Heated Vest for Persons With Spinal Cord Injury

Persons with higher levels of spinal cord injury (above the 2nd thoracic vertebrae; tetraplegia) are unable to maintain normal core body temperature (Tcore) when exposed to cool environments. In persons with tetraplegia, even limited exposure to cool temperatures may cause Tcore to approach hypothermic values and impair cognitive performance. Conversely, an increase in Tcore from subnormal to normal range may improve cognitive performance. Prior work has shown that cool seasonal temperatures have an adverse effect on personal comfort and the ability to perform vital daily activities of self-care in persons with tetraplegia. Interventions that address the vulnerability to hypothermia are limited. A self-regulating heated vest designed specifically for persons with tetraplegia is a novel and promising strategy to address this problem. By more effectively maintaining Tcore, the vest can decrease the adverse impact of cool temperatures on comfort, quality of life, and performance of vital daily tasks for Veterans with tetraplegia during the cooler seasons.

Persons with spinal cord injury (SCI), particularly cervical injuries (tetraplegia), are unable to effectively regulate core body temperature (Tcore) due to interruption of motor, sensory, and sympathetic pathways. Thus, control of distal extremity vasoconstriction (heat conservation) and shivering thermogenesis (heat production) are impaired, and the ability to maintain a constant Tcore is compromised. Persons with tetraplegia often report "feeling cold," frequently present with subnormal Tcore (35-36.5 degrees C), and are particularly vulnerable to hypothermia (Tcore\<35 degrees C) and associated impairment in cognitive performance, even when exposed to temperatures that are comfortable for able-bodied (AB) individuals. Cool seasonal temperatures have been shown to have a greater adverse effect on personal comfort, activities of daily living (ADLs), and vital daily activities in persons with tetraplegia than that of AB controls. Conversely, a minimal increase in Tcore from subnormal to normothermia, secondary to ambient heat may improve cognitive performance. Interventions addressing the tendency to poikilothermia and enhanced vulnerability to hypothermia in persons with tetraplegia are limited. Therefore, exploration of safe and efficacious bioengineering solutions to address the physiological, cognitive, and quality of life (QoL) issues associated with the routine exposure to cool temperatures that persons with tetraplegia often encounter is warranted.

The goals of this pilot study are to: 1) fully bench-test the heated vest for safety before performing any human subject testing; 2) study the safety and tolerability of a feedback-controlled heated vest in AB controls; and 3) study the efficacy of this heated vest to minimize the expected decline in Tcore and associated deterioration of cognitive performance during 2 hours of cool exposure in persons with tetraplegia.

In persons with tetraplegia, a two-condition (heated vest, non-heated vest) prospective study is being proposed to compare the physiological and cognitive responses to 2 hours of controlled cool exposure (18 degrees C) with a prototype heated vest vs. a similar, but non-heated vest (control condition). Eight subjects with tetraplegia (C3-T1, AIS A and B) and eight AB controls will be recruited for study participation. Before the prototype is tested on human subjects, it will have been fully bench tested and have satisfied all safety requirements and specifications. AB subjects will be observed to ensure the safety of the vest, which will be accomplished by determining the temperatures of the vest ( 39 degrees C) and subjective thermal sensation of no greater than "warm" during a cool condition that will be identical to the condition which subjects with SCI will be exposed. Subjects with tetraplegia will test the efficacy of the heated vest, i.e. preventing the expected decline in Tcore and cognitive performance and increase in thermal comfort.

After the feedback-controlled heated vest has been fully bench-tested and has satisfied all safety requirements (interior vest temperature does not exceed 39 degrees C at maximal power) and design specifications (lightweight, slim, easy to don doff), the following specific aims will be addressed:

Primary Specific Aim: In a cool thermal chamber (18 degrees C), AB controls will wear the heated vest at maximal setting for 120 minutes in the seated position to determine (1) maximum temperatures of all areas of the interior (user's side) of the heated vest and (2) subjective comfort of the heated vest (safety testing).

Primary Hypotheses: The study of AB controls will demonstrate (1) All areas under the vest will have temperatures 39 degrees C. (2) All subjects will report a thermal sensation no greater than "warm" this would include identification of "hot spots" (Zhang 9-point Thermal Sensation Scale).

Secondary Specific Aim: During exposure to a cool environment (18 degrees C) for up to 120 minutes in the seated position, persons with tetraplegia will wear the heated vest to determine (1) change in Tcore, (2) change in cognitive performance, and (3) change in thermal comfort (efficacy testing).

Secondary Hypotheses: In persons with tetraplegia wearing the heated vest compared to the same persons wearing the non-heated vest, it's expected that (1) 30% of the subjects will have a decline of 0.5 degrees C in Tcore compared with 80% in the control condition, (2) 30% of the subjects will demonstrate a decline of at least 1 T-score in at least one of the following measures: Interference of Stroop Color and Word test, Digit Span of Wechsler Adult Intelligence Scale-Fourth Edition, compared with 80% in the control condition, and (3) a greater percentage of subjects reporting increased thermal comfort (Zhang 6-point Comfort Scale).

Eligibility Criteria:
Inclusion Criteria:

Subjects with spinal cord injury (SCI) and able-bodied subjects will be recruited according to the following criteria:

* Duration of injury 1 year
* Neurological Level of SCI \[C3-T1\]; American Spinal Injury Association (ASIA) Impairment Scale (AIS) A \& B
* Euhydration

  * Subjects will be instructed to avoid caffeine and alcohol
  * maintain normal salt and water intake
  * avoid strenuous exercise for 24 hours prior to study

Exclusion Criteria:

* Known heart, kidney, peripheral vascular or cerebrovascular disease
* High blood pressure
* History of Traumatic Brain Injury (TBI) or diagnosed cognitive impairment
* Untreated thyroid disease
* Diabetes mellitus
* Acute illness or infection
* Dehydration
* Smoking
* Pregnant women
* BMI\>30 kg/m2
* Broken, inflamed, or otherwise fragile skin