The Effect of Graded Forced Expiration on Intraocular Pressure

The Effect of Graded Forced Expiration on Intraocular Pressure: A Study Using the Airofit Device

The primary objective of this study is to utilize the Airofit device to systematically measure and characterize the changes in intraocular pressure across its six different levels of forced expiration. This investigation will provide crucial quantitative data on the IOP-respiratory effort relationship, enhancing our understanding of IOP dynamics during controlled respiratory stress and establishing a new, standardized paradigm for such research.

Study Overview

• Status: Recruiting
• Conditions: Intraocular Pressure
• Intervention / Treatment: Other: Intraocular Pressure after forced expiration

Detailed Description

Intraocular pressure (IOP) is a key physiological parameter and the primary modifiable risk factor for glaucoma. Its dynamic nature is well-documented, with fluctuations known to occur due to a variety of factors, including posture, time of day, and bodily maneuvers. The Valsalva maneuver-forced exhalation against a closed glottis-is a classic example of a physiological stressor that can cause a transient, sharp increase in IOP. This occurs due to a rise in intrathoracic and episcleral venous pressure, impeding the outflow of aqueous humor.

While the effect of a maximal Valsalva is recognized, the quantitative relationship between graded levels of expiratory force and IOP remains poorly characterized. Previous studies have been limited by the inability to precisely control and measure respiratory effort, often relying on voluntary maneuvers that lack standardization and reproducibility.

The recent advent of portable respiratory muscle trainers, such as the Airofit device, offers a novel solution to this methodological challenge. This device enables the precise application of controlled, graded resistance to expiration across multiple predefined levels.

Therefore, the primary objective of this study is to utilize the Airofit device to systematically measure and characterize the changes in intraocular pressure across its six different levels of forced expiration. This investigation will provide crucial quantitative data on the IOP-respiratory effort relationship, enhancing our understanding of IOP dynamics during controlled respiratory stress and establishing a new, standardized paradigm for such research.

Methods

Study Design: A prospective, cross-sectional, single-visit study designed to measure the acute effect of a standardized respiratory exercise session on intraocular pressure (IOP).

Participants and Recruitment

A convenience sample of 60 adult participants will be recruited from outpatient clinics of physical medicine and rehabilitation of Usak university

Participants will be provided with a full information sheet and will sign a written informed consent form prior to any study procedures.

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Ata Baytaroglu, Asst. Prof.; Phone Number: +905379315396; Email: ata.baytaroglu@usak.edu.tr
• Study Contact Backup: Name: Serife N Ciftci, Asst. Prof.; Phone Number: +905379315396; Email: ciftciserifenur@gmail.com

Study Locations

• Turkey (Türkiye)
  • Uşak, Turkey (Türkiye), 64200
    • Recruiting
    • University of Usak
    • Contact: Ali Y Karahan; Phone Number: +905386921934; Email: ali.karahan@usak.edu.tr

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Aged 18 years or older.
• Willing and able to provide informed consent.
• Have a best-corrected visual acuity of 6/12 or better.
• Able to understand and follow instructions for using the Airofit device.
• Have an optic nerve cup/disc ratio not exceeding 0.5, and have a c/d difference between both eyes not exceeding 0.2.
• Did not have taken any anticholinergic medication, systemic beta-blockers, or corticosteroids within the last 3 months that could affect intraocular pressure levels.

Exclusion Criteria:

• a history of intraocular surgery,
• a history of uveitis,
• a spherical refractive error exceeding 3D,
• a history of regular topical treatment other than artificial tears

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Screening
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Forced expiration program; The participants will be equipped with the Airofit respiratory muscle trainer and will be provided with standardised instructions on performing forced expiration manoeuvres. Participants will be fitted with the Airofit respiratory muscle trainer and given standardized instructions on performing forced expiration maneuvers.; The protocol consisted of sequentially performing forced expiration at each of the device's six predefined resistance levels (Level 1 being the lowest, Level 6 the highest).; The sequence for each level will be identical and as follows:Exercise Phase: The participant will perform forced expiration maneuvers with the Airofit device for a duration of 5 minute at the specified resistance level.Immediate Post-Exercise Measurement: Within 5 seconds of completing the exercise minute, IOP will be measured. This measurement will be labeled accordingly: T1 (after Level 1), T2 (after Level 2), up to T6 (after Level 6).

Other: Intraocular Pressure after forced expiration; The experiment will entail the acquisition of a total of seven intraocular pressure (IOP) measurements from each subject.; T0: Baseline (pre-intervention, resting).; T1: Immediately after 1 minute of forced expiration at Level 1.; T2: Immediately after 1 minute of forced expiration at Level 2.; T3: Immediately after 1 minute of forced expiration at Level 3.; T4: Immediately after 1 minute of forced expiration at Level 4.; T5: Immediately after 1 minute of forced expiration at Level 5.; T6: Immediately after 1 minute of forced expiration at Level 6.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Intraocular Pressure Measurement	The intraocular pressure will be measured in both eyes using a calibrated Tonoref III non-contact tonometry (Nidek Co., Ltd., Gamagori, Aichi, Japan) and applanation tonometry (A900 tonometer, Costruzione Strumenti Oftalmici, Firenze, Italy) by a single examiner	T0: Baseline / T1: after 1 minute of forced expiration at Level 1 /T2: after 1 minute of forced expiration at Level 2/T3: Immediately after 1 minute of forced expiration at Level 3

Collaborators and Investigators

• Sponsor: Uşak University
• Investigators: Study Chair: Ali Y Karahan, Prof., University of Usak

Study record dates

Study Major Dates

• Study Start (Actual): December 15, 2025
• Primary Completion (Estimated): February 10, 2026
• Study Completion (Estimated): February 25, 2026

Study Registration Dates

• First Submitted: November 27, 2025
• First Submitted That Met QC Criteria: November 27, 2025
• First Posted (Estimated): December 10, 2025

Study Record Updates

• Last Update Posted (Actual): December 22, 2025
• Last Update Submitted That Met QC Criteria: December 15, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Other Study ID Numbers: AB&AYK

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No