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).
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
NONE
Enrollment
17
Heated vest that regulates its heat output based on the user's skin, the user's core temperature, and the ambient temperature
A similarly insulated (compared to the experimental vest), but non-heated vest
James J. Peters VA Medical Center, Bronx, NY
The Bronx, New York, United States
Change in Core Body Temperature (Tcore)
Tcore will be continuously monitored throughout baseline and thermal challenge periods (with heated \& non-heated vests) by a TX-2 Rectal probe and Iso-Thermex Multichannel Thermometer (Columbus Instruments, Columbus, OH). The probe will be placed 10 cm beyond the anal sphincter.
Time frame: Visits 2 & 3 (subjects with tetraplegia only): Continuously throughout baseline & Thermal Challenge (2 hrs) periods. The change in Tcore from baseline to the end of Thermal Challenge will be determined.
Change in Cognitive Performance: WAIS-IV (Wechsler Adult Intelligence Scale-Fourth Edition)
WAIS-IV Digit Span test has 3, 16-point sections (Forward, Backward, Sequence) and assesses attention, processing speed, and working memory. Cognitive battery is administered at BL, after Thermal Challenge (tetra only). Testing conditions are distraction-free. The Forward section has 16 numerical sequences of successive increasing length (each 1 point). Participant is read the numbers, then asked to repeat the test numbers in the same order. In Backward, participant is asked to repeat the numbers in reverse order. In Sequence portion, the participant is asked to repeat the numbers in ascending order. Sections add to a WAIS-IV Total Score of 48. The greater the score, the better the cognitive function. The minimum score, which would represent not being able to repeat even the first sequence of numbers, is 0. We report the difference in WAIS-IV score before and after the cold challenge. The more negative the difference, the more cognitive impairment after cold challenge.
Time frame: Visits 2 & 3 (subjects with tetraplegia only): At the end baseline (at 15 min) & end of Thermal Challenge (at 120 min) periods. The change in cognitive performance from baseline to the end of Thermal Challenge will be determined. Each WAIS is 10 min
Change in Cognitive Performance: Delayed Recall
Delayed Recall section of the Montreal Cognitive Assessment (MoCA): Subjects will be asked to repeat 5 simple words immediately and then recall them after a 5-minute delay to assess working memory. In scoring the MoCA, one point is awarded for each of the five words. Thus, the score ranges from 0 (no words remembered) to 5 (all words remembered). A higher score represents a more intact delayed recall capacity. We administered the Delayed Recall of the MoCA before and after the cold challenge, in both the heated vest (powered) and non-heated vest control condition. The reported measure is the mean difference in MoCA Delayed Recall scores before and after the cold challenge. Here, a more negative number represents a greater degree of impairment in delayed recall (working memory) after the cold challenge.
Time frame: Visits 2 & 3 tetraplegia only): At the end baseline (at 15 min) & end of Thermal Challenge (at 120 min) periods. The change in cognitive performance from baseline to the end of Thermal Challenge will be determined. Each assessment requires 6 min.
Change in Cognitive Performance: Stroop
Stroop Color and Word: Subjects will be asked to read words of colors, colors of fonts to assess attention and processing speed; color of fonts of words which describe conflicting colors to assess response inhibition (executive functioning). Each assessment is 4 min. The Stroop Test yields three scores. The Raw Word score is the number of words correctly completed on the Word page in 45 seconds. Similarly for Color, and Color-Word. For example, in the color-word section, a participant correctly identifying the color of 61 words, the score is 61. Greater scores reflects greater executive functioning. Zero is the minimum score, which corresponds to not being able to read any of the words of colors or colors of fonts. Each words of colors or color of fonts correctly identified in time confer 1 point. We report the difference in Word-Color before the cold challenge and after the cold challenge, for each intervention. Negative differences represent impaired executive function.
Time frame: Visits 2 & 3 (subjects with tetraplegia only): At the end baseline (at 15 min) & end of Thermal Challenge (at 120 min) periods. The change in cognitive performance from baseline to the end of Thermal Challenge will be determined.
Change in Thermal Comfort (TC)
Thermal Comfort will be measured every 10 minutes throughout BL and thermal challenge periods by the Zhang 6-point thermal comfort scale: +3 (very comfortable), +2 (comfortable), +1 (just comfortable), -1 (just uncomfortable), -2 (uncomfortable), and -3 (very uncomfortable). A greater frequency of +1, +2, and +3 scores are considered more desirable than -1, -2, and -3 scores during the Thermal Challenge. Each assessment requires only the time needed for the subject to respond (typically less than 10 seconds).
Time frame: Visits 1, 2, & 3 (all subjects): During baseline & every 10 minutes throughout Thermal Challenge (2 hrs). The change in TC from baseline to the end of Thermal Challenge will be determined.
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