Prehospital Lung Ultrasound: Impact on Diagnosis and Management in Patients with Acute Heart Failure

Abstract

Background/Objective: In the United States, one million hospitalizations occur each year due to acute heart failure (AHF), with a one-year mortality rate of 27%. Recent literature suggests that early diagnosis and treatment is associated with improved prognosis. We investigated the diagnostic accuracy of prehospital paramedic-performed lung ultrasound (LUS) and its impact on initial treatment of patients with AHF.
 Methods: Paramedics, previously trained in LUS, performed a 4-zone LUS protocol to evaluate for the presence or absence of pulmonary edema. Per protocol, presence of bilateral B-lines was diagnostic of AHF and treatment included nitroglycerin. Inclusion criteria were patients (>18 years old) with shortness of breath and at least one of the following: bilateral lower extremity edema, orthopnea, wheezing or rales on auscultation, increased work of breathing, tachypnea (RR>20) or hypoxia (oxygen saturation <92%). Patient data was collected in the hospital setting and evaluated by 2 separate physicians to determine final diagnoses of AHF. Paramedic data were analyzed for LUS image quality, accuracy of AHF diagnosis, and prehospital treatment.
 Results: Prehospital LUS was performed on 27 patients meeting inclusion criteria. Diagnostic accuracy for AHF yielded a sensitivity of 66.7% (95% CI 29.9%-92.5%) and specificity of 100% (95% CI 81.5%-100%). Of the 9 patients with AHF, 3 were not correctly identified despite having bilateral B-lines on LUS and 3 (33%) received prehospital nitroglycerin. Median LUS image quality was 4 (range 3-5) on a 5-point scale.
 Conclusion: Paramedic performed LUS was highly specific and moderately sensitive for the diagnosis of AHF, which is an improvement over diagnostic accuracy without the use of LUS (prior literature showing 14% sensitivity, 98% specificity). LUS slightly improved prehospital initiation of HF therapy (33% vs 28% previously reported). More training is needed to improve accuracy of LUS diagnosis and increase initiation of HF therapies in the prehospital setting.