The Role of Environmental Temperatures in Respiratory Control
ConditionWork of Breathing
Trial statusNot yet recruiting
Trial phaseNot applicable
Trial typeInterventional
Biological sexAll
Age18-40
SponsorIndiana University
About this trial
Warfighters are frequently exposed to environments and life-support systems that increase breathing resistance and the work of breathing (WOB), such as aircraft on-board oxygen generation systems and underwater breathing apparatuses. Elevated WOB increases the perception of breathing difficulty (dyspnea) and has been associated with impaired cognitive performance, including slower reaction time and reduced accuracy during attention-demanding tasks. These effects are particularly concerning in operational settings that require rapid decision-making and precise motor responses.
Despite growing recognition of this issue, critical gaps remain regarding strategies to mitigate the perceptual and cognitive consequences of elevated inspiratory resistance, especially under realistic operational stressors. The objective of this study is to determine whether exposing individuals to thermal stress alters breathing perception and cognitive performance during inspiratory resistance. Participants will perform inspiratory resistance breathing under thermoneutral, heat, and cold conditions to determine whether thermal stress amplifies WOB, breathing perception, and cognitive impairment.
Eligibility criteria
This trial accepts healthy volunteersQualifiers
Between the ages of 18-40 years old.
English speaking and reading.
Self-reported weekly activity of at least 120 minutes/week of high intensity exercise for the previous 2 years.
Normal pulmonary function assessed by a resting forced expiratory volume in 1 second over forced vital capacity (FEV1/FVC) > 75% of predicted.
Disqualifiers
History of smoking or recreational smoking, cardiovascular disease, renal disease, pulmonary disease (including asthma or exercise-induced asthma), neurological disease, and metabolic disease.
Are pregnant or could possibly be pregnant by self-report.
Are color blind.
Known allergy or hypersensitivity latex.
Trial design
Design model
Crossover
Treatments tested in this trial
Thermoneutral temperature environment
Other interventionDuring thermoneutral conditions 34°C water will be perfused through special suit while participants resting the chamber set to 24°C and 40% room humidity.
Cold temperature environment
Other interventionDuring the cold condition, 4°C water will be perfused through the special suit while participants rest in the chamber set to 4°C and 10% room humidity.
Hot temperature environment
Other interventionDuring the hot condition, 50°C water will be perfused through the special suit while participants rest in the chamber set to 40°C and 40% room humidity.
Treatment groups
15 Participants
are divided into 6 treatment groups6
Treatment groupsSee each treatment group below.
Group A: Thermoneutral temperature, then Cold temperature, then Hot temperatureActive comparator 3 interventions
Group B: Thermoneutral temperature, then Hold temperature, then Cot temperatureActive comparator 3 interventions
Group C: Cold temperature, then Thermoneutral temperature, then Hot temperatureActive comparator 3 interventions
Group D: Cold temperature, then Hot temperature, then Thermoneutral temperatureActive comparator 3 interventions
Group E: Hot temperature, then Thermoneutral temperature, then Cold temperatureActive comparator 3 interventions
Group F: Hot temperature, then Cold temperature, then Thermoneutral temperatureActive comparator 3 interventions
Trial outcomes
Primary outcomes
1
Change in Stroop Color-Word Test Time Performance
Time performance on the Stroop Color-Word Test (min:sec) will be measured every 45 minutes during each experimental breathing task.
Time frame
Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)2
Change in Stroop Color-Word Test Error Performance
The number of errors on the Stroop Color-Word Test will be measured every 45 minutes each experimental breathing task.
Time frame
Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)3
Change in Perception of Dyspnea Intensity
Participants will rate perception of dyspnea (breathing) intensity on a visual analog scale (VAS) every 45 minutes during each breathing task. The participant will draw a vertical marker line on a horizontal line (100mm), indicating their breathing perception from "not noticeable" (0mm) to "maximal imaginable intensity" (100mm).
Time frame
Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)4
Change in Perception of Dyspnea Unpleasantness
Participants will rate perception of dyspnea (breathing) unpleasantness on a visual analog scale (VAS) every 45 minutes during each breathing task. The participant will draw a vertical marker line on a horizontal line(100mm), indicating their breathing perception from "not unpleasant"(0mm) to "maximal imaginable unpleasantness" (100mm).
Time frame
Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)Secondary outcomes
1
Change in Diaphragm Thickness
Diaphragm thickness will be measured via Doppler ultrasound of the10th/11th rib space during functional residual capacity (FRC; rest) and end-inspiration, as well as during the maximal inspiratory pressure (MIP)test from FRC before and after each condition.
Time frame
Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)2
Change in Heart Rate Variability
Heart rate variability (beats per minute) will be measured continuously during each breathing task via 3-lead electrocardiograph (ECG).
Time frame
Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)3
Change in Peripheral Oxygen Saturation
Peripheral oxygen saturation will be measured continuously during each breathing task via pulse oximetry.
Time frame
Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)4
Change in Blood Pressure - Brachial Artery
Blood pressure will be measured every 10 minutes during each breathing task via a standard blood pressure cuff and auscultation of the brachial artery.
Time frame
Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)Sponsors and contacts
Click on the lead sponsor to view all of their trials.
Indiana University
Lead sponsor
United States Department of Defense
Collaborator
Source ClinicalTrials.gov
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