Development and validation of models to predict respiratory function in persons with long-term spinal cord injury

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.

A Secondary Analysis of Short- and Long-Term Variability of Inspiratory Muscle Performance in People Living With SCI

Objectives

To explore the expected variability in repeated short-term (ST) and long-term (LT) inspiratory muscle performance (IMP) in individuals with chronic spinal cord injury (SCI).

Methods

Maximal inspiratory pressure (MIP), sustained MIP (SMIP), and inspiratory duration (ID) were collected from 22 individuals with chronic SCI (C1-T9, American Spinal Injury Association Impairment Scale [AIS] A-C) over 18 months. ST data were collected four times within 2 weeks (n = 19). LT data were collected at two time points at least 7 months apart (n = 20).

Results

SMIP was the most reliable IMP assessment with an intraclass correlation coefficient (ICC) of 0.959, followed by MIP (ICC 0.874) and ID (ICC 0.689). The ID was the only ST measure to have a significant difference [MIP: F(3, 54) = 2.5, p = .07; SMIP: F(3, 54) = 1.3, p = .29; ID: F(1.4, 25.6) = 4.8, p = .03]. Post hoc analysis showed the mean day 1 ST ID measure was significantly different from both days 3 and 4. The percent change of ID from day 3 to day 6 was 11.6%. No LT measures differed significantly [mean change (SD) [95% CI] for MIP: 5.2 cm H2O (18.8) [-3.6, 13.9], p = .235; SMIP: 60.9 pressure time unit (166.1) [-16.9, 138.6], p = .118; ID: 0.1 s (2.5) [-1.1, 1.3], p = .855].

Conclusion

These data provide a foundation for understanding normal variance in ST and LT IMP in the SCI population. Change in MIP function outside 10% is likely a true and meaningful change and may help clinicians recognize individuals with SCI at risk for respiratory compromise. Future studies should explore changes in MIP and SMIP that are associated with meaningful functional changes.

Adherence to and impact of home-based high-intensity IMT in people with spinal cord injury: a pilot study

Study design

The pilot study was completed in 5 phases (Control and 4 phases of IMT) incorporating assessments at Baseline 1 (BL1), BL2, Follow-up 1 (F1), F2, F3, and F4.

Objective

To assess the adherence and impact of a daily high-intensity (80% of max) inspiratory muscle training (IMT) home program with once weekly supervision for people with spinal cord injury (SCI).

Setting

Assessments: research institution or zoom. IMT: participant’s home.

Methods

Participants completed daily IMT in IMT Phase 1 and 2, once weekly in IMT Phase 3, self-selected frequency in IMT Phase 4. All phases had one weekly supervised session except IMT Phase 4. Primary outcomes included adherence and a difficulty score [DS (0- not difficult to 10- the most difficult)]. Secondary outcomes included respiratory function and seated balance.

Results

Data from 10 people with chronic SCI (>1 year) (Cervical level of injury: 6, AIS: A-B, injury duration: 10.9 years 95% CI [3.9, 18.1]) were used in the analysis. Participants completed 69% of their training days in IMT Phase 1 and 65% overall reporting an average DS of 7.4 ± 1.4. Only one participant completed training during IMT Phase 4. One participant’s training load was reduced due to suspected overtraining. Maximal inspiratory pressure (MIP), sustained MIP (SMIP), and total power (TP), improved significantly (p < 0.05) from BL2 to F1.

Conclusion

Our data suggest that people with SCI can perform high-intensity IMT at home to improve inspiratory performance. It is strongly recommended that participants be intermittently monitored for adherence and safety.

ClinicalTrials.gov Registration number: NCT04210063.

Inspiratory Muscle Performance Is Related to Seated Balance Function in People With Spinal Cord Injury: An Observational Study

OBJECTIVE

To examine the relationship between inspiratory muscle performance (IMP) and functional sitting balance (FSB) in persons with chronic spinal cord injury (SCI). We hypothesized that a moderate correlation would be found between IMP and FSB and that individuals with better balance would have better IMP.

DESIGN

The SCI-specific modification of the Function in Sitting Test (FIST-SCI) measured FSB. The IMP measures included (1) maximal inspiratory pressure (MIP), (2) sustained MIP (SMIP), and (3) inspiratory duration. Upper extremity motor score (UEMS) and level of injury (LOI) were taken from International Standards for Neurological Classification of Spinal Cord Injury examinations. Spearman correlational analyses assessed relationships among these factors in the sample (N=37). Mann-Whitney U tests explored differences between 2 comparison group pairs (tetraplegia group [TG] vs paraplegia group [PG]; independent transfer group [ITG] vs assisted transfer group [ATG]). Regression analysis examined variables predictive of FSB in the TG.

SETTING

Research facility.

PARTICIPANTS

Volunteers with tetraplegia (n=21, American Spinal Injury Association Impairment Scale (AIS) A=8, B=7, C=6) and paraplegia (n=16, AIS A=9, B=4, C=3) (N=37).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

IMP, LOI, UEMS, FIST-SCI.

RESULTS

UEMS, MIP, SMIP, and LOI had moderate to high correlations with FIST-SCI scores (ρ=0.720 (P<.001), 0.480 (P=.003), 0.467 (P=.004), 0.527 (P=.001), respectively). UEMS, MIP, and FIST-SCI scores were higher in the PG and ITG than the TG and ATG, respectively (PG vs. TG P values=<.001, .008, .002, respectively, and ITG vs. ATG P values=<.001, .032, <.001, respectively). Further, SMIP and UEMS predicted FIST-SCI balance scores in the TG, accounting for 55% of total variance (P<.001) (FIST-SCI=11.88+0.03 [SMIP]+0.425 [UEMS]).

CONCLUSIONS

The relationship between IMP and balance appears preserved after SCI. FSB was predicted, in part, via UEMS and SMIP in the TG. Future research should focus on the effect of SCI-based breathing interventions on FSB.

Inspiratory Muscle Performance and Anthropometric Measures-Novel Assessments Related to Pulmonary Function in People with Spinal Cord Injury: A Pilot Study

OBJECTIVE

To investigate the feasibility and validity of using the novel axillary:umbilical (A:U) ratio and sustained maximal inspiratory pressure (SMIP) as supplementary measures in the assessment of respiratory function in people with spinal cord injury.

DESIGN

Pilot study with a single day of data collection. All measurements were taken with participants in their personal wheelchairs to best represent normal functioning and positioning for each individual.

SETTING

Research institution.

PARTICIPANTS

A convenience sample of 30 community dwelling volunteers with chronic spinal cord injury (C2-T12, American Spinal Injury Association Impairment Scale A-D) participated.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Participants underwent anthropometric measurements (trunk height, abdominal circumference, axillary circumference) and assessment of inspiratory muscle performance, incluidng maximal inspiratory pressure, SMIP, and inspiratory duration, as well as standard pulmonary function tests.

RESULTS

The A:U ratio and SMIP were recorded for all participants. The SMIP was significantly related to more respiratory performance measures than the maximal inspiratory pressure (P<.05) and the A:U ratio was significantly related to more respiratory performance measures than any other anthropometric measure (P<.05). Additionally, an A:U ratio cutoff point detected individuals with a peak expiratory flow ≥ 80% of their predicted value with a sensitivity and specificity of 85.7% and 91.3%, respectively (area under the curve: 0.92).

CONCLUSIONS

It is feasible to capture the A:U Ratio and SMIP in individuals with spinal cord injury. Further, the strong significant relationships of SMIP and the A:U ratio to respiratory performance measures suggests their clinical importance in the pulmonary assessment and risk stratification of people with chronic spinal cord injury.