The Role of Environmental Temperatures in Respiratory Control

NCT07470086 | Not Yet Recruiting

• 2 other identifiers: 28381 - Aim 3FOAAFRLAFOSR20240007
• Study Type: interventional
• Target: 15
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Work of Breathing

Keywords

Inspiratory Resistance; Dyspnea Perception; Cognitive Performance; Thermal Stress

Outcome Measures

Primary Outcomes (4)

• 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.

  Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)

• 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.

  Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)

• 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).

  Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)

• 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).

  Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)

Secondary Outcomes (8)

• Change in Diaphragm Thickness

  Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)

• Change in Heart Rate Variability

  Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)

• Change in Peripheral Oxygen Saturation

  Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)

• Change in Blood Pressure - Brachial Artery

  Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)

• Change in Blood Pressure - Finger Photoplethysmography

  Before and after each breathing task on Days 1, 2, 3 (each approximately 90 minutes in duration)

Study Arms (6)

Thermoneutral temperature, then Cold temperature, then Hot temperature

ACTIVE COMPARATOR

Participants will complete 3 experimental visits at which they will complete a breathing task under an assigned temperature condition. The order of condition exposure will be assigned via randomization.

Other: Thermoneutral temperature environment; Other: Cold temperature environment; Other: Hot temperature environment

Thermoneutral temperature, then Hold temperature, then Cot temperature

ACTIVE COMPARATOR

Participants will complete 3 experimental visits at which they will complete a breathing task under an assigned temperature condition. The order of condition exposure will be assigned via randomization.

Other: Thermoneutral temperature environment; Other: Cold temperature environment; Other: Hot temperature environment

Cold temperature, then Thermoneutral temperature, then Hot temperature

ACTIVE COMPARATOR

Participants will complete 3 experimental visits at which they will complete a breathing task under an assigned temperature condition. The order of condition exposure will be assigned via randomization.

Other: Thermoneutral temperature environment; Other: Cold temperature environment; Other: Hot temperature environment

Cold temperature, then Hot temperature, then Thermoneutral temperature

ACTIVE COMPARATOR

Participants will complete 3 experimental visits at which they will complete a breathing task under an assigned temperature condition. The order of condition exposure will be assigned via randomization.

Other: Thermoneutral temperature environment; Other: Cold temperature environment; Other: Hot temperature environment

Hot temperature, then Thermoneutral temperature, then Cold temperature

ACTIVE COMPARATOR

Participants will complete 3 experimental visits at which they will complete a breathing task under an assigned temperature condition. The order of condition exposure will be assigned via randomization.

Other: Thermoneutral temperature environment; Other: Cold temperature environment; Other: Hot temperature environment

Hot temperature, then Cold temperature, then Thermoneutral temperature

ACTIVE COMPARATOR

Participants will complete 3 experimental visits at which they will complete a breathing task under an assigned temperature condition. The order of condition exposure will be assigned via randomization.

Other: Thermoneutral temperature environment; Other: Cold temperature environment; Other: Hot temperature environment

Interventions

Thermoneutral temperature environment OTHER

During 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, then Hot temperature, then Thermoneutral temperature; Cold temperature, then Thermoneutral temperature, then Hot temperature; Hot temperature, then Cold temperature, then Thermoneutral temperature; Hot temperature, then Thermoneutral temperature, then Cold temperature; Thermoneutral temperature, then Cold temperature, then Hot temperature; Thermoneutral temperature, then Hold temperature, then Cot temperature

Cold temperature environment OTHER

During 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.

Cold temperature, then Hot temperature, then Thermoneutral temperature; Cold temperature, then Thermoneutral temperature, then Hot temperature; Hot temperature, then Cold temperature, then Thermoneutral temperature; Hot temperature, then Thermoneutral temperature, then Cold temperature; Thermoneutral temperature, then Cold temperature, then Hot temperature; Thermoneutral temperature, then Hold temperature, then Cot temperature

Hot temperature environment OTHER

During 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.

Cold temperature, then Hot temperature, then Thermoneutral temperature; Cold temperature, then Thermoneutral temperature, then Hot temperature; Hot temperature, then Cold temperature, then Thermoneutral temperature; Hot temperature, then Thermoneutral temperature, then Cold temperature; Thermoneutral temperature, then Cold temperature, then Hot temperature; Thermoneutral temperature, then Hold temperature, then Cot temperature

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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.
• Normal cognitive function assessed using the Montreal cognitive function test \[18\].
• Body mass index (BMI) ≤ 35 kg/m2.
• Females with a regular menstrual cycle that ranges from 21-35 days (eumenorrhea)

You may not qualify if:

• 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.
• Take selective serotonin reuptake inhibitors, stimulant medication, antibiotics, and chronically consume pain medication (Aleve, Tylenol, etc.).
• Resting blood pressure of \> 130mmHg systolic or 90 mmHg diastolic and/or resting pulse rate of \> 100 bpm.
• Females with irregular menstrual cycles (oligomenorrhea) that ranges from 36-90 days, and females with the absence of a menstrual cycle (amenorrhea).
• Taking birth control for the sole purpose of period cessation (eg., Mirena IUD)

Sponsors & Collaborators

• Indiana University: lead
• United States Department of Defense: collaborator

Study Sites (1)

Multidisciplinary Engineering and Sciences Hall (MESH)

Bloomington, Indiana, 47405, United States

Location

Central Study Contacts

Timothy D Mickleborough, PhD

CONTACT

812-855-0753; tmickleb@iu.edu

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Study Record Dates

• First Submitted: March 10, 2026
• First Posted: March 13, 2026
• Study Start (Estimated): October 1, 2028
• Primary Completion (Estimated): December 31, 2029
• Study Completion (Estimated): December 31, 2029
• Last Updated: March 13, 2026

Record last verified: 2026-03

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)