Lung POCUS for heart failure

30 Aug

By Nick Lim (EM Trainee, Ireland)

Most EM trainees who have done Level 1 Ultrasound training would be familiar with the use of Ultrasound in the detection of pneumothorax (sensitivity 86-98%). This compares very well to other established modalities like Chest x ray (Sensitivity 28-75%) and clinical exam (50%-60% sensitivity).

However, did you know that Lung Ultrasound can be used in the Undifferentiated dyspnoeic patient?

As a general rule, the sicker the patient, the more likely point of care ultrasound is going to be able to help guide you make a clinical decision that will improve a patients outcome.

The clinical conundrum that Ultrasound has helped me solve is differentiating Acute pulmonary oedema (CCF) vs Pneumonia vs Exacerbation COPD.

How good are Emergency Physicians at diagnosing CCF?

Multiple studies and meta analysis have shown that Emergency docs have at best a coin flip chance at diagnosing CCF in the ED.

– According to the PRIDE study (The N Terminal Pro BNP Investigation of Dyspnoea in the Emergency Department), EM Physicians missed 44% of CCF [2]

– According to another paper when the diagnosis was between CCF and COPD, EM Physicians were wrong 48% of the time! [3]

– Another paper would suggest that EM physicians would miss 33.5%, we are more likely to miss CCF if the patient has no history of CCF, a history of COPD and a normal or absent BNP [4]

The probe that you will want to use is the low frequency curvilinear probe.

Pic 1

Let’s divide the chest into Volpicelli’s 4 zones on each side.

Pic 2

With the probe marker facing cephalad, place the probe on the patients chest wall, you will be scanning each of the 4 zones.

Let’s talk CCF/pulmonary oedema vs CCF:

Presence of B lines in 2 of the 4 zones bilaterally would suggest a diagnosis of CCF. The positive likelihood ratio for this sonographic finding is 12, negative likelihood ratio is 0.06. We can use it to rule in or rule out CCF with the presence or absence of B lines bilaterally. [1]

B lines 2
multiple B lines on ultrasound
Pic 3
multiple B lines on ultrasound

How does this compare with the clinical signs of wheezing (COPD) and crackles (CCF)?

Wheezing for COPD has a positive likelihood ratio of 2.3-9 and a negative likelihood ratio of 0.7 – 0.8. We cannot rule COPD in or out just by the presence or absence of wheeze. [6], [7], [8]

Crackles for CCF has a positive likelihood ratio of 1.5 – 3.4 and a negative likelihood ratio of 0.5 – 0.61. We cannot rule in or rule out CCF with the presence or absence of crackles either! [2], [5], [9]

What about the Chest X ray?

Pic 4

For CCF – Positive likelihood ratio of 2.3 – 6.5 and a negative likelihood ratio of 0.43-0.95. Cannot use it to rule in or rule out CCF either. [5]

But hey, it’s all in the history and physical exam isn’t it?

Positive likelihood ratio – 0.6 – 4.0
Negative likelihood ratio – 1.19 – 0.4. [5]

No wonder we are so bad at diagnosing CCF. It is time to pick up the probe when faced with the undifferentiated dyspnoeic patient!

[1] : Point of care Ultrasonography for the diagnosis of Acute Pulmonary Oedema in Patients presenting with Acute Dyspnoea : A systematic review and Meta ananalysis. al Deeb M. et al Acad. Emerg Med. 2014 21(8). 843-852

[2] : The N-Terminal Pro BNP Investigation of Dyspnoea in the Emergency Department (PRIDE) Study – Am J Cardio 2005; 95:948-954

[3] : Diagnosing Acute Heart Failure in Patients with undifferentiated dyspnoea : A Lung and Cardiac Ultrasound (LuCUS) Protocol – Academic Emergency Medicine 2015 Feb: 22(2): 182-91. Russell FM et al

[4] : Clinical characteristics of Emergency department Heart failure patients initially diagnosed as non heart failure. BMC Emergency Medicine 2006. 6:11 Sean Collins et al

[5] : Diagnosing Acute Heart Failure in the Emergency Department : A systematic review and Meta analysis – Academic Emergency Medicine March 2016 23:3, 223-242. Martindale JL. et al

[6] Straus SE et al. Accuracy of history, wheezing, forced expiratory volume time in the diagnosis of COPD. J Gen Intern Med 2002;17(9):684-8

[7] Oshaug K et al. Should chest examination be reinstated in the early diagnosis of COPD? Int. J Chron Obstruct. Pulm Disease 2013;8:369-77

[8] Straus SE et al. The Accuracy of patient, wheezing and laryngeal measurements in diagnosing Chronic obstructive airway disease. CARE-COAD1 group. JAMA 2000; 283(14): 1853-57

[9] Wang CS et al. Does this dyspnoeic patient in the emergency department have congestive heart failure? JAMA 2005: 294(15): 1944-56

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