Flow Index: a New Method for Assessing Respiratory Drive in Critically Ill Patients Based on Electrical Impedance Tomography

Accurate assessment of respiratory drive is critical to the management of critically ill patients, but all currently used assessment methods have significant limitations. Oesophageal pressure monitoring, although the gold standard, is invasive and poorly tolerated by patients; airway obstruction pressure (P0.1) provides only intermittent assessment; and diaphragmatic electrical activity (EAdi) measurement requires special equipment and precise catheter positioning. Therefore, the development of a non-invasive, continuous respiratory drive monitoring method is of great clinical importance.

The aim of this study is to validate the reliability and clinical application value of a new parameter based on electrical impedance tomography (EIT)-derived Flow Index in assessing respiratory drive. We will recruit 150 critically ill patients requiring respiratory support and record both Flow Index and conventional respiratory drive metrics to assess their correlation and predictive value for clinical outcomes.

Data acquisition was performed using a standardised procedure: EIT monitoring was performed using a PulmoVista 500 with the electrode strip located between the 4th and 5th intercostal space, with the patient in a 15° semi-recumbent position. eit data were acquired continuously at a sampling rate of 50 Hz.

Simultaneously, we will record three reference measurements:

1. oesophageal pressure monitoring: continuous recording of pressure fluctuations using a balloon catheter
2. airway obstruction pressure (P0.1): measured using the ventilator integration function
3. diaphragmatic electrical activity (EAdi) recorded in selected patients

Research Title: Flow Index: A Novel Method Based on Electrical Impedance Tomography for Assessing Respiratory Drive in Critically Ill Patients - A Prospective Single-Center Study

Research Summary 1.1 Abstract

Research Title: Flow Index: A Novel Method Based on Electrical Impedance Tomography for Assessing Respiratory Drive in Critically Ill Patients - A Prospective Single-Center Study

Study Overview: This study aims to validate the reliability and clinical application value of a new parameter - Flow Index derived from Electrical Impedance Tomography (EIT) in assessing respiratory drive in critically ill patients. Through comparison with traditional respiratory drive indicators, it evaluates its value in predicting clinical outcomes. This is a prospective, observational single-center study.

Research Objectives:

Primary objectives:

Validate the correlation between Flow Index and traditional respiratory drive indicators Evaluate Flow Index's predictive value for clinical outcomes

Secondary objectives:

Determine the optimal threshold value for Flow Index Analyze the relationship between Flow Index and mechanical ventilation duration Analyze Flow Index's guidance value for oxygen therapy and mechanical ventilation strategies Evaluate Flow Index's correlation with ICU mortality

Research Intervention: This is an observational study mainly using non-invasive EIT monitoring technology while recording routine clinical monitoring indicators. No additional invasive procedures will be added.

Subject Participation Duration: Each subject from enrollment until ICU discharge or maximum 28 days

1.2 Technical Roadmap

Study Flow:

1. Sign informed consent, recruit subjects according to inclusion and exclusion criteria
2. Baseline Assessment:

   * Record baseline vital signs: heart rate, blood pressure, pulse oximetry, respiratory rate, APACHE II score
   * Record ventilator parameters, EIT ventilation parameters: EELI, GI, ROI, etc., and new indicator Flow Index
   * Record EIT blood flow parameters: ventilation-perfusion ratio, dead space percentage, shunt percentage, etc.

Follow-up Assessments:

* Day 1: Multimodal data synchronous collection (EIT Flow Index, esophageal pressure, P0.1 measurement, EAdi, n=30)
* Day 2: Physiological parameters, blood gas analysis; ventilator and oxygen therapy parameter adjustment records
* Day 7: Follow-up assessment (including safety); physiological parameters, blood gas analysis
* Day 28: Final assessment, including mechanical ventilation and oxygen therapy duration, 28-day mortality

  2. Research Background

2.1 Research Significance Respiratory function monitoring in critically ill patients is crucial for treatment decisions. Accurate assessment of respiratory drive can help clinicians optimize ventilation parameters, detect respiratory function changes timely, and prevent complications. While traditional monitoring methods like esophageal pressure monitoring are accurate but invasive, the Flow Index based on EIT proposed in this study, as a non-invasive and continuous monitoring method, has important clinical application value.

2.2 Research Background

Respiratory drive assessment and monitoring has been a research focus in critical care medicine. In vitro studies have shown that changes in respiratory drive are closely related to respiratory muscle function and lung injury. Animal experiments further confirm that continuous strong respiratory drive can lead to diaphragm injury and increased pulmonary inflammatory response. These basic studies provide important theoretical basis for clinical monitoring of respiratory drive.

In terms of clinical research, multiple international multicenter studies have confirmed that respiratory drive is closely related to the prognosis of mechanically ventilated patients. Data from Europe, America, Asia and other regions show that strong respiratory drive is associated with higher mortality, while early identification and intervention of respiratory drive may improve prognosis. A recent systematic review points out that the lack of ideal bedside monitoring tools is the main barrier to individualized treatment.

From an epidemiological perspective, with the development of critical care medicine, mechanical ventilation is increasingly used in intensive care units. Statistics show that about 30-40% of ICU patients need mechanical ventilation support, among which abnormal respiratory drive is a common clinical problem. Accurate assessment of respiratory drive is not only related to individual treatment plan development, but also closely related to rational allocation of public health resources.

This study aims to solve a key problem in clinical practice: how to accurately assess respiratory drive in a non-invasive and continuous way. Based on existing research foundation, the investigators propose to develop new monitoring parameters using electrical impedance tomography technology, which may provide better solutions for clinical practice. The development of such work not only has important clinical value, but will also promote the development and innovation of related technologies.

2.3 Expected Research Outcomes

This study expects to achieve important results in three aspects: scientific cognition, clinical application and technological innovation. In terms of scientific cognition, through systematic data collection and analysis, the investigators will elucidate the correlation between Flow Index and traditional respiratory drive indicators, deepen understanding of the relationship between impedance changes and respiratory physiology, and provide new theoretical basis for respiratory function monitoring. The research results will help determine the normal range and clinical warning threshold of Flow Index, laying foundation for subsequent research and application.

2.2 Research Background

Respiratory drive assessment and monitoring has been a research focus in critical care medicine. In vitro studies have shown that changes in respiratory drive are closely related to respiratory muscle function and lung injury. Animal experiments further confirm that continuous strong respiratory drive can lead to diaphragm injury and increased pulmonary inflammatory response. These basic studies provide important theoretical basis for clinical monitoring of respiratory drive.

In terms of clinical research, multiple international multicenter studies have confirmed that respiratory drive is closely related to the prognosis of mechanically ventilated patients. Data from Europe, America, Asia and other regions show that strong respiratory drive is associated with higher mortality, while early identification and intervention of respiratory drive may improve prognosis. A recent systematic review points out that the lack of ideal bedside monitoring tools is the main barrier to individualized treatment.

From an epidemiological perspective, with the development of critical care medicine, mechanical ventilation is increasingly used in intensive care units. Statistics show that about 30-40% of ICU patients need mechanical ventilation support, among which abnormal respiratory drive is a common clinical problem. Accurate assessment of respiratory drive is not only related to individual treatment plan development, but also closely related to rational allocation of public health resources.

This study aims to solve a key problem in clinical practice: how to accurately assess respiratory drive in a non-invasive and continuous way. Based on existing research foundation, the investigators propose to develop new monitoring parameters using electrical impedance tomography technology, which may provide better solutions for clinical practice. The development of such work not only has important clinical value, but will also promote the development and innovation of related technologies.

2.3 Expected Research Outcomes

This study expects to achieve important results in three aspects: scientific cognition, clinical application and technological innovation. In terms of scientific cognition, through systematic data collection and analysis, the investigators will elucidate the correlation between Flow Index and traditional respiratory drive indicators, deepen understanding of the relationship between impedance changes and respiratory physiology, and provide new theoretical basis for respiratory function monitoring. The research results will help determine the normal range and clinical warning threshold of Flow Index, laying foundation for subsequent research and application.

In terms of clinical application, the investigators expect to establish a standardized respiratory drive assessment process based on Flow Index. This includes determining the optimal monitoring position, data collection frequency, and analysis methods, and developing clinical application guidelines. By validating Flow Index's predictive value for clinical outcomes, it provides a new reference tool for treatment decisions in critically ill patients. Particularly for key clinical issues such as mechanical ventilation parameter adjustment and weaning timing determination, it provides more reliable decision-making basis for physicians.

In terms of technological innovation, this study will develop and improve respiratory drive monitoring algorithms based on EIT, forming monitoring methods with independent intellectual property rights. Through optimization of signal processing and data analysis methods, the accuracy and reliability of monitoring will be improved. The research results are expected to promote the improvement and innovation of bedside monitoring equipment and promote the development of related medical devices.

These expected outcomes will provide new tools and methods for improving the diagnosis and treatment level of critically ill patients, with important clinical translation value.

Eligibility Criteria:
Inclusion Criteria:

* Age ≥18 years,
* Acute respiratory failure requiring respiratory support
* Expected duration of support \>24 hours.

Exclusion Criteria:

* Contraindications to EIT (e.g., implantable cardiac devices)
* Severe haemodynamic instability (norepinephrine \>0.5 μg/kg/min)
* Chest gallery deformity
* Recent thoracic surgery
* Pregnancy
* Expected survival \<24 hours.