Breathlessness and exercise in spinal cord injury

The detection and sensory perception of inspiratory resistive loads in people with chronic tetraplegia

This study investigated sensations of breathing following tetraplegia. Fifteen people with chronic tetraplegia and fifteen healthy able-bodied controls matched for age, sex, height, and weight participated. Sensations of breathing were quantified by determining the threshold for detecting an added resistance during inspiration. In a separate task, the perceived magnitudes of six suprathreshold resistive loads were determined with a modified Borg scale. The detection threshold of 0.34 cmH₂O/L/s [standard deviation (SD) 0.14] in the tetraplegia group was higher than the 0.23 cmH₂O/L/s (SD 0.10) threshold for able-bodied controls (P = 0.004). Both participant groups perceived larger loads to be more effortful, with the Borg effort rating increasing linearly with the peak inspiratory pressure generated at each load. The relationship between Borg effort rating and peak inspiratory pressure was steeper in participants with tetraplegia than in able-bodied controls (P = 0.001), but there was no difference when pressure was divided by maximal inspiratory pressure (P = 0.95). Despite a higher detection threshold, the findings suggest that the perceived magnitude of a suprathreshold inspiratory load is not impaired in chronic tetraplegia and that load magnitude perception is related to the maximal, and not absolute, inspiratory muscle force.NEW & NOTEWORTHY Sensations of breathing are thought to be impaired following chronic tetraplegia. The detection threshold for an added resistive load during inspiration was higher in people with tetraplegia than in healthy able-bodied participants. However, for inspiratory loads above the detection threshold, the perceived magnitude of a resistive load as a function of the peak inspiratory pressure was greater in tetraplegia. Load magnitude perception was comparable between participant groups when peak pressure was divided by maximal inspiratory pressure.

Serotonin 1A Receptor Pharmacotherapy and Neuroplasticity in Spinal Cord Injury

Spinal cord injury is associated with damage in descending and ascending pathways between brainstem/cortex and spinal neurons, leading to loss in sensory-motor functions. This leads not only to locomotor reduction but also to important respiratory impairments, both reducing cardiorespiratory engagement, and increasing cardiovascular risk and mortality. Moreover, individuals with high-level injuries suffer from sleep-disordered breathing in a greater proportion than the general population. Although no current treatments exist to restore motor function in spinal cord injury (SCI), serotoninergic (5-HT) 1A receptor agonists appear as pharmacologic neuromodulators that could be important players in inducing functional improvements by increasing the activation of spared motoneurons. Indeed, single therapies of serotoninergic 1A (5-HT_1A) agonists allow for acute and temporary recovery of locomotor function. Moreover, the 5-HT_1A agonist could be even more promising when combined with other pharmacotherapies, exercise training, and/or spinal stimulation, rather than administered alone. In this review, we discuss previous and emerging evidence showing the value of the 5HT_1A receptor agonist therapies for motor and respiratory limitations in SCI. Moreover, we provide mechanistic hypotheses and clinical impact for the potential benefit of 5-HT_1A agonist pharmacology in inducing neuroplasticity and improving locomotor and respiratory functions in SCI.

Serotonin 1A agonist and cardiopulmonary improvements with whole-body exercise in acute, high-level spinal cord injury: a retrospective analysis

PURPOSE

High-level spinal cord injury (SCI) can result in spinal and supraspinal respiratory control deficits leading to insufficient ventilatory responses to exercise and training-related adaptations. We hypothesized a serotonin agonist, known to improve respiratory function in animal models, would improve adaptations to whole-body functional electrical stimulation (FES) exercise training in patients with acute high-level SCI.

METHODS

We identified 10 patients (< 2 years of injury with SCI from C4 to T3) in our program who had performed 6 months of FES-row training while on Buspirone (29 ± 17 mg/day) between 2012 and 2018. We also identified well-matched individuals who trained for six months but not on Buspirone (n = 11). A peak incremental FES-rowing exercise test and resting pulmonary function test had been performed before and after training.

RESULTS

Those on Buspirone demonstrated greater increases in peak oxygen consumption (VO₂peak: + 0.24 ± 0.23 vs. + 0.10 ± 0.13 L/min, p = 0.08) and peak ventilation (VEpeak: + 6.5 ± 8.1 vs. - 0.7 ± 6.9 L/min, p < 0.05) compared to control. In addition, changes in VO₂peak and VEpeak were correlated across all patients (r = 0.63, p < 0.01), but most strongly in those on Buspirone (r = 0.85, p < 0.01). Furthermore, changes in respiratory function correlated with increased peak tidal volume in the Buspirone group (r > 0.66, p < 0.05).

CONCLUSION

These results suggest Buspirone improves cardiorespiratory adaptations to FES-exercise training in individuals with acute, high-level SCI. The strong association between increases in ventilatory and aerobic capacities suggests improved respiratory function is a mechanism; however, controlled studies are needed to determine if this preliminary finding is reproducible.

Active Lifestyle Is Associated With Reduced Dyspnea and Greater Life Satisfaction in Spinal Cord Injury

OBJECTIVE

To assess the relations between measures of activity with dyspnea and satisfaction with life in chronic spinal cord injury (SCI).

DESIGN

Cross-sectional survey.

SETTING

Five SCI centers.

PARTICIPANTS

Between July 2012 and March 2015, subjects (N=347) with traumatic SCI ≥1 year after injury who used a manual wheelchair or walked with or without an assistive device reported hours spent away from home or yard on the previous 3 days, sports participation, and planned exercise.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Satisfaction with Life Scale (SWLS) and dyspnea. Dyspnea was defined as shortness of breath when hurrying on the level or going up a slight hill, going slower than people the same age on the level because of breathlessness, or stopping for breath when going at your own pace, or after about 100yd (or after a few minutes) on the level.

RESULTS

Dyspnea prevalence was 30%. Adjusting for asthma or chronic obstructive pulmonary disease, mobility mode, race, and season, there was a significant linear trend between greater SWLS scores and quartiles of time spent away from the home or yard (P=.0002). SWLS score was greater if participating in organized sports (P=.01), although was not significantly greater with planned exercise (P=.093). Planned exercise was associated with a reduced odds ratio (OR) of dyspnea (.57; 95% confidence interval [CI], .34-.95; P=.032), but organized sports was not (P=.265). Dyspnea was not significantly increased in persons who spent the fewest hours outside their home or yard (≤7h) compared with people who spent the most hours outside their home or yard (>23h) (OR=1.69; 95% CI, 0.83-3.44; P=.145).

CONCLUSIONS

In SCI, a planned exercise program is associated with less dyspnea. An active lifestyle characterized by greater time spent away from home or yard and sports participation is associated with greater SWLS scores.

Pulmonary function and spinal cord injury

Injury to the cervical and upper thoracic spinal cord disrupts function of inspiratory and expiratory muscles, as reflected by reduction in spirometric and lung volume parameters and static mouth pressures. In association, subjects with tetraplegia have decreased chest wall and lung compliance, increased abdominal wall compliance, and rib cage stiffness with paradoxical chest wall movements, all of which contribute to an increase in the work of breathing. Expiratory muscle function is more compromised than inspiratory muscle function among subjects with tetraplegia and high paraplegia, which can result in ineffective cough and propensity to mucus retention and atelectasis. Subjects with tetraplegia also demonstrate heightened vagal activity with reduction in baseline airway caliber, findings attributed to loss of sympathetic innervation to the lungs. Significant increase in airway caliber following inhalation of ipratropium bromide, an anticholinergic agent, suggests that reduction in airway caliber is not due to acquired airway fibrosis stemming from repeated infections or to abnormal hysteresis secondary to chronic inability of subjects to inhale to predicted total lung capacity. Reduced baseline airway caliber possibly explains why subjects with tetraplegia exhibit airway hyperresponsiveness to methacholine and ultrasonically nebulized distilled water. While it has been well demonstrated that bilateral phrenic nerve pacing or stimulation through intramuscular diaphragmatic electrodes improves inspiratory muscle function, it remains unclear if inspiratory muscle training improves pulmonary function. Recent findings suggest that expiratory muscle training, electrical stimulation of expiratory muscles and administration of a long-acting beta(2)-agonist (salmeterol) improve physiological parameters and cough. It is unknown if baseline bronchoconstriction in tetraplegia contributes to respiratory symptoms, of if the chronic administration of a bronchodilator reduces the work of breathing and/or improves respiratory symptoms. Less is known regarding the benefits of treatment of obstructive sleep apnea, despite evidence indicating that the prevalence of this condition in persons with tetraplegia is far greater than that encountered in able-bodied individuals.

Dyspnea during daily activities in chronic spinal cord injury

OBJECTIVE

To assess factors associated with breathlessness in chronic spinal cord injury (SCI) during daily activities.

DESIGN

Cross-sectional survey.

SETTINGS

Veterans Affairs SCI service and the community.

PARTICIPANTS

Four hundred forty-one participants 1 or more years post-SCI, and without acute illness, were recruited between 1994 and 2003 and were categorized according to their ability to walk unassisted, walk with an aid, or to move about by either hand-propelled wheelchair or motorized wheelchair (MWC).

INTERVENTIONS

Assessment of injury extent, respiratory symptoms, cigarette smoking, comorbid medical conditions, and spirometry.

MAIN OUTCOME MEASURES

Breathlessness during talking, eating, or dressing.

RESULTS

Breathlessness was more common in MWC users (20/85 users, 24%) than in nonusers (20/356, 6%). The main activity associated with breathlessness in 15 MWC users was talking (18%). In MWC users, the risk of breathlessness was related to lifetime cigarette smoking (odds ratio [OR]=1.02; 95% confidence interval [CI], 1.00-1.03 per pack year), and reports of chronic cough (OR=7.8; 95% CI, 2.0-32.7), and wheeze (OR=3.5; 95% CI, 1.04-13.6). SCI level, percentage of predicted forced vital capacity and forced expiratory volume in 1 second, and maximal inspiratory pressures were not related to breathlessness.

CONCLUSIONS

Breathlessness during selected daily activities (most commonly talking) was greatest in SCI participants who were most impaired with regard to mobility and was associated with reports of coughing, wheezing, and cigarette smoking.

Spirometry testing standards in spinal cord injury

STUDY OBJECTIVES

Because muscle paralysis makes it uncertain whether subjects with spinal cord injury (SCI) can perform spirometry in accordance with American Thoracic Society (ATS) standards, determinants of test failure were examined.

DESIGN

Cross-sectional study.

SETTING

Veterans Affairs (VA) medical center.

PARTICIPANTS

Veterans with SCI at VA Boston Healthcare System and nonveterans recruited by mail and advertisement.

MEASUREMENTS AND RESULTS

Two hundred thirty of 278 subjects (83%) were able to produce three expiratory efforts lasting > or = 6 s and without excessive back-extrapolated volume (EBEV). In 217 of 230 subjects (94%), FVC and FEV(1) were each reproducible in accordance with 1994 ATS standards. In the remaining 48 subjects, efforts with smooth and continuous volume-time tracings and acceptable flow-volume loops were identified. These subjects had a lower percentage of predicted FVC, FEV(1), and maximum expiratory and inspiratory pressures compared to the others, and a greater proportion had neurologically complete cervical injury (42% compared to 16%). In 19 subjects (40%), some expiratory efforts were not sustained maximally for > or = 6 s but had at least a 0.5-s plateau at residual volume (short efforts). In eight subjects (17%), some efforts were not short but had EBEV. In the remaining 21 subjects (44%), some efforts were short, some had EBEV, and some had both. If these efforts were not rejected, 262 of 278 subjects (94%) would have produced three acceptable efforts, and in 257 subjects (92%), the efforts were reproducible.

CONCLUSIONS

Subjects with SCI with the most impaired respiratory muscles and abnormal pulmonary function are able to perform spirometry reproducibly despite not meeting usual ATS acceptability standards. Exclusion of these subjects would lead to bias in studies of respiratory function in SCI. The modification of spirometry testing standards to include efforts with EBEV and with a 0.5-s plateau if < 6 s would reduce the potential for bias.

Spinal cord injury medicine. 4. Optimal participation in life after spinal cord injury: physical, psychosocial, and economic reintegration into the environment

This learner-directed module on spinal cord injury (SCI) presents a variety of perspectives of the process of personal and environmental adaptation for reintegration. Adaptation is unique to each person and does not predictably follow stages. Models used for understanding the process include biopsychosocial, ICIDH-2 (International Classification of Functioning, Disability and Health), and sector divisions of the environment. Home modification requires home (intermediate environment) evaluation and sociospatial behavioral mapping for planning and appropriation of remodeling in proportion to functional need and use. Options for access to the natural environment include specialized wheelchairs, climbing rigging, kayaks, and sail boats. Sports participation with adaptations is expanding and includes a larger variety of organizations and leagues. Economic needs are effectively anticipated with development of a life care plan. Procreative options to overcome infertility after SCI include vibratory stimulation for ejaculation, intravaginal insemination, intrauterine insemination, in vitro fertilization, and intracytoplasmic sperm injection. Approaches to requests for withdrawal of life-sustaining care include depression screening, pain evaluation, and assistance in accomplishment of person centered goals. Overall, community reintegration after SCI is continually improving because of better acceptance, accessibility, and technology for building adaptations.

OVERALL ARTICLE OBJECTIVES

(a) To review models and theories of medical intervention and disablement and (b) to demonstrate their application in rehabilitation practice by designing unique treatment plans that meet patient person-centered goals.