Jacob Finkle, DO | EM PGY 4
The Idea
Ultrasound is a known and proven useful commodity in the Emergency Department. It’s ability to rapidly diagnose and decrease length of stay in the Emergency Department is proven. Pre-hospital US is considered one of the top five research priorities according to the opinion of consensus meeting of a European expert panel to identify which US examinations can be reliably transferred to the pre hospital setting. Lung US has the ability to rapidly identify the lung profile - the identification of, interstitial edema, pleural effusions and the diagnosis of pneumothorax. Given that a rapid two point technique is often sufficient to rule in or rule out lung pathology, the use of Lung US could be extremely useful in the pre-hospital setting.
The Study
The study was a case controlled study in the pre hospital emergency setting in Italy performed between January 2016 and December 2016. The area included a major emergency department with 35,000 visits and a minor emergency department with 6,000 visits. Each of these hospitals had an emergency physician led advanced life support ambulance. The larger hospital’s ambulance contained a portable US sonosite. The smaller hospital was the control. The inclusion criteria was severe dyspnea as prevalent symptom most likely caused by CHF or COPD exacerbation and pulse oximetry was required to be less than 90%. The exclusion criteria were other causes of respiratory failure and patients less than 18 years old. Lung US was performed after clinical exam with a rapid two point technique in the upper anterior and basal lateral areas. The type of lung profile was recorded as type A - dry lung or type B - wet lung and the presence was noted as well. An interstitial syndrome was defined by the presence of > 3 B lines between two ribs in two or more regions bilaterally. The convex probe was used using the same US device. Sometimes a linear probe was used. In hospital assessment included a PE, lab work, blood gas, CXR, US, cardiac ECHO, and IVC evaluation. The in-hospital lung US was blinded with respect to the pre-hospital one and was performed early upon arrival. The study aimed to evaluate the feasibility of pre-hosptial lung US and improvement of both pharmacological and oxygen administration in the ambulance and of the blood gases analysis at arrival to the ED. The hospitalization rate and time spent in the ED between the two groups was also evaluated.
The Findings
A total of 30 patients were recruited affected by non traumatic respiratory failure. There were 12 subjects whose respiratory failure were caused by CHF and 18 by COPD who underwent US management. This was compared to 30 other subjects managed without ultrasound. The characteristics of the groups were all similar in terms of age, gender, type of respiratory failure, and pulse ox value. Pre hospital lung US was accurate for identifying the correct lung profile. B lines had a high sensitivity (100%) and specificity (94.4%), a high PPV and NPV (92.3 and 100%) for CHF. Pleural effusions diagnosis was not as accurate as B lines for CHF - sensitivity 83%, specificity 58.3 %, PPV 75%, NPV 70%. The number of patients who received an appropriate pharmacological treatment was higher in the US group, especially in those who were diagnosed with lung group A - dry lung indicating non cardiogenic cause of respiratory failure. The mean dose of furosemide was significantly lower than those in the non US group and those diagnosed with lung group B - wet lung the mean dosage of furosemide was large than the US group. Steroid administration was comparable between A and B lung groups. CPAP was used more in patients with an A profile and employed more in the US group. Blood gases analysis was not significantly different between the groups, nor were there any significant differences between the other lab work. The hospitalization rate was comparable between the 2 groups, however there was a reduction in overall time spent in the ED by the US group but the data didn ot reach a full statistical significance.
The Takeaway
Ultrasound in the pre-hospital setting has great potential and utility. Specifically relating to lung US it is easy and feasible. The learning curve is rapid. The differentiation between COPD and CHF can easily be made with the use of US and can help shed light on the etiology of the undifferentiated respiratory distress, potentially decrease harmful doses of non indicated medications in the field and reduce overall time spent in the ED. The study was small but promising, however larger studies should be performed to establish use of US in the pre hospital setting.