Pocket-sized Ultrasound versus Cardiac Auscultation in Diagnosing Cardiac Valve Pathologies: A Prospective Cohort Study

Background: Pocket-sized ultrasound devices are used to perform focused ultrasound studies (POCUS). We compared valve malfunction diagnosis rate by cardiac auscultation to POCUS (insonation), both conducted by medical students. Methods: A prospective cohort study was conducted among patients with and without clinically relevant valve dysfunction. Recruitment to the study group was based on the presence of at least one valve pathology of at least moderate severity identified on recent echocardiography study that was required for clinical reasons. Three final-year medical students examined the patients. Each patient underwent auscultation and a POCUS using a pocket-sized ultrasound machine. Sensitivity was defined as the percentage of patients correctly identified as having a valve disorder. Specificity was defined as correct identification of the absence of valve pathology. Results: The study included 56 patients. In 18 (32%), no valve pathology was found. Nineteen patients (34%) had at least two valvular pathologies. Sixty valve lesions were present in the whole cohort. Students' sensitivity for detecting any valve lesion was 32% and 64% for auscultation and insonation; respectively, specificity was similar. The sensitivity for diagnosing mitral regurgitation, mitral stenosis, and aortic regurgitation rose significantly by using POCUS compared to auscultation alone. When using POCUS, Students identified valve pathologies in 22 cases (39%) from the patients with at least two valve dysfunctions, and none when using auscultation. Conclusions: Final-year medical students' competency to detect valve dysfunction by performing cardiac auscultation is poor. Cardiac ultrasound-focused training significantly improved medical students' sensitivity for diagnosing a variety of valve pathologies.

Research on operating characteristics of a centrifugal pump with broken impeller

The operating characteristics of a centrifugal pump with broken impeller malfunction was studied by tests and numerical simulation. One blade was cut 1/4 as a broken impeller. The energy characteristics, vibration, internal flow, pressure fluctuation, and radial force of the pump were studied in detail. The test results show that as for the pump with broken impeller, the head decreased by 9.85% and efficiency decreased by 1.06% under 1.0 Q0. The vibration increase amplitudes at the outlet flange are the maximum. The APF (axial passing frequency) of all monitoring points increased significantly, and a new frequency – 5APF appeared, except for the inlet of the pump. It can be found that the low-speed region of blade fracture surface is more obvious than other blades through numerical simulation. The radial force of the broken impeller increased obviously and became more concentrated. Due to the broken blade, the peak-to-peak magnitude of pressure fluctuation at the tongue and pump outlet increased by 4.7% and 9.5% respectively. The research results provide some reference for the malfunction diagnosis of centrifugal pump.