This study aims to compare lung perfusion distribution between inspiratory breath-hold and expiratory breath-hold phases using the saline indicator method combined with electrical impedance tomography (EIT). A self-controlled crossover design will be used in which each participant undergoes both breath-hold conditions with standardized rapid intravenous saline injections. The primary objective is to evaluate changes in global and regional pulmonary perfusion under different lung volume states. The findings may improve understanding of perfusion redistribution with lung inflation and support optimized ventilatory strategies in clinical practice.
Age 18 to 65 years
Able to provide written informed consent
Able to perform standardized inspiratory and expiratory breath-hold maneuvers for at least 8 seconds
No known acute cardiopulmonary disease
Known severe cardiopulmonary disease (e.g., advanced chronic obstructive pulmonary disease, severe pulmonary hypertension, or heart failure)
Hemodynamic instability or clinically significant cardiac arrhythmia
Contraindication to intravenous saline administration or fluid bolus
Pregnancy or breastfeeding
Single group
Electrical Impedance Tomography Saline Indicator Procedure
Procedure/SurgeryParticipants undergo continuous electrical impedance tomography (EIT) monitoring with a circumferential electrode belt placed around the thorax. During the procedure, participants perform standardized inspiratory and expiratory breath-hold maneuvers. At each breath-hold phase, a rapid intravenous bolus of sterile saline (10-20 mL) is administered, followed by a saline flush, to generate transient impedance changes for lung perfusion imaging using the saline indicator technique. EIT data are recorded continuously before, during, and after each saline injection. Each participant undergoes both breath-hold conditions and serves as their own control.
Electrical Impedance Tomography Device
DeviceAn FDA-cleared electrical impedance tomography (EIT) device is used to noninvasively monitor thoracic impedance changes during the study procedures. The device is used solely for physiological monitoring and image acquisition and is not being evaluated for safety, performance, or a new indication.
Global Lung Perfusion Distribution
Quantitative assessment of global lung perfusion distribution derived from saline-induced impedance changes measured by electrical impedance tomography during inspiratory and expiratory breath-hold phases. Global perfusion is expressed as the percentage contribution of regional perfusion relative to total lung perfusion.
Global Lung Perfusion Heterogeneity Index
Spatial heterogeneity of lung perfusion quantified using a perfusion heterogeneity index derived from regional perfusion maps obtained with the electrical impedance tomography saline indicator technique.
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