Table 1.

Summary of the articles selected and their results.

Diagnostic assessment of dyspnea in prehospital settings (AHF or DCHF)
PU was useful for the diagnosis in 68% of dyspneic patients in the prehospital setting with no delay in treatment and/or transportation, PE being present in 100% of those with decompensated HF, in 17% of patients with ACS, and in 20% of patients with COPD (p < 0.01), PE thus being a diagnostic marker in patients with decompensated HF.13 In the diagnosis of HF on PU, the S = 100% and E = 95% were comparable to those of NT-proBNP (> 1.000 pg/mL), S = 92% and E = 89%, and superior to those of the modified Boston criteria, S = 85% and E = 86%. The combination of PU and NT-proBNP showed S and E of 100%.18
Diagnostic assessment of dyspnea in emergency settings (AHF or DCHF)
Studies reported S ranging from 70% to 96.2% and E from 54% to 75%,23-25,27,29,31 diagnostic reclassification ranging from 19% to 47%,23,24 with change in treatment in 43% of the cases,24 figures comparable to those of BNP > 500 (S = 75% and E = 83%).27 PU accuracy of 90% versus 67% (p = 0.0001) for clinical examination, and 81% (p = 0.04) for the combination of clinical examination + NT-proBNP + X-ray.25 PU was better for the diagnosis of DCHF (S = 100%) and of PNM (S = 75%) as compared to stethoscope auscultation (S = 89% and S = 73%, respectively).26 Interobserver agreement was better in the anterior/superior thoracic zones for both pairs expert/expert and expert/beginner,16 and the PU performed by beginners versus experts had S and E of 79-85% and 84-88%, respectively,17,37 and PPV of 64-75% and NPV of 90.9-94%.17,29 Global agreement with the gold-standard method for pulmonary edema interpretation on PU was 74%, higher than that with X-ray (58%, p< 0.0001).28 A combination of PU and US of IVC had S = 94.3%, E = 91.9%, NPV = 91.9% and PPV = 94.3% to differentiate AHF from pulmonary disease,29 and JVD-US is a sensitive test (S = 98.2%) to identify pulmonary edema in dyspneic patients with suspicion of congestive AHF.30 Studies have shown an LR(+) of PU of 3.88-4.8% and an LR(-) of PU of 0.20-0.50%24,31 for the diagnosis of AHF or DCHF, being higher than the LR(+) of NT‑proBNP [= 2.3] and similar to the LR(-) of NT-proBNP [= 0.24].31
Diagnostic assessment in intensive care settings (AHF or DCHF)
Agreement of PU with the final diagnosis was 84%, with S = 86% and E = 87% for cardiac pulmonary edema,32 and IVC values > 9 mm on B mode had S = 84.4% and E = 92.9% [LR(+) = 11.8, LR(-) = 0.16] for the diagnosis of cardiac dyspnea.33
Diagnostic assessment in outpatient settings
Primary outcome (hospitalization due to DCHF and all-cause death) was 4x more frequent in patients of the third tertile than in patients of the first tertile with B-lines ≥ 3 (p < 0.001), whose time alive or outside the hospital was shorter (p< 0.001).36 The finding of B-lines or PE or both increased the risk of death or hospitalization (p< 0.05)19 and correlated in a paired way with the estimates of PCWP (p < 0.001) and with the fluid impedance index (p < 0.001); the impedance monitoring alert detected clinical deterioration of HF with S = 92%, while B-lines ≥ 5 showed S = 83%.35 HF decompensation was present in 68% of the patients when the number of B-lines ≥ 15, and correlated with NT-proBNP > 1000 (p < 0.0001) and with an E/e’ ratio > 15 (p < 0.0001).34
Prognostic assessment
Event-free survival (all-cause death and re-hospitalization) of patients with HF and B-lines ≥ 30 was shorter than that of patients with B-lines < 30 (p < 0.0001) in 3 months10 and of patients with B-lines ≥ 15 in 6 months,11 and the presence of B-lines ≥ 30 was a predictor of death with BNP > 700 (p = 0.002).10
Therapeutic assessment
The number of B-lines reduced with treatment (p < 0.05), and the PU score showed a linear correlation with the radiologic (p < 0.05) and clinical scores (p < 0.05) and with BNP levels (p < 0.05).8
Assessment of PU as compared to other diagnostic methods
An increase in the number of B-lines correlated with LVEDV (p = 0.036);20 LV end-systolic diameter (p = 0.026);20 PW (p = 0.009);20 LV mass index (p = 0.001);20 RA volume index (p = 0.005);20 TR velocity (p = 0.005);20 measures of RA, DPAP, MPAP, PVR, all p < 0,005,21 and SPAP (p = 0.003-0,005),20-21 and, for each B-line, there was an increase of 1 mm Hg in SPAP and of 0.1 Woods units in RVP.21 In the analysis of the number of B-lines, the US device types used did not statistically differ (4 or 8 zones assessed; p= 0.67),22 but the clip duration did differ: 4 versus 2 seconds (p < 0.001 for 4 and 8 zones) and 6 versus 4 seconds (p = 0.057 for 4 zones; and p = 0.018 for 8 zones).22

AHF: acute heart failure; DCHF: decompensated chronic heart failure; HF: heart failure; PU: pulmonary ultrasound; COPD: chronic obstructive pulmonary disease; PE: pleural effusion; ACS: acute coronary syndrome; S: sensitivity; E: specificity; NPV: negative predictive value; PPV: positive predictive value; NT-proBNP: N-terminal pro-brain natriuretic peptide; LR(+): positive likelihood ratio; LR(-): negative likelihood ratio; US: ultrasound; X-ray: chest X-ray; PNM: pneumonia; IVC: inferior vena cava; JVD-US: jugular vein distension on ultrasound; PCWP: pulmonary capillary wedge pressure; BNP: brain natriuretic peptide; LVEDV: left ventricular end-diastolic volume; PW: posterior wall; LV: left ventricular; LA: left atrium; TR: tricuspid regurgitation; RA: right atrium; DPAP: diastolic pulmonary artery pressure; MPAP: mean pulmonary artery pressure; PVR: pulmonary vascular resistance; SPAP: systolic pulmonary artery pressure.