Detection of respiratory arousals using photoplethysmography (PPG) signal in sleep apnea patients

Respiratory events during sleep induce cortical arousals and manifest changes in autonomic markers in sleep disorder breathing (SDB). Finger photoplethysmography (PPG) has been shown to be a reliable method of determining sympathetic activation. We hypothesize that changes in PPG signals are sufficient to predict the occurrence of respiratory-event-related cortical arousal. In this study, we develop a respiratory arousal detection model in SDB subjects by using PPG features. PPG signals from 10 SDB subjects (9 male, 1 female) with age range 43-75 years were used in this study. Time domain features of PPG signals, such as 1) PWA--pulse wave amplitude, 2) PPI--peak-to-peak interval, and 3) Area--area under peak, were used to detect arousal events. In this study, PWA and Area have shown better performance (higher accuracy and lower false rate) compared to PPI features. After investigating possible groupings of these features, combination of PWA and Area (PWA + Area) was shown to provide better accuracy with a lower false detection rate in arousal detection. PPG-based arousal indexes agreed well across a wide range of decision thresholds, resulting in a receiver operating characteristic with an area under the curve of 0.91. For the decision threshold (PC(thresh) = 25%) chosen for the final analyses, a sensitivity of 68.1% and a specificity of 95.2% were obtained. The results showed an accuracy of 84.68%, 85.15%, 86.93%, and 50.79% with a false rate of 21.80%, 55.41%, 64.78%, and 50.79% at PC(thresh) = 25% or PPI, PWA, Area , and PWA + Area features, respectively. This indicates that combining PWA and Area features reduced the false positive rate without much affecting the sensitivity of the arousal detection system. In conclusion, the PPG-based respiratory arousal detection model is a simple and promising alternative to the conventional electroencephalogram (EEG)-based respiratory arousal detection system.

Wireless-based sleep technology for monitoring sleep apnea

Abstract: This paper covers the technical aspects of the wireless-based sleep technology for monitoring sleep apnea, which is a sleep disorder that can be detected via continuous monitoring. In this paper, a wireless system testbed is designed to monitor the patients for the signs of sleep apnea. The testbed is comprised of a number of biomedical sensors, which are used to monitor the related biological parameters related to the patient's sleeping mechanism, such as: nasal airflow, snoring, abdominal, leg, chest, and eye movements, blood oxygen level, blood pressure, and body position. The goal of this paper is to characterize the and model the data traffic generated from the biomedical sensors used in the sleep apnea study and find the network-centric lower traffic limits; minimum frequency deployment and minimum bandwidth required.

Investigating relative respiratory effort signals during mixed sleep apnea using photoplethysmogram

Sleep disordered breathing does show different types of events. These are obstructive apnea events, central apnea events and mixed sleep apnea (MSA) which have a central component with a pause in airflow without respiratory effort followed by an obstructive component with respiratory effort. The esophageal pressure (Pes) is the accurate method to assess respiratory effort. The aim of the present study is to investigate whether the features extracted from photo-plethysmogram (PPG) could relate with the changes in Pes during MSA. Therefore, Pes and PPG signals during 65 pre-scored MSA events and 10 s preceding the events were collected from 8 patients. Pulse intervals (PPI), Pulse wave amplitudes (PWA) and wavelet decomposition (Wv) of PPG signals at level 8 (0.15-0.32 Hz) were derived from PPG signals. Results show that significant correlations (r = 0.63, p < 0.01; r = 0.42, p < 0.05; r = 0.8, p < 0.01 for OSA part) were found between reductions in Pes and that in PPG based surrogate respiratory signals PPI, PWA and Wv. Results suggest that PPG based relative respiratory effort signal can be considered as an alternative to Pes as a means of measuring changes in inspiratory effort when scoring OSA and CSA parts of MSA events.

Discharge patterns of human tensor palatini motor units during sleep onset

Study Objectives: Upper airway muscles such as genioglossus (GG) and tensor palatini (TP) reduce activity at sleep onset. In GG reduced muscle activity is primarily due to inspiratory modulated motor units becoming silent, suggesting reduced respiratory pattern generator (RPG) output. However, unlike GG, TP shows minimal respiratory modulation and presumably has few inspiratory modulated motor units and minimal input from the RPG. Thus, we investigated the mechanism by which TP reduces activity at sleep onset.

Design: The activity of TP motor units were studied during relaxed wakefulness and over the transition from wakefulness to sleep.

Setting: Sleep laboratory.

Participants: Nine young (21.4 ± 3.4 years) males were studied on a total of 11 nights.

Intervention: Sleep onset.

Measurements and Results: Two TP EMGs (thin, hooked wire electrodes), and sleep and respiratory measures were recorded. One hundred twenty-one sleep onsets were identified (13.4 ± 7.2/subject), resulting in 128 motor units (14.3 ± 13.0/subject); 29% of units were tonic, 43% inspiratory modulated (inspiratory phasic 18%, inspiratory tonic 25%), and 28% expiratory modulated (expiratory phasic 21%, expiratory tonic 7%). There was a reduction in both expiratory and inspiratory modulated units, but not tonic units, at sleep onset. Reduced TP activity was almost entirely due to de-recruitment.

Conclusions: TP showed a similar distribution of motor units as other airway muscles. However, a greater proportion of expiratory modulated motor units were active in TP and these expiratory units, along with inspiratory units, tended to become silent over sleep onset. The data suggest that both expiratory and inspiratory drive components from the RPG are reduced at sleep onset in TP.

Further applications of doppler radar for non-contact respiratory assessment

This paper further investigates the use of Doppler radar for detecting and identifying certain human respiratory characteristics from observed frequency and phase modulations. Specifically, we show how breathing frequencies can be determined from the demodulated signal leading to identifying abnormalities of breathing patterns using signal derivatives, optimal filtering and standard statistical measures. Specifically, we report results on a robust method for distinguishing cessation of the normal breathing cycle. The proposed approach can have potential application in the management of sudden infant death syndrome(SIDS) and sleep apnea.

Comment on: Does bariatric surgery reduce the risk of major cardiovascular events? A retrospective cohort study of morbidly obese surgical patients.

The prevalence of morbid obesity has been shown to be increasing at an even greater rate than general obesity in many developed countries and is likely to continue to ncrease. The high risks of a range of chronic diseases associated with morbid obesity make this a critical ealthcare challenge. Although comprehensive epidemiologic data are not yet available for all the health risks associated with morbid obesity, it is likely to be associated with very high risks of diseases with a large impact on the individual and the health system, including diabetes, cardiovascular disease, sleep apnea, cancer, osteoarthritis, infertility, depression, and mortality.

How do early parenting centres support women with an infant who has a sleep problem?

Some women who have an infant experiencing sleep problems are so sleep deprived themselves that admission to an early parenting centre is needed to help them better manage the situation. This paper reports on a qualitative study that used focus group methods to interview familes who were admitted to an early parenting centre for persistent infant sleep problems. Results showed that parents needed a variety of strategies such as instructional, emotional and physical supports to develop confidence to manage infant's sleep disturbance at home.

Physical activity, emotional stress, sleep disturbances, and daily fluctuations in chronic fatigue symptomatology

The current study explored the relationships between physical and emotional stress and the symptomatology of chronic fatigue syndrome (CFS). Fifty-four CFS patients were studied using a longitudinal design. A self-report format was used to collect daily measures of major physical (sleep disturbance and physical activity) and emotional (subjective emotional stress level) stressors, as well as measures of levels of fatigue and secondary symptoms. The variables accounted for a moderate variance at the individual and occasion levels. Sleep disturbance and emotional stress were found to be positively associated with levels of fatigue and symptomatology, whereas physical activity was found to have a negative relationship with fatigue only. The severity of fatigue and symptoms were found to fluctuate daily in relation with the variables, indicating the complex nature of the associations.

Improving infant sleep and maternal mental health: a cluster randomised trial

Objectives: To determine whether a community-delivered intervention targeting infant sleep problems improves infant sleep and maternal well-being and to report the costs of this approach to the healthcare system.

Design: Cluster randomised trial.

Setting: 49 Maternal and Child Health (MCH) centres (clusters) in Melbourne, Australia.

Participants: 328 mothers reporting an infant sleep problem at 7 months recruited during October–November 2003.

Intervention: Behavioural strategies delivered over individual structured MCH consultations versus usual care.

Main outcome measures: Maternal report of infant sleep problem, depression symptoms (Edinburgh Postnatal Depression Scale (EPDS)), and SF-12 mental and physical health scores when infants were 10 and 12 months old. Costs included MCH sleep consultations, other healthcare services and intervention costs.

Results: Prevalence of infant sleep problems was lower in the intervention than control group at 10 months (56% vs 68%; adjusted OR 0.58 (95% CI: 0.36 to 0.94)) and 12 months (39% vs 55%; adjusted OR 0.50 (0.31 to 0.80)). EPDS scores indicated less depression at 10 months (adjusted mean difference –1.4 (–2.3 to –0.4) and 12 months (–1.7 (–2.6 to –0.7)). SF-12 mental health scores indicated better health at 10 months (adjusted mean difference 3.7 (1.5 to 5.8)) and 12 months (3.9 (1.8 to 6.1)). Total mean costs including intervention design, delivery and use of non-MCH nurse services were £96.93 and £116.79 per intervention and control family, respectively.

Conclusions: Implementing this sleep intervention may lead to health gains for infants and mothers and resource savings for the healthcare system.

What about the mother and family when an infant doesn`t sleep?

Becoming a new parent is a time of enormous change in the lifestyle of women, particularly as women are expected to take on prime responsibly for caring for the child. Motherhood can be exhausting and lonely as women cope with the demands of a new baby. These demands are exacerbated when infants do not sleep. This causes many parents to seek professional intervention with persistent infant sleep problems. Through focus group interviews, this study sought to understand the experiences of 28 women and families in how they coped with and managed an infant with sleep problems. Results indicated that women experienced major role confusion as they internalised the image that 'a good mother does it all'. Persistent infant crying and their own sleep deprivation exacerbated their loss of identity and shattered their self image, and caused anger and confusion in some partners. Each woman sought primary health care support through a five day residential stay in an Early Parenting Centre in Victoria. The women found that this professional support facilitated confidence building and feelings of normality. Most important, staff encouraged the women to feel good about themselves and their ability to manage future sleep problems.

Sleep quality and depression during pregnancy: a prospective study

For the first time, the relationship between depressive symptoms and sleep quality was explored prospectively during pregnancy. Participants (n = 273) completed the Pittsburgh Sleep Quality Index and Beck Depression Inventory at three 8-week intervals, starting from 15–23 weeks gestation. In addition to sleep quality and depression remaining relatively stable during pregnancy, findings revealed that sleep quality earlier in pregnancy predicted higher levels of depressive symptoms at later stage in pregnancy (after controlling for prior depression levels). In contrast, there was no evidence to suggest that depressive symptoms earlier in pregnancy impacted on sleep quality later on. Given that depressive symptomatology can lead to major depression and given the prevalence of pre- and postnatal depression, our findings suggest that screening for sleep problems during pregnancy may be of clinical significance.

Assessing Sleep during Pregnancy - a study across two time points examining the pittsburg sleep quality index and associations with depressive symptoms

Background and Purpose: Sleep quality seems to be an antecedent to depressive symptoms during pregnancy. We sought to 1) examine the psychometrics of the Pittsburgh Sleep Quality Index (PSQI) in pregnancy; 2) examine whether sleep quality predicted increases in depressive symptoms; and 3) compare PSQI scores across 3 or 2 levels of depressive symptoms.

Methods: Each of the 252 participants completed the Beck Depression Inventory (short form) and a sleep quality measure at mid and late pregnancy.

Results: PSQI total scores showed good internal consistency and construct validity. An improved model of the internal structure of the PSQI in pregnancy was found with 1 factor labeled Sleep Efficiency, a second labeled Night and Daytime Disturbances, and an Overall Sleep Quality component associated with, but separate from, both of these 2 factors. Although PSQI scores showed moderate stability over time, sleep disturbance scores increased in late pregnancy. Importantly, PSQI prospectively predicted increases in depressive symptoms.

Conclusions: Findings suggest that the PSQI is useful in pregnancy research. Findings also support the idea that sleep problems are prospective risk factors for increases in depressive symptoms during pregnancy. Practitioners are advised to screen for sleep quality during early pregnancy.