The hypoxic ventilatory response and hypoxic burden are predictors of the magnitude of ventilatory long-term facilitation in humans.

Mild intermittent hypoxia initiates progressive augmentation (PA) and ventilatory long-term facilitation (vLTF) in humans. The magnitude of these forms of plasticity might be influenced by anthropometric and physiological variables, as well as protocol elements. However, the impact of many of these variables on the magnitude of respiratory plasticity has not been established in humans.

The Clinical Relevance of Autonomic Dysfunction, Cerebral Hemodynamics, and Sleep Interactions in Individuals Living With SCI.

A myriad of physiological impairments is seen in individuals after a spinal cord injury (SCI). These include altered autonomic function, cerebral hemodynamics, and sleep. These physiological systems are interconnected and likely insidiously interact leading to secondary complications.

Racial differences in upper airway collapsibility and loop gain in young adult males.

Study Objectives: Previous studies reported that the apnea-hypopnea index was similar in young adult Black and White participants. However, whether this similarity reflects an analogous combination of apneas and hypopneas is unknown. Likewise, the physiological mechanisms underlying this similarity has not been explored.

Divergent Ventilatory and Blood Pressure Responses are Evident Following Repeated Daily Exposure to Mild Intermittent Hypoxia in Males with OSA and Hypertension.

Resting minute ventilation and ventilation during and following hypoxia may be enhanced following daily exposure to mild intermittent hypoxia (MIH). In contrast, resting systolic blood pressure (SBP) is reduced following daily exposure to MIH. However, it is presently unknown if the reduction in resting SBP following daily exposure, is coupled with reduced SBP responses during and after acute exposure to MIH.

The effect of brain serotonin deficiency on breathing is magnified by age.

Serotonin is an important mediator modulating behavior, metabolism, sleep, control of breathing, and upper airway function, but the role of aging in serotonin-mediated effects has not been previously defined. Our study aimed to examine the effect of brain serotonin deficiency on breathing during sleep and metabolism in younger and older mice. We measured breathing during sleep, hypercapnic ventilatory response (HCVR), CO production (VCO ), and O consumption (VO ) in 16-18-week old and 40-44-week old mice with deficiency of tryptophan hydroxylase 2 (Tph2), which regulates serotonin synthesis specifically in neurons, compared to Tph2 mice.

Pathophysiology of Obstructive Sleep Apnea in Aging Women.

The following review is designed to explore the pathophysiology of sleep apnea in aging women. The review initially introduces four endotypes (i.e.

Daily Exposure to Mild Intermittent Hypoxia Reduces Blood Pressure in Male Patients with Obstructive Sleep Apnea and Hypertension.

Daily exposure to mild intermittent hypoxia (MIH) may elicit beneficial cardiovascular outcomes. To determine the effect of 15 days of MIH and in-home continuous positive airway pressure treatment on blood pressure in participants with obstructive sleep apnea and hypertension. We administered MIH during wakefulness 5 days/week for 3 weeks.

A comprehensive review of respiratory, autonomic and cardiovascular responses to intermittent hypoxia in humans.

This review explores forms of respiratory and autonomic plasticity, and associated outcome measures, that are initiated by exposure to intermittent hypoxia. The review focuses primarily on studies that have been completed in humans and primarily explores the impact of mild intermittent hypoxia on outcome measures. Studies that have explored two forms of respiratory plasticity, progressive augmentation of the hypoxic ventilatory response and long-term facilitation of ventilation and upper airway muscle activity, are initially reviewed.

Variations in loop gain and arousal threshold during NREM sleep are affected by time of day over a 24-hour period in participants with obstructive sleep apnea.

We investigated whether time of day affects loop gain (LG) and the arousal threshold (AT) during non-rapid eye movement (NREM) sleep. Eleven men with obstructive sleep apnea (apnea-hypopnea index > 5 events/h) completed a constant-routine protocol that comprised 3-h sleep sessions in the evening [10 PM (1) to 1 AM], morning (6 AM to 9 AM), afternoon (2 PM to 5 PM), and subsequent evening [10 PM (2) to 1 AM]. During each sleep session LG and the AT were measured during NREM sleep with a model-based approach.

Effect of virtual reality-simulated exercise on sympathovagal balance.

Discovery of therapeutic avenues to provide the benefits of exercise to patients with enforced sedentary behavior patterns would be of transformative importance to health care. Work in model organisms has demonstrated that benefits of exercise can be provided to stationary animals by daily intermittent stimulation of adrenergic signaling. Here, we examine as a proof of principle whether exposure of human participants to virtual reality (VR) simulation of exercise can alter sympathovagal balance in stationary humans.

Increased Oxidative Stress, Loop Gain And The Arousal Threshold Are Clinical Predictors Of Increased Apnea Severity Following Exposure To Intermittent Hypoxia.

Purpose: We determined if oxidative stress prior to sleep onset is correlated to loop gain (LG) and the arousal threshold (AT) during non-rapid eye movement (NREM) sleep. We also explored if LG and AT are correlated with apnea severity and indices of upper airway collapsibility during NREM sleep.

Methods: Thirteen male participants with obstructive sleep apnea (apnea-hypopnea index > 5 events/hr) were administered an antioxidant or placebo cocktail while exposed to mild intermittent hypoxia in the awake state.

Exposure to mild intermittent hypoxia increases loop gain and the arousal threshold in participants with obstructive sleep apnoea.

Key Points: Repeated daily mild intermittent hypoxia has been endorsed as a therapy to promote the recovery of respiratory and limb motor dysfunction. One possible side-effect of this therapy is an increase in apnoeic event number and duration, which is particularly relevant to participants with motor disorders coupled with an increased incidence of sleep apnoea. In this study, we report that increases in apnoeic event number and duration, following exposure to daily intermittent hypoxia, are the result of an increase in respiratory loop gain and the arousal threshold, in participants with obstructive sleep apnoea.

Genetic depletion of 5-HT increases central apnea frequency and duration and dampens arousal but does not impact the circadian modulation of these variables.

We examined the impact of serotonin (5-HT) on the frequency and duration of central apneic events and the frequency of accompanying arousals during nonrapid and rapid eye movement (NREM and REM, respectively) sleep across the light/dark cycle. Electroencephalography, electromyography, core body temperature, and activity were recorded for 24 h following implantation of telemeters in wild-type (Tph2) and tryptophan hydroxylase 2 knockout (Tph2) male mice. The frequency and duration of central apneic events were increased, the number of apneic events coupled to an arousal was decreased, and the ventilatory sensitivity to hypoxia and hypercapnia was decreased in the Tph2 compared with the Tph2 mice during NREM sleep.

The impact of intermittent or sustained carbon dioxide on intermittent hypoxia initiated respiratory plasticity. What is the effect of these combined stimuli on apnea severity?

The following review explores the effect that intermittent or sustained hypercapnia coupled to intermittent hypoxia has on respiratory plasticity. The review explores published work which suggests that intermittent hypercapnia leads to long-term depression of respiration when administered in isolation and prevents the initiation of long-term facilitation when administered in combination with intermittent hypoxia. The review also explores the impact that sustained hypercapnia alone and in combination with intermittent hypoxia has on the magnitude of long-term facilitation.

Exposure to intermittent hypoxia and sustained hypercapnia reduces therapeutic CPAP in participants with obstructive sleep apnea.

Our purpose was to determine whether exposure to mild intermittent hypoxia leads to a reduction in the therapeutic continuous positive airway pressure required to eliminate breathing events. Ten male participants were treated with twelve 2-min episodes of hypoxia ([Formula: see text] ≈50 mmHg) separated by 2-min intervals of normoxia in the presence of [Formula: see text] that was sustained 3 mmHg above baseline. During recovery from the last episode, the positive airway pressure was reduced in a stepwise fashion until flow limitation was evident.

Impact of arousal threshold and respiratory effort on the duration of breathing events across sleep stage and time of night.

Purpose: The frequency and duration of breathing events are influenced by sleep stage and time of day. In the present study we examined if these modifications are linked to adaptations in the arousal threshold and/or the magnitude of respiratory effort during and immediately after breathing events.

Methods: Participants with sleep apnea slept for 3h in the evening and morning.

Sex differences in sleep disordered breathing in adults.

The prevalence of sleep disordered breathing is greater in men compared to women. This disparity could be due to sex differences in the diagnosis and presentation of sleep apnea, and the pathophysiological mechanisms that instigate this disorder. Women tend to report more non-typical symptoms of sleep apnea compared to men, and the presentation of apneic events are more prevalent in rapid compared to non-rapid eye movement sleep.

Intermittent hypoxia promotes recovery of respiratory motor function in spinal cord-injured mice depleted of serotonin in the central nervous system.

We examined the effect of repeated daily exposure to intermittent hypoxia (IH) on the recovery of respiratory and limb motor function in mice genetically depleted of central nervous system serotonin. Electroencephalography, diaphragm activity, ventilation, core body temperature, and limb mobility were measured in spontaneously breathing wild-type (Tph2(+/+)) and tryptophan hydroxylase 2 knockout (Tph2(-/-)) mice. Following a C2 hemisection, the mice were exposed daily to IH (i.