Baroreceptor reflex during forced expiratory maneuvers in individuals with chronic spinal cord injury

Abstract

Pulmonary and cardiovascular dysfunctions are leading causes of morbidity and mortality in patients with chronic Spinal Cord Injury (SCI). Impaired respiratory motor function and decreased Baroreflex Sensitivity (BS) are predictors for the development of cardiopulmonary disease. This observational case-controlled clinical study was undertaken to investigate if respiratory motor control deficits in individuals with SCI affect their ability to perform the Valsalva maneuver, and to determine if a sustained Maximum Expiratory Pressure (MEP) effort can serve as an acceptable maneuver for determination of the BS in the event that the Valsalva maneuver cannot be performed. The BS outcomes (ms/mmHg) were obtained using continuous beat-to-beat arterial blood pressure (BP) and heart rate (HR) recordings during Valsalva or MEP maneuvers in thirty nine individuals with chronic C3-T12 SCI. Twenty one participants (54%) reported signs of intolerance during the Valsalva maneuver and only 15 individuals (39%) were able to complete this task. Cervical level of injury was a significant risk factor (p = .001) for failing to complete the Valsalva maneuver, and motor-complete injury was a significant risk factor for symptoms of intolerance (p = .04). Twenty eight participants (72%) were able to perform the MEP maneuver; the other 11 participants failed to exceed the standard airway pressure threshold of 27 cmH2O. Neither level nor completeness of injury were significant risk factors for failure of MEP maneuver. When the required airway pressure was sustained, there were no significant differences between BS outcomes obtained during Valsalva and MEP maneuvers. The results of this study indicate that individuals with high-level and motor-complete SCI are at increased risk of not completing the Valsalva maneuver and that baroreflex-mediated responses can be evaluated by using sustained MEP maneuver when the Valsalva maneuver cannot be performed.

Cerebrospinal Fluid Pressure Dynamics as a Bedside Test in Traumatic Spinal Cord Injury to Assess Surgical Spinal Cord Decompression: Safety, Feasibility, and Proof-of-Concept

“…Previous studies have indeed shown that mainly patients with high-cervical motor-complete SCI are also less capable to sufficiently perform the Valsalva maneuver. 40 Therefore, our findings support the concept that CSFP response during Queckenstedt’s test is due to a relative intracranial volume change, whereas the Valsalva maneuver is mainly related to intrathoracic and intraabdominal pressure changes, associated with an increased intracranial venous filling, but also with a reverse flow to the spinal venous plexus.…”

Effects of Respiratory Training on Heart Rate Variability and Baroreflex Sensitivity in Individuals With Chronic Spinal Cord Injury

“…Participants were assessed in a seated position, without the aid of compression garments or abdominal binders 43, 44 . To assess BS, participants blew with maximal effort into a mouthpiece for the duration of an audible, 5s tone (5s MEP) 45 . Each event was attempted three times, with at least 30s rest in between events to allow BP values to return to baseline.…”

“…The slope of each phase is reported in ms/mmHg, which quantifies the change in RRI for every 1 mmHg increase or decrease of SBP 46–48 . Acceptable attempts were those between 5 and 7s in duration 49, 50 with a Pearson correlation coefficient > .80 47, 51, 52 ; BS outcomes were excluded if the maneuver did not meet 27 cmH 2 O 45 , or if they triggered spasms, autonomic dysreflexia, or coughs. The phases analyzed began with three consecutively increasing or decreasing RRIs 47, 52 ; the mean of all acceptable attempts was used for statistical analysis.…”

Cardiovascular Autonomic Dysfunction in Spinal Cord Injury: Epidemiology, Diagnosis, and Management

“…However, we recently demonstrated a modification of the Valsalva maneuver that affords individuals with high cord injury the ability to adequately perform the maneuver in the presence of respiratory muscle weakness. 73…”