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Sleep onset hypoventilation in chronic spinal cord injury.

ABSTRACT: A high prevalence of sleep-disordered breathing (SDB) after spinal cord injury (SCI) has been reported in the literature; however, the underlying mechanisms are not well understood. We sought to determine the effect of the withdrawal of the wakefulness drive to breathe on the degree of hypoventilation in SCI patients and able-bodied controls. We studied 18 subjects with chronic cervical and thoracic SCI (10 cervical, 8 thoracic SCI; 11 males; age 42.4 ± 17.1 years; body mass index 26.3 ± 4.8 kg/m(2)) and 17 matched able-bodied subjects. Subjects underwent polysomnography, which included quantitative measurement of ventilation, timing, and upper airway resistance (RUA) on a breath-by-breath basis during transitions from wake to stage N1 sleep. Compared to able-bodied controls, SCI subjects had a significantly greater reduction in tidal volume during the transition from wake to N1 sleep (from 0.51 ± 0.21 to 0.32 ± 0.10 L vs. 0.47 ± 0.13 to 0.43 ± 0.12 L; respectively, P < 0.05). Moreover, end-tidal CO2 and end-tidal O2 were significantly altered from wake to sleep in SCI (38.9 ± 2.7 mmHg vs. 40.6 ± 3.4 mmHg; 94.1 ± 7.1 mmHg vs. 91.2 ± 8.3 mmHg; respectively, P < 0.05), but not in able-bodied controls (39.5 ± 3.2 mmHg vs. 39.9 ± 3.2 mmHg; 99.4 ± 5.4 mmHg vs. 98.9 ± 6.1 mmHg; respectively, P = ns). RUA was not significantly altered in either group. In conclusion, individuals with SCI experience hypoventilation at sleep onset, which cannot be explained by upper airway mechanics. Sleep onset hypoventilation may contribute to the development SDB in the SCI population.

SUBMITTER: Bascom AT

PROVIDER: S-EPMC4562576 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

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Sleep onset hypoventilation in chronic spinal cord injury.

Bascom Amy T AT Sankari Abdulghani A Goshgarian Harry G HG Badr M Safwan MS

Physiological reports 20150801 8

A high prevalence of sleep-disordered breathing (SDB) after spinal cord injury (SCI) has been reported in the literature; however, the underlying mechanisms are not well understood. We sought to determine the effect of the withdrawal of the wakefulness drive to breathe on the degree of hypoventilation in SCI patients and able-bodied controls. We studied 18 subjects with chronic cervical and thoracic SCI (10 cervical, 8 thoracic SCI; 11 males; age 42.4 ± 17.1 years; body mass index 26.3 ± 4.8 kg/ ...[more]

PMID: 26290534

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Project description:With emerging applications of spinal cord electrical stimulation in restoring autonomic and motor function after spinal cord injury, understanding the neuroanatomical substrates of the human spinal cord after spinal cord injury using neuroimaging techniques can play a critical role in optimizing the outcomes of these stimulation-based interventions. In this study, we have introduced a neuroimaging acquisition and analysis protocol of the spinal cord in order to identify: (i) spinal cord levels at the lumbosacral enlargement using nerve root tracing; (ii) variability in the neuroanatomical characteristics of the spinal cord among individuals; (iii) location of the epidural stimulation paddle electrode and contacts with respect to the spinal cord levels at lumbosacral enlargement; and (iv) the links between the anatomical levels of stimulation and the corresponding neurophysiological motor responses. Twelve individuals with chronic, motor complete spinal cord injury implanted with a spinal cord epidural stimulator were included in the study (age: 34 ± 10.9 years, sex: 10 males, 2 females, time since injury: 8.2 ± 9.9 years, American Spinal Injury Association Impairment Scale: 6 A, 6 B). High-resolution MRI scans of the spinal cord were recorded pre-implant. An analysis of neuroanatomical substrates indicates that the length of the spinal column and spinal cord, location of the conus tip and the relationship between the spinal cord levels and vertebral levels, particularly at the lumbosacral enlargement, are variable across individuals. There is no statistically significant correlation between the length of the spinal column and the length of the spinal cord. The percentage of volumetric coverage of the lumbosacral spinal cord by the epidural stimulation paddle electrode ranges from 33.4 to 90.4% across participants. The location of the spinal cord levels with respect to the electrode contacts varies across individuals and impacts the recruitment patterns of neurophysiological responses. Finally, MRI-based spinal cord modelling can be used as a guide for the prediction and preplanning of optimum epidural stimulation paddle placement prior to the implant surgery to ensure maximizing functional outcomes. These findings highlight the crucial role that the neuroanatomical characteristics of the spinal cord specific to each individual play in achieving maximum functional benefits with spinal cord electrical stimulation.

Project description:Deficient ankle control after incomplete spinal cord injury (iSCI) often accentuates walking impairments. Transcutaneous electrical spinal cord stimulation (tSCS) has been shown to augment locomotor activity after iSCI, presumably due to modulation of spinal excitability. However, the effects of possible excitability modulations induced by tSCS on ankle control have not yet been assessed. This study investigated the immediate (i.e., without training) effects during single-sessions of tonic tSCS on ankle control, spinal excitability, and locomotion in ten individuals with chronic, sensorimotor iSCI (American Spinal Injury Association Impairment Scale D). Participants performed rhythmic ankle movements (dorsi- and plantar flexion) at a given rate, and irregular ankle movements following a predetermined trajectory with and without tonic tSCS at 15 Hz, 30 Hz, and 50 Hz. In a subgroup of eight participants, the effects of tSCS on assisted over-ground walking were studied. Furthermore, the activity of a polysynaptic spinal reflex, associated with spinal locomotor networks, was investigated to study the effect of the stimulation on the dedicated spinal circuitry associated with locomotor function. Tonic tSCS at 30 Hz immediately improved maximum dorsiflexion by +4.6° ± 0.9° in the more affected lower limb during the rhythmic ankle movement task, resulting in an increase of +2.9° ± 0.9° in active range of motion. Coordination of ankle movements, assessed by the ability to perform rhythmic ankle movements at a given target rate and to perform irregular movements according to a trajectory, was unchanged during stimulation. tSCS at 30 Hz modulated spinal reflex activity, reflected by a significant suppression of pathological activity specific to SCI in the assessed polysynaptic spinal reflex. During walking, there was no statistical group effect of tSCS. In the subgroup of eight assessed participants, the three with the lowest as well as the one with the highest walking function scores showed positive stimulation effects, including increased maximum walking speed, or more continuous and faster stepping at a self-selected speed. Future studies need to investigate if multiple applications and individual optimization of the stimulation parameters can increase the effects of tSCS, and if the technique can improve the outcome of locomotor rehabilitation after iSCI.

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Sleep onset hypoventilation in chronic spinal cord injury.

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Sleep onset hypoventilation in chronic spinal cord injury.

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