Towards Continuous and Ambulatory Blood Pressure Monitoring: Methods for Efficient Data Acquisition for Pulse Transit Time Estimation.

We developed a prototype for measuring physiological data for pulse transit time (PTT) estimation that will be used for ambulatory blood pressure (BP) monitoring. The device is comprised of an embedded system with multimodal sensors that streams high-throughput data to a custom Android application. The primary focus of this paper is on the hardware-software codesign that we developed to address the challenges associated with reliably recording data over Bluetooth on a resource-constrained platform. In particular, we developed a lossless compression algorithm that is based on optimally selective Huffman coding and Huffman prefixed coding, which yields virtually identical compression ratios to the standard algorithm, but with a 67-99% reduction in the size of the compression tables. In addition, we developed a hybrid software-hardware flow control method to eliminate microcontroller (MCU) interrupt-latency related data loss when multi-byte packets are sent from the phone to the embedded system via a Bluetooth module at baud rates exceeding 115,200 bit/s. The empirical error rate obtained with the proposed method with the baud rate set to 460,800 bit/s was identically equal to 0%. Our robust and computationally efficient physiological data acquisition system will enable field experiments that will drive the development of novel algorithms for PTT-based continuous BP monitoring.

Delayed prostate-specific antigen recurrence after radical prostatectomy: how to identify and what are their clinical outcomes?

OBJECTIVES: To identify factors that predict delayed (> 5 years) prostate-specific antigen recurrence (PSAR) after radical prostatectomy (RP) and to analyze the associated clinical outcomes. METHODS: A cohort of 4561 men who underwent RP between 1988 and 2008 was retrieved from the Duke University Prostate Center database. Among them, 1207 (26.5%) had PSAR and were included in this study. The cohort was then divided into 2 groups; PSAR before 5 years (early PSAR) and PSAR after 5 years (delayed PSAR), and Kaplan Meier analysis was performed. Univariate and logistic regression analysis was carried out to determine significant predictors of delayed PSAR, using factors such as race, age, body mass index, PSA, surgical margin status, pathologic Gleason sum, pathologic tumor stage, and prostate weight. RESULTS: There was a marginal difference between the early and delayed PSAR groups with regard to metastasis-free survival (P = .062). A significant difference in disease-specific survival was found between the 2 groups (P = .025). Patients with pathologic Gleason sums < 7 were more likely to have delayed PSAR as compared to those with pathologic Gleason sums > 7 (OR = 2.38). Patients with a PSA < 10 ng/mL were more likely to have delayed PSAR in comparison to those with PSA > 20 ng/mL (OR = 2.38). CONCLUSIONS: Approximately 90% of PSAR occurred within 5 years after RP. Lower pathologic Gleason sums and lower PSA at diagnosis were associated with delayed PSAR. Patients with delayed PSAR have a disease-specific survival advantage as compared to men with early PSAR.