Noninvasive cuffless blood pressure estimation using pulse transit time, Womersley number, and photoplethysmogram intensity ratio.

OBJECTIVE: Continuous cuffless blood pressure (BP) monitoring research has emerged as blood pressure is one of the dynamic parameters which reflects cardiac arrhythmias and rheological disorders without the drawbacks of current techniques. All the existing measurement techniques are cuff-based with drawbacks such as being discontinuous in nature, being uncomfortable for the patient, etc. Therefore, the goal is to develop an algorithm to estimate BP accurately using the pulse transit time (PTT), photoplethysmogram intensity ratio (PIR) and Womersley number (α) in a noninvasive way. APPROACH: The PTT technique holds the promise of real-time, cuffless, continuous BP monitoring in clinical settings. However, the non-Newtonian fluid nature of blood is considered insignificant in the conventional PTT model-based BP modeling. In the proposed work, α, representing viscous effects, along with PTT and PIR, is included in the algorithm since it is also one of the parameters that affects the BP. MAIN RESULTS: The proposed algorithm is evaluated with 42 healthy and 39 diseased subjects and compared with the other conventional techniques to evaluate the importance of viscous effects in BP, using performance metrics like mean ± standard deviation, and 95% confidence interval for bias and limits of agreement; a better estimate is achieved with the proposed algorithm. SIGNIFICANCE: The proposed algorithm reflects the influences of vasomotor tone and baroflex as well, which makes it suitable for the assessment of BP in both healthy and diseased subjects, with improved accuracy than the current measurement techniques.

Correlation of 2 hours and 24 hours creatinine clearance in renal donors after unilateral nephrectomy.

BACKGROUND: The kidney performs numerous specialised functions in an effort to maintain constancy of the internal composition of body fluids. AIM: This study was done to ascertain the feasibility of estimating creatinine clearance as an outpatient procedure over a 2 hours period instead of doing the study over a 24 hours period. MATERIAL AND METHODS: Eighteen renal donors, Twelve females and Six males, who were closely related to recipients, were chosen. This study was done on renal donors who attended the Nephrology Department of Rajiv Gandhi Government General Hospital, Madras Medical College, Chennai-03 India. To estimate creatinine clearance in 24 hours urine, 24 hours urine sample was collected from 9 am on the first day to 9 am on the next day, after first emptying the bladder. Then, creatinine clearance was calculated by using standard formula, CC=UV/ Pt X 1.73m(2)/BSA of the individual. RESULTS: There was no significant differences in mean creatinine clearance values by collecting 2 hours and 24 hours urine samples from renal donors in different stages of post nephrectomy period. It has been shown that 2 hours collection of urine sample is as good as 24 hours urine sample for estimating creatinine clearance. CONCLUSION: Hence it was proved that measurement of creatinine clearance could be done as an outpatient procedure, as the patient needed only 2 hours of hospital stay.