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The Role of Heliox in Respiratory Control

Optimizing Mind-Body Interactions in Respiratory Control During Operationally Relevant Environmental Stressors

Who can join

Ages 18 to 40 · All sexes · Healthy volunteers welcome

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)

About the study

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.

What is being tested

• Heliox inspirate (drug)

Sponsor: Indiana University · Participants: 15 · Started: Feb 3, 2026

Contact the study team

• Timothy D Mickleborough, PhD · Phone: 812-855-0753

Official record on ClinicalTrials.gov — NCT07424014

Locations in the U.S.

From ClinicalTrials.gov, data retrieved Oct 3, 2026. Each study sets its own eligibility; the study team decides who can join.