 2Oxford Respiratory Trials

Unit, Oxford Centre for Respiratory Medicine,Oxfordshire, UK

REFERENCES

1 Harris A, O’Driscoll BR, Turkington PM. Survey of major compli-cations of intercostal chest drain insertion in the UK. Postgrad.Med. J. 2010; 86: 68–72.

2 Hooper CE, Lee YC, Maskell NA. Setting up a specialist pleuraldisease service. Respirology 2010; 15: 1028–36.

3 Diacon AH, Brutsche MH, Solèr M. Accuracy of pleural puncturesites: a prospective comparison of clinical examination withultrasound. Chest 2003; 123: 436–41.

4 Hew M, Heinze S. Chest ultrasound in practice: a review of utilityin the clinical setting. Intern. Med. J. 2012; 42: 856–65.

5 Havelock T, Teoh R, Laws D et al.; BTS Pleural Disease GuidelineGroup. Pleural procedures and thoracic ultrasound: British Tho-racic Society Pleural Disease Guideline 2010. Thorax 2010;65(Suppl. 2): ii61–76.

6 Rahman NM, Singanayagam A, Davies HE et al. Diagnostic accu-racy, safety and utilisation of respiratory physician delivered tho-racic ultrasound. Thorax 2010; 65: 449–53.

7 Wraight WM, Tweedie DJ, Parkin IG. Neurovascular anatomy andvariation in the fourth, fi fth, and sixth intercostal spaces in themid-axillary line: a cadaveric study in respect of chest draininsertion. Clin Anat 2005; 18: 346–9.

8 Helm EJ, Rahman NM, Talakoub O et al. Course and variation ofthe intercostal artery by CT scan. Chest 2011; 143: 634–9.

9 Rahman NM, Ali NJ, Brown G et al.; British Thoracic SocietyPleural Disease Guideline Group. Local anaesthetic thoracos-copy: British Thoracic Society Pleural Disease Guideline 2010.Thorax 2010; 65(Suppl. 2): ii54–60.

10 Salamonsen M, Dobeli K, McGrath D et al. Physician-performedultrasound can accurately screen for vulnerable intercostal arter-ies prior to chest drainage procedures. Respirology 2013; 18:942–7.

Editorial892

© 2013 The AuthorsRespirology © 2013 Asian Pacific Society of Respirology

Respirology (2013) 18, 891–892