Hyperventilation Effects on Bodily Self-Consciousness

Overview

Key facts that identify this study and show where it stands today.

ClinicalTrials.gov ID: NCT07769710
Lead Sponsor: University of FribourgOTHER
Overall Status: Not yet recruiting
Study Type: Interventional
Phase: Not Applicable
Enrollment: 35Estimated
Last Update Posted: Aug 18, 2026Actual
Start Date: Sep 1, 2026Estimated
Primary Completion Date: Jul 31, 2027Estimated
Completion Date: Jul 31, 2027Estimated

Description

What the study is about and why it is being run, in the researchers' own words.

Official Title: Hyperventilation Effects on Bodily Self-Consciousness
Brief Summary: This study examines how voluntary fast, deep breathing (hyperventilation) affects the way healthy adults perceive their own body. Participants wear a virtual-reality (VR) headset and see a virtual body; a glowing halo around it either pulses exactly in time with their own breathing or is time-shifted. During the study, breathing, heart activity, blood-oxygen level, the carbon-dioxide content of exhaled air, and brain activity (EEG, measured non-invasively from the scalp) are recorded continuously, and participants complete questionnaires about their experience.

The aim is to understand whether and how altered breathing changes the interplay between what people see and what they feel inside their body, and thereby the sense of being located within one's own body. The study uses a 2×2 within-subjects design crossing Breathing (normal vs. hyperventilation) with Visual synchrony (synchronous vs. asynchronous), with the asynchronous and normal-breathing conditions serving as within-subject controls.

No medication is administered and no medical device is being tested; the instruments used serve only for monitoring and measurement. Participation involves a screening visit (including a short, ~5-minute guided-hyperventilation tolerance test) and an experimental visit.

Conditions

The medical conditions and diseases this study investigates.

Bodily Self-Consciousness
Interoception
Healthy Volunteers

Interventions

The treatments and procedures being evaluated in this study.

Voluntary hyperventilation (guided paced breathing)
Normal spontaneous breathing (within-subject control)
Synchronous respiratory-visual VR feedback

Participation

Who can join this study and the criteria used to decide.

Ages Eligible for Study: Adult (18-64)
Sexes Eligible for Study: All
Accepts Healthy Volunteers: Yes
Eligibility Criteria: Inclusion Criteria:

Healthy adult aged 18-55 years

Able to provide written informed consent

Normal or corrected-to-normal vision

Sufficient German or English to follow instructions and complete questionnaires

Tolerates the ~5-minute VR-guided hyperventilation test at screening

Exclusion Criteria:

Cardiovascular or cerebrovascular disease posing a risk during hyperventilation (e.g., myocardial infarction or stroke within 12 months, significant/unstable cardiac disease, heart failure, uncontrolled/severe hypertension, aneurysm, Moyamoya)

Respiratory disease (asthma, COPD, restrictive lung disease, pulmonary fibrosis, recent severe lung infection, dyspnoea at rest)

Haematological disease (sickle cell disease or trait, severe anaemia)

Neurological disease (epilepsy or seizures, severe/recurrent migraine, neurodegenerative disorder)

Psychiatric disorder (panic or severe anxiety disorder, psychosis or schizophrenia, severe bipolar disorder, acute major depression, acute addiction)

Metabolic disease (Type 1 or poorly controlled Type 2 diabetes, BMI > 35)

Pregnancy (confirmed by urine test at screening) or planned pregnancy during the study period

Medication affecting respiration or brain function

Physical inability to cooperate or to remain seated for the ~188-minute experimental visit

Insufficient understanding of study procedures and risks

Intolerable reaction to the hyperventilation tolerance test at screening

Design

How the study is designed and how its participant groups are organized.

Primary Purpose: Basic Science
Allocation: Randomized
Interventional Model: Crossover Assignment
Masking: None (Open Label)

Contacts

The people to reach with questions about this study or how to join it.

Parsa Yousefi, MasContact

parsa.yousefi@unifr.ch+41 26 308 16 03

Locations

Where the study is run and whether each site is currently recruiting.

University of Fribourg, Molecular Psychiatry Laboratory, (at Réseau fribourgeois de santé mentale, RFSM/FNPG)

Villars-sur-Glâne, 1752, Switzerland

Collaborators

The organizations and people involved in this study.

Lead Sponsor: University of FribourgOTHER

Similar Studies

Other registered studies that closely resemble this one.

Detailed Description

Background and rationale. Bodily self-consciousness (BSC) - the sense of owning a body and being located within it - depends on integrating exteroceptive (e.g., visual) and interoceptive (e.g., respiratory, cardiac) signals. Voluntary hyperventilation induces marked interoceptive and physiological changes and can alter states of consciousness. This study investigates whether hyperventilation modulates the visually driven manipulation of BSC, using a respiratory-visual full-body illusion.

Design. Single-centre experimental study with a 2x2 within-subjects design crossing Breathing (normal vs. voluntary paced hyperventilation) and Visual synchrony (a virtual body whose surrounding luminous halo is modulated synchronously vs. asynchronously with the participant's real-time respiration, recorded via a respiratory belt). The block order is fixed, with the normal-breathing block always preceding the hyperventilation block for safety and physiological reasons; within each block, the order of the synchronous and asynchronous VR exposures is randomised across participants from a computer-generated permuted-block list prepared before enrolment. The asynchronous and normal-breathing conditions serve as within-subject controls.

Intervention. Voluntary, guided paced hyperventilation is delivered as four cycles of approximately 10 minutes of deepened breathing under audio guidance (including a sustained-hyperventilation window for EEG), with continuous physiological monitoring: end-tidal CO2 (capnography), pulse oximetry (SpO2 and heart rate), ECG, and direct observation by trained study staff. After each breathing cycle, participants view for about 2 minutes a virtual body (avatar) positioned about 2 m ahead and seen from behind, in a first-person perspective, with the halo modulated synchronously or asynchronously with breathing. A normal, quiet-breathing condition in the same VR environment serves as the comparison.

Procedures. The study comprises two visits: (1) a screening visit with informed consent, health-history review, baseline physiology, and a short (~5-minute) VR-guided hyperventilation familiarisation/tolerance test; and (2) an experimental visit (~188 minutes) with the full protocol. A urine pregnancy test is performed at screening for participants of childbearing potential. Safety is governed by predefined tiered stop criteria and a recovery/discharge checklist, with an on-site emergency physician available for escalation.

No medicinal product is administered and no medical device is under investigation; all instruments are used within their intended purpose for monitoring and measurement. The study is an "other clinical trial" under Swiss law (Chapter 4 ClinO), risk category B, reviewed by the Cantonal Ethics Committee Bern (BASEC 2026-01385).