Physical realization of complex dynamical pattern formation in magnetic active feedback rings

We report the clean experimental realization of cubic-quintic complex Ginzburg-Landau physics in a single driven, damped system. Four numerically predicted categories of complex dynamical behavior and pattern formation are identified for bright and dark solitary waves propagating around an active magnetic thin film-based feedback ring: (1) periodic breathing; (2) complex recurrence; (3) spontaneous spatial shifting; and (4) intermittency. These nontransient, long lifetime behaviors are observed in self-generated microwave spin wave envelopes circulating within a dispersive, nonlinear yttrium iron garnet waveguide. The waveguide is operated in a ring geometry in which the net losses are directly compensated for via linear amplification on each round trip (of the order of 100~ns). These behaviors exhibit periods ranging from tens to thousands of round trip times (of the order of $\mu$s) and are stable for 1000s of periods (of the order of~ms). We present 10 observations of these dynamical behaviors which span the experimentally accessible ranges of attractive cubic nonlinearity, dispersion, and external field strength that support the self-generation of backward volume spin waves in a four-wave-mixing dominant regime. Three-wave splitting is not explicitly forbidden and is treated as an additional source of nonlinear losses. All observed behaviors are robust over wide parameter regimes, making them promising for technological applications. We present ten experimental observations which span all categories of dynamical behavior previously theoretically predicted to be observable. This represents a complete experimental verification of the cubic-quintic complex Ginzburg-Landau equation as a model for the study of fundamental, complex nonlinear dynamics for driven, damped waves evolving in nonlinear, dispersive systems. The reported dynamical pattern formation of self-generated dark solitary waves in attractive nonlinearity without external sources or potentials, however, is entirely novel and is presented for both the periodic breather and complex recurrence behaviors.

Dynamic vortex evolution of harmonically trapped coupled Bose–Einstein condensate with quintic nonlinearity

In this study, we investigate the evolution of vortex in harmonically trapped two-component coupled Bose–Einstein condensate with quintic-order nonlinearity. We derive the vortex solution of this two-component system based on the coupled quintic-order Gross–Pitaevskii equation model and the variational method. It is found that the evolution of vortex is a metastable state. The radius of vortex soliton shrinks and expands with time, resulting in periodic breathing oscillation, and the angular frequency of the breathing oscillation is twice the value of the harmonic trapping frequency under infinitesimal nonlinear strength. At the same time, it is also found that the higher-order nonlinear term has a quantitative effect rather than a qualitative impact on the oscillation period. With practical experimental setting, we identify the quasi-stable oscillation of the derived vortex evolution mode and illustrated its features graphically. The theoretical results developed in this work can be used to guide the experimental observation of the vortex phenomenon in ultracold coupled atomic systems with quintic-order nonlinearity.

Sleep Apnoea and Heart Failure

Heart Failure (HF) and Sleep-Disordered-Breathing (SDB) are two common conditions that frequently overlap and have been studied extensively in the past three decades. Obstructive Sleep Apnea (OSA) may result in myocardial damage, due to intermittent hypoxia increased sympathetic activity and transmural pressures, low-grade vascular inflammation and oxidative stress. On the other hand, central sleep apnoea and Cheyne-Stokes respiration (CSA-CSR) occurs in HF, irrespective of ejection fraction either reduced (HFrEF), preserved (HFpEF) or mildly reduced (HFmrEF). The pathophysiology of CSA-CSR relies on several mechanisms leading to hyperventilation, breathing cessation and periodic breathing. Pharyngeal collapse may result at least in part from fluid accumulation in the neck, owing to daytime fluid retention and overnight rostral fluid shift from the legs. Although both OSA and CSA-CSR occur in HF, the symptoms are less suggestive than in typical (non-HF related) OSA. Overnight monitoring is mandatory for a proper diagnosis, with accurate measurement and scoring of central and obstructive events, since the management will be different depending on whether the sleep apnea in HF is predominantly OSA or CSA-CSR. SDB in HF are associated with worse prognosis, including higher mortality than in patients with HF but without SDB. However, there is currently no evidence that treating SDB improves clinically important outcomes in patients with HF, such as cardiovascular morbidity and mortality.

Periodic breathing in patients with stable obstructive sleep apnea on long-term continuous positive airway pressure treatment: a retrospective study using CPAP remote monitoring data

Purpose The purpose of this study was to investigate the rate of periodic breathing (PB) and factors associated with the emergence or persistence of PB in patients with obstructive sleep apnea (OSA) by continuous positive airway pressure (CPAP) remote monitoring data. Methods This was a retrospective cohort study on 775 patients who had used the same model CPAP machine for at least 1 year as of September 1, 2020. The data were analyzed online using the dedicated analysis system. Using exporter software, average apnea/hypopnea index (AHI), average central apnea index (CAI), and average the rate of PB time (PB%) were cited. Results Among 618 patients analyzed (age 61.7 ± 12.2 years, male 89%, BMI 27.2 ± 4.9), the average duration of CPAP use was 7.5 ± 4.0 years. The median PB% in stable patients was low at 0.32%, and only 149 patients (24%) had a PB% above 1%. Multiple regression analysis of factors for the development of PB showed that the most important factor was atrial fibrillation (Af) with a coefficient of 0.693 (95% CI; 0.536 to 0.851), followed by QRS duration with a coefficient of 0.445 (95% CI; 0.304 to 0.586), followed by history of heart failure, male sex, comorbid hypertension, obesity, and age. The average PB% for paroxysmal Af was significantly lower than that for persistent and permanent Af. Conclusions The median PB% in stable patients on CPAP treatment was low at 0.32%, with only 24% of patients having PB% ≥ 1%. Persistent Af and an increase in QRS duration were found to be important predictors of increased PB%. Clinical trial registration UMIN000042555 2021/01/01.

P168 Pre and postnatal factors associated with periodic breathing in preterm infants

Introduction Immature cardio-respiratory control in preterm infants often manifests as periodic breathing (PB). A number of pre- and postnatal demographic and clinical factors, such as exposure to maternal smoking, respiratory support and medications may affect respiratory control. We aimed to identify specific factors affecting the frequency of PB in preterm infants before hospital discharge. Methods 32 healthy preterm infants (14M, 18F) born between 28–32 weeks of gestational age were studied for 2–3 hours with daytime polysomnography at 31–36 weeks (when they had been off respiratory support for ≥ 3 days). % sleep time spent in PB was calculated. Variables are reported as median (IQR) and were compared with Mann-Whitney U and Chi square tests, between infants who spent greater or less than the median time in PB. Results 29 infants (91%) exhibited at least one episode of PB. Median sleep time in PB was 9.6% (IQR 0.6, 15.6%). Infants with time in PB above the median spent fewer days on respiratory support (4.0 days (1.0, 7.5) vs 9.0 (6.5, 21.5) days, p=0.035), and were younger (post-menstrual age 33.8 (IQR 32.1, 34.5) vs 35.1 (IQR 32.4, 35.6) weeks, p= 0.039). Conclusions Of the large number of maternal and infant demographic and clinical variables examined, we found few associations with the time preterm infants spent in PB. Greater % time spent in PB was associated with earlier discontinuation of respiratory support, however larger studies are required to confirm these findings and to investigate if there are any long-term consequences.

Neuromodulatory Support for Breathing and Cardiovascular Action During Development

Neonatal survival requires precise control of breathing and cardiovascular action, with fatal consequences or severe injury without support. Prematurity presents multiple opportunities to disrupt cardiorespiratory regulation, leading to expressions of apnea of prematurity, periodic breathing, and inappropriate cardiovascular responses to apnea. Failed breathing control can result from altered breathing drives, typically arising from untimely development of sensory or motor coordination processes. Some drives, such as temperature, are a special concern in neonates with low body mass, enhancing susceptibility to rapid body cooling. Chemical drives, such as pH or CO2 or O2, may be inadequately developed; in some conditions, such as congenital central hypoventilation syndrome (CCHS), breathing responses to CO2 or low O2 may be reduced or absent, and coupling of cardiovascular responses to breathing changes are abolished. Sleep states exert profound influences on both chemical and temperature drives, with rapid eye movement (REM) sleep potentially modifying descending temperature influences, and state transitions significantly altering respiratory responses to chemical stimuli. In addition, neonates spend the majority of time in REM sleep, a state which induces a generalized inhibition of skeletal muscle activity that abolishes muscle tone to upper airway and thoracic wall muscles, enhancing the likelihood for obstructive sleep apnea. Although disrupted regulatory drives can often be replaced by positive (or negative) pressure ventilation, such as continuous positive airway pressure or enhanced by manipulating neurotransmitter action via caffeine, those approaches may exert negative consequences in the long term; the lungs of neonates, especially premature infants, are fragile, and easily injured by positive pressure. The consequences of caffeine use, acting directly on neural receptors, although seemingly innocuous in the near-term, may have long-term concerns and disrupts the integrity of sleep. The developmental breathing field needs improved means to support ventilation when one or more drives to respiration fail, and when the cardiovascular system, depending heavily on interactions with breathing, is compromised. Neuromodulatory procedures which manipulate the vestibular system to stabilize breathing or use tactile or proprioceptive stimuli to activate long-established reflexive mechanisms coupling limb movement with respiratory efforts can provide support for central and obstructive apnea, as well as for periodic breathing and cardiovascular action, particularly during sleep.

The timing of intermittent hypoxia differentially affects macronutrient intake and energy substrate utilization in mice.

Sleep apnea is a common sleep disorder characterized by periodic breathing cessation and intermittent hypoxia (IH). While previous studies have demonstrated that IH alone can influence metabolic outcomes such as body weight, it remains unclear how the timing of IH can specifically affect these outcomes. Here, we examine how pairing 10-hour periods of IH to either the animals' resting phase (e.g. IH during the day) or active phase (e.g. IH during the night) differentially affects body weight, macronutrient selection, energy expenditure, respiratory exchange rate, and glucose tolerance. We find that in contrast to mice exposed to IH during the night, mice exposed to IH during the day preferentially decrease their carbohydrate intake and switch to fat metabolism. Moreover when the IH stimulus was removed, mice that had been exposed to day IH continued to eat a minimal amount of carbohydrates and consumed a higher percentage of Kcal from fat for at least 5 days. These data demonstrate that food choice and substrate utilization are secondary to the timing of IH but not IH itself. Taken together, these data have key clinical implications for individuals with sleep apnea and particularly those who are also experiencing circadian disruption such as night-shift workers.

Severity of Central Sleep Apnea Does Not Affect Sleeping Oxygen Saturation During Ascent to High Altitude

Central sleep apnea (CSA) is characterized by periodic breathing (PB) during sleep, defined as intermittent periods of apnea/hypopnea and hyperventilation, with associated acute fluctuations in oxyhemoglobin saturation (SO2). CSA has an incidence of ~50% in heart failure patients but is universal at high-altitude (HA; ≥2,500 m), increasing in severity with further ascent and/or time at altitude. However, whether PB is adaptive, maladaptive, or neutral with respect to sleeping SO2 at altitude is unclear. We hypothesized that PB severity would improve mean sleeping SO2 during acclimatization to HA due to relative, intermittent hyperventilation subsequent to each apnea. We utilized portable sleep monitors to assess the incidence and severity of CSA via apnea-hypopnea index (AHI) and oxygen desaturation index (ODI), and peripheral oxygen saturation (SpO2) during sleep during two ascent profiles to HA in native lowlanders: (I) rapid ascent to and residence at 3,800 m for 9 days/nights (n=21) and (II) incremental ascent to 5,160 m over 10 days/nights (n=21). In both ascent models, severity of AHI and ODI increased and mean sleeping SpO2 decreased, as expected. However, during sleep on the last night/highest altitude of both ascent profiles, neither AHI nor ODI were correlated with mean sleeping SpO2. In addition, mean sleeping SpO2 was not significantly different between high and low CSA. These data suggest that CSA is neither adaptive nor maladaptive with regard to mean oxygen saturation during sleep, owing to the relative hyperventilation between apneas, likely correcting transient apnea-mediated oxygen desaturation and maintaining mean oxygenation.