Sleep medicine, especially for the SAS, has received increasing attention in recent years. One of the primary health implications of SAS is its impact on the cardiovascular system. Due to the fact that 90¢H of the SAS are OSA, the diagnose and treatment for OSA have simulated great interest. It has been shown that HRV (Heart Rate Variability) interacts with the autonomic nervous system, which in turn, correlated with OSA. Consequently, many signal processing methods have been applied to analyze HRV with the hope that features that correlate HRV and OSA can be found. For the reason, the goal of this work is to develop signal processing methods to explore the interaction between HRV and OSA. In performing such tasks, conventional approaches converts HRV signal to analog from by using interpolation. This work will maintain the original digital form of the HRV. Our results will be compared with the results obtained by the conventional analog method. Finally, the HRV band that has the strongest correlation with the OSA will be reported.

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Stress is the feeling of emotional strain in response to a perceived threat that disturbs the homeostasis and affects our health and well-being. Short-term stress has some beneficial effects such as improving alertness and performance and boosting memory, but prolonged stress responses can have deleterious effects on human health, including tissue damage and disease. Thus regulating stress levels is important for dealing with difficult situations to mitigate negative impacts. Prevailing approaches to treating stress have some limitations and drawbacks. Slow breathing/Resonant frequency breathing or HRV biofeedback and Music Therapy are some of the widely used methods for dealing with stress and anxiety. These methods are thought to stimulate the vagus nerve that promotes autonomic balance and hence reduce symptoms of stress. The current study investigated the effects of relaxing music and Slow breathing/Resonance frequency breathing on heart rate variability and respiration as well as on subjective measures of perceived stress. Although relaxing techniques are often administered in group classes, research studies in groups are rare. To our knowledge, this is the first study to investigate the effects of music listening and slow breathing in reducing stress evoked by watching a stressful movie in a group setting. The study sought to evaluate the effectiveness of the aforementioned interventions in reducing stress, measured by psychophysiological and self-report measures. Thirty-two participants were recruited and randomly assigned to two groups (Music, Breathing). We hypothesized that after watching the stressful movie, the Breathing group would show greater physiological and self-report changes marking greater stress reduction compared to the Music group. Results indicated that slow Breathing affected perceived stress as well as HRV, whereas Music affected perceived stress, but had no significant effect on HRV. Also, results indicated that Slow Breathing and not Music reduced the complexity of heart and respiration signals. Moreover, the study found that respiration and heart rhythm synchronized maximally during slow breathing. The results suggest that the interventions studied in this research can be used as an effective stress reduction tool in a group setting. / Thesis / Master of Science (MSc)

This is a master thesis project written at the School of Technology and Health within KTH, Flemingsberg. It consisted of making improvements in an existing application for tablets used for training HRV biofeedback that was developed as part of an earlier master thesis within the same school. The software involves the user in paced breathing according to an established method. The method with HRV biofeedback visualises and trains HRV while the user performs paced breathing. This means that the user maximises the variations of time between heart beats which may have potential to reduce stress and sustain health. To improve the software developed earlier at KTH a new graphical user interface was implemented in form of a simple game. In addition further aspects of the program were improved. Furthermore, this thesis tried to find evidence for the optimal frequency and duration of HRV biofeedback training for healthy individuals. For this purpose a literature review was performed, showing a lack of evidence for the effectiveness of HRV biofeedback training in healthy individuals. Therefore a study protocol was developed that can be used in future studies aimed at finding the optimal dosage of HRV biofeedback. / Det här är en rapport från ett examensarbete på masternivå utfört på KTH, Skolan för teknik och hälsa i Flemingsberg. Arbetet handlar om att vidareutveckla en mobil applikation för surfplattor som utvecklats i ett tidigare masterprojekt. Programmet engagerar användaren i andning efter en specifik metod. Metoden med HRV biofeedback bygger på att visualisera och träna upp HRV medan man andas. Detta innebär att maximera de varierande tidsintervallen mellan hjärtats slag vilket har potential att fungera som en behandlingsmetod för att reducera stress och bibehålla god hälsa. Genom att programmera i Java och implementera en ny spelvy i det existerande programmet har applikationen förbättrats. Även andra aspekter av programmet har förbättrats. Arbetet har också inneburit att hitta svar på frågor om optimal dosering och frekvens för träning med HRV biofeedback för att detta ska kunna ge långsiktiga effekter på HRV. En litteraturstudie utfördes för att finna svar på dessa frågor. Det saknas dock studier som påvisar positiva långvariga effekter på hjärtats variabilitet hos friska personer. Därför har ett testprotokoll föreslagits vilket kan vara en grund för att i framtiden göra en studie för att vidare utforska dessa frågor.

The aim of this study is to examine heart rate variability (HRV) alteration after the injection of atropine and saline and to determine if ensemble averaging affects the outcome of frequency domain analysis. The HRV data is pre-processed using ensemble averaging and then frequency domain and statistical analysis is done. The HRV readings originate from a previous study of four rats. Ensemble averaging reduces the mean drift effect in the data. The original and ensemble is then processed through an Fast Fourier Transform (FFT). The results show that the ensembled data allows frequency peaks and changes to be seen more clearly than the FFT of the original data set. Through statistical analysis it is also shown that the change in HRV from the atropine injection is much greater than the change in HRV from the saline injection.

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Epileptic seizures are often un-witnessed and can result in hypoxic brain damage or can be fatal due to injuries, status epilepticus or sudden unexpected death in epilepsy (SUDEP). The first aim of this thesis was to investigate some of the physiological parameters that accompany an epileptic seizure and may be useful in a seizure alarm system. The second aim was to investigate aspects of cardiac dysfunction during clinical and sub-clinical seizures that may be potential contributing factors in SUDEP. Percentage heart rate change and oxygen saturation were studied prospectively during 527 epileptic seizures in 50 patients aged from one-day full term neonate to 60 years with a variety of seizure types (absences, generalised tonic clonic seizures, myoclonic seizures, tonic seizures and focal seizures) and in normal physiological events (e.g. coughing, turning in bed). Higher percentage heart rate change occurred during epileptic seizures (21.8%) than during normal physiological events (16.4%) p<0.001. Diagnostic testing of clinically significant seizures i.e seizures that could potentially lead to serious consequences if left undetected (n=61) had a sensitivity of 91% and specificity of 75% when percentage heart rate change and hypoxaemia parameters were combined. Percentage heart rate change and oxygen saturation could be used as reliable indicators of a seizure when set at specific levels and distinguish clinically significant seizures from normal physiological events. These parameters can now be used to develop a reliable alarm system to detect epileptic seizures at night. Prolongation of QTc and increased vagal tone may be possible mechanisms underlying SUDEP. Corrected Q-T cardiac repolarisation time 5 minutes before and throughout 156 epileptic seizures were analysed using four corrective formulae (Bazett, Hodge, Fridericia and Framingham). All formulae indicated statistically significant lengthening of the corrected Q-T during epileptic seizures (p<0.001) compared to pre-seizure values. All formulae agreed that the greatest lengthening of the corrected QT beyond normal limits occurred during right temporal lobe seizures in two patients. Reflex and tonic vagal activity utilising R-R intervals was assessed in 33 sub-clinical seizures occurring during stages 3 or 4 sleep and was compared to matched counts of R-R interval non-ictal baseline studies from the same stage of sleep in each patient. Altered vagal activity occurred during total sub-clinical seizures compared to baseline studies (p<0.001). Lengthening of the corrected Q-T and changes in cardiac vagal tone during epileptic seizures may have a role in the patho-physiology of SUDEP.

"Diabetic cardiovascular autonomic neuropathy (DCAN) is common in patients with diabetes mellitus, and causes abnormalities in heart rate control as well as central and peripheral nervous system dynamics. A good understanding of DCAN is not established yet. An effective way to detect diabetes mellitus at an early stage is still undiscovered, which method is highly desired by researchers and patients. One reason why the pathogenesis of DCAN is unclear is that non- invasive assessment of DCAN in humans and animals has been problematic. The non-stationary and non- linear natures of the interested physiological signals have placed great limitation on traditionally algorithms. To overcome this limitation, this work proposes a series of time- varying, nonlinear and non-invasive methods to assess cardiac autonomic dysregulation from ECG and PPG records. Including a non-stationary method called PDM, which is based on principal dynamic mode (PDM) analysis of heart rate variability (HRV), nonstationary power spectral density called TVOPS-VFCDM and also standard spectrum analysis method of HRV. We are also able to study and analyze a series of long term and short term ECG and PPG data. In a pilot study, ECG was measured via telemetry in conscious 4 month old C57/Bl6 controls and in Akita mice, a model of insulin- dependent type I diabetes, while PPG was measured via tail pulse oximetry system from 2 month old to 4 month old. The results indicate significant cardiac autonomic impairment in the diabetic mice in comparison to the controls at 4 month old and such impairment start to present at 3 month old. Further, both immunohistochemistry and Western blot analyses show a reduction in nerve density in Akita mice as compared to the control mice, thus, corroborating our data analysis records."

Even though the sleep apnea breathing occurs during the sleep,but it also affects the daytime's physiological status.Since sleep apnea breathing increases the risk of getting cardiovascular diseases,sleep disordered breathing has attracted significant amount attention.Conventional diagnosis processes for sleep disorder breathing is complex and time-consuming,therefore many efforts have been made in developing simplified physiological signal feature to detect sleep disorder breathing.To simplify the process of diagnosis,this study uses the ECG signals to differentiate patients and healthy subjects.In addition to traditional HRV features,this study also test a newly proposed ECG feature called degree of spectrum concentration which characterizes the degree of periodicity of the ECG waveform. Our experimental results show that sleep apnea patients have higher degree of spectrum concentration than healthy subjects.This work also tests the mutliscale entropy of this degree of spectrum concentration signal.The results demonstrate that complexity of the degree of spectrum concentration signal of the patients is higher than that of the healthy subjects.Finally,our results also detect differences between different age groups.

No description available.