Characteristics of cardiovascular responses to an orthostatic challenge in trained spinal cord-injured individuals

Responses to Valsalva's maneuver in spinal cord injury do not broadly relate to vasoconstrictor capacity

PURPOSE

A blood pressure stabilization during late phase II of Valsalva's maneuver may be utilized to confirm sympathetic vasoconstrictor control after a spinal cord injury. This study investigated whether Valsalva response was predictive of hemodynamics during tilt or isometric handgrip.

METHODS

Presence/absence of Valsalva response was compared to heart rate, mean arterial pressure, leg blood flow, and vascular resistance during head-up tilt and isometric handgrip to fatigue in 14 adults with spinal cord injury from C7 to T12 and 14 controls. Statistics were performed with two-way repeated measure analysis of variance (ANOVA), post hoc t-tests for between-group comparisons, and Mann-Whitney U tests for within-group.

RESULTS

In total, six participants with spinal cord injury lacked a blood pressure stabilization for Valsalva's maneuver. However, this was not related to vasoconstrictor responses during the other tests. The groups had similar heart rate and blood pressure changes during tilt, though leg blood flow decreases and vascular resistance increases tended to be smaller at 20° tilt in those with spinal cord injury (p = 0.07 and p = 0.11, respectively). Participants with spinal cord injury had lower heart rates and markedly smaller blood pressure increases during handgrip (both p < 0.05). There were no group differences in leg blood flow, but those with spinal cord injury demonstrated a blunted vascular resistance increase by the final 10% of the handgrip (p < 0.01).

CONCLUSIONS

Valsalva response was not consistent with hemodynamics during other stimuli, but some individuals evidence increases in sub-lesional vascular resistance to isometric handgrip comparable to controls, suggesting a sympathoexcitatory stimulus may be critical to provoke hemodynamic responses after spinal cord injury.

ORTHOSTATIC SUPPORT IN PARAPLEGIC AND AMPUTEE PATIENTS: A CONTROLLED TRIAL

Introduction

Functional incapacity caused by physical alterations leads to significant limitations in daily activities and has a major impact on the return of people with disabilities to the social space and the workplace. This calls for an evaluation of the long-term influence of the use of a device specially developed for orthostatic posture on the physiological, biomechanical and functional parameters of amputees and spinal cord patients.

Objective

The objective was evaluate the effect of postural support device use on function, pain, and biomechanical and cardiologic parameters in spinal cord injury and amputees patients compared to a control group.

Methods

The orthostatic device was used by the participants for a period of ten consecutive days, for three cycles of 50 minutes each day, and a 15-day follow-up. Participants were positioned and stabilized using adjustable straps on the shoulders, trunk, and hips. The primary outcome was brief pain inventory. Fifteen participants were included the control group, 15 in the amputee group, and 15 in the spinal cord group.

Results

Our results demonstrate that the use of the device allows the orthostatic position of amputees and spinal cord patients evaluated for ten days, leading to improved functionality and pain in the spinal cord and amputee groups compared to the control group. In addition, no changes were observed for secondary outcomes, indicating that the use of the device did not cause harm interference to patients.

Conclusion

The long-term use of the orthostatic device is beneficial for improving functionality, reduce pain in amputees and spinal cord injury patients. Level of evidence II; Therapeutic Studies - Investigating the results of treatment.

Cardiac autonomic modulation in response to postural transition during a virtual reality task in individuals with spinal cord injury: A cross-sectional study

PURPOSE

The postural transition from sitting to standing is a moment of dysautonomic occurrence in individuals with Spinal Cord Injury (SCI). Different tools can be used to minimize this event, such as virtual reality. Thus, we aimed to analyze cardiac autonomic modulation in individuals with SCI during postural transition from the sitting to orthostatism position using a cognitive virtual reality (VR) task.

METHODS

Individuals with and without SCI were positioned on the Easy Stand® device, sitting at rest, at 0° considering the angle between the seat and the floor, elevation at 45°, and orthostatism at 90°, for 5 minutes in each position. Heart rate variability (HRV) measures of sympathovagal balance were collected (heart rate receiver: Polar V800). The groups were subdivided into two groups, one that performed VR as an intervention during the postural angle changes and another group that did not perform VR.

RESULTS

We evaluated 76 individuals, 40 with a medical diagnosis of SCI and 36 who composed the able-bodied control group without SCI, matched by age and sex. The HRV results showed that the SCI group who performed the task in VR demonstrated no significant difference in parasympathetic activation and global variability between the sitting versus 90° positions. There was better sympathovagal balance in SCI and able-bodied control groups who performed the VR task between the sitting versus 90° positions.

CONCLUSION

The use of a VR task seems to contribute to better sympathovagal balance, with the potential to reduce dysautonomia during postural changes.

The Use of Orthostatic Device for 90 Minutes Does Not Change Cardiovascular and Biomechanical Parameters of Patients with Spinal Cord Injury

Background

Changes in autonomic function are often caused by spinal cord injuries, which lead to limited orthostatic positioning in these patients.

Objective

To investigate the cardiovascular and biomechanical parameters during 90 min of postural elevation equipment usage comparing spinal cord injury and healthy subjects.

Methods

A device was used that allowed patients with spinal cord injuries to remain in an orthostatic posture for 90 min. During this period, the physiological parameters were measured every 15 min. Cardiovascular parameters (heart rate, oxygen saturation, blood pressure, and autonomic nervous system) and biomechanical parameters of the plantar pressure distribution were evaluated. For blood pressure, heart rate, oxygen saturation, and autonomic nervous system, a two-way analysis of variance was applied. The mixed-effect model was applied to plantar pressure. The significance level was set at p < 0.05 for all statistical analyses.

Results

No differences were observed between the groups in systolic blood pressure (F = 0.07), diastolic blood pressure (F = 0.14), heart rate (F = 0.56), and oxygen saturation (F = 0.23) at any of the time intervals throughout the experiment (p > 0.05). No statistical difference was observed in the mean plantar pressure values between the groups (p = 0.35) during the period in which they remained in the orthostatic position.

Conclusion

The present study showed the absence of differences between spinal cord injury patients and control participants using the orthostatic device in terms of cardiovascular and biomechanical parameters over 90 min.

Monitoring spinal cord hemodynamics and tissue oxygenation: a review of the literature with special focus on the near-infrared spectroscopy technique

STUDY DESIGN

Review.

OBJECTIVES

Clinical studies have shown that the hemodynamic management of patients following acute spinal cord injury (SCI) is an important aspect of their treatment for maintaining spinal cord (SC) perfusion and minimizing ischemic secondary injury to the SC. While this highlights the importance of ensuring adequate perfusion and oxygenation to the injured cord, a method for the real-time monitoring of these hemodynamic measures within the SC is lacking. The purpose of this review is to discuss current and potential methods for SC hemodynamic monitoring with special focus on applications using near-infrared spectroscopy (NIRS).

METHODS

A literature search using the PubMed database. All peer-reviewed articles on NIRS monitoring of SC published from inception to May 2019 were reviewed.

RESULTS

Among 125 papers related to SC hemodynamics monitoring, 26 focused on direct/indirect NIRS monitoring of the SC.

DISCUSSION

Current options for continuous, non-invasive, and real-time monitoring of SC hemodynamics are challenging and limited in scope. As a relatively new technique, NIRS has been successfully used for monitoring human cerebral hemodynamics, and has shown promising results in intraoperative assessment of SC hemodynamics in both human and animal models. Although utilizing NIRS to monitor the SC has been validated, applying NIRS clinically following SCI requires further development and investigation.

CONCLUSIONS

NIRS is a promising non-invasive technique with the potential to provide real-time monitoring of relevant parameters in the SC. Currently, in its first developmental stages, further clinical and experimental studies are mandatory to ensure the validity and safety of NIRS techniques.