Recruiting

Heliox

Sponsor:

Indiana University

Code:

NCT07424014

Conditions

Work of Breathing

Eligibility Criteria

Sex: All

Age: 18 - 40

Healthy Volunteers: Accepted

Interventions

Heliox inspirate

Study Details

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 reducing mechanical WOB alters breathing perception and cognitive performance during inspiratory resistance. Participants will breathe either normal-density air or a low-density helium-oxygen gas mixture (heliox) to determine whether reducing mechanical WOB lowers perceived breathing effort and improves cognitive function.

Conditions

Work of Breathing

Study ID

NCT07424014

Start date

Feb 3, 2026

Status verified date

Mar, 2026

Completion date

May 31, 2027

Anticipated

Primary completion date

May 31, 2027

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18 - 40

Healthy Volunteers: Accepted

Inclusion Criteria:

  • 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)

Exclusion Criteria:

  • 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)

Study Design

Enrollment

15 participants

Anticipated

Allocation

Randomized

Intervention Model

Crossover

Primary purpose

Basic Science

Interventions and Outcome Measures

Arms

active comparator: Room Air, then Heliox Inspirate

Participants will complete 2 full length breathing tasks, one under each condition. The order of condition exposure will be assigned via randomization.

active comparator: Heliox Inspirate, then Room Air

Participants will complete 2 full length breathing tasks, one under each condition. The order of condition exposure will be assigned via randomization.

Interventions

Heliox inspirate

This intervention corresponds to Arm 1 titled "room air and heliox inspirate". This corresponds with the first phase/period of this study.

Primary outcome measure

  • Change in Stroop Color-Word Test Time Performance [ Time Frame: Before and after each Day 1 breathing task (approximately 60 minutes in duration) ]
  • Change in Stroop Color-Word Test Error Performance [ Time Frame: Before and after each Day 1 breathing task (approximately 60 minutes in duration) ]
  • Change in Perception of Dyspnea Intensity [ Time Frame: Before and after each Day 1 breathing task (approximately 60 minutes in duration) ]
  • Change in Perception of Dyspnea Unpleasantness [ Time Frame: Before and after each Day 1 breathing task (approximately 60 minutes in duration) ]

Central Contacts and Locations

Central contacts

Timothy D Mickleborough, PhD

812-855-0753tmickleb@iu.edu

Locations

Multidisciplinary Engineering and Sciences Hall (MESH)

Recruiting

Bloomington, Indiana, United States, 47405

Contacts

Scott M Clarke

812-856-3244scotclar@iu.edu

Zachary J Schalder, PhD

812-855-6953zschlade@iu.edu

Principal Investigator:

Timothy D Mickleborough, PhD

More Information

Sponsor

Indiana University

Last update posted

Mar 12, 2026

Last verified

Mar, 2026

Keywords

  • Inspiratory Resistance
  • Dyspnea Perception
  • Cognitive Performance

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-09. This information was provided to ClinicalTrials.gov by Indiana University on 2026-03-12.