The Feasibility of Pulmonary Perfusion Assessment Using Sodium Bicarbonate Contrast With Electrical Impedance Tomography: A Prospective Pilot Study

The goal of this observational pilot study is to learn if sodium bicarbonate can be used safely and effectively as a contrast agent to map lung blood flow using electrical impedance tomography (EIT) in adults on mechanical ventilation. Electrical impedance tomography (EIT) is a bedside imaging method that uses a soft belt with small sensors around the chest to track changes in electrical signals related to breathing and blood flow.

The main questions are:

Does sodium bicarbonate create clear, readable lung blood flow images with EIT? Are these images similar in quality and pattern to images made with hypertonic saline (10% sodium chloride)? Is the short-term safety profile acceptable, including effects on blood pressure, heart rhythm, and blood tests?

Researchers will compare two contrast agents within the same participant to see if image quality and lung blood flow patterns match:

Hypertonic saline (10% sodium chloride) Sodium bicarbonate (5%)

Participants will:

Have an EIT belt placed around the chest during routine ICU care Pause the ventilator briefly during image capture to reduce motion Receive two small intravenous boluses through an existing central line, one of hypertonic saline and one of sodium bicarbonate, with time between doses Have routine monitoring of vital signs; blood gases and electrolytes may be checked per clinical care Be observed for any short-term side effects Findings from this study will show whether sodium bicarbonate is a practical and safe option for EIT-based lung blood flow assessment and will guide larger future studies.

Study Overview

• Status: Recruiting
• Conditions: Pneumonia; Critical Illness; Acute Respiratory Failure; Acute Respiratory Distress Syndrome (ARDS); Feasibility of Contrast-enhanced Electrical Impedance Tomography (EIT) for Pulmonary Perfusion Assessment in Mechanically Ventilated Adults

Detailed Description

This single-center, prospective, observational pilot study evaluates sodium bicarbonate as a conductivity contrast agent for electrical impedance tomography (EIT) to assess pulmonary perfusion in mechanically ventilated adults. EIT uses a belt with surface electrodes placed at a standard chest level to measure changes in electrical impedance. A small intravenous bolus of a conductive solution produces a short first-pass signal that can be analyzed to map relative lung blood flow.

Procedure:

Placement: An EIT belt is positioned around the thorax and signal quality is verified.

Acquisition: Perfusion-focused recordings are obtained during brief end-expiratory pauses on the ventilator to limit breathing-related signal changes.

Contrast sequence: Each participant receives two small contrast boluses through a central venous catheter in a prespecified order with adequate washout between injections:

10% sodium chloride (hypertonic saline) 5% sodium bicarbonate Monitoring: Continuous bedside monitoring (for example, heart rhythm and blood pressure) accompanies each acquisition. Blood gases and electrolytes may be obtained in temporal proximity to injections when clinically available.

Data handling and endpoints:

Image quality is assessed by predefined criteria for analyzable recordings and signal strength adequate for first-pass analysis.

Regional perfusion patterns from sodium bicarbonate are compared within participants to patterns from hypertonic saline to evaluate similarity in image quality and distribution.

Short-term safety is described by changes in vital signs and clinically available laboratory values, and by recording adverse events possibly related to the boluses.

This pilot uses a small convenience sample appropriate for feasibility work and is not designed to detect differences in long-term clinical outcomes. Results will inform parameter selection and sample size for subsequent studies that use EIT to assess lung blood flow.

• Study Type: Observational
• Enrollment (Estimated): 41

Contacts and Locations

• Study Contact: Name: qiancheng xu, PhD; Phone Number: +86-18297529106; Email: qianchengxu@wnmc.edu.cn

Study Locations

• China
  • Anhui
    • Wuhu, Anhui, China, 241001
      • Recruiting
      • The First Affiliated Hospital of Wannan Medical College (Yijishan Hospital of Wannan Medical College)
      • Contact: qiancheng xu, PhD; Phone Number: +86-18315329399; Email: xu19871011@163.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Critically ill adult patients admitted to a mixed intensive care unit, receiving invasive mechanical ventilation and equipped with a central venous catheter. All participants undergo a single bedside electrical impedance tomography examination with sequential bolus injections of hypertonic saline and 5% sodium bicarbonate for pulmonary perfusion assessment.

Description

Inclusion Criteria:

• Age ≥ 18 years
• Admitted to the intensive care unit (ICU)
• Receiving invasive mechanical ventilation with controlled or assisted-controlled mode
• Presence of a central venous catheter suitable for contrast bolus injection
• Hemodynamically stable (no ongoing cardiopulmonary resuscitation; no uncontrolled shock judged by treating physician)
• Expected to remain on mechanical ventilation for the duration of the EIT examination
• Written informed consent obtained from the patient or legally authorized representative

Exclusion Criteria:

• Known pregnancy
• Known allergy, intolerance, or contraindication to sodium bicarbonate or hypertonic saline
• Severe arrhythmia or unstable cardiovascular status in which small bolus injection is deemed unsafe by the treating physician
• Uncontrolled agitation or conditions that preclude correct EIT belt placement (e.g., extensive chest wounds, large chest dressings, chest wall deformity that prevents belt use)
• Implanted electronic devices or metallic implants in the thoracic area considered a contraindication to EIT by the manufacturer's instructions
• End-stage disease with expected survival of only a few hours, in whom participation is not appropriate as judged by the treating physician
• Participation in another interventional trial that, in the opinion of the investigator, could interfere with EIT measurements or safety assessment

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Mechanically Ventilated ICU Cohort; Adult ICU participants on controlled mechanical ventilation with a central venous catheter. Participants undergo bedside electrical impedance tomography (EIT) perfusion imaging during brief end-expiratory pauses. Two small intravenous contrast boluses are given in a prespecified sequence with adequate washout: 10% sodium chloride (hypertonic saline) and 5% sodium bicarbonate. Continuous physiologic monitoring is performed; blood gases/electrolytes may be obtained per clinical care. No randomization. Within-participant comparison of image quality, perfusion patterns, and short-term safety. Observational; EIT monitor used per routine care.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Proportion of analyzable sodium bicarbonate-enhanced EIT perfusion recordings	Feasibility defined as the proportion of 5% sodium bicarbonate (NaHCO3) EIT perfusion acquisitions that meet predefined analyzable image quality criteria (clear first-pass bolus curve, no noncorrectable artifacts, successful reconstruction over expected thoracic region). Reported as n analyzable / n attempted, with 95% CI.	During the single EIT session on the study day (from contrast injection to completion of image reconstruction; within ~2 hours of enrollment)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Overall first-pass impedance reduction amplitude (AU): NaCl vs NaHCO3	Median (IQR) amplitude of overall first-pass impedance reduction for 10% NaCl vs 5% NaHCO3 with within-participant comparison and statistical test; also summarize per ROI (1-4).	During the single EIT session (immediately after each bolus).
Global V/Q match and mismatch (%): NaCl vs NaHCO3	Percent V/Q match and V/Q mismatch derived from EIT for each agent; report median (IQR), within-participant differences, and corresponding P values.	During the single EIT session.
Global intrapulmonary shunt (%) and dead space (%): NaCl vs NaHCO3	Report shunt and dead space percentages for both agents (median [IQR]) with within-participant comparison and P values.	During the single EIT session.
Agreement between agents for global V/Q indices (ICC and Bland-Altman)	Intraclass correlation coefficients (95% CIs) and Bland-Altman bias/limits of agreement between NaCl and NaHCO3 for global V/Q match, shunt, and dead space.	Derived from paired acquisitions within the same session on the study day.
Correlation between agents for global and regional parameters (Pearson R)	Pearson correlation coefficients (R, P) between NaCl and NaHCO3 for global V/Q match, shunt, dead space, and ROI-level V/Q match, ventilation, and perfusion.	Same-session paired measurements on the study day.
Correlation of EIT-derived global indices with PaO2/FiO2	Pearson correlations (R, P) between PaO2/FiO2 and EIT-derived V/Q mismatch, dead space, and shunt for each contrast agent analyzed separately.	Paired with each EIT acquisition on the study day.

Collaborators and Investigators

• Sponsor: First Affiliated Hospital of Wannan Medical College

Study record dates

Study Major Dates

• Study Start (Actual): September 26, 2024
• Primary Completion (Estimated): September 25, 2026
• Study Completion (Estimated): September 25, 2026

Study Registration Dates

• First Submitted: April 14, 2026
• First Submitted That Met QC Criteria: April 14, 2026
• First Posted (Actual): April 21, 2026

Study Record Updates

• Last Update Posted (Actual): April 21, 2026
• Last Update Submitted That Met QC Criteria: April 14, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Mechanical Ventilation; Feasibility Study; Intensive Care Unit (ICU); Electrical Impedance Tomography (EIT); Pulmonary Perfusion; Contrast-Enhanced EIT; Sodium Bicarbonate Contrast; Hypertonic Saline (10% NaCl); First-Pass Impedance Signal; Ventilation-Perfusion (V/Q) Matching
• Additional Relevant MeSH Terms: Pathologic Processes; Disease Attributes; Respiratory Tract Infections; Infections; Respiratory Tract Diseases; Lung Diseases; Respiration Disorders; Pathological Conditions, Signs and Symptoms; Respiratory Distress Syndrome; Critical Illness; Pneumonia
• Other Study ID Numbers: 2024-117

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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