Videoplethysmography is currently recognized as a promising noninvasive heart rate measurement method advantageous for ubiquitous monitoring of humans in natural living conditions. Although the method is considered for application in several areas including telemedicine, sports and assisted living, its dependence on lighting conditions and camera performance is still not investigated enough. In this paper we report on research of various image acquisition aspects including the lighting spectrum, frame rate and compression. In the experimental part, we recorded five video sequences in various lighting conditions (fluorescent artificial light, dim daylight, infrared light, incandescent light bulb) using a programmable frame rate camera and a pulse oximeter as the reference. For a video sequence-based heart rate measurement we implemented a pulse detection algorithm based on the power spectral density, estimated using Welch’s technique. The results showed that lighting conditions and selected video camera settings including compression and the sampling frequency influence the heart rate detection accuracy. The average heart rate error also varies from 0.35 beats per minute (bpm) for fluorescent light to 6.6 bpm for dim daylight.
Nitric oxide (NO) is known to be a neuromodulator with dual proconvulsive and anticonvul- sive action. Valeriana officinalis (VAL) was previously believed to be antiepileptic, but is today known as a sedative and sleep regulator. Seizures may be associated with abnormal electrocardio- graphic changes and cardiac dysfunction arising from epilepsy may be related with neuronal nitric oxide (nNO). This study was aimed to investigate the effects of the neuronal nitric oxide synthase (nNOS) inhibitor 7-Nitroindazole (7-NI) and VAL on seizure behaviours and electrocar- diographic parameters in the pentylentetrazole (PTZ)-kindled seizure model.
Wistar rats were randomised into saline control, PTZ-kindled, 7-NI, VAL and VAL+PTZ, 7-NI+PTZ and VAL+7-NI+PTZ groups. Latency, stage, frequency of seizures, blood pressure (BP), heart rate (HR) and corrected QT (QTc) values were evaluated.
Frequency and stage of seizures, BP and HR increased, while seizure latency decreased and QTc was prolonged in the PTZ-kindled group. 7-NI and VAL had no effects on BP and HR variables under normal conditions, but ameliorated the seizure stage and frequency of seizures. 7-NI treatment also resulted in a reduction of the increased BP and prolonged QTc values observed in PTZ-kindled rats.
Considering these results, QTc prolongation may be used as a predictor for recurrent seizures. 7-NI and VAL exhibited different effects on seizures and ECG variables. 7-NI shows potential as an anticonvulsant drug agent in epileptic patients with cardiac dysfunctions and those additional studies including in-vivo experiments are essential.
The study on cognitive workload is a field of research of high interest in the digital society.
The implementation of ‘Industry 4.0’ paradigm asks the smart operators in the digital factory
to accomplish more ‘cognitive-oriented’ than ‘physical-oriented’ tasks. The Authors propose
an analytical model in the information theory framework to estimate the cognitive workload
of operators. In the model, subjective and physiological measures are adopted to measure
the work load. The former refers to NASA-TLX test expressing subjective perceived work
load. The latter adopts Heart Rate Variability (HRV) of individuals as an objective indirect
measure of the work load. Subjective and physiological measures have been obtained by
experiments on a sample subjects. Subjects were asked to accomplish standardized tasks
with different cognitive loads according to the ‘n-back’ test procedure defined in literature.
Results obtained showed potentialities and limits of the analytical model proposed as well as
of the experimental subjective and physiological measures adopted. Research findings pave
the way for future developments.
I n t r o d u c t i o n: Stress is an ubiquitous phenomenon in the modern world and one of the major risk factors for cardiovascular disease. Th e aim of our study was to evaluate the effect of various acute stress stimuli on autonomic nervous system (ANS) activity, assessed on the basis of heart rate (HRV) and blood pressure (BPV) variability analysis.
Ma t e r i a l s a n d M e t h o d s: The study included 15 healthy volunteers: 9 women, 6 men aged 20– 30 years (23.3 ± 1.8). ANS activity was assessed by HRV and BPV measurement using Task Force Monitor 3040 (CNSystems, Austria). ECG registration and Blood Pressure (BP) measurement was done 10 minutes at rest, 10 minutes aft er the stress stimulus (sound signal, acoustic startle, frequency 1100 Hz, duration 0.5 sec, at the intensity 95 dB) and 10 minutes aft er the cold pressor test. The cold pressor test (CPT) was done by placing the person’s hand by wrist in ice water (0–4°C) for 120 s.
R e s u l t s: Every kind of stress stimulation (acoustic startle; the CPT) caused changes of HRV indicator values. The time domain HRV analysis parameters (pNN50, RMSSD) decreased aft er acoustic stress and the CPT, but were signifi cantly lower after the CPT. In frequency domain HRV analysis, significant differences were observed only aft er the CPT: (LF-RRI 921.23 ms2 vs. 700.09 ms2; p = 0.009 and HF-RRI 820.75 ms2 vs. 659.52 ms2; p = 0.002). The decrease of LF-RRI and HF-RRI value aft er the CPT was significantly higher than after the acoustic startle (LF-RRI 34% vs. 0.4%, p = 0.022; HF-RRI 19.7% vs. 7% ms2, p = 0.011). The decreased value of the LF and HF components of HRV analysis are indicative of sympathetic activation. Nonlinear analysis of HRV indicated a significant decrease in the Poincare plot SD1 (p = 0.039) and an increase of DFAα2 (p = 0.001) in response to the CPT stress stimulation. Th e systolic BPV parameter LF/HF-sBP increased signifi cantly aft er the CPT (2.84 vs. 3.31; p = 0.019) and was higher than aft er the acoustic startle (3.31 vs. 3.06; p = 0.035). Signifi cantly higher values of diastolic BP (67.17 ± 8.10 vs. 69.65 ± 9.94 mmHg, p = 0.038) and median BP (83.39 ± 8.65 vs. 85.30 ± 10.20 mmHg, p = 0.039) were observed in the CPT group than in the acoustic startle group.
C on c l u s i o n s: Th e Cold Pressor Test has a greater stimulatory eff ect on the sympathetic autonomic system in comparison to the unexpected acoustic startle stress. Regardless of whether the stimulation originates from the central nervous system (acoustic startle) or the peripheral nervous system (CPT), the final response is demonstrated by an increase in the low frequency components of blood pressure variability and a decrease in the low and high frequency components of heart rate variability.
Alcohol is a recognized teratogen that affects various aspects of fetal development. Tissue that is particularly susceptible to its teratogenicity is neuronal tissue. The effect of prenatal alcohol exposure (PAE) on the central nervous system has been extensively studied, yet the knowledge on the influence of PAE on the autonomic nervous system is scarce. The purpose of this article is to review the current state of knowledge about the impact of PAE on the autonomic nervous system. Studies conducted on the PAE animal model have shown that prenatal alcohol exposure is associated with significant alterations in the autonomic nervous system, but the mechanisms and consequences are not yet clearly defined. It was established that PAE causes decreased heart rate variability (HRV) in fetal cardiotocography. Several studies have revealed that later, in infancy and childhood, reduced parasympathetic activity with or without compensating sympathetic activity is observed. This may result in behavioral and attention disorders, as well as an increased predisposition to sudden infant death syndrome. Both animal and human studies indicate that the relationship between PAE and autonomic dysfunction exists, however large, well-designed, prospective studies are needed to confirm the causal relationship and characterize the nature of the observed changes.