scholarly journals Tetraplegia is associated with enhanced peripheral chemoreflex sensitivity and ventilatory long-term facilitation

2015 ◽  
Vol 119 (10) ◽  
pp. 1183-1193 ◽  
Author(s):  
Abdulghani Sankari ◽  
Amy T. Bascom ◽  
Anas Riehani ◽  
M. Safwan Badr
Keyword(s):  
Heart Rate ◽  
Minute Ventilation ◽  
Low Frequency ◽  
Time Period ◽  
Cord Injury ◽  
Chemoreflex Sensitivity ◽  
Peripheral Chemoreflex ◽  
Long Term Facilitation ◽  
Mixed Gases

Cardiorespiratory plasticity induced by acute intermittent hypoxia (AIH) may contribute to recovery following spinal cord injury (SCI). We hypothesized that patients with cervical SCI would demonstrate higher minute ventilation (V̇e) following AIH compared with subjects with thoracic SCI and able-bodied subjects who served as controls. Twenty-four volunteers (8 with cervical SCI, 8 with thoracic SCI, and 8 able-bodied) underwent an AIH protocol during wakefulness. Each subject experienced 15 episodes of isocapnic hypoxia using mixed gases of 100% nitrogen (N2), 8% O2, and 40% CO2to achieve oxygen saturation ≤90% followed by room air (RA). Measurements were obtained before, during, and 40 min after AIH to obtain ventilation and heart rate variability data [R-R interval (RRI) and low-frequency/high-frequency power (LF/HF)]. AIH results were compared with those of sham studies conducted in RA during the same time period. Individuals with cervical SCI had higher V̇e after AIH compared with able-bodied controls (117.9 ± 23.2% vs. 97.9 ± 11.2%, P < 0.05). RRI decreased during hypoxia in all individuals (those with cervical SCI, from 1,009.3 ± 65.0 ms to 750.2 ± 65.0 ms; those with thoracic SCI, from 945.2 ± 65.0 ms to 674.9 ± 65.0 ms; and those who were able-bodied, from 949 ± 75.0 to 682.2 ± 69.5 ms; P < 0.05). LH/HF increased during recovery in individuals with thoracic SCI and those who were able-bodied (0.54 ± 0.22 vs. 1.34 ± 0.22 and 0.67 ± 0.23 vs. 1.82 ± 0.23, respectively; P < 0.05) but remained unchanged in the group with cervical SCI. Our conclusion is that patients with cervical SCI demonstrate ventilatory long-term facilitation following AIH compared with able-bodied controls. Heart rate responses to hypoxia are acutely present in patients with cervical SCI but are absent during posthypoxic recovery.

Long Term Effects of Low Frequency (10 Hz) Vagus Nerve Stimulation on EEG and Heart Rate Variability in Crohn's Disease: A Case Report

2014 ◽  
Vol 7 (6) ◽  
pp. 914-916 ◽  
Author(s):  
Didier Clarençon ◽  
Sonia Pellissier ◽  
Valérie Sinniger ◽  
Astrid Kibleur ◽  
Dominique Hoffman ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Crohn’S Disease ◽  
Case Report ◽  
Vagus Nerve ◽  
Nerve Stimulation ◽  
Vagus Nerve Stimulation ◽  
Low Frequency ◽  
Long Term Effects

Long-term facilitation of ventilation is not present during wakefulness in healthy men or women

2002 ◽  
Vol 93 (6) ◽  
pp. 2129-2136 ◽  
Author(s):  
A. S. Jordan ◽  
P. G. Catcheside ◽  
F. J. O'Donoghue ◽  
R. D. McEvoy
Keyword(s):  
Repeated Measures ◽  
Human Subjects ◽  
Minute Ventilation ◽  
Upper Airway ◽  
Menstrual Phase ◽  
Healthy Human ◽  
Dilator Muscle ◽  
Obstructive Sleep ◽  
Long Term Facilitation

Obstructive sleep apnea (OSA) is more common in men than in women for reasons that are unclear. The stability of the respiratory controller has been proposed to be important in OSA pathogenesis and may be involved in the gender difference in prevalence. Repetitive hypoxia elicits a progressive rise in ventilation in animals [long-term facilitation (LTF)]. There is uncertainty whether LTF occurs in humans, but if present it may stabilize respiration and possibly also the upper airway. This study was conducted to determine 1) whether LTF exists during wakefulness in healthy human subjects and, if so, whether it is more pronounced in women than men and 2) whether inspiratory pump and upper airway dilator muscle activities are affected differently by repetitive hypoxia. Twelve healthy young men and ten women in the luteal menstrual phase were fitted with a nasal mask and intramuscular genioglossal EMG (EMGgg) recording electrodes. After 5 min of rest, subjects were exposed to ten 2-min isocapnic hypoxic periods (∼9% O2 in N2, arterial O2 saturation ∼80%) separated by 2 min of room air. Inspired minute ventilation (V˙i) and peak inspiratory EMGgg activity were averaged over 30-s intervals, and respiratory data were compared between genders during and after repetitive hypoxia by using ANOVA for repeated measures. V˙i during recovery from repetitive hypoxia was not different from the resting level and not different between genders. There was no facilitation of EMGgg activity during or after repetitive hypoxia. EMGgg activity was reduced below baseline during recovery from repetitive hypoxia in women. In conclusion, we have found no evidence of LTF of ventilation or upper airway dilator muscle activity in healthy subjects during wakefulness.

scholarly journals Endurance training attenuates the increase in peripheral chemoreflex sensitivity with intermittent hypoxia

2017 ◽  
Vol 312 (2) ◽  
pp. R223-R228 ◽  
Author(s):  
Amanda J. Miller ◽  
Charity L. Sauder ◽  
Aimee E. Cauffman ◽  
Cheryl A. Blaha ◽  
Urs A. Leuenberger
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Endurance Training ◽  
Intermittent Hypoxia ◽  
Muscle Sympathetic Nerve Activity ◽  
Interval Training ◽  
Control Subjects ◽  
Healthy Humans ◽  
Chemoreflex Sensitivity ◽  
Peripheral Chemoreflex

Patients with heart failure and sleep apnea have greater chemoreflex sensitivity, presumably due to intermittent hypoxia (IH), and this is predictive of mortality. We hypothesized that endurance training would attenuate the effect of IH on peripheral chemoreflex sensitivity in healthy humans. Fifteen young healthy subjects (9 female, 26 ± 1 yr) participated. Between visits, 11 subjects underwent 8 wk of endurance training that included running four times/wk at 80% predicted maximum heart rate and interval training, and four control subjects did not change activity. Chemoreflex sensitivity (the slope of ventilation responses to serial oxygen desaturations), blood pressure, heart rate, and muscle sympathetic nerve activity (MSNA) were assessed before and after 30 min of IH. Endurance training decreased resting systolic blood pressure (119 ± 3 to 113 ± 3 mmHg; P = 0.027) and heart rate (67 ± 3 to 61 ± 2 beats/min; P = 0.004) but did not alter respiratory parameters at rest ( P > 0.2). Endurance training attenuated the IH-induced increase in chemoreflex sensitivity (pretraining: Δ 0.045 ± 0.026 vs. posttraining: Δ −0.028 ± 0.040 l·min−1·% O2 desaturation−1; P = 0.045). Furthermore, IH increased mean blood pressure and MSNA burst rate before training ( P < 0.05), but IH did not alter these measures after training ( P > 0.2). All measurements were similar in the control subjects at both visits ( P > 0.05). Endurance training attenuates chemoreflex sensitization to IH, which may partially explain the beneficial effects of exercise training in patients with cardiovascular disease.

scholarly journals Changes in Heart Rate Variability of Depressed Patients after Electroconvulsive Therapy

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Erica B. Royster ◽  
Lisa M. Trimble ◽  
George Cotsonis ◽  
Brian Schmotzer ◽  
Amita Manatunga ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Depressive Symptoms ◽  
Electroconvulsive Therapy ◽  
Low Frequency ◽  
Frequency Component ◽  
High Frequency Component ◽  
Acute Changes ◽  
The Impact

Objective. As few, small studies have examined the impact of electroconvulsive therapy (ECT) upon the heart rate variability of patients with major depressive disorder (MDD), we sought to confirm whether ECT-associated improvement in depressive symptoms would be associated with increases in HRV linear and nonlinear parameters. Methods. After providing consent, depressed study participants (n=21) completed the Beck Depression Index (BDI), and 15-minute Holter monitor recordings, prior to their 1st and 6th ECT treatments. Holter recordings were analyzed for certain HRV indices: root mean square of successive differences (RMSSD), low-frequency component (LF)/high-frequency component (HF) and short-(SD1) versus long-term (SD2) HRV ratios. Results. There were no significant differences in the HRV indices of RMSDD, LF/HF, and SD1/SD2 between the patients who responded, and those who did not, to ECT. Conclusion. In the short term, there appear to be no significant improvement in HRV in ECT-treated patients whose depressive symptoms respond versus those who do not. Future studies will reveal whether diminished depressive symptoms with ECT are reliably associated with improved sympathetic/parasympathetic balance over the long-term, and whether acute changes in sympathetic/parasympathetic balance predict improved mental- and cardiac-related outcomes.

Chronic intermittent hypoxia reduces ventilatory long-term facilitation and enhances apnea frequency in newborn rats

2008 ◽  
Vol 294 (4) ◽  
pp. R1356-R1366 ◽  
Author(s):  
Cécile Julien ◽  
Aida Bairam ◽  
Vincent Joseph
Keyword(s):  
Intermittent Hypoxia ◽  
Gradual Increase ◽  
Minute Ventilation ◽  
Whole Body ◽  
Male Rat ◽  
Chronic Intermittent Hypoxia ◽  
Protective Mechanism ◽  
Rat Pups ◽  
Long Term Facilitation

Ventilatory long-term facilitation (LTF; defined as gradual increase of minute ventilation following repeated hypoxic exposures) is well described in adult mammals and is hypothesized to be a protective mechanism against apnea. In newborns, LTF is absent during the first postnatal days, but its precise developmental pattern is unknown. Accordingly, this study describes this pattern of postnatal development. Additionally, we tested the hypothesis that chronic intermittent hypoxia (CIH) from birth alters this development. LTF was estimated in vivo using whole body plethysmography by exposing rat pups at postnatal days 1, 4, and 10 (P1, P4, and P10) to 10 brief hypoxic cycles (nadir 5% O2) and respiratory recordings during the following 2 h (recovery, 21% O2). Under these conditions, ventilatory LTF (gradual increase of minute ventilation during recovery) was clearly expressed in P10 rats but not in P1 and P4. In a second series of experiments, rat pups were exposed to CIH during the first 10 postnatal days (6 brief cyclic exposures at 5% O2 every 6 min followed by 1 h under normoxia, 24 h a day). Compared with P10 control rats, CIH enhanced hypoxic ventilatory response (estimated during the hypoxic cycles) specifically in male rat pups. Ventilatory LTF was drastically reduced in P10 rats exposed to CIH, which was associated with higher apnea frequency during recovery. We conclude that CIH from birth enhances hypoxic chemoreflex and disrupts LTF development, thus likely contributing to increase apnea frequency.

scholarly journals Ampakine CX717 potentiates intermittent hypoxia-induced hypoglossal long-term facilitation

2016 ◽  
Vol 116 (3) ◽  
pp. 1232-1238 ◽  
Author(s):  
S. M. Turner ◽  
M. K. ElMallah ◽  
A. K. Hoyt ◽  
J. J. Greer ◽  
D. D. Fuller
Keyword(s):  
Ampa Receptors ◽  
Intermittent Hypoxia ◽  
Motor Output ◽  
Mechanically Ventilated ◽  
Cord Injury ◽  
Burst Amplitude ◽  
Recording Conditions ◽  
Post Hoc ◽  
Long Term Facilitation

Glutamatergic currents play a fundamental role in regulating respiratory motor output and are partially mediated by α-amino-3-hydroxy-5-methyl-isoxazole-propionic acid (AMPA) receptors throughout the premotor and motor respiratory circuitry. Ampakines are pharmacological compounds that enhance glutamatergic transmission by altering AMPA receptor channel kinetics. Here, we examined if ampakines alter the expression of respiratory long-term facilitation (LTF), a form of neuroplasticity manifested as a persistent increase in inspiratory activity following brief periods of reduced O2 [intermittent hypoxia (IH)]. Current synaptic models indicate enhanced effectiveness of glutamatergic synapses after IH, and we hypothesized that ampakine pretreatment would potentiate IH-induced LTF of respiratory activity. Inspiratory bursting was recorded from the hypoglossal nerve of anesthetized and mechanically ventilated mice. During baseline (BL) recording conditions, burst amplitude was stable for at least 90 min (98 ± 5% BL). Exposure to IH (3 × 1 min, 15% O2) resulted in a sustained increase in burst amplitude (218 ± 44% BL at 90 min following final bout of hypoxia). Mice given an intraperitoneal injection of ampakine CX717 (15 mg/kg) 10 min before IH showed enhanced LTF (500 ± 110% BL at 90 min). Post hoc analyses indicated that CX717 potentiated LTF only when initial baseline burst amplitude was low. We conclude that under appropriate conditions ampakine pretreatment can potentiate IH-induced respiratory LTF. These data suggest that ampakines may have therapeutic value in the context of hypoxia-based neurorehabilitation strategies, particularly in disorders with blunted respiratory motor output such as spinal cord injury.

scholarly journals Postfatigue potentiation of the paralyzed soleus muscle: evidence for adaptation with long-term electrical stimulation training

2006 ◽  
Vol 101 (2) ◽  
pp. 556-565 ◽  
Author(s):  
Richard K. Shields ◽  
Shauna Dudley-Javoroski ◽  
Andrew E. Littmann
Keyword(s):  
Electrical Stimulation ◽  
Soleus Muscle ◽  
Neuromuscular Electrical Stimulation ◽  
Low Frequency ◽  
Home Based ◽  
Early Implementation ◽  
Cord Injury ◽  
Low Frequency Fatigue ◽  
Output Behavior

Understanding the torque output behavior of paralyzed muscle has important implications for the use of functional neuromuscular electrical stimulation systems. Postfatigue potentiation is an augmentation of peak muscle torque during repetitive activation after a fatigue protocol. The purposes of this study were 1) to quantify postfatigue potentiation in the acutely and chronically paralyzed soleus and 2) to determine the effect of long-term soleus electrical stimulation training on the potentiation characteristics of recently paralyzed soleus muscle. Five subjects with chronic paralysis (>2 yr) demonstrated significant postfatigue potentiation during a repetitive soleus activation protocol that induced low-frequency fatigue. Ten subjects with acute paralysis (<6 mo) demonstrated no torque potentiation in response to repetitive stimulation. Seven of these acute subjects completed 2 yr of home-based isometric soleus electrical stimulation training of one limb (compliance = 83%; 8,300 contractions/wk). With the early implementation of electrically stimulated training, potentiation characteristics of trained soleus muscles were preserved as in the acute postinjury state. In contrast, untrained limbs showed marked postfatigue potentiation at 2 yr after spinal cord injury (SCI). A single acute SCI subject who was followed longitudinally developed potentiation characteristics very similar to the untrained limbs of the training subjects. The results of the present investigation support that postfatigue potentiation is a characteristic of fast-fatigable muscle and can be prevented by timely neuromuscular electrical stimulation training. Potentiation is an important consideration in the design of functional electrical stimulation control systems for people with SCI.

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