Positional Effects on Lung Ventilation and Perfusion in Obesity

NCT ID: NCT07341113

Last Updated: 2026-01-20

Basic Information

• Recruitment Status: ACTIVE_NOT_RECRUITING
• Total Enrollment: 40 participants
• Study Classification: OBSERVATIONAL
• Study Start Date: 2025-12-01
• Study Completion Date: 2026-01-31

Brief Summary

Electrical Impedance Tomography (EIT) is a non-invasive, bedside monitoring tool that provides real-time information on regional ventilation and perfusion. In particular, EIT has the potential to guide individualized mechanical ventilation in obese patients by revealing how gravitational and positional factors alter regional lung behavior. Assessing the effects of different horizontal positions on both ventilation and perfusion may help optimize respiratory management strategies tailored to body habitus. By comparing obese and non-obese healthy participants across different positions, this study aims to provide novel insights into the postural effects on lung aeration and perfusion distribution, and to highlight the role of EIT in tailoring individualized ventilation strategies.

Detailed Description

This will be a observational, physiological study involving healthy volunteers divided into two groups: Obese group (BMI 30 - 40 kg/m²) and non-obese group (BMI 18.5 - 24.9 kg/m²). Each participant will serve as their own control across body positions. Baseline measurements will be obtained in upright sitting, followed by randomized order of supine, Trendelenburg (30°), prone, left lateral, and right lateral. Participants' demographic and anthropometric data, including height, weight, chest circumference, waist circumference, and hip circumference, will be recorded. Medical history, current medication use, smoking status, and cumulative smoking exposure (pack-years) will be documented.

Electrical Impedance Tomography (EIT) measurements will be performed using the Infivision ET1000 device. All study procedures will take place in a private room within the General Intensive Care Unit of Koç University Hospital, with privacy ensured throughout the protocol. After removal of upper body clothing, an appropriately sized EIT belt, selected according to chest circumference, will be positioned circumferentially around the thorax at the level of the axillae. A pulse oximetry probe will be applied, and continuous monitoring of heart rate and peripheral oxygen saturation will be maintained during all measurements.

Following a 5-minute stabilization period in the upright sitting position, baseline EIT measurements will be obtained. The following parameters will be recorded: percentage of ventral ventilation, percentage of dorsal ventilation, percentage of ventral perfusion, percentage of dorsal perfusion, Match Index (MI), Dead Space Index (DI), Shunt Index (SI), Global Inhomogeneity Index (GI), and Center of Ventilation (CoV). To minimize potential carry-over effects, the sequence of positions will be randomized individually for each participant. Randomization will be performed using computer-generated random sequences (randomizer.org), with predefined randomization sets created prior to study initiation.

Each position will be maintained for approximately 5 minutes. In each position, end-expiratory lung impedance difference (ΔEELI) will be measured using the upright sitting position as the reference. The total duration of the study protocol is expected to be approximately 30 minutes per participant. The study will be completed once all measurements have been obtained in all positions.

Conditions

Obesity (Disorder); Ventilation Homogeneity; Perfusion; Ventilation Perfusion Mismatch; Position Differences; Electrical Impedance Tomography (EIT)

Study Design

• Observational Model Type: CASE_CROSSOVER
• Study Time Perspective: PROSPECTIVE

Study Groups

Non-obese group

Non-obese healthy individuals with BMI between 18.5 - 25 kg/m²

Standardized body positioning

Intervention Type: OTHER

Standardized changes in body position (supine, Trendelenburg, prone, and lateral positions) performed solely for physiologic assessment of ventilation and perfusion using electrical impedance tomography. This does not constitute a therapeutic or preventive intervention.

Obese group

Obese healthy individuals with BMI between 30 - 40 kg/m²

Standardized body positioning

Intervention Type: OTHER

Standardized changes in body position (supine, Trendelenburg, prone, and lateral positions) performed solely for physiologic assessment of ventilation and perfusion using electrical impedance tomography. This does not constitute a therapeutic or preventive intervention.

Interventions

Standardized body positioning

Standardized changes in body position (supine, Trendelenburg, prone, and lateral positions) performed solely for physiologic assessment of ventilation and perfusion using electrical impedance tomography. This does not constitute a therapeutic or preventive intervention.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

-BMI between 18-25 kg/m² or 30-40 kg/m²

Exclusion Criteria

• Individuals with a body mass index (BMI) between 25 and 30 kg/m²,
• Pregnancy
• Respiratory tract infection within the previous two weeks
• Anatomical abnormalities of the chest wall that may interfere with Electrical Impedance Tomography (EIT) measurements.

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 65 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Koç University

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Principal Investigators

Evren Şentürk, MD

Role: STUDY_DIRECTOR

Koç University School of Medicine

Locations

Koç University Hospital

Istanbul, , Turkey (Türkiye)

Countries

Turkey (Türkiye)

References

De Jong A, Wrigge H, Hedenstierna G, Gattinoni L, Chiumello D, Frat JP, Ball L, Schetz M, Pickkers P, Jaber S. How to ventilate obese patients in the ICU. Intensive Care Med. 2020 Dec;46(12):2423-2435. doi: 10.1007/s00134-020-06286-x. Epub 2020 Oct 23.

Reference Type: BACKGROUND

PMID: 33095284 (View on PubMed)

Other Identifiers

2025.510.IRB2.232

Identifier Type: -

Identifier Source: org_study_id