2,015 research outputs found
Assessment of respiratory flow cycle morphology in patients with chronic heart failure
Breathing pattern as periodic breathing (PB) in chronic heart failure (CHF) is associated with poor prognosis and high mortality risk. This work investigates the significance of a number of time domain parameters for characterizing respiratory flow cycle morphology in patients with CHF. Thus, our primary goal is to detect PB pattern and identify patients at higher risk. In addition, differences in respiratory flow cycle morphology between CHF patients (with and without PB) and healthy subjects are studied. Differences between these parameters are assessed by investigating the following three classification issues: CHF patients with PB versus with non-periodic breathing (nPB), CHF patients (both PB and nPB) versus healthy subjects, and nPB patients versus healthy subjects. Twenty-six CHF patients (8/18 with PB/nPB) and 35 healthy subjects are studied. The results show that the maximal expiratory flow interval is shorter and with lower dispersion in CHF patients than in healthy subjects. The flow slopes are much steeper in CHF patients, especially for PB. Both inspiration and expiration durations are reduced in CHF patients, mostly for PB. Using the classification and regression tree technique, the most discriminant parameters are selected. For signals shorter than 1 min, the time domain parameters produce better results than the spectral parameters, with accuracies for each classification of 82/78, 89/85, and 91/89 %, respectively. It is concluded that morphologic analysis in the time domain is useful, especially when short signals are analyzed.Peer ReviewedPostprint (author's final draft
Resonance as the Mechanism of Daytime Periodic Breathing in Patients with Heart Failure
Rationale: In patients with chronic heart failure, daytime oscillatory breathing at rest is associated with a high risk of mortality. Experimental evidence, including exaggerated ventilatory responses to CO2 and prolonged circulation time, implicates the ventilatory control system and suggests feedback instability (loop gainâ>â1) is responsible. However, daytime oscillatory patterns often appear remarkably irregular versus classic instability (Cheyne-Stokes respiration), suggesting our mechanistic understanding is limited.
Objectives: We propose that daytime ventilatory oscillations generally result from a chemoreflex resonance, in which spontaneous biological variations in ventilatory drive repeatedly induce temporary and irregular ringing effects. Importantly, the ease with which spontaneous biological variations induce irregular oscillations (resonance âstrengthâ) rises profoundly as loop gain rises toward 1. We tested this hypothesis through a comparison of mathematical predictions against actual measurements in patients with heart failure and healthy control subjects.
Methods: In 25 patients with chronic heart failure and 25 control subjects, we examined spontaneous oscillations in ventilation and separately quantified loop gain using dynamic inspired CO2 stimulation.
Measurements and Main Results: Resonance was detected in 24 of 25 patients with heart failure and 18 of 25 control subjects. With increased loop gainâconsequent to increased chemosensitivity and delayâthe strength of spontaneous oscillations increased precipitously as predicted (râ=â0.88), yielding larger (râ=â0.78) and more regular (interpeak interval SD, râ=ââ0.68) oscillations (Pâ<â0.001 for all, both groups combined).
Conclusions: Our study elucidates the mechanism underlying daytime ventilatory oscillations in heart failure and provides a means to measure and interpret these oscillations to reveal the underlying chemoreflex hypersensitivity and reduced stability that foretells mortality in this population
Modelling the human pharyngeal airway: validation of numerical simulations using in vitro experiments
In the presented study, a numerical model which predicts the flow-induced
collapse within the pharyngeal airway is validated using in vitro measurements.
Theoretical simplifications were considered to limit the computation time.
Systematic comparisons between simulations and measurements were performed on
an in vitro replica, which reflects asymmetries of the geometry and of the
tissue properties at the base of the tongue and in pathological conditions
(strong initial obstruction). First, partial obstruction is observed and
predicted. Moreover, the prediction accuracy of the numerical model is of 4.2%
concerning the deformation (mean quadratic error on the constriction area). It
shows the ability of the assumptions and method to predict accurately and
quickly a fluid-structure interaction
Modulations of Heart Rate, ECG, and Cardio-Respiratory Coupling Observed in Polysomnography
The cardiac component of cardio-respiratory polysomnography is covered by ECG and heart rate recordings. However their evaluation is often underrepresented in summarizing reports. As complements to EEG, EOG, and EMG, these signals provide diagnostic information for autonomic nervous activity during sleep. This review presents major methodological developments in sleep research regarding heart rate, ECG and cardio-respiratory couplings in a chronological (historical) sequence. It presents physiological and pathophysiological insights related to sleep medicine obtained by new technical developments. Recorded nocturnal ECG facilitates conventional heart rate variability analysis, studies of cyclical variations of heart rate, and analysis of ECG waveform. In healthy adults, the autonomous nervous system is regulated in totally different ways during wakefulness, slow-wave sleep, and REM sleep. Analysis of beat-to-beat heart-rate variations with statistical methods enables us to estimate sleep stages based on the differences in autonomic nervous system regulation. Furthermore, up to some degree, it is possible to track transitions from wakefulness to sleep by analysis of heart-rate variations. ECG and heart rate analysis allow assessment of selected sleep disorders as well. Sleep disordered breathing can be detected reliably by studying cyclical variation of heart rate combined with respiration-modulated changes in ECG morphology (amplitude of R wave and T wave)
Assessment of respiratory flow cycle morphology in patients with chronic heart failure
Breathing pattern as periodic breathing (PB) in chronic heart failure (CHF) is associated with poor prognosis and high mortality risk. This work investigates the significance of a number of time domain parameters for characterizing respiratory flow cycle morphology in patients with CHF. Thus, our primary goal is to detect PB pattern and identify patients at higher risk. In addition, differences in respiratory flow cycle morphology between CHF patients (with and without PB) and healthy subjects are studied. Differences between these parameters are assessed by investigating the following three classification issues: CHF patients with PB versus with non-periodic breathing (nPB), CHF patients (both PB and nPB) versus healthy subjects, and nPB patients versus healthy subjects. Twenty-six CHF patients (8/18 with PB/nPB) and 35 healthy subjects are studied. The results show that the maximal expiratory flow interval is shorter and with lower dispersion in CHF patients than in healthy subjects. The flow slopes are much steeper in CHF patients, especially for PB. Both inspiration and expiration durations are reduced in CHF patients, mostly for PB. Using the classification and regression tree technique, the most discriminant parameters are selected. For signals shorter than 1 min, the time domain parameters produce better results than the spectral parameters, with accuracies for each classification of 82/78, 89/85, and 91/89 %, respectively. It is concluded that morphologic analysis in the time domain is useful, especially when short signals are analyzed
The Different Facets of Heart Rate Variability in Obstructive Sleep Apnea
Obstructive sleep apnea (OSA), a heterogeneous and multifactorial sleep related breathing disorder with high prevalence, is a recognized risk factor for cardiovascular morbidity and mortality. Autonomic dysfunction leads to adverse cardiovascular outcomes in diverse pathways. Heart rate is a complex physiological process involving neurovisceral networks and relative regulatory mechanisms such as thermoregulation, renin-angiotensin-aldosterone mechanisms, and metabolic mechanisms. Heart rate variability (HRV) is considered as a reliable and non-invasive measure of autonomic modulation response and adaptation to endogenous and exogenous stimuli. HRV measures may add a new dimension to help understand the interplay between cardiac and nervous system involvement in OSA. The aim of this review is to introduce the various applications of HRV in different aspects of OSA to examine the impaired neuro-cardiac modulation. More specifically, the topics covered include: HRV time windows, sleep staging, arousal, sleepiness, hypoxia, mental illness, and mortality and morbidity. All of these aspects show pathways in the clinical implementation of HRV to screen, diagnose, classify, and predict patients as a reasonable and more convenient alternative to current measures.Peer Reviewe
Sleep-time predictors of cardiovascular complications in surgical peripheral arterial disease
ABSTRACT
Patients with peripheral arterial disease (PAD) undergoing surgical revascularisation are in high risk of postoperative cardiovascular complications and death, due to advancing age and multiple comorbidities in the population. In addition, PAD needing surgery represents a severe form of systemic atherosclerosis but the exact underlying pathophysiology of acute myocardial infarction (AMI) in these patients is unclear and predicting outcome especially in the long-term is challenging.
Obstructive sleep apnoea (OSA) is increasingly common in the general population and independently associated with various manifestations of cardiovascular disease or their risk factors; OSA is highly prevalent in patients with coronary artery disease (CAD), stroke, hypertension and diabetes. To expand this knowledge, we determined the prevalence and severity (in terms of the apnoeahypopnoea index, AHI) of OSA in surgical PAD as well as its impact on the incidence of major adverse cardiovascular and cerebrovascular events (MACCE) in this patient group.
Heart rate variability (HRV) reflects fluctuations in sympathetic and parasympathetic activation responsible for neurocirculatory control in various physiological and pathophysiological situations. Depressed HRV is associated with increased cardiovascular morbidity and mortality following AMI and major surgery. In this study, the alterations of nocturnal HRV and their association with the severity of OSA and incidence of MACCE in patients with PAD was assessed, including the fractal correlation properties of HRV. HRV in a control group of 15 healthy subjects was also examined.
Patients scheduled for sub-inguinal vascular surgery (n=84, age 67±9 years) underwent polysomnography and HRV analyses. OSA was detected in 86% of patients and in 56% it was moderate or severe. Age, male gender, depressed left ventricular function and decreasing high density lipoprotein/cholesterol ratio (HDL/Chol) predicted the presence and severity of OSA. The latter two remained significant after adjusting for age and gender. OSA with AHI â„20/hour, used as a cut-off in the outcome analyses, predicted a higher risk of MACCE (p=0.001) along with pre-existing CAD (p=0.001), decreasing HDL/Chol (p=0.048) and <4 years history of PAD (p=0.018).
HRV was altered in patients with PAD when compared to controls but the time domain measures were mostly unchanged. In the frequency domain, low frequency power was generally lower, high frequency power was mostly higher and fractal correlation was consistently lower. Very low frequency power was increased the most in patients with AHI 10-20/hour when compared to <10/hour while those with AHI â„20/hour had lower fractal correlation in the morning. Patients suffering a MACCE had lower high frequency power during S3-4 and rapid eye movement sleep.
In conclusion, OSA is associated with worsening atherosclerosis and predicts MACCE after vascular surgery. HRV alterations, although associated with PAD, have limited predictive value.
Keywords: atherosclerosis, peripheral arterial disease, sleep apnoea, heart rate variabilityTIIVISTELMĂ
Unenaikaiset sydÀnkomplikaatioiden ennustetekijÀt kirurgista hoitoa vaativassa perifeerisessÀ valtimotaudissa
PerifeeristÀ valtimotautia sairastavilla potilailla on suuri leikkauksenjÀlkeisten sydÀnkomplikaatioiden riski johtuen yhÀ iÀkkÀÀmmÀstÀ vÀestöstÀ sekÀ lukuisista rinnakkaissairauksista. LisÀksi perifeerinen valtimotauti merkitsee vaikea-asteista yleistynyttÀ ateroskleroosia, mutta sydÀninfarktin tarkka syntymekanismi nÀillÀ potilailla on epÀselvÀ ja erityisesti pitkÀn aikavÀlin ennusteen arviointi on haastavaa.
Obstruktiivinen uniapnea yleistyy vÀestössÀ ja sillÀ on itsenÀinen yhteys useisiin sydÀn- ja verisuonisairauksiin ja niiden riskitekijöihin; uniapnea on erittÀin yleinen sepelvaltimotauti-, aivohalvaus-, verenpainetauti- ja diabetespotilailla. TÀmÀn tietopohjan laajentamiseksi tÀssÀ tutkimuksessa mÀÀritettiin uniapnean esiintyvyys ja vaikeusaste (mÀÀrittÀjÀnÀ apnea-hypopneaindeksi, AHI) vaikea-asteista yleistynyttÀ ateroskleroosia sairastavilla potilailla sekÀ sen vaikutus vakavien sydÀn- ja aivotapahtumien ilmaantuvuuteen.
SydÀmen sykevaihtelu kuvastaa autonomisen hermoston toiminnan muutoksia, jotka puolestaan vastaavat verenkierron sÀÀtelystÀ erilaisissa fysiologisissa ja patofysiologisissa tilanteissa. Alentunut sykevaihtelu on yhteydessÀ lisÀÀntyneeseen kardiovaskulaariseen sairastuvuuteen ja kuolleisuuteen sairastetun sydÀninfarktin tai suuren leikkauksen jÀlkeen. TÀssÀ tutkimuksessa arvioitiin yöllisen sydÀmen sykevaihtelun muutosten yhteyttÀ uniapnean vaikeusasteeseen sekÀ vakavien sydÀn- ja aivotapahtumien ilmaantuvuuteen, mukaan lukien sykevaihtelun fraktaalikorrelaatio-ominaisuudet. Tutkimuksessa analysoitiin sykevaihtelu myös 15 terveen henkilön vertailuryhmÀltÀ.
Nivustason alapuoliseen verisuonileikkaukseen meneville potilaille (n=84, ikĂ€ 67±9 vuotta) tehtiin unipolygrafia ja sykevaihteluanalyysi. Uniapnea todettiin 86 %:lla potilaista ja 56 %:lla se oli kohtalainen tai vaikea. IkĂ€, miessukupuoli, heikentynyt vasemman kammion toiminta ja alentunut HDL-kolesterolin suhde kokonaiskolesteroliin ennustivat uniapneaa ja sen vaikeutumista; 2 viimeksi mainittua sĂ€ilyivĂ€t merkitsevinĂ€ ikĂ€- ja sukupuolivakioinnin jĂ€lkeen. AHI â„20/tunti, joka valittiin kynnysarvoksi pÀÀtetapahtumaanalyyseihin, ennusti merkitsevĂ€sti vakavia sydĂ€n- ja aivotapahtumia (p=0.001). Muita merkitseviĂ€ tekijöitĂ€ olivat sepelvaltimotauti (p=0.001), alentunut HDL-suhde (p=0.048) ja lyhyt (alle 4 vuotta) perifeerisen valtimotaudin kesto ennen leikkaushoidon tarvetta (p=0.018).
Sykevaihtelu oli muuttunut valtimotautipotilailla verrattuna kontrolleihin, mutta aikakenttĂ€parametrit sĂ€ilyivĂ€t lĂ€hes ennallaan. Pienitaajuuksinen sykevaihtelu oli yleisesti vĂ€hĂ€isempÀÀ, suuritaajuuksinen enimmĂ€kseen voimakkaampaa ja fraktaalikorrelaatio johdonmukaisesti heikompaa. Hyvin pienitaajuuksinen vaihtelu oli eniten lisÀÀntynyt AHI 10-20/tunti -alaryhmĂ€ssĂ€ verrattuna AHI <10/tunti -ryhmÀÀn, mutta AHI â„20/tunti -potilailla aamun fraktaalikorrelaatio oli heikompaa. Potilaiden, jotka saivat vakavia sydĂ€n- ja aivotapahtumia, suuritaajuusvaihtelu oli heikompaa syvĂ€n unen ja vilkeunen aikana.
JohtopÀÀtöksinÀ todetaan, ettÀ uniapnea on yhteydessÀ vaikeutuvaan valtimotautiin sekÀ ennustaa vakavia sydÀn- ja aivotapahtumia verisuonileikkauksen jÀlkeen sykevaihtelun muutosten ennustearvon ollessa tÀssÀ aineistossa hyvin rajallinen.
Avainsanat: ateroskleroosi, perifeerinen valtimotauti, uniapnea, sykevaihtel
Sleep medicine: Practice, challenges and new frontiers
Sleep medicine is an ambitious cross-disciplinary challenge, requiring the mutual integration between complementary specialists in order to build a solid framework. Although knowledge in the sleep field is growing impressively thanks to technical and brain imaging support and through detailed clinic-epidemiologic observations, several topics are still dominated by outdated paradigms. In this review we explore the main novelties and gaps in the field of sleep medicine, assess the commonest sleep disturbances, provide advices for routine clinical practice and offer alternative insights and perspectives on the future of sleep research
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