Compensatory muscle activation during forced respiratory tasks in individuals with chronic spinal cord injury

Long-Term Pulmonary Function Postspinal Cord Injury

OBJECTIVE

To investigate mean values of pulmonary function tests (PFT) at specific time points to assess long-term progression in patients with spinal cord injury (SCI).

DESIGN

Retrospective cohort study from 1997-2022.

SETTING

National rehabilitation hospital, providing scheduled admission for potential SCI-related issues. Follow-up assessments are recommended annually, guiding the observation period into consecutive 1-year intervals.

PARTICIPANTS

This study included 1394 adult patients who were admitted at least twice to the National Rehabilitation Center between 1997 and 2022, selected from an initial pool of 1510. Overall, 116 patients were excluded owing to the absence of any PFT results.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Changes in PFT values over time, specifically assessing for a potential 2-phase pattern after injury. The hypothesis that PFT values would initially improve before declining was formulated based on existing literature.

RESULTS

Significant changes in pulmonary function were noted among 1394 adults with SCI. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) initially increased within the first 1-2 years after injury but declined to below baseline levels after 6 years. Pronounced changes occurred between <1 year and 1-2 years after injury (FVC: Δ=4.89, SE=0.87, P<.001; FEV1: Δ=4.28, SE=1.09, P=.002) and 1-2 years to >6 years (FVC: Δ= -5.83, SE=0.94, P<.001; FEV1: Δ= -6.49, SE=1.18, P<.001). No significant changes in the FEV1/FVC ratio. Motor completeness was significantly associated with the increase and decline phase, showing a steeper increase and less decline compared with the motor-incomplete group.

CONCLUSIONS

Pulmonary function in SCI initially increases but declines over time, falling below initial levels by 6 years. Further evaluation with more complete datasets is warranted to elucidate the factors influencing these changes.

The effect of craniocervical flexion and neck endurance exercises plus pulmonary rehabilitation on pulmonary function in spinal cord injury: a pilot single-blinded randomised controlled trial

STUDY DESIGN

Randomised controlled trial with computerised allocation, assessor blinding and intention-to-treat analysis.

OBJECTIVE

This study wanted to prove that cervicocranial flexion exercise (CCFE) and superficial neck flexor endurance training combined with common pulmonary rehabilitation is feasible for improving spinal cord injury people's pulmonary function.

SETTING

Taoyuan General Hospital, Ministry of Health and Welfare: Department of Physiotherapy, Taiwan.

METHOD

Thirteen individuals who had sustained spinal cord injury for less than a year were recruited and randomised assigned into two groups. The experimental group was assigned CCFEs and neck flexor endurance training plus normal cardiopulmonary rehabilitation. The control group was assigned general neck stretching exercises plus cardiopulmonary rehabilitation. Lung function parameters such as forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC, peak expiratory flow rate (PEFR), inspiratory capacity (IC), dyspnoea, pain, and neck stiffness were recorded once a week as short-term outcome measure.

RESULT

The experimental group showed significant time effects for FVC (pre-therapy: 80.4 ± 21.4, post-therapy: 86.9 ± 16.9, p = 0.021, 95% CI: 0.00-0.26) and PEFR (pre-therapy: 67.0 ± 33.4; post-therapy: 78.4 ± 26.9, p = 0.042, 95% CI: 0.00-0.22) after the therapy course. Furthermore, the experimental group showed significant time effects for BDI (experimental group: 6.3 ± 3.0; control group: 10.8 ± 1.6, p = 0.012, 95% CI: 0.00-0.21).

CONCLUSION

The exercise regime for the experimental group could efficiently increase lung function due to the following three reasons: first, respiratory accessory muscle endurance increases through training. Second, posture becomes less kyphosis resulting increasing lung volume. Third, the ratio between superficial and deep neck flexor is more synchronised.

IRB TRIAL REGISTRATION

TYGH108045.

CLINICAL TRIAL REGISTRATION

NCT04500223.

Predicting extubation in patients with traumatic cervical spinal cord injury using the diaphragm electrical activity during a single maximal maneuver

BACKGROUND

The unsuccessful extubation in patients with traumatic cervical spinal cord injuries (CSCI) may result from impairment diaphragm function and monitoring of diaphragm electrical activity (EAdi) can be informative in guiding extubation. We aimed to evaluate whether the change of EAdi during a single maximal maneuver can predict extubation outcomes in CSCI patients.

METHODS

This is a retrospective study of CSCI patients requiring mechanical ventilation in the ICU of a tertiary hospital. A single maximal maneuver was performed by asking each patient to inhale with maximum strength during the first spontaneous breathing trial (SBT). The baseline (during SBT before maximal maneuver), maximum (during the single maximal maneuver), and the increase of EAdi (ΔEAdi, equal to the difference between baseline and maximal) were measured. The primary outcome was extubation success, defined as no reintubation after the first extubation and no tracheostomy before any extubation during the ICU stay.

RESULTS

Among 107 patients enrolled, 50 (46.7%) were extubated successfully at the first SBT. Baseline EAdi, maximum EAdi, and ΔEAdi were significantly higher, and the rapid shallow breathing index was lower in patients who were extubated successfully than in those who failed. By multivariable logistic analysis, ΔEAdi was independently associated with successful extubation (OR 2.03, 95% CI 1.52-3.17). ΔEAdi demonstrated high diagnostic accuracy in predicting extubation success with an AUROC 0.978 (95% CI 0.941-0.995), and the cut-off value was 7.0 μV.

CONCLUSIONS

The increase of EAdi from baseline SBT during a single maximal maneuver is associated with successful extubation and can help guide extubation in CSCI patients.

Changes in respiratory structure and function after traumatic cervical spinal cord injury: observations from spinal cord and brain

Respiratory difficulties and mortality following severe cervical spinal cord injury (CSCI) result primarily from malfunctions of respiratory pathways and the paralyzed diaphragm. Nonetheless, individuals with CSCI can experience partial recovery of respiratory function through respiratory neuroplasticity. For decades, researchers have revealed the potential mechanism of respiratory nerve plasticity after CSCI, and have made progress in tissue healing and functional recovery. While most existing studies on respiratory plasticity after spinal cord injuries have focused on the cervical spinal cord, there is a paucity of research on respiratory-related brain structures following such injuries. Given the interconnectedness of the spinal cord and the brain, traumatic changes to the former can also impact the latter. Consequently, are there other potential therapeutic targets to consider? This review introduces the anatomy and physiology of typical respiratory centers, explores alterations in respiratory function following spinal cord injuries, and delves into the structural foundations of modified respiratory function in patients with CSCI. Additionally, we propose that magnetic resonance neuroimaging holds promise in the study of respiratory function post-CSCI. By studying respiratory plasticity in the brain and spinal cord after CSCI, we hope to guide future clinical work.

Improved pulmonary function is associated with reduced inflammation after hybrid whole-body exercise training in persons with spinal cord injury

NEW FINDINGS

What is the central question of this study? Does 12 weeks of functional electrical stimulation (FES) rowing exercise training lead to suppressed systemic inflammation and an improvement in pulmonary function in persons with sub-acute spinal cord injury (SCI)? What is the main finding and its importance? Twelve weeks of FES rowing exercise improves pulmonary function and the magnitude of improvement is associated with reductions in inflammatory biomarkers. Thus, interventions targeting inflammation may lead to better pulmonary outcomes for person with sub-acute SCI.

ABSTRACT

The current study was designed to test the hypotheses that (1) reducing systemic inflammation via a 12-week functional electrical stimulation rowing exercise training (FESRT) prescription results in augmented pulmonary function, and (2) the magnitude of improvement in pulmonary function is inversely associated with the magnitude of systemic inflammation suppression in persons with sub-acute (≤2 years) spinal cord injury (SCI). We conducted a retrospective analysis of a randomized controlled trial (NCT#02139436). Twenty-one participants were enrolled (standard of care (SOC; n = 9) or FESRT (n = 12)). The exercise prescription was three sessions/week at 70-85% of peak heart rate. A two-way analysis of covariance and regression analysis was used to assess group differences and associations between pulmonary function, log transformed high-sensitivity C-reactive protein (hsCRPlog ) and white blood cell count (WBC). Following FESRT, clinically significant improvements in forced expiratory volume in 1 s (FEV1 ; 0.25 (0.08-0.43) vs. -0.06 (-0.26 to 0.15) litres) and forced vital capacity (0.22 (0.04-0.39) vs. 0.08 (-0.29 to 0.12) litres) were noted and systemic WBC (-1.45 (-2.48 to -0.50) vs. 0.41 (-0.74 to 1.56) μl) levels were suppressed compared to SOC (mean change (95% confidence interval); P < 0.05). Additionally, both ΔhsCRPlog and ΔWBC were predictors of ΔFEV1 (r2  = 0.89 and 0.43, respectively; P < 0.05). Twelve weeks of FESRT improves pulmonary function and reduces WBC in persons with sub-acute SCI. The potency of FESRT to augment pulmonary function may depend on adequate suppression of systemic inflammation.

Inspiratory muscle reflex control after incomplete cervical spinal cord injury

In healthy individuals, loading inspiratory muscles by brief inspiratory occlusion produces a short-latency inhibitory reflex (IR) in the electromyographic (EMG) activity of scalene and diaphragm muscles. This IR may play a protective role to prevent aspiration and airway collapse during sleep. In people with motor and sensory complete cervical spinal cord injury (cSCI), who were able to breathe independently, this IR was predominantly absent. Here, we investigated the reflex response to brief airway occlusion in 16 participants with sensory incomplete cSCI [American spinal injury association impairment scale (AIS) score B or C]. Surface EMG was recorded from scalene muscles and the lateral chest wall (overlying diaphragm). The airway occlusion evoked a small change in mouth pressure resembling a physiological occlusion. The short-latency IR was present in 10 (63%) sensory incomplete cSCI participants; significantly higher than the IR incidence observed in complete cSCI participants in our previous study (14%; P = 0.003). When present, mean IR latency across all muscles was 58 ms (range 29-79 ms), and mean rectified EMG amplitude decreased to 37% preocclusion levels. Participants without an IR had untreated severe obstructive sleep apnea (OSA), in contrast to those with an IR, who had either had no, mild, or treated OSA (P = 0.002). Insufficient power did not allow statistical comparison between IR presence or absence and participant clinical characteristics. In conclusion, spared sensory connections or intersegmental connections may be necessary to generate the IR. Future studies to establish whether IR presence is related to respiratory morbidity in the tetraplegic population are required.NEW & NOTEWORTHY Individuals with incomplete cSCI were tested for the presence of a short latency reflex inhibition of inspiratory muscles, by brief airway occlusion. The reflex was 4.5 times more prevalent in this group compared with those with complete cSCI and is similar to the incidence in able-bodied people. Participants without this reflex all had untreated severe OSA, in contrast to those with an IR, who either had no, mild, or treated OSA. This work reveals novel differences in the reflex control of inspiratory muscles across the cSCI population.

Ultrasonographic evaluation of diaphragm thickness and excursion in patients with cervical spinal cord injury

Objective: To evaluate the diaphragm thickness and excursion in patients with cervical spinal cord injury and reliability of diaphragmatic ultrasonography.Design: A Pilot Case-Control Study.Setting: China Rehabilitation Research Center (CRRC) /Beijing BO AI Hospital.Participants: Sixty participants with cervical spinal cord injury and sixty control participants were eligible for inclusion in this study.Interventions: Ultrasonographic evaluation of the diaphragm.Outcome Measures: All demographic data were evaluated. Diaphragm thickness, thickening ratio, and diaphragm excursions were assessed at the end of quiet tidal breathing and maximal inspiration. The reliability of inter- and intra-ultrasonography operators were evaluated.Results: Diaphragm thickness was significantly higher in patients with cervical spinal cord injury than the control group (P < 0.001). Diaphragmatic excursion of the right hemidiaphragm was significantly greater in patients with cervical spinal cord injury than the control group (P < 0.001) at the end of quiet tidal breathing. No difference was found in diaphragmatic excursion between two groups (P = 0.32) at the end of maximal inspiration. No significant difference was shown between two groups in thickening ratio. Intraclass correlation coefficients of inter-and intra-ultrasonography operators for the thickness and excursions of the diaphragm were greater than 0.93.Conclusion: Compared with the control group the diaphragm in patients with cervical spinal cord injury is hypertrophied and the diaphragm excursion is greater. Ultrasound is a highly reliable tool for the evaluation of diaphragm thickness and excursion in patients with cervical spinal cord injury.Trial Registration: This trail was registered in Chinese Clinical Trial Registry (NO. ChiCTR-ROC-17010973).

Neurophysiological Changes in the First Year After Cell Transplantation in Sub-acute Complete Paraplegia

Neurophysiological testing can provide quantitative information about motor, sensory, and autonomic system connectivity following spinal cord injury (SCI). The clinical examination may be insufficiently sensitive and specific to reveal evolving changes in neural circuits after severe injury. Neurophysiologic data may provide otherwise imperceptible circuit information that has rarely been acquired in biologics clinical trials in SCI. We reported a Phase 1 study of autologous purified Schwann cell suspension transplantation into the injury epicenter of participants with complete subacute thoracic SCI, observing no clinical improvements. Here, we report longitudinal electrophysiological assessments conducted during the trial. Six participants underwent neurophysiology screening pre-transplantation with three post-transplantation neurophysiological assessments, focused on the thoracoabdominal region and lower limbs, including MEPs, SSEPs, voluntarily triggered EMG, and changes in GSR. We found several notable signals not detectable by clinical exam. In all six participants, thoracoabdominal motor connectivity was detected below the clinically assigned neurological level defined by sensory preservation. Additionally, small voluntary activations of leg and foot muscles or positive lower extremity MEPs were detected in all participants. Voluntary EMG was most sensitive to detect leg motor function. The recorded MEP amplitudes and latencies indicated a more caudal thoracic level above which amplitude recovery over time was observed. In contrast, further below, amplitudes showed less improvement, and latencies were increased. Intercostal spasms observed with EMG may also indicate this thoracic “motor level.” Galvanic skin testing revealed autonomic dysfunction in the hands above the injury levels. As an open-label study, we can establish no clear link between these observations and cell transplantation. This neurophysiological characterization may be of value to detect therapeutic effects in future controlled studies.

Ultrasonography of Diaphragm Can Predict Pulmonary Function in Spinal Cord Injury Patients: A Pilot Case-Control Study

BACKGROUND Ultrasonography of the diaphragm is an under-utilized instrument in cervical spinal cord injury patients. We conducted a pilot study to first compare the difference of diaphragm thickness and the excursion between patients with cervical spinal cord injury and healthy volunteers, and second to correlate diaphragmic ultrasonography and pulmonary function in cervical spinal cord injury patients. MATERIAL AND METHODS Thirty patients with C4-C5 cervical spinal cord injury of more than 1 year and thirty healthy volunteers were included in this study. All demographic data were evaluated. All participants underwent diaphragmic ultrasonography evaluation and pulmonary function test. Diaphragm thickness of both sides and diaphragm excursions of the right hemi-diaphragm were obtained at the end of quiet tidal breathing and maximal inspiration. We compared diaphragmatic thickness and excursions, and we analyzed the relationship between diaphragmatic ultrasonography and pulmonary function. RESULTS All spinal cord injury patients had restrictive pulmonary dysfunction compared to the control group of healthy volunteers. Diaphragm thickness on both sides was significantly increased in spinal cord injury patients. Diaphragmatic excursion in spinal cord injury patients was increased on the right hemi-diaphragm during tidal breathing. However, the right hemi-diaphragmatic excursion was no difference in both groups during maximal inspiration. Right hemi-diaphragmatic excursion during deep breathing correlated positively with expiratory volume in 1 second (P<0.01) and forced vital capacity (P<0.01). Right hemi-diaphragm thickness at end of maximum inspiration correlated positively with expiratory volume in 1 second (P<0.01) and forced vital capacity (P<0.01). Left hemi-diaphragm thickness at end of maximum inspiration correlated positively with expiratory volume in 1 second (P<0.01) and forced vital capacity (P<0.01). CONCLUSIONS Diaphragm thickness and motion of the cervical spinal cord injury patients were different from controls. Pulmonary function was impaired in spinal cord injury patients. Ultrasonography of the diaphragm as a non-invasive method that is correlated with pulmonary function.

Muscles of Breathing: Development, Function, and Patterns of Activation

This review is a comprehensive description of all muscles that assist lung inflation or deflation in any way. The developmental origin, anatomical orientation, mechanical action, innervation, and pattern of activation are described for each respiratory muscle fulfilling this broad definition. In addition, the circumstances in which each muscle is called upon to assist ventilation are discussed. The number of "respiratory" muscles is large, and the coordination of respiratory muscles with "nonrespiratory" muscles and in nonrespiratory activities is complex-commensurate with the diversity of activities that humans pursue, including sleep (8.27). The capacity for speech and adoption of the bipedal posture in human evolution has resulted in patterns of respiratory muscle activation that differ significantly from most other animals. A disproportionate number of respiratory muscles affect the nose, mouth, pharynx, and larynx, reflecting the vital importance of coordinated muscle activity to control upper airway patency during both wakefulness and sleep. The upright posture has freed the hands from locomotor functions, but the evolutionary history and ontogeny of forelimb muscles pervades the patterns of activation and the forces generated by these muscles during breathing. The distinction between respiratory and nonrespiratory muscles is artificial, as many "nonrespiratory" muscles can augment breathing under conditions of high ventilator demand. Understanding the ontogeny, innervation, activation patterns, and functions of respiratory muscles is clinically useful, particularly in sleep medicine. Detailed explorations of how the nervous system controls the multiple muscles required for successful completion of respiratory behaviors will continue to be a fruitful area of investigation. © 2019 American Physiological Society. Compr Physiol 9:1025-1080, 2019.

Muscle-specific endurance of the trapezius muscles using electrical twitch mechanomyography

BACKGROUND

Symptoms of fatigue and pain are often reported for the trapezius muscle in the shoulder. The present study evaluated endurance in the trapezius muscles of healthy participants using electric twitch mechanomyography (ETM).

METHODS

Surface electrodes and a tri-axial accelerometer were placed over the left trapezius muscle. Muscles were stimulated for 3 min each at 2 Hz, 4 Hz and 6 Hz. Maintenance of acceleration during muscle twitches was used to calculate an endurance index (EI). Subjects (n = 9) were tested on two separate days to assess reproducibility of the trapezius EI measurements. The endurance measurements were made on the wrist flexor and vastus lateralis muscles for comparison. Near infrared spectroscopy was used to measure muscle oxygenation (HbO₂) during the stimulation protocol (n = 8).

RESULTS

Mean (SD) EI was 84.9% (8.7%), 63.3% (19.1%) and 41.7% (20.0%) for 2 Hz, 4 Hz and 6 Hz, respectively. The coefficients of variation were 7.4%, 11.3% and 24.0% for 2 Hz, 4 Hz and 6 Hz, respectively. EI values were significantly lower in the trapezius compared to arm and leg muscles (p < 0.05). HbO₂ values were unchanged from resting values with electrical stimulation.

CONCLUSIONS

The EI as measured by ETM may provide a reproducible method of evaluating function in trapezius muscles that is not influenced by oxygen saturation.

Respiratory functional and motor control deficits in children with spinal cord injury

Children with spinal cord injury (SCI) are at high risk for developing complications due to respiratory motor control deficits. However, underlying mechanisms of these abnormalities with respect to age, development, and injury characteristics are unclear. To evaluate the effect of SCI and age on respiratory motor control in children with SCI, we compared pulmonary function and respiratory motor control outcome measures in healthy typically developing (TD) children to age-matched children with chronic SCI. We hypothesized that the deficits in respiratory functional performance in children with SCI are due to the abnormal and age-dependent respiratory muscle activation patterns. Fourteen TD (age 7±2 yrs., Mean±SD) and twelve children with SCI (age 6±1 yrs.) were evaluated by assessing Forced Vital Capacity (FVC); Forced Expiratory Volume in 1sec (FEV₁); and respiratory electromyographic activity during maximum inspiratory and maximum expiratory airway pressure measurements (PI_max and PE_max). The results indicate a significant reduction (p<.01) of FVC, FEV₁ and PE_max values in children with SCI compared to TD controls. During PE_max assessment, children with SCI produced significantly decreased (p<.01) activation of respiratory muscles below the neurological level of injury (rectus abdominous and external oblique muscles). In addition, children with SCI had significantly increased (p<.05) compensatory muscle activation above the level of injury (upper trapezius muscle). In the TD group, age, height, and weight significantly (p<.05) contributed towards increase in FVC and FEV₁. In children with SCI, only age was significantly (p<.05) correlated with FVC and FEV₁ values. These findings indicate the degree of SCI-induced respiratory functional and motor control deficits in children are age-dependent.