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

N/ANot Yet RecruitingNCT07603037

First Affiliated Hospital of Wannan Medical College12 enrolled

Overview

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.

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.

Study Type

INTERVENTIONAL

Allocation

Purpose

BASIC_SCIENCE

Masking

NONE

Enrollment

Interventions

NitroglycerinDRUG

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.

NicardipineDRUG

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.

Eligibility

Sex: ALLMin age: 18 Years

Medical Language ↔ Plain English

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.

Outcomes

Primary Outcomes

Change in Ventilation-Perfusion Matching Index

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.

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

Change in Physiological Dead Space Fraction (Vd/Vt)

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.