Changes in venous refilling time from childhood to adulthood in subjects with apparently normal veins

Walking instead of standing

Background: Leg discomfort is common in the general population. Volume increase and discomfort in the lower legs especially occur in occupations with long standing or sitting periods and less movement. Are both related to each other? Patients and methods: A time-controlled standing period of 15 min was performed in this nonrandomized controlled study to investigate the change and temporal relationship of volume increase and the occurrence of lower leg discomfort. Sensations of discomfort and the urge to move were queried using a numerical rating scale from 0 to 10 (NRS). Correlation analysis was conducted between the lower leg volume and the data regarding the discomfort and urge to move in each subject. Further, linear mixed effect models were performed to detect a causal relationship between the lower leg volume and the sensations of discomfort/urge to move in the standing period. Results: Lower leg volume increased by an average of 63 ml (p<0.001) during the standing period. The sensations of discomfort increased by a mean of 3.46 points on the NRS (p<0.001) during orthostasis. Participants' urge to move increased by 3.47 points on the NRS (p<0.001) during the standing period. A significant correlation was shown between the increase of lower leg volume and the occurrence of discomfort sensation in 9 out of 15 subjects (p<0.05) and between the increase of lower leg volume and the urge to move in 11 out of 15 subjects (p<0.05). Association was shown between volume increase and symptoms in linear mixed effects models. Conclusions: Prolonged standing with lack of movement leads to an increase in the lower leg volume and a sensation of discomfort in venous healthy subjects. Causal relationships are indicated between these variables by linear mixed effects models.

A Review of Photoplethysmography-based Physiological Measurement and Estimation, Part 2: Multi-input Methods

Photoplethysmography can be used to estimate many physiological parameters based on features extracted from the measured waveform. Following the single parameter estimations that have been reviewed in part 1 of this paper, we here review methods where the waveform is used in conjunction with other measured physiological signals. Being a low-cost, non-invasive, and user friendly technique, many PPG-based physiological data extraction methods are being researched. The parameters reviewed that can be estimated using the PPG waveform plus additional inputs include cardiac output, blood pressure, venous function assessment, blood oxygen saturation, and fetal heart rate and fetal oxygen saturation. The different processing techniques, algorithms and methods are reviewed in addition to providing a comparison of results with the reference standards to validate the different methods. Future research considerations for each parameter estimation are also discussed. This paper could be helpful for future research on PPG based wearable devices for physiological multi-parameter estimations.

How posture influences venous blood flow in the lower limbs: results of a study using photoplethysmography

Prolonged standing or sitting is one of the factors for chronic venous insufficiency. The aim of the study was to determine the impact of static load of the lower limbs on the functioning of the venous system. The study included 10 healthy young participants, with no peripheral venous disease. All participants took part in examinations in two variants: variant 1, sitting for 20 min with the lower limbs bent in the knee joints at 90°; variant 2, standing for 20 min with no additional load. Before and after each test, the venous refilling time (VRT) was determined using photoplethysmography. Statistical analysis demonstrated that the VRT was significantly shortened only after application of variant 2. Furthermore, even variants with small loads applied to healthy young participants can induce in them effects on the parameters describing the peripheral circulation.

Effect of Graduated Compression Stockings on Venous Blood Velocity in Supine Resting Hospitalized Patients

The effects of graduated compression stockings (GCSs) on venous blood velocity were measured in 26 hospitalized medical patients while supine at rest. Peak blood velocity in the right femoral vein was 21.6 cm/s without GCS and 23.0 cm/s with GCS [not significant (NS)]. Peak blood velocity in the right popliteal vein was 12.5 cm/s without GCS and 15.0 cm/s with GCS (NS). Mean blood velocity in the right femoral vein did not increase significantly with GCS, but mean blood velocity in the right popliteal vein increased marginally from 5.0 cm/s to 5.8 cm/s ( P = .05). Among 11 patients with venous insufficiency (refilling time ≤19 s), neither peak nor mean blood velocity in the femoral or popliteal veins increased significantly with GCS. In conclusion, thigh-length GCS in hospitalized patients had little or no effect on popliteal or femoral vein blood velocity while supine at rest, irrespective of whether the patients had venous insufficiency.

Photoplethysmography and its application in clinical physiological measurement

Photoplethysmography (PPG) is a simple and low-cost optical technique that can be used to detect blood volume changes in the microvascular bed of tissue. It is often used non-invasively to make measurements at the skin surface. The PPG waveform comprises a pulsatile ('AC') physiological waveform attributed to cardiac synchronous changes in the blood volume with each heart beat, and is superimposed on a slowly varying ('DC') baseline with various lower frequency components attributed to respiration, sympathetic nervous system activity and thermoregulation. Although the origins of the components of the PPG signal are not fully understood, it is generally accepted that they can provide valuable information about the cardiovascular system. There has been a resurgence of interest in the technique in recent years, driven by the demand for low cost, simple and portable technology for the primary care and community based clinical settings, the wide availability of low cost and small semiconductor components, and the advancement of computer-based pulse wave analysis techniques. The PPG technology has been used in a wide range of commercially available medical devices for measuring oxygen saturation, blood pressure and cardiac output, assessing autonomic function and also detecting peripheral vascular disease. The introductory sections of the topical review describe the basic principle of operation and interaction of light with tissue, early and recent history of PPG, instrumentation, measurement protocol, and pulse wave analysis. The review then focuses on the applications of PPG in clinical physiological measurements, including clinical physiological monitoring, vascular assessment and autonomic function.