Pulmonary lung Doppler signals: normative data in a pediatric population compared with adults

Lung Doppler signals (LDS) acquired via transthoracic echocardiography is a novel technology previously reported in adults for use in detecting pulmonary hypertension. The aim of this study was to characterize LDS in healthy children to establish normative pediatric LDS data, and compare the pediatric data to the previously published healthy adult LDS. In this prospective, two-center study, LDS were acquired in children without cardiopulmonary disease using a 2 MHz transthoracic pulsed Doppler transducer. The data were processed to obtain Doppler velocity patterns corresponding to phases of the cardiac cycle. Signals were analyzed using a parametric Doppler signal-processing package and performance evaluation of the trained classifiers was performed using cross validation method. Pediatric signals were then compared to a retrospective cohort of healthy adults. Eighty-six healthy pediatric subjects (mean age 9.1 ± 5.1 years) and 79 healthy adult controls (mean age 59.7 ± 10.7 years) were included. The normative LDS velocity profiles were defined for pediatric subjects and then compared to adults; the highest discriminating LDS parameters between healthy children and adults were acceleration of atrial (A) signal contraction (46 ± 18 vs. 90 ± 34; p < 0.001), peak systolic (S) signal velocity (10.0 ± 3.5 vs. 11.7 ± 3.5; p < 0.001), and ratio of peak diastolic (D)-to-atrial (A) signal velocity (1.4 ± 0.5 vs. 0.4 ± 0.3; p < 0.001). The sensitivity and specificity of this LDS based method to discern between healthy children and adult subjects was 98.6% and 97.4%, respectively. Subgroup analyses between younger (2-8 years) and older (9-18 years) pediatric LDS yielded significant differences between atrial (A) acceleration (43.7 ± 33.9 vs. 47.7 ± 42.1; p = 0.04) and diastolic (D)-to-atrial (A) signal velocity (1.2 ± 0.5 vs. 1.5 ± 0.5; p = 0.01) but not systolic (S) signals (0.14 ± 0.05 vs. 0.14 ± 0.05; p = 0.97). In this study, we defined the normal LDS profile for healthy children and have demonstrated differences in LDS between children and adults. Specifically, healthy children had lower atrial contraction power, differences in ventricular compliance and increased chronotropic response. Further studies are warranted to investigate the application of this technology, for example as a tool to aid in the detection of pulmonary hypertension in children.