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NCT Number: NCT07603037

EIT Evaluation of Different Antihypertensive Agents on the Ventilation-Perfusion Ratio in Patients With Acute Respiratory Failure

This prospective, single-center interventional study aims to evaluate the effect of two commonly used intravenous antihypertensive agents - nicardipine and nitroglycerin - on lung ventilation-perfusion (V/Q) distribution in patients with acute respiratory failure complicated by hypertension. Electrical Impedance Tomography (EIT) will be used for noninvasive monitoring of pulmonary ventilation and perfusion distribution before and after drug administration.

The study will compare the changes in V/Q ratio, oxygenation index, and hemodynamic variables after administration of the two drugs. The findings are expected to provide evidence for the optimal antihypertensive strategy in critically ill patients with respiratory failure and to clarify whether specific vasodilators exacerbate or improve ventilation-perfusion mismatch.

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Key information

Conditions

Acute Respiratory Failure (ARF) Acute Aortic Syndrome Aneurysm Aortic Diseases Aortic Dissection Aortic Dissection (Subset) Cardiovascular Diseases Dissection, Blood Vessel Hypertension Pulmonary Perfusion Imbalance Vascular Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

The First Affiliated Hospital of Wannan Medical College (Yijishan Hospital of Wannan Medical College)

Wuhu, Anhui, 241001, China

Location contact

Shengsheng Tao

CONTACT

[email protected]

86-18315329399

About this study

Eligible adult patients diagnosed with acute respiratory failure (PaO₂/FiO₂ ≤ 300 mmHg) and concomitant hypertension (including post-surgical or aortic dissection cases) admitted to the ICU will be enrolled after stabilization.

After baseline EIT and blood gas measurements, participants will sequentially receive nitroglycerin and nicardipine under controlled conditions, with each medication infused over a standardized time period while continuously monitoring vital signs.

EIT-derived ventilation and perfusion images will be acquired at baseline, 30 minutes after nitroglycerin, and 30 minutes after nicardipine.

The primary endpoint is the change in the regional ventilation-perfusion matching index (V/Q-MI). Secondary endpoints include changes in oxygenation, arterial blood gases, and hemodynamic parameters.

All data will be statistically analyzed using paired comparisons and multivariate regression to assess drug-specific effects on pulmonary gas exchange.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Diagnosis of acute respiratory failure with PaO₂/FiO₂ ≤ 300 mmHg, requiring invasive mechanical ventilation.

Requires intravenous antihypertensive infusion (such as nicardipine or nitroglycerin) to maintain controlled and stable blood pressure during ICU treatment.

Written informed consent obtained from the patient or the legally authorized representative.

Exclusion criteria

Body mass index (BMI) ≥ 50 kg/m² or presence of massive subcutaneous edema interfering with EIT signal acquisition.

Implanted cardiac pacemaker, defibrillator, or any metallic thoracic device that may distort impedance measurements.

Hemodynamic instability or severe hypotension occurring during drug titration. Pregnancy or lactation. Known hypersensitivity or contraindication to nicardipine or nitroglycerin. Use of phosphodiesterase-5 inhibitors, such as sildenafil, tadalafil, or vardenafil, within the clinically relevant washout period.

Severe anemia, markedly increased intracranial pressure, or other clinical conditions in which nitroglycerin administration is considered inappropriate by the treating physician.

Incomplete clinical documentation preventing accurate evaluation of primary endpoints.

Treatment and study plan

Nitroglycerin

Drug

Continuous intravenous infusion of nitroglycerin for blood pressure reduction in acute respiratory failure. The drug is administered at an initial rate of 5 µg/min, titrated up to 100 µg/min as needed to maintain target mean arterial pressure (MAP 65-85 mmHg). Each infusion period lasts 30 minutes under stable mechanical ventilation. Hemodynamic parameters, arterial blood gases, and electrical impedance tomography (EIT) data are recorded at Baseline, 30 min, and 60 min. A washout phase is observed before crossover to the second intervention.

Other names: Glyceryl Trinitrate; Nitroglycerin Injection; Tridil®

nicardipine

Drug

Continuous intravenous infusion of nicardipine for blood pressure control during mechanical ventilation. The infusion begins at 1 mg/h and is titrated up to 5 mg/h according to real-time blood pressure monitoring to maintain target MAP 65-85 mmHg. Each infusion period lasts 30 minutes. Electrical impedance tomography (EIT) is used to record ventilation-perfusion matching, dead-space, and shunt fraction at Baseline, 30 min, and 60 min. After completion, a 30-minute washout period or until baseline hemodynamics are restored precedes the next crossover phase.

Other names: Cardene; Nicardipine Hydrochloride

Primary outcomes

  1. Change in Ventilation-Perfusion Matching Index

    Time frame: Baseline (prior to infusion), 30 minutes after infusion initiation, 60 minutes after infusion initiation.

    The ventilation-perfusion matching index quantifies the correlation between regional ventilation and perfusion signals derived from EIT imaging. The index ranges from 0 to 1; higher values indicate better matching.

  2. Change in Physiological Dead Space Fraction (Vd/Vt)

    Time frame: Baseline, 30 minutes, and 60 minutes.

    Physiological dead space is calculated as (PaCO₂ - PeCO₂)/PaCO₂, supplemented by EIT-based regional ventilation analysis. The expected range is 0 to 0.8; higher values indicate greater alveolar wastage and poorer gas exchange.

  3. Change in Intrapulmonary Shunt Fraction (%)

    Time frame: Baseline, 30 minutes, and 60 minutes.

    The shunt fraction represents the percentage of non-oxygenated blood flowing through the lungs without gas exchange. It is computed as Qs/Qt = (CCO₂ - CaO₂) / (CCO₂ - CvO₂), approximated by EIT regional perfusion measurement. Typical range 0-40 %; higher values indicate worse oxygenation efficiency.

Secondary outcomes

  1. Change in Pulmonary Perfusion Distribution

    Time frame: Baseline, 30 minutes, and 60 minutes.

    Regional perfusion ratio analyzed via EIT contrast impedance variation after saline bolus indicator; expressed as percentage of dependent to non-dependent lung regions. Higher ratios reflect more homogeneous perfusion.

  2. Change in Pulmonary Ventilation Distribution

    Time frame: Baseline, 30 minutes, and 60 minutes.

    Regional ventilation heterogeneity index calculated from EIT ventilation waves; value ranges 0-1, where higher values represent less homogeneous ventilation.

  3. Change in Oxygenation Index (PaO₂/FiO₂ Ratio)

    Time frame: Baseline, 30 minutes, and 60 minutes.

    Ratio of arterial oxygen partial pressure to fraction of inspired oxygen, unit mmHg; range ≤ 300 mmHg inclusion criterion; higher values indicate better oxygen exchange.

Study contacts

Contact information is provided by the study sponsor or research team.

qiancheng xu, PhD

CONTACT

[email protected]

+86-18297529106

Sponsors and collaborators

Lead sponsor

First Affiliated Hospital of Wannan Medical College

Other

Registry information

Official study title

Effect of Nicardipine and Nitroglycerin on the Ventilation-Perfusion Ratio in Patients With Acute Respiratory Failure Using Electrical Impedance Tomography: A Prospective Pilot Study

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
May 22, 2026
Registry last updated
Jul 2, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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