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 then 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 experiment is to determine whether modifying the sensory perception of breathing alters breathing perception and cognitive performance during inspiratory resistance. Auditory feedback of ventilation will be manipulated (normal, reduced, or amplified) to assess whether altering breathing-related sensory input affects breathing perception and cognitive performance without changing mechanical load.
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
Crossover
Treatments tested in this trial
Ambient Noise
Other interventionParticipants will complete the breathing task with ambient (or normal) auditory feedback (\~10 decibels).
Increased Auditory Feedback
Other interventionParticipants will complete the breathing task with increased auditory feedback of ventilation (\~70 decibels). Specifically, a small microphone will be placed in the device that participants breathe through to increase the sound of the participants breath.
Noise Distraction
Other interventionParticipants will complete the breathing task without auditory feedback of ventilation. Specifically, participants will wear noise cancelling headphones and will listen to a self-selected music playlist at a constant volume (\~80 decibels).
Treatment groups
6
Treatment groupsSee each treatment group below.
Trial outcomes
Primary outcomes
Change in Stroop Color-Word Test Time Performance
Time performance on the Stroop Color-Word Test (min:sec) will be measured every 10 minutes during each breathing task.
Change in Stroop Color-Word Test Error Performance
The number of errors on the Stroop Color-Word Test will be measured will be measured every 10 minutes during each breathing task.
Change in Perception of Dyspnea Intensity
Participants will rate perception of dyspnea (breathing) intensity on a visual analog scale (VAS) every 5 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).
Change in Perception of Dyspnea Unpleasantness
Participants will rate perception of dyspnea (breathing) unpleasantness on a visual analog scale (VAS) every 5 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).
Secondary outcomes
Change in Diaphragm Thickness
Diaphragm thickness will be measured via Doppler ultrasound of the 10th/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.
Change in Heart Rate Variability
Heart rate variability (beats per minute) will be measured continuously during each breathing task via 3-lead electrocardiograph (ECG).
Change in Peripheral Oxygen Saturation
Peripheral oxygen saturation will be measured continuously during each breathing task via pulse oximetry.
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.
Sponsors and contacts
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Indiana University
Lead sponsor
United States Department of Defense
Collaborator
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