Written by Dr Cian McDermott, Emergency Physician & Director of Emergency Ultrasound Education, Mater University Hospital, Dublin, Ireland | @cianmcdermott
Reviewed by Dr Rachel Liu, Emergency Physician & Director of Point-of-Care Ultrasound Education, Yale School of Medicine, New Haven, CT USA | @rubbleEM
Whether you are the ultrasound educational lead for your hospital/ trust, a routine user or interested novice we’re sure that you will have seen lots of exciting data on twitter (using the #POCUSforCOVID hashtag), suggesting that USS has a role in the diagnosis and perhaps prognosis of Covid-19. Maybe you’re self isolating right now and looking to get trained up on this new disease ready to return to the hospital soon. Like you, we were excited to read how Lung ultrasound (LUS) can show early changes that may be as reliable as CT and probably better than CXR. You may even own one of the new handheld ultrasound devices and spend your quiet hours scanning your own chest in less than the time it takes to boil the kettle, and then posting the results on Instagram (Ed – we know who you are).
We are USS enthusiasts, we openly admit that but we are also evidence based emergency physicians, so before you just accept our word that USS is a revolution in Covid-19 diagnostics, we need to look at. the evidence, the practicalities and the experience of those who are already using it in practice. Let’s examine the evidence.
What we know about Lung Ultrasound so far…
- LUS is established and proven for the diagnosis of acute respiratory failure however the evidence is rapidly evolving regarding LUS in COVID19
- Lung US (LUS) shows characteristic changes in COVID19 infection, similar to other patterns of viral pneumonitis. Focal B lines, small sub-pleural consolidations and pleural line thickening may occur
- CXR is a poor screening test for COVID19 while CT is best used for complications arising from COVID infection
- Lung US may be used as a decision support and risk stratification tool. It is quick to perform, may be done at the bedside and adds much to the evaluation of your patient
- Balance this with the exposure to HCW by performing this test and the expertise required to interpret the images
Do we need LUS – what’s the evidence?
Can we use CXR to diagnose COVID19? What’s all the fuss about?
Plain chest radiography is recognised as an inferior diagnostic test compared with both CT and LUS for the diagnosis of acute respiratory failure and may miss up to 40% of confirmed COVID19 cases (Guan et al. 2020)
Virus particles are small and lodge in terminal alveoli close to the pleural interface and these peripheral changes are readily seen using lung US (“A Preliminary Study on the Ultrasonic Manifestations of Peripulmonary Lesions of Non-Critical Novel Coronavirus Pneumonia (COVID-19)” 2020).
Lung abnormalities on CT may preceed physical symptoms of COVID and this technology has been used extensively in the management of the early outbreak in China (Peng et al. 2020).
However CT is a finite resource, decontamination protocols are not well defined and are time-consuming. It may be a perilous journey to CT with a critically-ill patient and this technology should be reserved for complications of COVID19 infection, to rule out other causes of illness such as pulmonary embolism and for procedural performance and confirmation.
LUS has been shown to be comparable to CT for COVID19 detection (Huang et al., n.d.; Peng et al. 2020). LUS may be more feasible and practical alternative since it is a bedside test, quick to repeat, is low cost and avoids radiation exposure (Peng et al. 2020).
Should we introduce LUS to our ED?
Right now before the COVID19 surge phase, it is reasonable to use traditional imaging modalities such as CXR bearing in mind the limitations of this diagnostic test
If your ED struggles with capacity, you will need a quick, reliable bedside test to aid risk stratification and prognostication of COVID19 disease burden. In this situation, LUS may be the best option
It is neither resource nor time intensive to achieve basic competency in LUS techniques and your ED should consider upskilling key personell (Arbelot et al. 2020). The global FOAMed community provides easy access to many web based learning packages to aid a new learner, see section below
However any bedside procedure may result in increased potential for COVID19 exposure for HCWs that are invaluable to your healthcare system.
Clinical findings – what should I look for?
Remember how normal lung sonoanatomy appears?
At the anterior chest surface we expect to see
- Pleural line is thin, sharp and smooth and lies inferior to and bordered on each side by dark rib shadows. A lines appear inferior to the pleural line in normal lung
At the posterior chest surface we expect to see
- lung curtain move with respiration across at the liver/ spleen-diaphragm interface
Abnormal LUS findings in COVID19 (Huang et al., n.d.)
- B-lines are short-path reverbation artefacts that are found in many pathological and non- pathological states. In COVID19 these may appear in characterisitc focal, multifocal and confluent patterns
- Small sub-pleural consolidation may be seen. These are small hypoechoic areas inferior to the pleural line
- In COVID19, a pleuropathy develops and this becomes thickened and develops an irregular appearance. You may also notice skip lesions – normal pleura alongside thickened pleura with associated B- lines
- Bilateral basal consolidation with dynamic bright air bronchograms may be present.
- Large volume pleural effusions are uncommon – if you see this, consider other pathology
Videos courtesy of Dr Justin Kirk Bayley, Consultant Anaesthetist and Intensivist, Royal Surrey County Hospital, Guildford, UK | @PARADicmSHIFT
If you see A lines, significant lung involvement is unlikely
In early or mild COVID19, B lines predominate and you may see small sub-pleural consolidation
As disease progresses B lines increase in number and occur closer together as well at sites distant to the lung base. These patients may benefit from increased level of positive end expiratory pressure
Severe COVID19 will manifest as lung consolidation posteriorly and at the lung bases. There may be secondary bacterial infection. These patients may benefit form early aggressive ventilation and proning strategies in the intensive care unit
Dr Yale Tung Chen (@yaletung) is an Emergency Physician in Madrid, Spain that has journaled his sonographic lung images during the course of his COVID19 infection
Primary sources like this on FOAMed are an invaluable source of learning as COVID19 evolves
There is evidence that lung abnormalities may preceed clinical symptoms therefore any abnormal B line pattern may be significant (Peng et al. 2020). A small number of cases have emerged that show CT findings despite a negative PCR test for COVID19 (Xie et al. 2020). It is reasonable to assume that LUS would also have been abnormal in these cases therefore typical sonographic findings are a powerful indicator of COVID19 infection
Personal experience In our ED, we have noticed that dyspneic patients are isolated early and funnelled down the COVID pathway. ‘COVID bias’ may result in late diagnosis of other common causes of acute dyspnea. Early focussed US at the bedside may prevent this.
For example in acute pulmonary oedema, the B line pattern comes from a smooth, thin pleural line whereas in COVID19 we may notice a moth-eaten appearance to the pleural line and areas of B-lines interspersed with normal lung . The key to differentiating these conditions lies in a careful examination of the pleural line
Also be careful not to overcall your findings – LUS becomes more difficult to interpret in the presence of chronic lung conditions such as COPD and pulmonary fibrosis
How should I scan the lungs?
In general, principles and techniques of lung US are the same regardless of your patient’s COVID infection risk
- Linear transducer is better for visualising superficial structures. This may be used to view pleural line thickening, small superficial effusions, skip lesions and B-lines
- Curvi-linear transducer may be better for posterior pathology such as consolidation, hepatization and bronchograms
- Pick a single transducer to avoid extra contamination and time
Hold the transducer close to the surface using the index finger and the thumb. Fingers of the insonating hand should be spread out to stabilise the transducer and hand position. Brace the insonating hand against the surface being scanned. These techniques will facilitate small adjustments of the transducer and will allow greater detail to be shown on the screen
Traditional lung scan protocols suggests evaluation of several anterior and lateral zones often neglecting posterior zones
Chinese authors have described COVID19 pathology using a 12-zone protocol (Huang et al., n.d.). It is possible to perform a study of 6 chest areas in less than 2 minutes (Cox et al. 2020) and a rapid focused LUS protocol may be the best approach. The Intensive Care Society have endorsed this approach as part of the FUSIC lung module (Advanced Solutions International, Inc n.d.)
Modifications to further minimise risk
Since COVID is found in postero-basal zones it may be more useful for the point of care provider to
- start by scanning the patient’s back using linear transducer in vertical orientation
- start medial to the scapula sliding inferior to the lower rib border and moving laterally towards the traditional PLAPS point
- evaluate each rib space first with the transducer in a vertical (crossing the ribs) orientation
- evaluate each rib space again with the transducer in a horizontal orientation (between the ribs) especially if any abnormalities are seen
- finish by scanning lateral zones of the lung in the mid-axillary line
- Scanning at the intercostal space with transducer in a transverse orientatation between the ribs (rather than across the ribs) allows finer details to be seen eg thickened pleural line, sub-pleural consolidation or small effusions
- Scan with patient-facing away from the operator to minimize healthcare worker exposure to COVID. The US machine may be less contaminated if placed behind the patient
- Be careful to scan with the transducer perpendicular to the pleural line rather than the patient’s skin surface. If the pleural line is indistinct then this may be interpreted as a false positive thickened pleural line. A sharp pleural line may be found by fanning the transducer face towards or away from the midline
LUS Decision Algorithm in COVID19
There is no single best use diagnostic algorithm for LUS in COVID19. Your workflow will depend on what patients you see and how your have organised your Emergency Department, your access to PCR testing as well as advanced lung imaging. Your use of LUS may change depending on the phase of the COVID19 surge (Soldati et al., 2020)
You may decide to use LUS in your triage area to identify normal lung (A-line pattern) and patients that are suitable for discharge and self-isolation
You may decide to defer scanning the sickest patients sice they are likely to progress to advanced imaging in a more controlled settings. Bear in mind that US may dentify other non-COVID pathology. Your intensive care colleagues may also use LUS to guide ventilation strategies in this group
The intermediate group of COVID patients (non-critical care, not suitable for discharge) may benefit most from LUS
- look for B-line pattern progression from focal to confluent indicating worsening disease. These findings may preceed hypoxia
- consider CT thorax for patients that show worsening LUS findings. LUS may be useful to help ration and/ or determine optimum timing of CT imaging
It is important to exercise caution in this intermediate patient group since LUS may show sub-pleural consolidation and multiple B lines patterns yet the patient may not be hypoxic.
LUS should be thought of as a dynamic data point as part of a clinical decision-making tree
Personal experience In our hospital, we have subdivided our COVID Respiratory Area into
- COVID RED – requires critical care intervention
- COVID ORANGE – oxygen requirement, not critical illness
- COVID GREEN – no oxygen reuirement
- Forward streaming zone – to govern flow of patients to these areas
In the pre-surge phase, we anticipate that LUS will prove most useful in our triage tent to identify clinically well patients and also in the COVID ORANGE zone to help risk stratify patients that are likely to progress to critical care
Cleaning & Disinfection
US machine decontamation strategies are vitally important to prevent patient-to-patient COVID19 transmission and may be the main reason that you experience push back from your infection control team
There is no single best approach but these are a few things to bear in mind to keep both you and your equipment free from COVID contamination
- place a dedicated machine in the COVID ‘hot zone’
- wear gloves when handling machine from cubicle to cubicle
- cover machine with large plastic sheet or part of a gown
- cover entire transducer with plastic sheath or cover non essential parts with drapes
- strip away all ECG leads, gel bottles extra buckets, straps from your machine
- clean cables, screen, legs, wheels
- use single-use gel packets rather than gel bottles
- use a touchscreen device to minimise keyboard, knob handling handline
- wait for up to 3 minutes ‘drytime’ after using disinfectant wipes before you use the machine again
- use your machine in battery mode – precharge and remove all electrical charging cable
- use a handheld device eg Lumify or Butterfly systems with the advantage that images are uploaded to the cloud for remote reviewing
Much of this material is ‘crowdsourced’ from expert user groups and is evolving with the disease pattern. There are many practical and innovative approaches about how to protect and decontaminate the US systems seen on twitter
Personal experience In our ED, we use a dedicated mobile touch screen US system in the COVID RED resuscitation area as well as the COVID ORANGE isolation area. I have been using a curved linear probe thus far. We have started using disposible packets of coupling gel per patient instead of gel bottles. No educational or unnecessary scans are performed. Machines are cleaned by the user following each patient encounter with non-alcohol wipes approved by the manufacturer. Transducers are sheathed in plastic covers for invasive high risk procedures such as vascular access, paracentesis or thoracocentesis
Now for some COVID19 cases….
These are examples of how we see USS being used during the pandemic. They are vignettes to illustrate the points made above.
Case 1 A worried but well 35 male office worker has non-specific coryzal symptoms. He is afebrile, not hypoxic and has a dry cough. He wants to know if he has COVID19
In our Emergency Department, this patient will be streamed from our triage area with a mask to a dedicated ‘COVID Green’ assessment zone.
You scan his chest while wearing appropriate PPE and see an A-line pattern. There are minimal B lines present. You reassure him that while he may still have the condition, his lungs look unaffected. You usher him home without additional imaging, advise self isolation and ask him to return if his symptoms deteriorate
Learning point – consider the of use normal LUS in conjunction with other clinical features to risk stratify clinically well patients
Case 2 A 63 retired librarian presents to the ED feeling more dyspneic than usual. She has had a pacemaker fitted recently for sick sinus syndrome. She has oxygen saturations of 93% and is persistently hypotensive, 95/70mHg. You are worried that this lady may have early COVID19 and she is moved to your COVID-RED resuscitation area
As part of her resuscitation room evaluation, you scan heart and lungs. Parasternal long axis view shows a moderate sized pericardial effusion that appears to compress the right ventricular cavity in diastole – you are concerned about cardiac tamponade. LUS shows a scattered B line pattern with a smooth appearance of the pleural line
You alert the cardiology team and she is taken to the interventional suite – 300ml of frank blood is drained from her pericardial sac and haemodynamic parameters immediately improve. Full body CT shows no pulmonary signs of COVID19 and no malignancies are reported. Pacemaker wires had perforated the ventricle – this is likely to have been the cause of the effusion
Learning point – US should be used as part of a multi system evaluation in critically ill patients
Case 3 A 59 male arrives in respiratory distress – increased work of breathing, oxygen saturation of 75% on room air. He reports a dry cough and feeling feverish for the previous week. You are highly suspicious for COVID19 and alert the ICU team that this patient will need early respiratory support
LUS shows bilateral basal consolidation – confluent B lines, dynamic air bronchograms that signify severely impaired gas exchange. Focussed cardiac US shows grossly normal left ventricular function and a flat, underfilled IVC
Your patient is transferred to ICU and mechanical ventilation is initiated without delay
Learning point – use LUS to risk stratify disease burden and guide early airway and fluid management in COVID19 infection
Ultimately we all want to know if LUS can help with triage, risk stratification, disposition or treatment guidance in COVID19. Right now the answers are unclear but common sense seems to indicate ‘maybe’? This all should be weighed in the context of infection control practices and how we are managing in the phase before the surge
We still need to use ultrasound for things we use it for now, on people who might also have COVID19. When community transmission and the predicted surge occurs we will assume everyone with every complaint has COVID19. Then ultrasound will be needed more than ever….
More great learning resources….
This is my list of the best FOAMed LUS learning resources – compiled using #POCUSforCOVID
LUS learning resources
- Jacob Avila’s viral pneumonia video on coreultrasound.com
- Westernsono LUS video series
- Ultrasound Leadership Academy free Lung module
- Dr Elke Platz video https://vimeo.com/399493405/61220290e6
- FUSIC COVID19 resources including Lung ‘How to Scan’ video
Discussions about LUS in COVID
- Butterfly webinar
- UltrasoundGEL POCUS in COVID-19
- ACEP town hall LUS discussion
- UH Cleveland EM Residency videos
High yield twitter commentators
Advanced Solutions International, Inc. n.d. “FUSIC_Accreditation.” Accessed March 23, 2020. https://www.ics.ac.uk/ICS/FUSIC/ICS/FUSIC/FUSIC_Accreditation.aspx?hkey=c88fa5cd-5c3f-4c22-b007-53e01a523ce8.
Arbelot, Charlotte, Felippe Leopoldo Dexheimer Neto, Yuzhi Gao, Hélène Brisson, Wang Chunyao, Jie Lv, Carmen Silvia Valente Barbas, et al. 2020. “Lung Ultrasound in Emergency and Critically Ill Patients: Number of Supervised Exams to Reach Basic Competence.” Anesthesiology, January. https://doi.org/10.1097/ALN.0000000000003096.
Cox, Eline G. M., Renske Wiersema, Adrian Wong, Iwan C. C. van der Horst, Nora A. Spraakman, Jildau A. Meinderts, Justin D. Postma, et al. 2020. “Six versus Eight and Twenty-Eight Scan Sites for B-Line Assessment: Differences in Examination Time and Findings.” Intensive Care Medicine, March. https://doi.org/10.1007/s00134-020-06004-7.
Guan, Wei-Jie, Zheng-Yi Ni, Yu Hu, Wen-Hua Liang, Chun-Quan Ou, Jian-Xing He, Lei Liu, et al. 2020. “Clinical Characteristics of Coronavirus Disease 2019 in China.” The New England Journal of Medicine, February. https://doi.org/10.1056/NEJMoa2002032.
Huang, Yi, Sihan Wang, Yue Liu, Yaohui Zhang, Chuyun Zheng, Yu Zheng, Chaoyang Zhang, et al. n.d. “A Preliminary Study on the Ultrasonic Manifestations of Peripulmonary Lesions of Non-Critical Novel Coronavirus Pneumonia (COVID-19).”
Peng, Qian-Yi, Xiao-Ting Wang, Li-Na Zhang, and Chinese Critical Care Ultrasound Study Group (CCUSG). 2020. “Findings of Lung Ultrasonography of Novel Corona Virus Pneumonia during the 2019-2020 Epidemic.” Intensive Care Medicine, March. https://doi.org/10.1007/s00134-020-05996-6.
Poggiali, Erika, Alessandro Dacrema, Davide Bastoni, Valentina Tinelli, Elena Demichele, Pau Mateo Ramos, Teodoro Marcianò, Matteo Silva, Andrea Vercelli, and Andrea Magnacavallo. 2020. “Can Lung US Help Critical Care Clinicians in the Early Diagnosis of Novel Coronavirus (COVID-19) Pneumonia?” Radiology, March, 200847.
Soldati, G., Smargiassi, A., Inchingolo, R., Buonsenso, D., Perrone, T., Briganti, D. F., Perlini, S., Torri, E., Mariani, A., Mossolani, E. E., Tursi, F., Mento, F., & Demi, L. (2020). Is there a role for lung ultrasound during the COVID-19 pandemic? Journal of Ultrasound in Medicine: Official Journal of the American Institute of Ultrasound in Medicine. https://doi.org/10.1002/jum.15284