Karen Soueidan

Electrocardiogram-Assisted Blood Pressure Estimation

Accurate automatic noninvasive assessment of blood pressure (BP) presents a challenge due to conditions like arrhythmias, obesity, and postural changes that tend to obfuscate arterial amplitude pulsations sensed by the cuff. Researchers tried to overcome this challenge by analyzing oscillometric pulses with the aid of a higher fidelity signal-the electrocardiogram (ECG). Moreover, pulse transit time (PTT) was employed to provide an additional method for BP estimation. However, these methods were not fully developed, suitably integrated, or tested. To address these issues, we present a novel method whereby ECG-assisted oscillometric and PTT (measured between ECG R-peaks and maximum slope of arterial pulse peaks) analyses are seamlessly integrated into the oscillometric BP measurement paradigm. The method bolsters oscillometric analysis (amplitude modulation) with more reliable ECG R-peaks provides a complementary measure with PTT analysis (temporal modulation) and fuses this information for robust BP estimation. We have integrated this technology into a prototype that comprises a BP cuff with an embedded conductive fabric ECG electrode, associated hardware, and algorithms. A pilot study has been undertaken on ten healthy subjects (150 recordings) to validate the performance of our prototype against United States Food and Drug Administration approved Omron oscillometric monitor (HEM-790IT). Our prototype achieves mean absolute difference of less than 5 mmHg and grade A as per the British Hypertension Society protocol for estimating BP, with the reference Omron monitor.

A prototype of an integrated blood pressure and electrocardiogram device for multi-parameter physiologic monitoring

We present a prototype of an integrated blood pressure (BP) and electrocardiogram (ECG) device for multi-parameter physiologic monitoring. A standard BP pressure cuff and an ordinary wristband have been modified to incorporate in them dry ECG electrodes made of thin conductive fabric. The modified BP cuff and wristband are coupled with commercially available hardware and software to harvest simultaneous arterial pulse wave and ECG data from the arm and wrist of the other hand. Software has been written for assessing multiple physiologic parameters from the harvested pulse wave and ECG signals. We provide an initial validation of the performance of our prototype by conducting a study on six healthy subjects.

The effect of blood pressure variability on the estimation of the systolic and diastolic pressures

Systolic (SBP) and diastolic (DBP) blood pressure are two parameters that are widely used in clinical and personal health monitoring and that are subject to significant physiological variability. The estimation of SBP and DBP is therefore subject to two sources of uncertainty: 1) measurement error, and 2) physiological variability. According to the ANSI/AAMI SP10 standard, the measurement error of an automated sphygmomanometer is limited to ±5 mmHg relative to simultaneous reference readings by at least two trained observers employing a calibrated manometer. In order to directly compare the contributions of physiological variability and measurement error to SBP and DBP estimation uncertainty, we analyzed continuous short recordings of arterial pulses (≪ 5 min) and calculated the percentage of beats in which the SBP and DBP exceeds ±5 mmHg relative to the mean value in the analyzed interval. In a group of ICU patients, this percentage was 33.0% for SBP and 14.9% for DBP on average, while in a group of healthy individuals this percentage was 27.5% for SBP and 17.8% for DBP on average. True outliers occurred in 5.17% of the SBP and 12.2% of the DBP values in ICU patients, and 3.27% of the SBP and 3.63% of the DBP values in healthy individuals. These results indicate that blood pressure variability is an important contributor to SBP and DBP estimation uncertainty, and devices that intelligently determine the best time to initiate a recording and the frequency of recordings may alleviate this uncertainty.

Flow-Dependent Uptake of 123I-CMICE-013, a Novel SPECT Perfusion Agent, Compared with Standard Tracers

Rotenone derivatives have shown promise in myocardial perfusion imaging (MPI). CMICE-013 is a novel 123I-labeled rotenone derivative developed for SPECT MPI. The objective of this study was to assess the image quality of CMICE-013 and compare its uptake with tetrofosmin, sestamibi, and 201Tl in vivo in a porcine model of stress-induced myocardial ischemia. Methods: Microspheres were injected simultaneously with the radiotracer injections at rest and stress to measure blood flow. Mimicking a 1-d tetrofosmin protocol, stress imaging used 3 times as much activity and occurred 1 h after the rest injection. SPECT images were obtained at both rest and stress. After imaging, the heart was sectioned into 44–50 pieces. In each heart sample, the tracer uptake was measured in a γ counter. The images were aligned, and the decay-corrected ratio of the signals at rest and stress was used to separate the well-counter signal into rest and stress components. The uptake at rest and stress was compared with microsphere flow measurements. Results: The CMICE-013 images showed good contrast between the heart and surrounding organs, with heart-to-liver and heart-to-lung uptake ratios similar to those of the standard tracers. Uptake of CMICE-013 was 1.5% of the injected dose at rest and increased more rapidly with increased blood flow than did the standard SPECT tracers. The percentage injected dose of CMICE-013 taken up by the heart was greater (P < 0.05) than 201Tl, tetrofosmin, or sestamibi at flows greater than 1.5 mL/min/g. Conclusion: CMICE-013 is a promising new SPECT MPI agent.